Presentation on theme: "Total Dissolved Solids: The Challenges Ahead US EPA Region 3 Freshwater Biology Team Wheeling, WV."— Presentation transcript:
Total Dissolved Solids: The Challenges Ahead US EPA Region 3 Freshwater Biology Team Wheeling, WV
Freshwater Biology Team, EPA R3, EAID, OMA FBT Members –Amy Bergdale, Frank Borsuk, Kelly Krock, Maggie Passmore, Greg Pond, Louis Reynolds Assist the states in methods development, bioassessment, biocriteria Assist EPA R3 in use of biological data –WQS, monitoring, TMDLs, NPDES, superfund, etc. –Perform special studies
Background Many states have identified ionic toxicity, conductivity and/or total dissolved solids (TDS) as a stressor or pollutant in their integrated lists. EPA has also identified TDS (and component ions) as a stressor impairing aquatic life. EPA lacks aquatic life criteria for TDS mixtures. Some TMDLs have been deferred due to lack of criteria. We also need criteria for effluent limits for discharge permits.
What We Know Some component ions are toxic to aquatic life. Ex. Mount et al 1997, acute endpoints K + > HCO 3 - =Mg 2+ > Cl - > SO 4 2- Laboratory fish are more tolerant than laboratory inverts. Test duration important. Chronic endpoints important. Resident fish are more tolerant than resident inverts.
Mount et al C. Dubia More Sensitive to TDS than D. magna or fatheads.
What We Know Ion mixtures have varying toxicity Ion mixtures source specific –Alkaline coal mine drainage (HCO 3 -, Mg 2+, Ca 2+, SO 4 2- ) –Marcellus Shale Brine (Na +, Cl -,SO 4 2- ) –Coal Bed Methane (Na +, HCO 3 -,SO 4 2- )
What We Know Effects synergistic, additive, or ameliorative Depends on the ions and their concentrations In some systems (e.g. Appalachian headwater streams) lab controlled toxicity tests are not a good predictor of instream aquatic life use impairment.
Two Webinars on TDS (2009) Toxicity testing approaches to develop criteria for individual ions –Surrogate organisms –Iowa: chloride and sulfate –Illinois: sulfate Empirical approaches –bioassessment and water quality data to develop a criterion for an ion mixture: –Ex. Alkaline mine drainage in southern WV and KY Appalachian streams.
The Case for Single Ion Criteria Lab experiments are controlled Other stressors are excluded Toxicity testing data deemed more defensible Pollutant specific criteria instead of integrative parameters such as TDS or conductivity –Easier to implement than narrative criteria –Easier to check compliance –Permit writers understand it Can still incorporate site-specific conditions Resources will focus on source reduction Regulating TDS futile; Ion mixtures too complex.
Chloride LC50 vs. Hardness C. dubia
Chloride LC50 vs. Sulfate C. dubia
Iowa Cl Criteria
Iowa Sulfate Criteria
Illinois Sulfate Criterion Also Based on Acute Tests
Illinois Sulfate Criterion
Illinois states that Sensitive organisms reside in receiving streams with sulfate concentrations of 2,000 mg/L. Illinois Sulfate Criterion
The Case for an Empirical Approach Context is important. Aquatic life in small Appalachian streams is not the same as in Iowa or Illinois! We must protect the resident aquatic life uses. Unlike Illinois, we routinely see aquatic life use impairment downstream of alkaline mine drainage. Elevated TDS, hardness and alkalinity, in the absence of other stressors (e.g. habitat, low pH, metals violations). TDS and component ions are strongly correlated to this impairment.
OH KY WV PA VA Context is Important. What aquatic life are we trying to protect? What is the natural water quality? What is the effluent quality?
Conductivity % Mayflies Unmined Mined Independent Datasets Confirm Sensitivity (West Virginia southern coal fields)
EPA EIS data (WV) based on mean monthly WQ concentrations (n=13 months) TDS and Ions strongly Correlated To mayflies And impairment
>1000 CONDUCTIVITY % Ephemerella % Sensitive Mayflies Epeorus Ephemerella Ameletus Drunella Cinygmula Paraleptophlebia Epeorus Ephemerella Ameletus Drunella Cinygmula Paraleptophlebia Is aquatic life in small Appalachian streams more sensitive to TDS pollution than that in midwestern streams? Sensitive Mayflies: >1000 CONDUCTIVITY
>1000 CONDUCTIVITY % Isonychia What aquatic life is found in the midwest? Perhaps more TDS-tolerant invertebrates? Facultative/Tolerant Mayflies:
The Case for an Empirical Approach The concentrations of ions that are correlated with high probability of aquatic life use impairment are much lower than the toxicity testing data imply would be protective. –Suggests that common toxicity testing organisms are not as sensitive as resident aquatic invertebrates. –Many of the toxicity test results have been based on acute tests. The tests and endpoints should be chronic and the toxicity tests should test sensitive life stages. There may be seasonal issues due to insect life cycles. Empirical data may help us determine the more sensitive resident species. Bioassessment endpoints are the best tool to capture the total effect of a complex ion mixture.
