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+ > 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.
Mount et al
1997.
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 (HCO3- , Mg2+,
Ca2+, SO42- )
– Marcellus Shale Brine (Na+, Cl-,SO42-)
– Coal Bed Methane (Na+, HCO3- ,SO42-)
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
LC 50 VS. Hardness
10000
LC50 (mg/l)
LC50 = 440.74*(Hardness)0.2144
R2 = 0.8246
1000
100
10
100
Hardness (Caco3 mg/l)
1000
Chloride LC50 vs. Sulfate
C. dubia
LC 50 VS. Sulfate
10000
LC50 (mg/l)
LC50 = 1736.9*(Sulfate)-0.0588
R2 = 0.3153
1000
100
10
100
Sulfate (mg/l)
1000
Iowa Cl Criteria
Iowa Sulfate Criteria
Illinois Sulfate Criterion Also
Based on Acute Tests
Illinois Sulfate Criterion
Illinois Sulfate Criterion
Illinois states that “Sensitive organisms reside in receiving streams with sulfate
concentrations of 2,000 mg/L.”
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.
Context is Important. What PA
aquatic life are
we trying to protect? What is the natural
water quality? What is the effluent quality?
OH
WV
KY
VA
NPDES discharge
Bio-Monitoring
Effluent Dominated Streams
Heptageniidae
Epeorus
Mayflies represent ~25-50% of Abundance; ~1/3rd biodiversity
In natural, undegraded Appalachian streams
E. Fleek, NC DWQ
Heptageniidae
Heptagenia
Ephemerellidae
We use conductivity as a surrogate for TDS
4500
KY Appalachian
Headwaters
(sandstone)
y = 0.7821x - 28.661
4000
2
3500
R = 0.9754
TDS
3000
2500
2000
1500
1000
500
0
0
500
1000
1500
2000
2500
3000
Conductivity
3500
4000
4500
We also use conductivity as a surrogate for sulfate
(Kentucky Data)
2500
y = 0.574x - 54.165
R2 = 0.93
SO4
2000
1500
1000
500
0
0
500
1000
1500
2000
Conductivity
2500
3000
3500
West Virginia Data
3.5
3
log SO 4
2.5
2
1.5
1
y = 1.2148x - 1.042
R2 = 0.94
0.5
0
1.5
1.7
1.9
2.1
2.3
2.5
log Cond
2.7
2.9
3.1
3.3
3.5
Using Empirical Data
• Note
– conductivity of 500-1000 uS/cm approximates
sulfate of 200-400 mg/l
– Iowa sulfate criteria ranges 500-2000 mg/l
– Illinois sulfate criteria in range of 1000-1500
mg/l
Resident Mayflies Very Sensitive
80
(Eastern Kentucky Coalfields)
70
Reference
%Ephemeroptera
60
Mined
50
Mined/Residential
40
Note: strong nonlinear “threshold” response
30
20
10
0
0
500
1000
Conductivity
1500
2000
2500
Independent Datasets Confirm Sensitivity
(West Virginia southern coal fields)
90
80
% Mayflies
70
60
50
40
Mined
Unmined
30
20
10
0
0
500
1000
1500
Conductivity
2000
2500
3000
EPA EIS data (WV)
based on mean monthly WQ concentrations (n=13 months)
TDS and
Ions
strongly
Correlated
To mayflies
And
impairment
Spearman's Correlation Coefficients
n=89
# Ephem Taxa % Ephem
TDS
-0.88
-0.86
Conductivity
-0.87
-0.86
SULFATE
-0.87
-0.85
CALCIUM
-0.87
-0.85
MAGNESIUM
-0.86
-0.83
POTASSIUM
-0.85
-0.82
SELENIUM
-0.74
-0.72
NITRATE/NITRITE NITROGEN
-0.72
-0.69
pH
-0.64
-0.60
SODIUM
-0.60
-0.59
IRON, DISSOLVED
-0.57
-0.61
CHLORIDE
-0.39
-0.46
MANGANESE
-0.34
-0.35
NICKEL
-0.31
-0.31
TOTAL ORGANIC CARBON
-0.31
-0.35
COPPER
-0.05
-0.13
TSS
-0.03
0.03
Temperature
-0.02
-0.02
D.O.
0.02
-0.02
ALUMINUM
0.07
0.10
BARIUM
0.10
0.05
ZINC
0.19
0.16
LEAD
0.25
0.23
bold values = p<0.05
Is aquatic life in small Appalachian streams more sensitive
to TDS pollution than that in midwestern streams?
