Presentation on theme: "Protocols for Use of Five Passive Samplers"— Presentation transcript:
1Protocols for Use of Five Passive Samplers Welcome – Thanks for joining us.ITRC’s Internet-based Training ProgramProtocols for Use of Five Passive SamplersAll groundwater samplers or sampling methodologies attempt to collect a well-water sample which is representative of the groundwater adjacent to the well. The ITRC Passive Sampler Team has defined a passive groundwater sampler as one that is able to acquire a sample from a discrete position in a well without active media transport induced by pumping or purge techniques. Passive sampling is synonymous with no-purge sampling and can be used as a substitute or replacement for any current groundwater sampling technology. Passive samplers have been used in every state in the U.S. and in many other countries. Passive samplers are easy to use; eliminate purge-water production (therefore, there is little or no disposal cost); reduce field sampling variability resulting in highly reproducible data; decrease field labor and project management costs for long-term monitoring; allow rapid field sample collection; sample discrete intervals in a well; are practical for use where access is difficult or discretion is desirable; can be deployed in series to provide a vertical contaminant profile; and have virtually no depth limit.This training supports the understanding and use of the ITRC Protocols for Use of Five Passive Samplers to Sample for a Variety of Contaminants in Groundwater (DSP-5, 2007). The five technologies included in this document include diffusion samplers (Regenerated Cellulose Dialysis Membrane Sampler and Rigid Porous Polyethylene Sampler), equilibrated grab samplers (Snap Sampler™ and HydraSleeve™ Sampler); and an accumulation sampler (GORE™ Module). The training starts with information common to all five samples then focuses on each sampler as instructors describe the sampler and explain how it works; discuss deployment and retrieval of the sampler; highlight advantages and limitations; and present results of data comparison studies.ITRC (Interstate Technology and Regulatory Council)Training Co-Sponsored by: US EPA Technology Innovation and Field Services Division (TIFSD) (www.clu-in.org)ITRC Training Program: Phone:ITRC Protocols for Use of Five Passive Samplers to Sample for a Variety of Contaminants in Groundwater (DSP-5, 2007)Sponsored by: Interstate Technology and Regulatory Council (www.itrcweb.org) Hosted by: US EPA Clean Up Information Network (www.cluin.org)
2Housekeeping Course time is 2¼ hours Phone line participants Do NOT put this call on hold*6 to mute; #6 to unmuteQuestion & Answer breaksPhone - unmute #6 to ask question out loudSimulcast - ? icon at top to type in a questionTurn off any pop-up blockersMove through slidesArrow icons at top of screenList of slides on leftFeedback form available from last slide – please complete before leavingThis event is being recordedArchives accessed for freeAlthough I’m sure that some of you are familiar with these rules from previous CLU-IN events, let’s run through them quickly for our new participants.We have started the seminar with all phone lines muted to prevent background noise. Please keep your phone lines muted during the seminar to minimize disruption and background noise. During the question and answer break, press #6 to unmute your lines to ask a question (note: *6 to mute again). Also, please do NOT put this call on hold as this may bring unwanted background music over the lines and interrupt the seminar.You should note that throughout the seminar, we will ask for your feedback. You do not need to wait for Q&A breaks to ask questions or provide comments using the ? icon. To submit comments/questions and report technical problems, please use the ? icon at the top of your screen. You can move forward/backward in the slides by using the single arrow buttons (left moves back 1 slide, right moves advances 1 slide). The double arrowed buttons will take you to 1st and last slides respectively. You may also advance to any slide using the numbered links that appear on the left side of your screen. The button with a house icon will take you back to main seminar page which displays our agenda, instructor bios, links to the slides and additional resources. Lastly, the button with a computer disc can be used to download and save today’s presentation slides.Download slides as PPT or PDFGo to slide 1Submit comment or questionReport technical problemsMove back 1 slideGo to seminar homepageGo to last slideMove forward 1 slide2
3ITRC Disclaimer and Copyright Although the information in this ITRC training is believed to be reliable and accurate, the training and all material set forth within are provided without warranties of any kind, either express or implied, including but not limited to warranties of the accuracy, currency, or completeness of information contained in the training or the suitability of the information contained in the training for any particular purpose. ITRC recommends consulting applicable standards, laws, regulations, suppliers of materials, and material safety data sheets for information concerning safety and health risks and precautions and compliance with then-applicable laws and regulations. ECOS, ERIS, and ITRC shall not be liable for any direct, indirect, incidental, special, consequential, or punitive damages arising out of the use of any information, apparatus, method, or process discussed in ITRC training, including claims for damages arising out of any conflict between this the training and any laws, regulations, and/or ordinances. ECOS, ERIS, and ITRC do not endorse or recommend the use of, nor do they attempt to determine the merits of, any specific technology or technology provider through ITRC training or publication of guidancedocuments or any other ITRC document.Here’s the lawyer’s fine print. I’ll let you read it yourself, but what it says briefly is:We try to be as accurate and reliable as possible, but we do not warrantee this material.How you use it is your responsibility, not ours.We recommend you check with the local and state laws and experts.Although we discuss various technologies, processes, and vendor’s products, we are not endorsing any of them.Finally, if you want to use ITRC information, you should ask our permission.Copyright 2010 Interstate Technology & Regulatory Council, 444 North Capitol Street, NW, Suite 445, Washington, DC 200013
4ITRC (www.itrcweb.org) – Shaping the Future of Regulatory Acceptance Host organizationNetworkState regulatorsAll 50 states, PR, DCFederal partnersITRC Industry Affiliates ProgramAcademiaCommunity stakeholdersWide variety of topicsTechnologiesApproachesContaminantsSitesProductsTechnical and regulatory guidance documentsInternet-based and classroom trainingDOEDODEPAThe Interstate Technology and Regulatory Council (ITRC) is a state-led coalition of regulators, industry experts, citizen stakeholders, academia and federal partners that work to achieve regulatory acceptance of environmental technologies and innovative approaches. ITRC consists of all 50 states (and Puerto Rico and the District of Columbia) that work to break down barriers and reduce compliance costs, making it easier to use new technologies and helping states maximize resources. ITRC brings together a diverse mix of environmental experts and stakeholders from both the public and private sectors to broaden and deepen technical knowledge and advance the regulatory acceptance of environmental technologies. Together, we’re building the environmental community’s ability to expedite quality decision making while protecting human health and the environment. With our network of organizations and individuals throughout the environmental community, ITRC is a unique catalyst for dialogue between regulators and the regulated community.For a state to be a member of ITRC their environmental agency must designate a State Point of Contact. To find out who your State POC is check out the “contacts” section at Also, click on “membership” to learn how you can become a member of an ITRC Technical Team.4
5ITRC 2-day Classroom Training: Vapor Intrusion Pathway ITRC Course Topics Planned for 2010 – More information atPopular courses from 2009New in 2010Decontamination and Decommissioning of Radiologically-Contaminated FacilitiesEnhanced Attenuation of Chlorinated OrganicsIn Situ Bioremediation of Chlorinated Ethene - DNAPL Source ZonesLNAPL Part 1: An Improved Understanding of LNAPL Behavior in the SubsurfaceLNAPL Part 2: LNAPL Characterization and RecoverabilityPerchlorate Remediation TechnologiesPerformance-based Environmental ManagementPhytotechnologiesProtocol for Use of Five Passive SamplersQuality Consideration for Munitions ResponseDetermination/Application of Risk-Based ValuesUse of Risk Assessment in Management of Contaminated SitesDecision Framework for Applying Attenuation Processes to Metals and RadionuclidesLNAPL Part 3: Evaluating LNAPL Remedial Technologies for Achieving Project GoalsMining WasteRemediation Risk Management: An Approach to Effective Remedial Decisions and More Protective CleanupsMore details and schedules are available from under “Internet-based Training” and “Classroom Training.”ITRC 2-day Classroom Training: Vapor Intrusion Pathway55
6Meet the ITRC Instructors Kimberly McEvoyNew Jersey Department of Environmental ProtectionTrenton, New JerseyHugh RieckUS Army Corps of EngineersOmaha, NebraskaKimberly McEvoy is a Senior Geologist with the New Jersey Department of Environmental Protection (NJDEP) in the Site Remediation Program in Trenton, New Jersey. Before joining the NJDEP, Kimberly worked for five years as a geologist with private environmental consulting companies located in Philadelphia, New Jersey, and Maryland, where she became familiar with various environmental regulations and guidelines associated with groundwater sampling. In 2000, she was hired as a regulator within the NJDEP Bureau of Groundwater Pollution Assessment, advising consultants and private citizens on how to collect a representative groundwater sample. At this time, she was introduced to the work of the ITRC Passive Sampler Team by a coworker who was deploying polyethylene diffusion bags (PDBs) and the regenerated cellulose dialysis (RCD) samplers to collect pore water from stream sediments. Kimberly 's interest led her to become a co-leader of the ITRC Diffusion/Passive Sampler Team in She currently investigates unknown sources of groundwater contamination for the NJDEP Bureau of Environmental Measures and Site Assessment (BEMSA) and has taken over as Team Leader. She has helped the team develop two ITRC-supported technical documents and speaks, on behalf of the team, on the value and usefulness of passive sampling technologies at various conferences across the country. Her goal for the team is to help identify the validity of passive sampling approaches to the regulatory and consulting communities to the point that these technologies are not considered "innovative" sampling techniques but are accepted approaches to collect groundwater samples. Kimberly earned a bachelor's degree in geological science from Pennsylvania State University in State College, Pennsylvania in 1998.Hugh Rieck is a geologist with the US Army Corps of Engineers - Hazardous, Toxic, and Radioactive Waste Center of Expertise (HTRW-CX) in Omaha, Nebraska. Before joining the HTRW-CX in 2006, Hugh worked six years as a hydrologist with the Arizona Department of Environmental Quality Superfund Programs Section, where he became interested in problems of groundwater sampling for environmental investigations. He began his involvement with the ITRC Diffusion/Passive Sampling team shortly after its inception in 2001 and was an alternate instructor for the ITRC Internet-based training course for the use of polyethylene-based passive diffusion bag (PDB) samplers in Prior to his state regulatory experience, Hugh worked 13 years as a research geologist