Examples of ambient toxicity Chronic effects were detected in samples with field conductivity >1800 µS/cm. There is NO dilution capacity in these streams.
Chronic Effects Levels Estimated conductivity at EC25 % ranged from with an average of 820 µS/cm. This range is slightly higher than where we see effects with resident biota.
C. dubia more tolerant than resident Aquatic Life All sites were rated impaired using the genus level GLIMPSS (<66), which directly measures aquatic life use impairment. The resident biota are more sensitive than the WET surrogate, C. dubia. Cant use C. dubia alone to express safe thresholds, but it can be used as an indicator of the more toxic discharges. Ref for GLIMPSS Not tox tested
Using Empirical Data Linear regression Quantile regression Conditional Probability Analysis Regression Trees Note –conductivity of uS/cm approximates sulfate of mg/l –Iowa sulfate criteria ranges mg/l –Illinois sufate criteria in range of mg/l
Ex. Conditional Probability Approach Paul and McDonald (2005) CPA relies on a large dataset to develop criteria. –Simply asks what is the probability of impairment given conductivity value x? P(y|x) where y is impairment threshold (IBI), and x is some TDS or conductivity value. J. Paul (EPA, RTP, in review) found –100% chance of MAHA sites being impaired when conductivity >575 and –100% chance of Florida streams impaired when conductivity >750
N=949 RBP HAB>130 Ex: CPA: WV DEP data: Summer pH>6 Conductivity Probability of impairment Probability of Impairment Over 90% when Cond > 500
How do these empirical results compare to Iowas Sulfate Criteria? We have not reviewed any bioassessment data from Iowa. R3 Empirical examples suggest impairment at sulfate mg/l
Water Quality Based Approach to Pollution Control Determine Protection Level (EPA Criteria/State WQS) Conduct WQ Assessment (Identify Impaired Waters) Set Priorities (Rank/Target Waterbodies) Evaluate Appropriateness of WQS for Specific Waters (Reaffirm WQS) Define and Allocate Control Responsibilities (TMDL/WLA/LA) Establish Source Controls (Point Source, NPS) Monitor and Enforce Compliance (including instream bioassessments) Measure Progress
Recommendations Do not rely solely on toxicity testing to determine protective limits. Consider chronic toxicity testing endpoints. Consider dilution ratios. Combine toxicity testing and empirical data approaches when field data are available.
Recommendations Prepare a technical support document on TDS –reflects acute and chronic toxicity testing literature –offers some examples of empirical datasets and how they would be used to characterize aquatic life, and develop, refine or evaluate criteria and permits.
Recommendations Always use bioassessments to assess aquatic life uses downstream of discharges with TDS. These data should feed back into the permit and possibly result in site specific criteria. –Reflect all toxicants in discharge –Protect actual aquatic life that should be residing in that stream type
Ongoing Research - Surrogates Toxicity of TDS to surrogate lab organisms –Review literature for TDS –Develop empirical datasets between TDS and aquatic life –Acute and chronic tests with mining effluent and reconstituted salts and surrogate organisms (e.g. C. dubia) USGS Columbia Lab, Duluth EPA Lab Preliminary Data… Hassell et al 2006
Ongoing Research - Natives Metal and osmotic ecophysiology Deploy insects in situ – sample individuals in a time course –Measure growth, metal and electrolyte content, subcellular compartmentalization of metals –Explain any differences in metal tolerance, bioaccumulation and toxicity Laboratory Exposures –Monitor oxygen consumption, osmoregulatory status and Adenosine triphosphate (ATP) levels –Characterize energetic costs to living in high conductivity Outcome –Provide information on whether metal uptake is contributing to impairment –Provide information on mechanism for TDS impairment North Carolina State Buckwalter et al, 2007
Discussion Where do we go from here? Technical Barriers? Non-Technical Barriers? What do you need from EPA? What can you expect from EPA? How do we advance aquatic life criteria? How do we advance TMDL development?