Sensitive Mayflies:
40
70
60
% Sensitive Mayflies
% Ephemerella
30
20
10
50
40
Epeorus
Ephemerella
Ameletus
Drunella
Cinygmula
Paraleptophlebia
30
20
10
0
0
CONDUCTIVITY
CONDUCTIVITY
What aquatic life is found in the midwest?
Perhaps more TDS-tolerant invertebrates?
Facultative/Tolerant Mayflies:
50
80
Isonychia, Tricorythodes, Baetis, Caenis
70
% Tolerant Mayflies
% Isonychia
40
30
20
10
60
50
40
30
20
10
0
0
CONDUCTIVITY
CONDUCTIVITY
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
EC 25 Reproduction (%)
C. dubia Chronic Effects
120
100
80
60
40
20
0
0
1000
2000
3000
Sp. Cond. Field (us/cm)
Chronic effects were detected in samples with field conductivity
>1800 µS/cm.
There is NO dilution capacity in these streams.
Chronic Effects Levels
EC 25 Reproduction (%)
C. dubia Chronic Effects
120
100
80
60
40
20
0
0
500
1000
1500
Sp. Cond. Estimated @ EC25 (uS/cm)
Estimated conductivity at EC25 % ranged from 448-1243 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
Ref for
GLIMPSS
Not tox
tested
Stream Resident Biota More Sensitive Than WET
Surrogate
100
80
60
GLIMPSS
40
EC25
20
0
0
500
1000
1500
2000
2500
3000
Sp. Cond. Field (uS/cm)
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.
Using Empirical Data
•
•
•
•
•
Linear regression
Quantile regression
Conditional Probability Analysis
Regression Trees
Note
– conductivity of 500-1000 uS/cm approximates sulfate
of 200-400 mg/l
– Iowa sulfate criteria ranges 500-2000 mg/l
– Illinois sufate criteria in range of 1000-1500 mg/l
Ex: Linear Regression
Regression of GLIMPSS by log COND (R²=0.476)
Active
Model
Conf. interval (Mean 90%)
Conf. interval (Obs. 90%)
100
90
80
GLIMPSS
70
60
50
40
30
20
10
125 uS/cm
0
1
1.5
2
880 uS/cm
2.5
log COND
3
3.5
Ex: Quantile Regression (summer)
IMPAIRMENT THRESHOLD
N=535
Ex: Quantile Regression (spring)
IMPAIRMENT THRESHOLD
N=276
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
Probability of impairment
Ex: CPA: WV DEP data: Summer pH>6
Probability of
Impairment
Over 90% when
Cond > 500
N=949
RBP HAB>130
Conductivity
Ex: Regression Tree (MTM/VF EIS)
%EPHEM
Mean=20.45
SD=18.236
N=64
SULFATE<350.66
Mean=4.04
SD=5.945
N=30
Mean=12.5
SD=6.720
N=7
PRE
0.726
0.758
0.819
0.855
0.872
0.882
CONDUCTIVITY<433.1
Mean=23.83
SD=6.393
N=8
Mean=38.4
SD=11.196
N=26
SULFATE<15.6
Mean=34.0
SD=9.799
N=14
Mean=44.1
SD=10.179
N=12
ZINC<0.023
Mean=29.66
SD=9.077
N=9
All Ions, Metals, pH, Hardness
MAGNESIUM<6.9
Mean=40.13
SD=7.688
N=5
0.726
0.032
0.062
0.036
0.017
0.010
88.2% variance
Mean=34.94
SD=11.947
N=34
Mn DISS.<0.0074
Mean=1.45
SD=2.040
N=23
Split Variable
Improvement
1
SULFATE
2 Mn DISS
3 CONDUCTIVITY
4
SULFATE
5 ZINCTOTAL
6 MAGNESIUM
Mean=39.95
SD=11.966
N=6
Mean=48.33
SD=6.533
N=6
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 200-400 mg/l
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)
Establish Source
Controls
(Point Source, NPS)
Set Priorities
(Rank/Target Waterbodies)
Evaluate Appropriateness
of WQS for Specific Waters
(Reaffirm WQS)
Define and Allocate
Control Responsibilities
(TMDL/WLA/LA)
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
•
Outcome
•
North Carolina State
– Monitor oxygen consumption,
osmoregulatory status and
Adenosine triphosphate (ATP)
levels
– Characterize “energetic costs”
to living in high conductivity
– Provide information on whether
metal uptake is contributing to
impairment
– Provide information on
mechanism for TDS impairment
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?