with the U.S. Geological Survey, where he specialized in the application of paleomagnetic stratigraphy to investigations of geologic records of climate change. He earned a bachelor's degree in 1974 and master's degree in 1983 in geology and earth science from Northern Arizona University in Flagstaff, Arizona.Louise Parker has been a Research Physical Scientist at the U.S. Army Engineer Research and Development Center's Cold Regions Research and Engineering Laboratory (ERDC-CRREL) in Hanover, NH for over 25 years. She has a broad background in environmental chemistry and microbiology. Since the early 1990s, her primary research focus has been groundwater monitoring and sampling, and analyte/material interactions, with over 60 publications, presentations, and workshops. Recent research studies have examined the suitability of direct-push (DP) monitoring wells for long-term monitoring and passive groundwater sampling methods. Older studies examined sorption of organic contaminants and leaching of constituents by sampling and well casing materials, decontamination of sampling devices, and the affects of harsh environments on sampling and well casing materials. Since 2002, she has been a member of the ITRC Sampling, Characterization, and Monitoring Team, where she has worked on a technical regulatory document on the use DP wells. Since 2003, she has also a member of the ITRC Diffusion/Passive Sampler team, where she has worked on an overview document on passive groundwater sampling techniques and a technical regulatory document on five passive groundwater sampling methods. Louise earned a bachelor's degree in microbiology from the University of New Hampshire in Durham, NH in 1972 and a master's degree in food science from the University of Massachusetts in Amherst, MA in 1979.Louise ParkerU.S. Army Engineer Research and Development CenterHanover, New Hampshire
7What you will learn… What is passive sampling? What passive samplers offerQuantitative dataCost savings (40-70%)How passive samplers reflect aquifer conditionsTechnical and regulatory guidanceAcceptance of passive samplingClasses and types of passive samplersThe Team defines passive sampler as a device that collects a sample of water, or selectively targeted constituents of water, from a specific depth interval in well (or other location), under ambient conditions (i.e. without the use of a pump). Use of the sampler does not affect the conditions in the well or the sampled medium.Passive samplers can collect information about aquifer conditions and contaminant migration by different mechanisms than conventional active (i.e. pumped) sampling techniques. They can provide information that would be cost-prohibitive by any other means. In environmental investigations, passive samplers can often replace conventional sampling methods to collect groundwater samples that will meet Data Quality Objectives at significantly lower cost. The principal exception being drinking water quality compliance; therefore they are not recommended for drinking water sampling.All passive (no-purge) samplers collect quantitative data. The principal distinguishing aspect of passive samplers is that they collect information about conditions at a specific depth within a well. In contrast, pumped samples (low-flow or high volume purge) actively draws in water from above, below and/or adjacent to the screened interval; therefore, collect a flow-weighted average groundwater sample.Passive Samplers:Do not rely on purge samplingSave money and time since no purge water disposal costs.Are depth-specific; therefore; can profile contaminant concentrations within the screened interval of a well which can aid in refining your Site Conceptual Model, targeting monitoring, and Remedial Process Optimization.ITRC and other references give Technical and Regulatory Guidance on the applicability, usability and value of passive sampling, and provide a basis for consultants and regulators to evaluate passive samplers for their appropriate application. The team has identified three classes of passive groundwater sampling devices, based on their underlying operating mechanisms. The five most mature examples of passive samplers samplers covered in this document and training represent all three classes.
8Passive Sampler Team Diffusion Sampler Team formed in 2000 Initial goalDevelop guidance on polyethylene diffusion bags (PDBs) for collection of volatile organic compounds (VOCs) in groundwater1st passive sampling device - diffusion type sampler (DSP-3)Limited in analyte capabilitiesIncreased interest and development of passive devicesTransition to “Passive Sampler Team”What technologies are being developed and what they can do?Disseminate guidance on passive sampling technologiesBe premier resource on the use of passive sampling technologiesPromote adoption of regulatory guidance (i.e., acceptance)The ITRC Diffusion Sampler Team was formed in 2000 and currently is known as the ITRC Passive Sampler Team. This name change occurred in the beginning of 2006 when the team recognized that passive sampler technologies were being validated in lab and field studies and starting to replace the traditional sampling methods. Passive methods will not entirely replace conventional pumped sampling in all situations – for example, initial “broad-brush” site reconnaissance scale sampling, or drinking water compliance, but will rather complement and refine data from pumped methods, usually at substantially lower per-sample cost.The ITRC Passive Sampler Team Technical and Regulatory Guidance has been used to provide a basis for acceptance of passive sampling techniques. There is growing confidence and acceptance of passive sampling techniques, particularly in the last five years, among regulatory agencies, consultants, and their clients as awareness increases and understanding of how they work, how to use them correctly (including better definition of the sampling objectives, sampling plan strategies, and field techniques), how to interpret the data (what the data represent). Passive samplers, including the well-known polyethylene diffusion bag (PDB), have been deployed at sites in every state across the country. More rapid acceptance has been hindered by a lack of understanding of the reasons for, or discomfort with differences between results by different methods, particularly between passive samples and historical pumped data. The field of groundwater sampling has broadened by the development of passive sampling techniques. There is a changing paradigm in groundwater sampling for environmental investigations.The emergence and development of a variety of passive groundwater sampling techniques during the last decade or so is providing data of focus, reproducibility, and ability to target objectives that we’ve not typically had available to us before (at least not without extraordinary effort and expense). Data generated by passive sampling techniques can be more informative, more consistent, and quite often acquired at a much lower “per-sample” cost than conventional or low-flow pumped samples. However, passive sampling techniques represent groundwater conditions somewhat differently than pumped samples, and are driving a need to re-examine our understanding and interpretation of all groundwater sampling data, including seldom considered biases inherent in historical pump and purge sampling, whether low-flow or high flow 3-casing volume purge.
9What Does a Purge Sample Represent? Active transport of water induced either by pumping or hand-purgingOften draws water from above and below as well as adjacent to the screened interval/open boreholeFlow-weighted averageBased on indicator parameter stabilization or evacuation of the sampling system (i.e., volume purge)Gas exchange and mixingMay elevate turbidityMobilization of colloids and sedimentMobilization of normally immobile NAPL microglobulesCompliance with drinking water standardsThe ITRC Diffusion/Passive Sampler Team recognized that passive sampler technologies were being validated in lab and field studies and starting to replace the traditional sampling methods. Passive methods will not entirely replace conventional pumped sampling in all situations – for example, initial “broad-brush” site reconnaissance scale sampling, or drinking water compliance, but will rather complement and refine data from pumped methods, usually at substantially lower per-sample cost.Purge sampling defined as:* 3-volume purging: volume based purge with pump equipment or hand-bailing* low-flow purge: parameter stabilization based purge , no volume restrictions, only flow restrictions and parameter identifiers that determine when to collect a sampleField experiments, laboratory simulations and numerical modeling support the position that samples are derived from the entire screen zone under low-flow pumping conditions. Varljen, et. al. 2006Describe the physical aspect of collecting a sample by purging vs passive for various compliance levels
10What Does a Passive Sample Represent? No active transport of water induced by pumping or purgingSamples are collected from a specific depthRely on sampling device and well water being in ambient equilibrium with the formation water during deployment periodReduce disturbance to the well and aquifer typically caused by bailing or over-pumpingReduce turbidityRepresent “natural conditions”To retain consistency throughout the training module and published documents, the team has used the above general definitions that are used throughout the documents and training modules. The Team uses the term “passive” synonymously with “no-purge”.Unfiltered samples can be used to get a better estimation of the true mobile contaminant load.The emergence and development of a variety of passive groundwater sampling techniques during the last decade or so is providing data of focus, reproducibility, and ability to target objectives that we’ve not typically had available to us before (at least not without extraordinary effort and expense). Data generated by passive sampling techniques can be more informative, more consistent, and quite often acquired at a much lower “per-sample” cost than conventional or low-flow pumped samples. However, passive sampling techniques represent groundwater conditions very differently than pumped samples, and are driving a need to re-examine our understanding and interpretation of all groundwater sampling data, including seldom considered biases inherent in historical pump and purge sampling, whether low-flow or high flow 3-casing volume purge.
11Advantages of Passive Samplers Highly reproducible dataProvides low turbidity samplesDisposable/dedicated - no decontamination between wellsDecrease costsField labor Rapid field deployment and collectionLeave in quarterlyLittle or no disposal cost (no purge-water)Samples discrete intervalsVertical contaminant profilingMonitor zone of highest contaminant influxEasy to use – minimal equipment needsNo depth limit“Green” sampling methodAdvantages apply to all 5 technologies discussed in this ITRC Protocol Document (DSP-5) and training module. None of these passive sampling devices use moving parts, they are easy to handle, carry, and deploy since they have minimal equipment needs. Due to their ease of use, passive devices can be valuable tools when you need to sample areas where there is difficult access or when you desire discretion.To-date, no depth limit has been identified by the Team. Passive sampling devices have been deployed in wells up to 700-feet below ground surface. Passive technologies have replaced low-flow sampling techniques due to depth limitations with pumps sampling at depth under low-flow pump rates. For example, a groundwater sampling projects was using low-flow to sample wells 100-feet or less deep; however, there where problems with the pumps sampling at a low-flow rate at depths greater than 100-feet so passive sampling device was used to sample wells greater than 100-feet deep to supplement low-flow sampling techniques.
