Presentation on theme: "Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method 1631 Overview of Sampling and Analysis William Telliard U.S. EPA Office."— Presentation transcript:
1 Mercury Collection and Analysis in Ambient and Effluent Waters using EPA Method Overview of Sampling and Analysis William Telliard U.S. EPA Office of Science and Technology
2 Contamination Control Philosophy Ensure any object or substance that contacts the samples is nonmetallic and free from any material that may contain metals of concernMercury must be eliminated or reduced to a level that will not compromise the measurementSample bottlesSampling equipmentReagentsLaboratory environmentLaboratory glassware and equipment
3 Equipment Cleaning Preclean All equipment and containers must be non-metallicClean all sampling equipment and containers using detergent, mineral acids, and reagent water as described in Method 1669Verify cleanlinessGenerate acceptable equipment blanksDemonstrates equipment and containers are free from contaminationStorageFill cleaned sample containers with 0.1% (v/v) ultrapure HCl and individually double-bagBag or wrap all sampling equipment for storage and shipment
4 Sample Collection Using Method 1669 “Clean Hands/Dirty Hands”A two-person sampling team is requiredOne person is designated “Clean Hands” and performs all operations involving direct contact with the sample and bottlesThe other person is designated “Dirty Hands” and is responsible for operation of machinery and activities not involving direct contact with the sampleSampling personnel must wear clean, non-talc gloves, and may need to wear other clothing, such as disposable coveralls or nylon windsuits, caps, and shoulder-length glove liners, to prevent sample contamination
5 Sample Collection Using Method 1669 The presence of potential sources of contamination is of extreme importance in site selectionTo minimize contamination—Collect samples facing upstream and upwindAvoid collecting samples during precipitation eventsDuring a 9 POTW Great Lakes study, the Hg field blank collected on the only rainy day had a Hg concentration 3 times higher than any other field blank in the studyCollect samples as far as possible from metal supports, bridges, wires, and heavily traveled roads
6 Sample Collection Using Method 1669 (cont.) Method includes procedures for collection of samples for determination of total recoverable metals and dissolved metalsSample FiltrationFor dissolved metals, samples are filtered through a 0.45-um capsule filter at the field siteA continuous-flow sampling system with an in-line filter can simplify sample collection and filtrationSample PreservationConducted in the field or in the laboratoryField preservation must be performed in a glove bag or a designated clean area
7 Quality Assurance/Quality Control Equipment BlanksBottle blanksSampler Check BlanksField BlanksMust be collected to assess the likelihood of contamination in the samples.Field blanks are collected before samplesField DuplicatesCollected to assess precision of the sampling and analytical processes
8 Blanks and Definitions Equipment BlankBottle Blank - generated by filling a sample bottle with reagent water acidified to pH < 2, allowing the bottle to stand for 24 hours, and analyzing the waterSampler Check Blank - generated at the lab by processing reagent water through the sampling equipment using the same procedures that will be used in the field, and collecting and analyzing the waterField Blank - generated by filling a large carboy with reagent water in the laboratory, transporting the container to the field, processing the reagent water through the entire sampling equipment system, and analyzing the sample
9 SummaryRigorous sample handling procedures are necessary to ensure samples are not contaminatedStringent QC is necessary to ensure the validity of the analytical resultsNot all of the procedures described in Method 1669 may be necessary for effluent samplingLevel of protection required depends on sampling environment, monitoring levels of interest, and metals of interestThe low levels of Hg (<36 ng/L) found in a 9 POTW Great Lakes Study suggests these clean techniques may be required for some metals
10 Laboratory Analysis using Method 1631 For determination of mercury in filtered and unfiltered water by oxidation, purge and trap, desorption, and cold-vapor atomic fluorescence spectrometry (CVAFS)Method detection limit is 0.2 ng/L and the range is ng/LThe ease of contamination samples cannot be overemphasizedMethod includes suggestions for improvements in facilities and analytical techniques that minimize contamination and maximize the ability of the laboratory to make reliable trace metals determinationsPerformance-basedAccompanied by Method 1669
11 Laboratory Analysis using Method 1631 (cont.) A mL sample is collected directly into a specially cleaned, pretested, fluoropolymer bottle using appropriate sample handling techniquesFor dissolved mercury, the sample is filtered through a 0.45 uM capsule filterThe sample is preserved by adding 5mL/L of pretested HCl or 5 mL/L BrCl solution.BrCl solution is added to oxidize all Hg compounds to Hg(II)The sample is pre-reduced with NH2OH-HCl to destroy the free halogens
12 Laboratory Analysis using Method 1631 (cont.) The sample is then reduced with SnCl to convert Hg(II) to volatile Hg(0).The Hg(0) is separated from solution by purging with nitrogen onto a gold-coated sand trapThe trapped Hg is thermally desorbed from the gold trap into an inert gas stream that carries the released Hg(0) into the cell of a CVAFS for detectionQuality is assured through calibration and testing of the oxidation, purging, and detection systems.
14 Figure 2. Automated Mercury Fluorescence System (Method 245.7)
15 Clean Spaces GuidanceDraft guidance on the establishment of trace metal clean rooms in existing facilities was completed in April 1995, with minor revisions in January The guidance includes:A general design of a trace metals clean laboratory;Delineation of the hierarchy of cleanliness needed within the laboratory, including change rooms;Description of HEPA-filtered air and clean water supplies, which are essential in a trace metals laboratory; andDetailed descriptions of materials and modifications used to construct a trace metals clean room in an existing laboratory.
16 Clean Spaces Guidance (cont.) Basic requirementsmetal free work surfaces and hoodspositive pressure with HEPA-filtered airclean waterAchieved with commercially available materialsInstalled into existing facilitiesPaint the walls with metal-free paint (epoxy- or latex-based) to which has been added a small amount of sulfur powder to react with mercury that could diffuse out of the underlying surfacesAll metal fixtures and appliances should be replaced with non-metal counterparts
17 Analysis TipsClean all work surfaces in which samples will be processedReagent water should be monitored for HgSamples known to contain high levels of mercury (greater than 100 ng/L) should be diluted prior to bringing them into the clean room or areaSample processing and analysis should occur as far as possible from sources of airborne contaminationEffluent from the CVAFS should pass through either a column of activated charcoal or a trap containing gold or sulfur to amalgamate or react mercury vapors
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