1. An Introduction to the Biotic Ligand Model (BLM)
An Introduction to the Biotic Ligand Model (BLM)
WQSA: Introduction to the BLM

2. Generalized BLM Framework
Generalized BLM Framework
Competing Cations
Metal ion
M+2
Free H+
Ca+2
Na+
Organic
Ligand
Complexes
Inorganic
Gill Surface
(biotic ligand)
Metal Binding
Site
M OH+
M CO3+
M Cl+
M - DOC
WQSA: Introduction to the BLM

3. Biotic Ligand Model Free Ion Model (1993): Chemical model
Biotic Ligand Model
Free Ion Model (1993): Chemical model
Gill Model (1996):Toxicological model
Refinement and incorporation into criterion ( )
WQSA: Introduction to the BLM

4. Biotic Ligand Model: What does it do?
Biotic Ligand Model: What does it do?
Complements the existing Guideline procedures.
Provides a way to account for the effect of water chemistry, in addition to hardness, on metal bioavailability and toxicity.
Should lead to an improved capability to assess the potential for adverse effects to aquatic biota.
WQSA: Introduction to the BLM

5. BLM Parameters (realities and assumptions)
BLM Parameters (realities and assumptions)
Inorganic
Values from thermodynamic database
Organic
Values from calibration to chemical measurements with Organic Matter
Biotic
Values derived from a limited number of accumulation datasets
Most parameters assumed to be consistent for other organisms, since ion-transport mechanisms are similar
LA50 used account for variation in species sensitivity
BLM parameter values:
This slide summarizes the parameter values that are used in the BLM
The chemical parameters represent thermodynamic values that should remain constant for all BLM applications
Biotic ligand parameters may change, but limited data exists for several fish
During BLM development we have assumed that values for binding parameters are the same for all organisms
To adjust model sensitivity, the only parameter that will be changed is the LA50.
WQSA: Introduction to the BLM

6. Problem with Metals Criteria
Problem with Metals Criteria
The same metal concentration exerts different degrees of toxicity from time to time and from place to place.
The BLM formulates the key controlling constituents as pH, Ca, Na, CO3, and DOC.
WQSA: Introduction to the BLM

7. Current Water Quality Criteria (WQC)
Current Water Quality Criteria (WQC)
WQC do not typically reflect the effects of other water chemistry factors that are also known to affect metal toxicity.
WQSA: Introduction to the BLM

8. Effect of Hardness on Toxicity
Effect of Hardness on Toxicity
Fathead Minnow Data
Effect of Hardness on Copper Toxicity to Fathead Minnows
(Erickson et al., 1996) 5 4
R2=0.954 3
Copper LC50 (umol/L) 2 1 50
100
150
200
Hardness (mg/L as CaCO3)
WQSA: Introduction to the BLM

9. Limits of Hardness Normalization
Limits of Hardness Normalization
Potentially under-protective at low pH.
Over-protective at higher DOC.
Requires Water Effect Ratio (WER) for correction.
WQSA: Introduction to the BLM

10. USEPA Site-specific WQC Methods
USEPA Site-specific WQC Methods
Three methods are available for use:
Recalculation procedure
Water Effect Ratio (WER) procedure
Resident species procedure
WQSA: Introduction to the BLM

11. The Alternative: Biotic Ligand Model
The Alternative: Biotic Ligand Model
The BLM quantitatively evaluate the effects of other factors affecting toxicity thus providing an alternative way to evaluate a WER.
WQSA: Introduction to the BLM

12. Comparison of Approaches
Comparison of Approaches
BLM versus WER
WER: Comprehensive in scope, but sampling error is high, precision low.
BLM: Limited in model formulation, but sampling error low.
BLM is implemented as hardness normalization replacement (directly into criterion).
WQSA: Introduction to the BLM

13. Question: can accumulation be uniquely related to a toxic effect?
Question: can accumulation be uniquely related to a toxic effect?
(Data: MacRae, 1994 and 1999) ) %
TOTAL Cu = 10 ug/L ( y i t a l
100 r t o M t u o r 80 T w o b n i a 60 R
GILL LA50 e l i
~10 nmol/g n w e v u J 40 r u o H - 2 1 20 10 20 30 40 50
24-Hour Gill Cu (nmol/g wet weight)
WQSA: Introduction to the BLM

14. Importance of Organic Matter
Importance of Organic Matter
Data from Clemson U. (WERF BLM Project)
WQSA: Introduction to the BLM

15. Predicted Versus Measured LC50s
Predicted Versus Measured LC50s
K+2 added
WQSA: Introduction to the BLM

16. Summary & Conclusions Water chemistry affects metal toxicity.
Summary & Conclusions
Water chemistry affects metal toxicity.
Metal concentration, complexation and competition are important.
Toxicity can be predicted by knowing the metal: biotic ligand concentration (i.e., LA50).
Same concepts apply to other metals ….. Must consider thermodynamics
WQSA: Introduction to the BLM

17.
Beginning with consideration of species sensitivity, we will explore how the BLM may be applied to other organisms and to other metals (e.g., Ag, Cd, Ni, Pb and Zn).
WQSA: Introduction to the BLM

18. Application to Organisms
Application to Organisms
+LA50
-LA50
WQSA: Introduction to the BLM

19. Cu BLM: Ceriodaphnia dubia
Cu BLM: Ceriodaphnia dubia
1000
100
Predicted LC50 (ug/L) 10 1 1 10
100
1000
WQSA: Introduction to the BLM