12Limitations of Passive Samplers May have volume/analyte limitationsContaminant stratification requires consideration before deployingWell must restabilize before sample collectionLimitations apply to all 5 technologies discussed in this ITRC Protocol Document (DSP-5) and training module.As in all groundwater sampling events, these samplers may require special consideration in wells having a layer of free product [re: sample integrity]Other consideration to be addressed by any sampler that are not considered limitations but deployment considerations that may affect the quality of the sample collected by the sampler:- must be submerged in the screened interval during deployment- require the aquifer be in hydraulic communication with the screened portion of the well
13Passive Sampler Team Publications User’s Guide for Polyethylene-Based Passive Diffusion Bag Samplers to Obtain VOC Concentrations in Wells (March 2001, DSP-1)Jointly developed with USGSBasic principles for deploymentTechnical and Regulatory Guidance for Using Polyethylene Diffusion Bag Samplers to Monitor VOCs in Groundwater (February 2004, DSP-3)Easy to use for groundwater and surface waterQuantify savings (40-70%)Technology Overview of Passive Sampler Technologies (March 2006, DSP-4)Main application was groundwater samplingSummarized 12 passive sampling technologiesITRC Protocols for Use of Five Passive Samplers to Sample for a Variety of Contaminants in Groundwater (February 2007, DSP-5 )Details on “mature” passive sampling technologies from Overview Document (DSP-4)The Team initially had coordinated an effort with USGS to assess the applicability of one type of passive sampler - the Polyethylene Diffusion Bag (PDB). Basically, DSP-1 was the first document the Team had worked on together. The Team used the research and the USGS organization to collect and analyze information regarding the use and value of the PDB to assist in groundwater sampling projects for limited volatile organic compounds (VOCs). Basically, replace purge sampling techniques for VOCs only. The issuance of this USGS research led to the Teams first Tech Reg document and Internet Training. In addition, led to the development of the Diffusion Sampler website as a forum to discuss the PDB.The Guidance on Polyethylene Diffusion Bags (DSP-3) provides basic principles of passive sampling and general considerations that should be made when performing any groundwater sampling event. An archive of the associated ITRC Internet-based training, titled “Passive Diffusion Bag Samplers for Volatile Organic Compounds in Groundwater” is available atThe Overview Document (DSP-4) was generated to provide a summary of developing and mature passive sampler technologies that were being used to sample groundwater. This document provides general information on technologies such as development status, cost, applicability, case studies, vender information, etc. Cost information is available in Table Technology availability and cost.These documents provide background and studies which are a good reference if you are not familiar with passive sampling. ITRC’s Passive Sampler Team documents can be downloaded for free at the ITRC website (www.itrcweb.org) under “Guidance Documents” and “Diffusion Samplers.”
14Classes of Passive Samplers Diffusion Samplers: analytes reach and maintain equilibrium via diffusion through membraneRegenerated-Cellulose Dialysis Membrane (Dialysis) SamplerRigid Porous Polyethylene (RPP) SamplerEquilibrated Grab Samplers: collect a whole-water sample instantaneouslySnap Sampler™HydraSleeve™ SamplerAccumulation Sampler: rely on diffusion and sorption to accumulate analytes in samplerGORE™ ModuleIdentified more mature technologies from Overview Document (DSP-4)“Maturity” defined as validation of sampler by lab and field testingTeam found that consultants and regulators had questions on how to use technologies so the team decided to provide guidance on using the “mature” technologies from ITRC Overview Document (DSP-4).This training module is based on the ITRC Protocol Document (DSP-5) and basic principles found in the polyethylene diffusion bag Tech/Reg. Document. (Technical and Regulatory Guidance for Using Polyethylene Diffusion Bag Samplers to Monitor Volatile Organic Compounds in Groundwater (February 2004, DSP-3), available at under “Guidance Documents” and “Diffusion Samplers”)We try to stress that passive sampling relies on basic groundwater principles that should be considered when performing any sampling event. There is no “special” criteria or studies that need to be performed when implementing general sampling.
15Ambient Flow Through a Well Relies on flow through in the well screenScreened zone is in active exchange with formation waterWater above screen may be “stagnant”ReferencesASTM, 2002Powell R.M., and R.W. Puls, 1993Robin, M.J.L. and R.W. Gillham, 1987Typical ambient flow in a formation is horizontal. You may not see only horizontal flow within the well. There can be both horizontal and vertical flow components within a screened or open interval. Formation water migrating through the well screen or open interval, reaching equilibrium within the well, may flow vertically, either upward or downward, through the well screen to zones of lower hydraulic head (more specifically, toward zones of a lower pressure head component of total hydraulic head).Contrast ambient with induced flow. Groundwater sampling is performed to collect a sample of formation quality water from the screened or open portion of a well. Induced flow involves the active transport of water, while ambient flow allows water to naturally flow through the formation across a screened interval; therefore, a passive device would represent the water that comes in contact with the device under ambient equilibrium conditions.General formula used for water in the well to be representative of the aquifer:the rate of solute contribution from the aquifer to the well must equal the rate of in-well contaminant loss, including outflow and volatilization.Powell, R.M., and R.W. Puls Passive Sampling of Groundwater Monitoring Wells Without Purging: Multilevel Well Chemistry and Tracer Disappearance. Journal of Contaminant Hydrology 12:American Society of Testing Materials (ASTM) Standard Practice for Low-Flow Purging and Sampling for Wells and Devices Used for Ground-Water Quality Investigations. ASTM Subcommittee D18.21: Designation DRobin, M.J.L. and R.W. Gillham Field Evaluation of Well Purging Procedures. Ground Water Monitoring Review 7, no. 4:
16General Deployment Device suitable for analytes of interest Sample volumei.e., QA/QC and duplicatesAppendix A: Minimum VolumesDeployment periodDevice and site specificWell restabilizationSampler equilibrationDeployment depthShould not be arbitraryDepends on well or site specific data quality objectives (DQOs)Sampler represents a depth intervalThese are general considerations before the selection or deployment of a passive sampling technology. Retrieval considerations should point out a prompt transfer of sample to sampler container once extracted from the well.Deployment period = the period of time that accounts for both restabilization of the well and the equilibration of the well water and sampler materialsRestabilization = the period of time well water requires to reach its ambient state following physical agitationEquilibration = the period of time required for well water and or sampler material to reach chemical equilibrium with the formation waterTeam’s general consensus is that the deployment period is a minimum of 2 weeks which is a conservative estimate to cover most restabilization and equilibration time considering most groundwater conditions; however, specific samplers and specific conditions might accommodate less deployment times.e.g. Longer deployment times should be considered for low-yield wells to account for a longer restabilization period once a sampler is introduced into the well. Passive samplers may be a practical approach since they...do not pump, drawing in contamination from other zones or dry out welldisplace water but can collect sample within intervalTeam has prepared a “Limited Volumes for Analysis” table with minimum volume requirements, if volume is a concern. Available in Appendix A of “ITRC Protocols for Use of Five Passive Samplers to Sample for a Variety of Contaminants in Groundwater” (DSP-5, 2007). ITRC’s Passive Sampler team documents are available at the ITRC website (www.itrcweb.org) under “Guidance Documents” and “Diffusion Samplers.”
17Contaminant Stratification Stratification is well-specificMajority of wells are not stratifiedContaminant stratification in an aquifervs.in the wellYou can have:Stratified or unstratified contaminant distributions in aquifersContaminant concentrations in the well may not reflect the same stratification in the aquifer due to vertical flow.Unstratified aquifers will yield unstratified wells. This drawing shows stratified contaminants flowing to a well.For stratified contaminant distributions in aquifers, some wells show contaminants that tend to maintain their position in the well (e.g. BTEX toward the water table—point to upper contaminant zone or dense contaminant could sink to bottom—point to lower contaminant);Stratified contaminants can also disperse and diffuse while in the open well bore, which tends to flow-weight and average the contaminant concentrations (a flow-weighted average of the influx of clean and contaminated water--point to clean and contaminated water entering the well)Stratified contaminants can also redistribute by vertical pressure differentials (in this picture, an upward gradient might be reflected by a clean zone below the level of the contaminant plume)
18Contaminant Stratification (continued) No stratificationTotal BTEX Concentration (mg/L)1604008001200140150170Water Table180PDB SamplesPurge SampleStratification in a wellDepth (feet)1520Low-flowsample25PDBsamples30Depth (feet below top of casing)35PDB = Polyethylene Diffusion BagDiagram A: Lack of stratification in the well may be due to the presence of vertical flow or reflect uniform contaminant distribution in the aquifer.Diagram B: Stratification was identified in the well screen. Longer screened or open intervals increase the likelihood of stratification.Pumped samples would not be able to identify stratification since it collects a flow-weighted average concentration from zones above and below the intake point.404550204060Toluene (µg/L)
19Contaminant Distribution Multiple samplers deployed through screened or open intervalCan represent contaminant concentrations over water columnVertical flow profiling, depending data quality objectives (DQOs), determines primary input/exit of groundwater flowBorehole flowmeterInterval packer/pump testsProfiling techniques can aid inRefining site conceptual modelRemedial process optimization (RPO)Profiling techniquesTarget a specific depth intervalCan monitor interval with highest concentrationConservative approach for long-term monitoringGroundwater sampling is performed to collect a sample of formation quality water from the screened or open portion of a well.To lower the cost of multiple vertical profile samples, samples can be analyzed with field analytical screening tools or by a certified laboratory for appropriate indicator parameters.
