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Total Dissolved Solids: The Challenges Ahead

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Presentation on theme: "Total Dissolved Solids: The Challenges Ahead"— Presentation transcript:

1 Total Dissolved Solids: The Challenges Ahead
US EPA Region 3 Freshwater Biology Team Wheeling, WV

2 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

3 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.

4 What We Know Some component ions are toxic to aquatic life.
Ex. Mount et al 1997 , acute endpoints K+ > HCO3- =Mg2+ > Cl- > SO42- Laboratory fish are more tolerant than laboratory inverts. Test duration important. Chronic endpoints important. Resident fish are more tolerant than resident inverts.

5 Mount et al 1997. C. Dubia More Sensitive to TDS than D. magna or fatheads.

6 What We Know Ion mixtures have varying toxicity
Ion mixtures source specific Alkaline coal mine drainage (HCO3- , Mg2+, Ca2+, SO42- ) Marcellus Shale Brine (Na+, Cl-,SO42-) Coal Bed Methane (Na+, HCO3- ,SO42-)

7 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.

8 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.

9 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.

10 Chloride LC50 vs. Hardness C. dubia

11 Chloride LC50 vs. Sulfate C. dubia

12 Iowa Cl Criteria

13 Iowa Sulfate Criteria

14 Illinois Sulfate Criterion Also Based on Acute Tests

15 Illinois Sulfate Criterion

16 Illinois Sulfate Criterion
Illinois states that “Sensitive organisms reside in receiving streams with sulfate concentrations of 2,000 mg/L.”

17 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.

18 Context is Important. What aquatic life are we trying to protect
Context is Important. What aquatic life are we trying to protect? What is the natural water quality? What is the effluent quality? PA OH WV KY VA

19 Effluent Dominated Streams
NPDES discharge Bio-Monitoring Effluent Dominated Streams

20 Heptageniidae Epeorus Ephemerella E. Fleek, NC DWQ Mayflies represent ~25-50% of Abundance; ~1/3rd biodiversity In natural, undegraded Appalachian streams Heptageniidae Heptagenia Ephemerellidae

21 We use conductivity as a surrogate for TDS
y = x R 2 = 500 1000 1500 2000 2500 3000 3500 4000 4500 Conductivity TDS KY Appalachian Headwaters (sandstone)

22 We also use conductivity as a surrogate for sulfate (Kentucky Data)

23 West Virginia Data log Cond log SO y = 1.2148x - 1.042 R2 = 0.94 0.5 1
0.5 1 1.5 2 2.5 3 3.5 1.7 1.9 2.1 2.3 2.7 2.9 3.1 3.3 log Cond log SO 4

24 Using Empirical Data Note
conductivity of uS/cm approximates sulfate of mg/l Iowa sulfate criteria ranges mg/l Illinois sulfate criteria in range of mg/l

25 Resident Mayflies Very Sensitive (Eastern Kentucky Coalfields)
80 70 Reference 60 Mined 50 Mined/Residential 40 %Ephemeroptera Note: strong nonlinear “threshold” response 30 20 10 500 1000 1500 2000 2500 Conductivity

26 Independent Datasets Confirm Sensitivity
(West Virginia southern coal fields) 90 80 70 60 50 % Mayflies 40 Mined Unmined 30 20 10 500 1000 1500 2000 2500 3000 Conductivity

27 EPA EIS data (WV) based on mean monthly WQ concentrations (n=13 months)
TDS and Ions strongly Correlated To mayflies And impairment

28 Is aquatic life in small Appalachian streams more sensitive to TDS pollution than that in midwestern streams? Sensitive Mayflies: 40 70 Epeorus Ephemerella Ameletus Drunella Cinygmula Paraleptophlebia 60 30 50 40 20 % Sensitive Mayflies % Ephemerella 30 20 10 10 0-200 >1000 0-200 >1000 CONDUCTIVITY CONDUCTIVITY

29 Facultative/Tolerant Mayflies:
What aquatic life is found in the midwest? Perhaps more TDS-tolerant invertebrates? Facultative/Tolerant Mayflies: 50 10 20 30 40 50 60 70 80 % Tolerant Mayflies 0-200 >1000 CONDUCTIVITY Isonychia, Tricorythodes, Baetis, Caenis 40 30 20 % Isonychia 10 0-200 >1000 CONDUCTIVITY

30 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.

31 Examples of ambient toxicity
Chronic effects were detected in samples with field conductivity >1800 µS/cm. There is NO dilution capacity in these streams.

32 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.

33 C. dubia more tolerant than resident Aquatic Life
Ref for GLIMPSS Not tox tested 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. Can’t use C. dubia alone to express “safe” thresholds, but it can be used as an indicator of the more toxic discharges.

34 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

35 Ex: Linear Regression

36 Ex: Quantile Regression (summer)

37 Ex: Quantile Regression (spring)

38 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

39 Ex: CPA: WV DEP data: Summer pH>6
Probability of Impairment Over 90% when Cond > 500 Probability of impairment N=949 RBP HAB>130 Conductivity

40 Ex: Regression Tree (MTM/VF EIS)
Split Variable PRE Improvement SULFATE 2 Mn DISS 3 CONDUCTIVITY SULFATE 5 ZINCTOTAL 6 MAGNESIUM %EPHEM Mean=20.45 SD=18.236 N=64 SULFATE<350.66 88.2% variance Mean=4.04 Mean=34.94 SD=5.945 SD=11.947 N=30 N=34 Mn DISS.<0.0074 CONDUCTIVITY<433.1 Mean=1.45 Mean=12.5 Mean=23.83 Mean=38.4 SD=2.040 SD=6.720 SD=6.393 SD=11.196 N=23 N=7 N=8 N=26 SULFATE<15.6 Mean=34.0 Mean=44.1 SD=9.799 SD=10.179 N=14 N=12 ZINC<0.023 MAGNESIUM<6.9 Mean=29.66 Mean=40.13 Mean=39.95 Mean=48.33 SD=9.077 SD=7.688 SD=11.966 SD=6.533 N=9 N=5 N=6 N=6 All Ions, Metals, pH, Hardness

41 How do these empirical results compare to Iowa’s Sulfate Criteria?
We have not reviewed any bioassessment data from Iowa. R3 Empirical examples suggest impairment at sulfate mg/l

42 Water Quality Based Approach to Pollution Control
Determine Protection Level (EPA Criteria/State WQS) Measure Progress Conduct WQ Assessment (Identify Impaired Waters) Monitor and Enforce Compliance (including instream bioassessments) Set Priorities (Rank/Target Waterbodies) Handout 2-6 Water Quality Based Approach is outlined in Sec. 302 of the Act Show Video? (Do we need to review transcript to make sure it is OK?) Establish Source Controls (Point Source, NPS) Evaluate Appropriateness of WQS for Specific Waters (Reaffirm WQS) Define and Allocate Control Responsibilities (TMDL/WLA/LA)

43 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.

44 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.

45 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

46 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

47 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

48 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?

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