20Data Quality Objectives (DQOs) Prior to implementation, all parties should agree on DQOsFor instanceVertical contaminant distribution may be a DQO so multiple samplers deployed in a well may be advised (vertical profiling)Long-term monitoring projects, a single sampler may be appropriate for the DQOIs your sampling method meeting the DQOs?Do all parties agree?Site-specific DQOs guide the design of sampling programs including the selection of sampling devices.Because of these potential differences, it is essential that all parties involved in the implementation of passive samplers at regulated sites identify and agree on DQOs, data evaluation techniques, and data end use beforehand.If acceptance criteria are met, then a passive sampler may be approved for use in that well.Low-temporal concentration variability: historical sampling results comparisonHigh-temporal concentration variability: side-by-side comparison may be more useful
21Data Quality Objectives (DQOs) (continued) Pumping moves water toward intake from the induced flow field in proportion to hydraulic conductivityDQOs defineSampling goalTarget analytesHydrologic concernsPumping methodsDraw groundwater into the well screen from an undefined areaExample: 3-volume purge and low flowPassive methodsSample depth-specific intervals in wellGroundwater moves through the well screen under ambient flow conditionsEvery groundwater sampling technique characterizes contamination differently!A representative DQO process, as it is used by the Department of Energy (DOE), can be found atOLD SPEAKING POINT:When replacing one type of sampling method with another the Team finds that a comparison study may be required for approval of the new method. The Team has found that side by side tests or historical sampling results are the most common ways of comparing techniques. The Team has found that 80 to 90 percent of these comparison studies show similar (I.e. compare well) or the same results.ADDED:One comparison study conducted at the former McClellan Air Force Base will be referred to as the McClellan Study in upcoming slides of some of the passive sampling technologies. To date, this is the only large-scale federally funded study comparing passive samplers, volume purge sampling, and low-flow purge and sampling. If interested in this report, we encourage you to also look at the sampling protocols to understand the reported results.Pump Intake
22Regulatory Perspective Does your state have any Statutes, Regulations, or Guidance that prohibit or impede the use of passive sampling technologies for the collection of groundwater samples? (16 state responses: Appendix B)No regulatory or statutory prohibitions to using passives samplers“De facto” acceptance of passive samplers in 50 states and worldwideNew Jersey Department of Environmental Protection guidance on polyethylene diffusion bags (PDBs) (2005)Regulatory agencies use ITRC Polyethylene Diffusion Bag (PDB) guidance for state guidancePassive samplers have been used16 States responded (April 14, 2006)The principles of polyethylene diffusion bags (PDBs) are applicable to all passive samples.While a lack of specific regulatory barriers or prohibitions, and the acknowledgment the de facto use and acceptance of PDBs (and other passive devices) by some regulatory agencies, leaves open the opportunity to use passive samplers, most regulatory agencies remaining silent on the question, and having no official policy or guidance, can itself be a hindrance to their use. This regulatory vacuum needs to be corrected to streamline review and approval of passive sampling proposals and encourage the appropriate use of the best sampling technique to meet data quality objectives by the most efficient means available. Reluctance to use passive samplers may be due in large part to this lack of specific regulatory policy; not everyone wants to be a “pioneer.”
23In SummaryPassive samples collect analytes that come in contact with the sampler under ambient flowValue of passive samplersInexpensiveBroad analyte capabilitiesReduced sampler errorAssist in site characterization identifyingStratificationTarget zones for remediationMigration pathways1:1 correlation may not occurDiscrete concentration vs. flow weighted concentrationMay reflect nature of sampling methodi.e., dilution during purging, pumping versus passiveTests have shown that contaminant concentrations from the passive samplers adequately represent local ambient conditions within the screened interval despite whether the contaminant concentrations are higher or lower than the conventional method. This result may be because the pumped samples incorporated water containing higher or lower concentrations either from other water-bearing zones not directly adjacent to the well screen (Vroblesky and Petkewich; 2000), or from mixing of chemically stratified zones (Vroblesky and Peters, 2000)Side-by-side with current sampling method- Deploy pump and passive at same time, retrieving passive sampler first, or- Deploy passive independently, recover immediately prior to placing pump in wellThese methods are how the team recommends a side-by-side comparison study; however, these methods minimized temporal variability but we can never eliminate spatial variability.Only about 20% of the comparisons are not 1:1
24Questions and Answers Covered so far Introduction to passive (no-purge) samplingAdvantages/limitationsGeneral considerations when using passive samplersRegulatory perspectivesNowQuestions and answersNext – technical aspects for five passive samplersDiffusion Samplers: analytes reach and maintain equilibrium via diffusion through membraneRegenerated-Cellulose Dialysis Membrane (Dialysis) SamplerRigid Porous Polyethylene (RPP) SamplerEquilibrated Grab Samplers: collect a whole-water sample instantaneouslySnap Sampler™HydraSleeve™ SamplerAccumulation Sampler: rely on diffusion and sorption to accumulate analytes in samplerGORE™ ModuleQuestions addressed in this class: What is passive (no-pump) sampling, what passive samples represent, and how do passive sample data compare (or not compare) to pumped sample data? How should we interpret passive sampler data?Passive samplers have very broad applicability and could be used at every site in the US that collects groundwater samplers. Expanding our sampling toolbox offers the opportunity to select the most cost effective method.They are not recommended for demonstrating compliance to drinking water standards.
25Diffusion SamplersDiffusion Samplers: analytes reach and maintain equilibrium via diffusion through membraneRegenerated-Cellulose Dialysis Membrane (Dialysis) SamplerRigid Porous Polyethylene (RPP) SamplerEquilibrated Grab Samplers: collect a whole-water sample instantaneouslySnap Sampler™HydraSleeve™ SamplerAccumulation Sampler: rely on diffusion and sorption to accumulate analytes in samplerGORE™ ModuleDiffusion samplers typically are filled initially with deionized (or distilled) water. Analytes from the well water diffuse over time through the sampler membrane and into the sampler, so that concentrations inside the samplers approach equilibrium with those present in the well water. Equilibrium diffusion samplers using a polyethylene membrane, the polyethylene diffusion bag (PDB) sampler, have been previously tested and rapidly increased in use over the last 6 years or so. But, because diffusion samplers using a polyethylene membrane are limited to sampling only VOCs, other diffusion samplers have been developed that can sample for all VOCs, inorganic constituents (cations, anions, trace metals, nutrients), and some semi-volatile organics (explosives and dissolved organic carbon).The two types of diffusion-based samplers discussed in this training are the cellulose membrane diffusion sampler, and the rigid porous polyethylene sampler. Both can sample a wide variety of analyte types.Because diffusion samplers are depth-specific, they can reflect only the analyte concentrations in the well water to which they are exposed under ambient ground water flow conditions. One of the most important considerations in interpreting data from passive sampling is having an in-depth understanding of how a specific well, and the sampling methodology used to sample that well, represent conditions in the aquifer.
26Diffusion Sampler Basics The diffusion process is described by Fick’s Law. This simplified general form of Fick’s Law shows that, given the proper amount of time, dissolved chemical concentrations on either side of a semi-permeable membrane will come to equilibrium. As portrayed on the left, the diffusion sampler is initially filled with de-ionized water (low concentration). Analytes outside the sampler in the well water diffuse into the sampler until the concentrations on either side of the membrane are equal.The concentration gradient across the membrane drives the diffusion; the rate of diffusion diminishes as the sampler approaches equilibrium. The rate of diffusion also is strongly affected by temperature; the warmer the water the more quickly equilibrium will be approached. The diffusion coefficient, D, contains the term for temperature, and also is analyte dependent. In this general form, the distance term, L, reflects membrane thickness and other membrane properties affecting the time required for equilibration.It is important to note that this process is reversible. If analyte concentrations in the well water decrease, analytes will diffuse back out of the sampler over time toward a new equilibrium; the sampler will follow, with some time lag, changes in analyte concentrations in the well water. However, this reversibility can be of particular concern when the samplers are retrieved and volatile constituents (VOCs) are analytes of interest. VOCs begin to diffuse out of the sampler as soon as the sampler is exposed to air, or any medium having lower concentration of VOC analytes. Exposure to heat and wind will accelerate VOC loss. The sample must be transferred from the diffusion sampler and sealed in the laboratory container (VOA vial) promptly upon retrieval. Depending on specific conditions, measurable VOC loss can occur within a few minutes.Different membrane materials are used for their different diffusion properties, but the principles remains the same.
27Diffusion Sampler Advantages Groundwater sampling time in the field is decreased – no pumping neededEliminates purge water and disposal costsExcludes turbidity from groundwater samples – no filtering neededDisposable – no cleaning or cross-contaminationRegenerated CelluloseDialysis Membrane (Dialysis)Rigid Porous Polyethylene (RPP)Several of the general advantages of diffusion samplers were mentioned in the introductory slides but bear repeating.- The sampling time needed in the field to recover a diffusion sampler and deploy another for the next sampling event is much shorter than the time it takes to pump and stabilize a well prior to low-flow sample collection. (3x-6x shorter). This significant saving of time for field personnel substantially lowers field sampling costs.- The amount of water removed from the well is minimized. Most, if not all of the water recovered by a diffusion sampler is transferred into the sample containers for shipment to the laboratory.- Diffusion sampler membranes have small pore sizes that eliminate or greatly reduce turbidity. The samplers are themselves essentially big filters, so no field filtering is necessary.- Diffusion samplers are disposable so no cleaning steps are needed and there are no cross-contamination issues between wells.
28Regenerated-Cellulose Dialysis Membrane Sampler Basics Fully assembled Dialysis sampler ready for deploymentReferred to as the “Dialysis Sampler”Regenerated-cellulose dialysis membraneFilled with deionized waterHydrophilic membraneCurrently must be constructedMembrane sizes2.5-inch diameter for 4-inch wells1.25-inch diameter for 2-inch wellsSample volumes2.5-inch x 2 ft long contains 2 liters1.25-inch x 2 ft long contains 500 mlsPore size is 18 AngstromsDeveloped by U.S. Geological Survey (USGS)The regenerated-cellulose dialysis membrane diffusion sampler is commonly referred to as simply the “dialysis sampler.” It was first developed about 6 years ago by researchers at the US Geological Survey. It uses a tubular membrane made of regenerated cellulose dialysis material, filled with deionized water, and suspended in the water column in the open interval of a well. After a sufficient equilibration period, the sampler is removed and the water transferred to appropriate containers for transport to the laboratory.Because the dialysis membrane is hydrophilic, water molecules, ions, and dissolved compounds pass through the membrane. [As opposed to the polyethylene membranes which are hydrophobic so water and ions can not pass through them.] The cellulose membrane material has an average pore size of about 18 Angstroms ( microns), and thus is a very effective particulate filter excluding even colloidal size clay particles. Thus, turbidity is minimal and the sample will contain only truly dissolved concentrations, and not analytes adsorbed onto suspended material.Currently, dialysis samplers are not commercially available so they must be constructed by the user prior to deployment. The cellulose membrane material comes as roles of lay-flat in tubing, available in different sizes – 1.25-inch diameter which fits inside a 2-inch diameter well, and 2.5-inch diameter which fits inside a 4-inch diameter. A 1.25-inch diameter by 2 ft long sampler contains ~500 ml of sample, and a 2-foot long 2.5-inch diameter sampler contains ~2 liters. The material has a sulfide-based preservative which must be washed off. Once wet, the samplers should be kept wet (submerged) until deployment to avoid drying and cracking of the membrane. Construction of a sampler typically takes about 20 minutes, but can differ based on specific configuration (fittings, accessories, etc.). Samplers can be slipped into nylon mesh sleeves (as pictured) to protect the membrane from abrasion or tearing during placement into and retrieval from the well. The mesh also allows convenient and secure attachment to the deployment line using plastic “zip” ties.
29Dialysis Equilibration Times Determined in laboratory in bench-scale tests95% or greater equilibrium reached in dialysis samplers within1-7 days for most cations and trace metals1-3 days for all VOCs on 8260B list (including MTBE)1-3 days for anions, silica, DOC, CH4, sulfide7-14 days for explosives compounds28 days or more for Hg, Ag, SnAs with all diffusion samplers, once deployed in a well, dialysis samplers must remain completely submerged for the entire deployment period, and be allowed to equilibrate for the appropriate amount of time for the chemicals of interest.The equilibration times shown here for general categories of analytes were determined by USGS and US Army researchers in periodically stirred batch tests in the lab. A more detailed list of analytes tested in the laboratory is given in Table 5-2 of the ITRC Protocol Document (DSP-5).Most of the common analytes that have been tested come to equilibrium in the dialysis samplers within 1 to 14 days. Only mercury, silver, and tin were found to take longer than 14 days. Under field conditions where groundwater is flowing through the open interval of the well, chemical equilibration may occur at somewhat different rates due to temperature differences and other considerations, but a 14-day rule-of-thumb for deployment should be enough for most situations.
30Dialysis Sampler Advantages Collects inorganic and organic chemical constituentsQuick equilibration and deployment times – generally 1-2 weeksRelatively inexpensive to constructExcludes turbidity from groundwater samples – no filtering neededSample volume can be up to 2 LAn important characteristic of dialysis samplers is that, unlike PDBs, they can collect both organic and inorganic constituents. Dialysis samplers are slightly more expensive to construct than PDBs but are still inexpensive compared to renting or buying pumps and related equipment.Because of their small pore size, dialysis samplers exclude particulates from the collected groundwater sample so no field filtering is needed.The volume collected can easily be adjusted by varying the length and/or diameter of the sampler when it is constructed. A typical practical limitation might be about 2 liters. Keep in mind that longer samplers will integrate concentrations over a longer depth interval in the well, and require a longer water column in the screened interval so that the entire sampler remains completely submerged during the entire deployment period.
31Dialysis Sampler Limitations Must construct sampler from raw materialsSamplers must be kept wet between construction and deploymentMembrane can biodegrade within 4-6 weeksNot a problem for shorter deploymentsCan maintain integrity for longer periods in very cold waterSamplers lose water volume slowly (<3% per week)Not a problem for short deploymentsInternal support for high ionic strength waters is availableField-ready dialysis samplers are not commercially available and must be constructed.As previously mentioned, the cellulose material should be thoroughly rinsed in DI water to remove preservative, and must be kept hydrated between the time they are constructed and the time they are deployed in a well to prevent drying and cracking.Regenerated cellulose is a biodegradable material, that is, it is food for some bacteria. The rate of biodegradation is well-specific, depending on the level of biological activity, which is in turn largely dependent on temperature. These membranes have been shown to biodegrade in wells in temperate climates within 4 to 6 weeks, however some recent results have shown that their integrity is maintained for six months and longer in very cold water. Nonetheless, most analytes tested thus far equilibrate quickly enough through the dialysis membrane so this limitation should not adversely affect their usefulness for sampling in most wells.Because diffusion is a two-way process and the cellulose membrane is permeable to water, not only are dissolved analytes in the well water diffusing into the sampler, but water molecules are also diffusing outward in an attempt to dilute the well water. Fortunately, the gradient for ions diffusing inward is higher that the gradient for water molecules diffusing outward. In general, tests have shown that less than 3% per week of the samplers original volume is lost through this process. This loss may be a more significant problem in high ionic strength waters. An internal support can be inserted inside the dialysis membrane to ensure that a minimum volume of water will still be retained inside the sampler.
32Dialysis Field Comparison Results 10001000Ethylbenzene (µg/L)Chloride (mg/L)1010LRLLRL0.11/2 MDL1/2 MDLLow-Flow Purging0.10.11010000.110100010001000These graphs show examples of field comparison results from a study by Imbrigiotta et al. (ESTCP final report, 2007) for one aromatic VOC (ethylbenzene), one chlorinated VOC (vinyl chloride), one anion (chloride), and one cation (manganese).Each graph shows the concentrations recovered by the dialysis sampler on the x-axis vs. the concentrations recovered by low-flow purging on the y-axis. Each red diamond represents one comparison from one well. If both sampling techniques recover equal concentrations, all red diamonds should be on the 1:1 correspondence line.The white area of each graph is where concentrations are above the laboratory reporting limit (LRL) for the parameter being shown. The yellow area of the graph is where concentrations are between the reporting limit and one-half the minimum detection limit (1/2 MDL). The pink area of the graph is where concentrations are less than one-half the detection limit.As you can see for all of the parameters plotted, all graphs show reasonably close agreement between the concentrations recovered by dialysis samplers and low-flow purging.Deviations, such as those seen at low concentrations for ethylbenzene, are most likely due to water of different chemistry being drawn into the well during purging than was in the open interval during the dialysis sampler equilibration period. In fact, PDB and dialysis sampler VOC results agreed very well in these same wells.Vinyl Chloride (µg/L)10Manganese (µg/L)LRL10LRL0.1From: Imbrigiotta et al. (2007)1/2 MDL1/2 MDL0.0010.10.0010.11010000.1101000Dialysis Sampler
33See Table 5-3 in ITRC Protocols Document (DSP-5) Dialysis Field Comparison Results (Dialysis Samplers vs Purging Methods)Parameters with favorable resultsVOCsCations and anionsMost trace metalsExplosive compoundsOthers (silica, ethene, CO2, CH4, TDS, SC, DOC)Parameters with questionable resultsp-Isopropyltoluenen-Butylbenzenes-ButylbenzeneNickelSulfideField comparisons between dialysis samplers and low-flow purging have found equal recoveries of:Most chlorinated VOCs (PCE, TCE, cisDCE, DCE, transDCE, VC, 111-TCA, 11-DCA, CM, Chloroform, MC, DCDFM, 12DBE)Most aromatic VOCs (BTEX, Styrene, 124-TMB, 135-TMB, iso-propylbenzene, t-butylbenzene, n-propylbenzene, naphthalene)Ethers (MTBE, 1,4-Dioxane)Cations and anions (Ca, Mg, Na, K, alkalinity, Cl, SO4, NO3, Br, F)Most trace metals (Fe, Mn, Al, As, Ba, Cd, Cr, Cu, Mo, Pb, Sb, Se, V, Zn)Explosive compounds (e.g. RDX, HMX)Dissolved gases, ethene, CO2, CH4, and TDS, silica, DOCThe only parameters with questionable field comparison to low-flow results include a few aromatic VOCs (for which dialysis sampler results did compare favorably to PDBs in side by side tests), nickel, which was present only below reporting limit concentration, and sulfide which was recovered in equal or higher concentrations in the dialysis sampler than in the low-flow purged samples. More investigation is needed into these last few parameters to determine if these differences are found at other sites.A more detailed list of results for various analytes is given in Table 5-3 of the ITRC Protocol document (DSP-5) available the ITRC website (www.itrcweb.org) under “Guidance Documents” and “Diffusion Samplers.”See Table 5-3 in ITRC Protocols Document (DSP-5)
34Dialysis Sampler Summary Collects both organic and inorganic chemical constituentsDo not require filtration of samplesEquilibrate within 1-2 weeks for most constituentsDeployment times 1-2 weeks in most wellsDialysis samplers recover comparable concentrations ofVOCs vs. PDB samplersVOCs and most inorganics vs. low-flow and purging and samplingDialysis samplers should not be used whenSampling for mercury, silver, or tinEquilibration will take longer than 4 weeksTotal concentrations are neededDialysis samplers should be used with caution whenSampling for nickel and sulfideDialysis samplers can collect both organic and inorganic chemical constituents in groundwater.Dialysis samplers do not require field filtration of samples. They collect only the truly dissolved concentrations.Bench-scale testing showed that dialysis samplers chemically equilibrate within 1-2 weeks for most inorganic constituents and VOCs.Deployment times in most wells are generally 1-2 weeks.Field comparisons showed dialysis samplers recover VOCs equal to PDB samplers.Field comparisons have also shown dialysis samplers recover VOCs and most inorganics equal to low-flow purging.Only chemical constituents tested that did not seem to diffuse well through the dialysis membrane were mercury, silver, and tin - possibly due to the formation of metal-organic complexes that either sorb to the membrane or are so large that they don’t diffuse readily through the pore spaces.The potential for biodegradation should be included if dialysis samplers are to be considered for deployment periods or equilibration times that might extend longer than four (4) weeks, although they have been deployed for up to six months in very cold water (ice) without measurable degradation.Dialysis samplers should not be used if total concentrations are required (concentrations that must include analytes adsorbed on to colloidal particles that remain suspended by Brownian motion and are naturally mobile under ambient flow in the aquifer).Sampling for nickel and sulfide needs to be further tested.
35Rigid Porous Polyethylene (RPP) Samplers CapMade of rigid, porous polyethylenePore sizes 6-15 microns5 inches long1.5 inches in diameterFilled with deionized waterStandard size holds mLRigid Porous Polyethylene (RPP) samplers were developed by Don Vroblesky of the USGS, and are commercially available.The RPP sampler is constructed from a rigid cylinder of foam-like porous polyethylene having a wall thickness of about 2 mm. The pore size in the material ranges from about 6 to 15 microns. The outside diameter is approximately 1.5 inch and the individual samplers are limited to about 5 inches in length. If made longer, the higher head pressure in the sampler forces the water inside to “leak” out through the pores when not submerged.The RPP sampler is filled with de-ionized, analyte-free water, capped at one end and a Delrin plug inserted into the other end. The one pictured on the left is equipped with a second smaller plug. Use of the smaller plug will minimize potential loss of VOCs by any vacuum that may be created by the plug’s removal when transferring sampler contents into the laboratory containers.The picture on the right shows an RPP ready for shipment. The RPP is shipped in a mesh liner for protection during deployment and retrieval, and for convenient attachment to the deployment line using cable ties (“zip” ties). RPPs are shipped in a water filled polyethylene bag to ensure that the pores stay water filled. If the pore spaces become blocked by air bubbles, the aqueous diffusion pathway is interrupted and diffusion of analytes into the sampler may be greatly reduced or not occur at all.Water soluble analytes pass through the pores until equilibrium is reached between the water in the sampler and the water to which the sampler is exposed. In bench studies, equilibrium time ranged from hours to days, depending on diffusion properties of the specific analyte. The more water soluble the analyte, the quicker the equilibrium. The general rule of thumb for all diffusion samplers, that they should be deployed not less than 14 days, ensures that most analytes will have equilibrated in an RPP sampler. These samplers can remain deployed in wells for a quarter, but can be expected to maintain integrity for much longer, though there is little information regarding longer deployments. Biofouling has been considered as a potential problem, but has not been reported for any of the long-term (quarterly or longer) for any passive sampling device.Delrin plugIn protective mesh ready for deployment and packaged in disposable water-filled sleeve for shipping
36Select RPP Analytes and Equilibration Times Equilibration time (days)Dissolved gases14Perchlorate, chloride, hexavalent chromium, nitrate, sulfate, soluble ironMethane, ethane, ethene (MEE)Water soluble VOAs (i.e. MTBE, MEK, Acetone, 1,4-Dioxane)Water soluble SVOCs (i.e. NDMA, phenols)Dissolved metals (priority pollutant list)21 (all except silver and copper)Explosives (i.e. HMX, TNB, RDX and TNT)21Please see the tables in Chapter 6 of the Protocol Document (DSP-5) for more detailed equilibration data. New analytes are being added as field studies continue.Additional field studies on low-solubility (hydrophobic) VOCs and SVOCs are needed. In laboratory batch studies in sealed carboys, concentrations of the hydrophobic VOCs and SVOCs were depleted in the test solution, but were not found in the water in the samplers (see Tables 6.5 and 6.7 in the Protocol Document (DSP-5). These results are consistent with a conclusion the hydrophobic analytes were adsorbed onto the sampler itself. It’s thought that with longer equilibration times, and an effectively unlimited volume of contaminated water moving through the wells screen, that the sampler and water within it would eventually reach equilibrium, but field studies are needed to confirm this.
37RPP AdvantagesCan be used to collect most inorganic and limited organic analytesAre commercially available and field-readyCan be stacked when additional volume neededExcludes particles larger than the pore space of the samplerRPP Samplers have the same general advantages as other passive samplers:eliminate purge water collectionare easily deployed and retrievedreduce field sampling costs significantlymay not be a substitute for field filtering using a standard 0.45 micron filter.
38RPP LimitationsMust be stored and shipped fully immersed in deionized waterHave not been tested for all analytesMultiple samplers are needed to obtain sufficient volume for multiple Analyte types and/or QA/QCRequires advanced analytical techniques to analyze for SVOCsEquilibrium times for less water soluble VOCs and SVOCs are not currently knownTo prevent air from entering and blocking the pore spaces of the polyethylene material, field-ready RPPs are shipped sealed in water-filled pouches.Wells must be 2 inches or more in diameter to accommodate the diameter of the RPPs.RPPs provide only mL of sample; if additional sample volume is needed, multiple RPPs must be stacked. As with several of the passive samplers discussed today, it is very important that you discuss the small sample volume with your laboratory to ensure they are prepared to meet your measurement quality objectives (method detection limits (MDL), reporting limits (RL), etc. ) with the limited volume. Ensure that they have equipment that will allow them to use less volume that typically requested. For instance, the standard minimum volume required for SVOCs by EPA Method 8270 is 1000 mL. Theoretically, using solid phase extractors and large volume injectors you would need no more than 10 mL of sample, though most labs would still request mL of sample if available. The evolving trend toward more flexible performance-based approaches to environmental measurement that continue to meet project DQOs, is moving away from prescriptive requirements of the past.A table giving minimum volumes required to meet standard DQOs for many common analytical methods is provided as Appendix A of the Protocol Document (DSP-5). The volumes are those required for a single analysis, without MS/MSD, re-runs, etc.).It’s not yet known how long it would take for VOCs and SVOCs to equilibrate. However, RPPs are frequently co-deployed with a polyethylene diffusion bag (PDB) - the RPPs for water-soluble analytes and the PDB for hydrophobic VOCs. For example, the combination of passive devices can monitor 1,4-dioxane and 1,1,1-TCA concurrently.
39McClellan AFB Multi-analyte, Multi-sampler Study (Parsons 2005) Metals:1,4-Dioxane:Anions:Hex Cr:VOCs:RPPs Sample Concentration (µg/L)For All Datay = 0.941xR2 =This study at the former McClellan AFB, California, compared 4 diffusion-based sampling devices and 2 equilibrated grab samplers against low-flow and conventional 3-volume well purging sampling. This graph depicts results from RPP samplers compared to low-flow pumped sample results.The authors concluded that RPPs “appear to be a technically viable method for monitoring hexavalent chromium, metals and anions. Although concentrations of VOCs and 1,4-dioxane obtained using this method are statistically similar to low-flow concentrations of these analytes, they tended to be biased low relative to concentrations obtained using the three-volume purge method.” 1 It is important to remember that the different purging methods and passive sampling may sample the well somewhat differently, depending on well-specific hydrologic characteristics.As mentioned before, laboratory studies have shown that RPPs should not be used for VOCs unless further equilibration studies are completed. Subsequent field studies have shown that they work well for 1,4-dioxane. The next two slides illustrate side-by-side tests for dioxane.1. Parsons Results Report for the Demonstration of No-Purge Groundwater Sampling Devices at Former McClellan Air Force Base, California. Prepared for the U.S. Army Corps of Engineers Omaha District, the Air Force Center for Environmental Excellence and the Air Force Real Property Agency. 7-2.Low-Flow Purge Sample Concentration (µg/L)
40RPP Representative Field Study for 1,4-Dioxane at a North Carolina Site y = 0.852xn = 9RPP (mg/L)This correlation plot depicts the low-concentration results from paired samples collected from multiple wells by RPP and low-flow methods.The interest in RPPs for this particular project was because a number of the wells at this site are very deep (some more than 200 feet). The depth of the well screens was below the low-flow pumps operating capability. The RPPs were tested against low-flow pumps in 10 wells at the site from 23 to 110 feet deep to see how they compared to decide whether they were a viable option for the deep wells. The concentrations of 1,4-Dioxane were low in these wells (0.010 to 0.22 mg/L) with the exception of one well, V-23, where the concentration was approximately 3 mg/L.The next page depicts the results from all wells, including V-23.Low Flow (mg/L)Each point on the plot represents a single-constituent data pair of each sampling method.
41RPP Representative Field Study for 1,4-Dioxane at a North Carolina Site RPP (mg/L)R2 = 0.999y=1.073xn=10Including the data from V-23 well gives an R2 of and y=1.073x, but the scale of this plot makes the lower concentrations data points difficult to distinguish.RPPs are now deployed at this site on an on-going basis. This study is described in the Protocol document (DSP-5) Section and Table 6.10.Low Flow (mg/L)Each point on the plot represents a single-constituent data pair of each sampling method.
42RPP Summary Can be used to sample for Most inorganicsWater soluble VOCs and SVOCsIt’s not currently known if they can be used for water-insoluble VOCs and SVOCsCan be used in deep wellsCan be used in conjunction with PDBsDisposable samplerNo decontamination requiredRPP Samplers may be used to sample for most inorganics, but further studies are needed to determine suitability for some organics, especially less water soluble VOCs and SVOCs.Depth limitations have not been encountered for any of the passive sampling devices.
43Diffusion Sampler Summary Regenerated CelluloseDialysis MembraneRigid Porous Polyethylene (RPP)RPP and Dialysis Membrane samplers can be used for VOCs, SVOCs, metals, anions, and cationsMinimum deployment time for RPP and Dialysis sampler is ~2 weeksCompare well with conventional methodsCollect samples at a discrete interval in well screenRPP sampler can be used for quarterly or longer deploymentsMajor limitation of RPP sampler is sample volumeMajor limitation of Dialysis sampler is that it undergoes biodegradation*RPP and Dialysis Membrane Samplers are diffusion samplers that provide the important advantages of passive sampling, and can be used for a much broader range of analytes than the Polyethylene Diffusion Bag (PDB) sampler.
44Equilibrated Grab Samplers Diffusion Samplers: analytes reach and maintain equilibrium via diffusion through membraneRegenerated-Cellulose Dialysis Membrane (Dialysis) SamplerRigid Porous Polyethylene (RPP) SamplerEquilibrated Grab Samplers: collect a whole-water sample instantaneouslySnap Sampler™HydraSleeve™ SamplerAccumulation Sampler: rely on diffusion and sorption to accumulate analytes in samplerGORE™ ModuleWe try to stress that passive sampling relies on basic groundwater principles that should be considered when performing any sampling event. There is no “special” criteria or studies that need to be performed when implementing general sampling.
45Equilibrated Grab Samplers Collects sample from discrete interval in well screenCollect “whole water” samples that can be tested for any analyteCollects samples in “real time”Equilibration period allowsWell to recover from sampler placementMaterials to equilibrate with analytes in well waterTechnologiesSnap Sampler™HydraSleeve™ SamplerSnap Sampler™Because these samplers do not rely on diffusion or sorption, they can collect a sample that is in real time.Typically, these samplers are placed in the well, and left for an equilibration period.After the equilibration period, the sample is collected.Allowing the well to recover from placing the sampler in the wellyou allow the flow pattern in the well to reestablish itself &you reduce the possibility of falsely elevating turbidity in your samplesthrough agitation.By allowing the materials to equilibrate with the analytes in the well water,you eliminate possible biases due to sorption that can occur betweensome types of analytes and the sampler.We want to stress that losses due to sorption can occur with any type of sampler(including bailers and the tubing used in e.g. low-flow sampling)if there is not an adequate equilibration between the analytes and the materials.The two devices in this class included in the ITRC Protocol Document (DSP-5) are the HydraSleeve™ Sampler and the Snap Sampler™.Both of these devices are commercially available.HydraSleeve™ Sampler
46Snap SamplerTM Components 125 mLSampler body with trigger mechanismBottlesHave two openings & spring-activated caps40-mL VOA glass vialsFits in 2-inch wells125-mL HDPE bottles350-mL HDPE bottlesFits in 4-inch wellsTrigger lineMechanicalElectronicPneumaticDocking station40 mLDescription of the Snap Sampler™ technology can be found in section 4 of the ITRC Protocol Document (DSP-5).Snap Samplers™ are typically dedicated devices.Snap Sampler™ bottles are unique in that they have openings on two ends andcaps that are connected by an internal Teflon-coated spring.To deploy the sampler:Place the bottles in the sampler.Place the end caps in an open position using the release pins on the sampler.Attach the trigger line to the sampler and then use the trigger line to lower the device into the well.
47Snap SamplerTM – Collecting a Sample Sample bottles deployed & remain in open positionEquilibration periodMinimum of 1 to 2 weeksCan be used for quarterly, semi-annual, or annual samplingPull handle on trigger line to close bottle (i.e., collect sample)Samples sealed in situNo sample transfer required at the surfaceBecause the sample bottle is closed in the well, there is no chance of interaction ofthe sample with the water column as the sample is removed from the well.Samples can be sent to the laboratory in the same bottle the sample was collected in.Or they can be transferred to other sample bottles.E.g., contents of 125-mL sample bottle could be poured into two 50-mL sample bottles, one for anions and one for metalsThe 40 ml VOA vials are compatible with common autosampler equipment.Acid can be added if preservative is needed without having to open the sample bottle.This procedure is discussed in more detail in the ITRC Protocol Document (DSP-5).
48Snap SamplerTM Advantages No analyte restrictionsReduced sampling variabilityMinimal agitation of well during samplingCollect samples with ambient turbidityBottles remain sealed under in-situ conditionsNo sample transferNo exposure to weather, surface contamination, etc.Some studies have shown better recovery of volatiles and gasesBecause these samples do not agitate the water column, particles from the formation are less likely to be entrained in the samples.
49Snap SamplerTM Limitations Sample VolumeMultiple bottles are needed to obtain volume for multiple analyte types and/or QA/QCTrigger lines are fixed length and thus cannot be readily moved to other wellsLarger volume can be collected by using large sample bottles (i.e., 350-mL) or by deploying multiple samplers either on multiple trigger lines or in series on the same trigger line.The more sample bottles deployed along a trigger line, the longer the interval in well that you are sampling.Up to 6 samplers depending on type of trigger mechanism and sampling depth.
50Snap SamplerTM – VOC Field Study 100001000100Snap Sampler VOC (ug/L)101Comparison from Boeing Santa Susanna Field Laboratory in Chatsworth, California. Zimmerman, Laura, Beth Parker, Amanda Pierce, John Cherry, Sandy Britt, Ramon Arevena, 2009, Use of Snap Sampler and CSIA in Investigations of TCE Natural Attenuation in Fractured Sandstone, Proceedings of the Groundwater Resources Association of California Conference: Groundwater Monitoring: Design, Analysis Communication & Integration with Decision Making, Orange, California, February 25-26, 2009.Good correlation (as shown by the high correlation coefficient)“Y” values (or slope) slightly >1Indicates Snap Sampler™ yields slightly higher concentrations than the low-flow sample.This difference may be because of the unique features of this sampler, i.e., there is no sample transfer or exposure to the atmosphere.0.1Low Flow VOC (ug/L)Very good correlationsSlightly higher concentration values with Snap SamplerTM than low-flow
51Snap SamplerTM – Multi-analyte Field Study 1000001000010001001010.10.01Study at former McClellan Air Force Base(Parsons Inc. 2005)AnionsSnap Sampler™ Concentration (µg/L)VOCs1,4 DioxaneSnap Sampler™ also showed excellent correlations with volume-based purge methods.R2 = 0.99 for all analyte comparisons to low flowLow-Flow Purge Sample Concentration (µg/L)
52Snap Sampler™ Summary Sample all analyte types Volume limited for long analyte listSamples are sealed at the point of collectionNo transfer of sample requiredData correlates well with standard sampling methodsMore information on the Snap Sampler™ technology can be found in section 4 of the ITRC Protocol Document (DSP-5).I have conducted several studies on the Snap Sampler. These tests included both laboratory and field studies. The laboratory studies compared concentrations of analytes taken from a standpipe with control samples taken from the standpipe. Analytes included VOCs, explosives, and a suite of inorganics including metals. Field studies sampled for VOCs, explosives, and inorganic analytes. The results from these studies can be found in two reports available at our website (below) and another that will be published by Fall 2010.
53HydraSleeve™ Components Sampler sleeveReed valveThis sampler is simple in design and easy to use.Information on this sampler can be found in Section 3 of the ITRC Protocol Document (DSP-5).ComponentsPolyethylene sleeveTop loading reed style check valveReusable stainless steal weight and clipDischarge tubeHS are designed to fit2-in wells, (1.5 inches OD)4-in wells (2.5 inches OD)Also 1-in wells and ¾-in wells.To assemble these samplers, simplyUnfoldClip weight to bottomAttach tether (line) to topDischarge tubeReusable sampler weight
54HydraSleeve™ Sample Collection FullSampleIntervalTo deploy the HydraSleeve™, lower the sampler through the water column.The sampler remains empty as the sampler is lowered through the water column andduring the equilibration period.To collect a sample,Pull the HydraSleeve™ upward >1 foot per second(~the speed a bailer is recovered).Hydrostatic pressure opens reed valve allowing sleeve to move outward to collect the waterIn essence you are collecting a “core sample of the water column”The mechanism is much like pulling on a sock.When the sampler is full, the reed valve closes,Reed valve remains closed as the sampler is recovered from the well.This prevents interaction between the water column and the sample inside the sampler.Once the sampler is at the surface, the sample should be transferred immediately to the sample bottles.Done by puncturing sampler with discharge tube.Sampling interval within well is ~1.5 times the length of the samplerFillingEmpty
55HydraSleeve™ Advantages Fits in most diameter wellsCan sample all types of analytesSample Volume2-inch HS collects 650 mL to 1 L4-inch HS collects 1250 mL to 2 LEasy to use with minimal trainingCan sampleVery deep wellsCrooked wellsCan collect low turbidity samplesNo associated notes.
56HydraSleeve™ Limitations Sample VolumeCustom samplers can be fabricated in a wider diameter and/or longer length to maximize sample volume for longer analyte listsWork with lab regarding minimum sample volumeUsing table in Appendix A of the ITRC Protocol Document, DSP-5No associated notes.
57HydraSleeve™ – Field Study (1 of 2) 2-inch diameter well in Northern California (Geomatrix Inc., 2000)Concentration (ppb)Good agreement between the VOC concentrations in the purged samples vs. those taken with the HydraSleeve™ Sampler.This example was the first well that HydraSleeve was ever deployed in.HydraSleeve™Purge/Sample
58HydraSleeve™ – Field Study (2 of 2) Former McClellan Air Force Base (Parsons Inc., 2005)Comprehensive comparison ofLow-flow and 3-well volume purged samplesSamples collected using 6 no-purge samplersAnalytes includedVOCs, 1,4 dioxane, anions, metals, and hexavalent chromiumStudy Findings“The HydraSleeve and Snap SamplerTM produced results most similar to the higher concentrations obtained by low-flow and 3-well volume purging and sampling methods”“Appears to be a technically viable method for monitoring all of the compounds in the demonstration”Available on ITRC Diffusion/Passive Sampler team web site: Technical publicationsI also conducted several studies on an earlier version of the HydraSleeve (before the reed valve was developed). In those tests, we conducted laboratory studies with known concentrations of VOCs, explosives, pesticides, and metals and a field study that we conducted in one of our wells that was contaminated with TCE. The results from these studies can be found in a report available at our website (below) and in a journal paper published in Ground Water Monitoring and Remediation 24(3):
59HydraSleeve™ Sampler Summary Sample all analyte typesSample volumes up to 2 LCan be used inDeep wellsCrooked wellsComparable results to conventional pumped methodsCan be left in well for quarterly, semi-annual, or annual samplingDisposable samplerNo decontamination requiredInexpensive to ship (100 samplers will fit in an overnight envelope)
60Equilibrated Grab Samplers Summary Snap Sampler™HydraSleeve™ SamplerSamples can be analyzed for all analyte typesProviding there is adequate sample volumeCollect whole water samples in real-timeCan be used for quarterly, semi-annual, or annual sampling eventsUse an equilibration period to reduce sampling biasesCollect samples at a discrete interval in well screenCompare well with conventional methodsNo associated notes.
61Accumulation Samplers Diffusion Samplers: analytes reach and maintain equilibrium via diffusion through membraneRegenerated-Cellulose Dialysis Membrane (Dialysis) SamplerRigid Porous Polyethylene (RPP) SamplerEquilibrated Grab Samplers: collect a whole-water sample instantaneouslySnap Sampler™HydraSleeve™ SamplerAccumulation Sampler: rely on diffusion and sorption to accumulate analytes in samplerGORE™ ModuleWe try to stress that passive sampling relies on basic groundwater principles that should be considered when performing any sampling event. There is no “special” criteria or studies that need to be performed when implementing general sampling.
62Accumulation Samplers Rely on diffusion and sorptionExamples of accumulation samplersSemi-permeable Membrane Devices (SPMD)Polar Organic Chemical Integrative Sampler (POCIS)Passive In-situ Concentration Extraction Sampler (PISCES)GORE™ ModuleMore information on other accumulation samplers is availableOverview of Passive Sampler Technologies (March 2006, DSP-4)Rely on diffusion through a membrane and sorption by some type of sorbent material (either granular or liquid) housed within the sampler membrane.This Gore Module is discussed in Section 2 of the ITRC Protocol Document (DSP-5) and is commercially available.
63GORE™ Module Components Knot (secure to wellhead)Attachment LineLoop to attach lineTag with unique serial numberAdsorbentWeightThis sampler is also known as the GORE-SORBER Module(figure on the left).The module comes in its own sample vialVial and sampler have a unique serial number for identifying sample.Size of the module is ~ the length and diameter of a soda straw.Module consists of:a tube made of GORE-TEX® membrane,which is a vapor-permeable, waterproof membrane.& 2 packets of the sorbent material.To deploy sampler (figures on right):Attach tether line and weights to bottom.After collecting sampler,blot dry with paper towel, place in vial, ship to labSampler can be used for sampling VOCs and SVOCsGORE™ ModuleSection 2 in ITRC Protocol Document (DSP-5)Attachment LineStainless steel weights
64GORE™ Module Sample Collection Dissolved compounds partition to vapor (Henry’s Law)Diffusion through hydrophobic, vapor-permeable membraneAdsorption onto mediaDuplicate samplesGORE-TEX® MembraneVapors passthroughThe figure on the left shows the membrane at high magnification.The dark areas represent the pore space in the membrane.The figure on the right shows conceptually how the analytes partition to the vapor phase, diffuse through the membrane, & are sorbed by the sorbent material.While liquid water is prevented from passing through the membrane into the interior of the sampler.Liquid waterremainsoutsideAdsorbents
65GORE™ Module Analysis No adsorbent transfer in field Thermal desorption/GC/MSVOCs and SVOCsUS EPA Method 8260/8270, modified for thermal desorptionFor analysis the adsorbent is transferred directly to the thermal desorption tube in the lab.There is minimal sample (adsorbent) handling and exposure to ambient air.Thermal desorption is used rather than solvent extraction be cause it allows for lower detection capability.
66GORE™ Module Advantages Sample small diameter wells and multi-level systems>0.25 inchesCrooked wellsNo minimum sample volume limitationNo need to refrigerate samplesMinimal water disruption - ~10 mls displacementShort sampling period - 15 minutes to 4 hoursLonger-term deployment – sub ppb concentrationsUS EPA ETV verified (Einfeld and Koglin, 2000)No associated notes.
67GORE™ Module Limitations Sole source supplier and laboratory analysisOrganic compounds onlyCompound detection limited by vapor pressureData reportingMeasured mass (µg)Concentrations are calculated by GORE based onMeasured mass, sampling rate, time, water temperature, and water pressureReference Section of ITRC Protocol Document (DSP-5)W.L GOREThe sampling rate refers to the uptake of compounds by the GORE™ Module, mass uptake over time.The sampling rate has been determined experimentally in the lab by Gore.This rate is then corrected for water temperature and water pressure conditions in each well.
68Low-flow sampling data GORE™ Module – VOC Field Study Military Base, Mid-Atlantic United States1,1,2,2-TetrachloroethaneGORE™ Module dataLow-flow sampling dataThe contour map on the left illustrates the total mass recovered with the GORE™ Module (not concentration data).The map on the right illustrates the results of low-flow sampling (in ug/L).This data is provided by the manufacturer.Strong spatial correlation with low-flow samplingGreater sensitivity & better plume delineation
69GORE™ Module – VOC Field Study Dry Cleaner, Southeastern United States PCE, TCE, cis-1,2-DCE (ug/L)300002000010000y = xR2=0.982N=12Concentration - BailerC1,2-DCETCEPCELinearSamples collected with a bailer following low-flow purgingGORE™ Module samples were taken firstCalculated concentrations are shownThis data is provided by the manufacturer.In the summer 2010, I will be conducting the first of two demonstrations of this technology in groundwater monitoring wells. The first site we are testing has chlorinated VOCs and the second site will have hydrocarbon contamination. This work is sponsored by ESTCP and will be available as an ESTCP report on our website under technical publications.Concentration – GORE™ ModuleCompared to slow purge and disposable bailerGood correlation
70GORE™ Module Summary Accumulation sampler Easy field deployment Passive operationCompounds partition to vapor, then diffuse to adsorbentEasy field deploymentSmall diameter wellsShort sampling periodAble to detect very low analyte concentrationsCollect samples at a discrete interval in well screenData reportedMass measured or as concentrations (calculated)Data comparable with conventional samplingCan only be used for organic compoundsThe details of the sampler are described in Section 2 of the ITRC Protocol Document (DSP-5).Because sampler can detect very low concentrations of analytes, it can provide in some cases more accurate delineation of the groundwater plumes.Sampler is only able to recover dissolved organic compounds with sufficient volatility to partition to the vapor phase.
71Overall Summary for Protocols for Use of Five Passive Samplers Passive Samplers offerQuantitative dataCost savingsUse is dependent upon the DQOsTech & Reg GuidanceAcceptanceDiffusion SamplersRPP & DialysisEquilibrated Grab SamplersSnap Sampler™ & HydraSleeve™Accumulation SamplerGORE™ ModuleCollect samples at a discrete interval in well screen
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