20. Cu BLM: Daphnia pulex ) L / g u ( 5 C L D E T C I D E R P
Cu BLM: Daphnia pulex 1 10
100
1000
CT DEP (Dunbar, 1996)
Table 1, WQC Document Data ) L / g u ( 5 C L D E T C I D E R P 1 10
100
1000
MEASURED LC50 (ug/L)
WQSA: Introduction to the BLM

21. Cu BLM: Invertebrate Summary
Cu BLM: Invertebrate Summary
1000
D. magna
D. pulicaria
H. azteca
C. dubia
D. pulex
100
BLM Predicted Cu LC50 (ug/L) 10 1 1 10
100
1000
Measured Cu LC50 (ug/L)
WQSA: Introduction to the BLM

22.
Cu BLM 1 10
100
1000
10000
Fathead minnows, Lab
Fathead minnows, Field +
D. pulex (CT DEP, Dunbar, 1996) P R E D I C T L 5 ( u g / ) + + + + + + + + + + + + + + + + + 1 10
100
1000
10000
MEASURED LC50 (ug/L)
WQSA: Introduction to the BLM

23.
Ag BLM
WQSA: Introduction to the BLM

24. Cadmium solubility exceeded
Cd BLM
Rainbow Trout Data
10000
Davies et al, 1993 *
Cusimano et al, 1986
1000 ) L
Hollis et al / g
Pascoe et al u ( 5
Cadmium solubility exceeded C L
100 d C D E * T C I 10 D E R P * 1 *
0.1
0.1 1 10
100
1000
10000
MEASURED Cd LC50 (ug/L)
WQSA: Introduction to the BLM

25. Ni BLM: Fathead Minnow Results
Ni BLM: Fathead Minnow Results
BLM Predicted vs Measured Ni LC50 for Fathead Minnows
1000
Meyer et al., 1999 (1-6g, LA50=291 nmol/g)
Pickering and Henderson, 1966 ( 1-2g, LA50=51 nmol/g)
Schubauer-Berigan et al., 1993 ( < 24 hr old, LA50=6.7 nmol/g)
100
BLM Predicted Ni LC50 (mg/L) 10 1 1 10
100
1000
Measured Ni LC50 (mg/L)
WQSA: Introduction to the BLM

26. Ni BLM: Fathead Minnow & Invertebrate Results
A Comparison of BLM Predicted vs Measured Nickel LC50
1000
Fathead Minnows, 1-6 g
Fathead Minnows, 1-2 g
100
Fathead Minnows, < 24hr old
Daphnia magna
Ceriodaphnia dubia 10
BLM Predicted Ni LC50 (mg/L)
Ceriodaphnia dubia 1
pH effects
0.1
0.01
0.01
0.1 1 10
100
1000
Measured Ni LC50 (mg/L)
WQSA: Introduction to the BLM

27.
Pb BLM
WQSA: Introduction to the BLM

28. Zn BLM All available datasets - Rainbow trout 100,000 10,000 1000
Zn BLM
All available datasets - Rainbow trout
100,000
>
Actual LC50 Greater
10,000
>
1000
PREDICTED Zn LC50 (ug/L)
100 10 10
100
1000
10,000
100,000
MEASURED Zn LC50 (ug/L)
WQSA: Introduction to the BLM

29. San Francisco Bay Case Study
San Francisco Bay Case Study
BLM Application to Mytilus edulis 1 10
100
Measured Cu EC50 (ug/L)
CONTROLS
(TOC = 1.0 mg/L)
BLM Predicted vs.Observed EC50s for M. edulis
(Data: City of San Jose WPCP)
BLM Predicted Cu EC50 (ug/L)
WQSA: Introduction to the BLM

30. Validation of BLM For Mytilus
Validation of BLM For Mytilus
BLM Results Multiple Estuaries
WQSA: Introduction to the BLM

31. How did EPA incorporate the BLM into the criteria process?
Characterize the water chemistry for sufficient number of taxonomic groups to meet minimum data requirements.
Normalize acute studies (LC50) to standard water condition using the BLM.
Use normalized data to calculate 5 percentile FAV.
A LA50 is associated to this FAV.
Given site-specific water chemistry, this LA50 is used by the BLM to evaluate a site-specific FAV.
The site-specific AWQC = FAV/2.

32. Advantages of using the BLM
Advantages of using the BLM
 Water chemistry data are cheaper to obtain than are bioassays.
 Historical data may be used providing for the capability to make hind-casts.
 Improves our understanding of how water chemistry affects metal availability and toxicity.
 A combination of bioassay-based methods and computational methods may be used.
WQSA: Introduction to the BLM

33. EPA Draft Copper Criteria
EPA Draft Copper Criteria
Released December 2003
Draft document:
BLM-normalized freshwater criterion.
BLM model used as a replacement for the hardness equation.
Allows prediction of acute WQC using an approach similar to that of predicting organism toxicity.
WQSA: Introduction to the BLM

34. Summary and Conclusions
Summary and Conclusions
Species sensitivity has important implications for the derivation of site-specific water quality criteria.
The BLM has been successfully applied to a number of organisms with varying sensitivity to copper and other metals.
The BLM can be used to calculate site specific copper criteria that agrees remarkably well with bioassay-based WER studies.
BLM may eliminate the need for WER studies.
WQSA: Introduction to the BLM

35. Summary and Conclusions
Summary and Conclusions
The BLM compares well in freshwater environments.
A site-specific criteria can be developed in less time and with lower costs.
The BLM can be used to develop estimates of spatial or temporal variation in metal bioavailability.
WQSA: Introduction to the BLM

36. Cited and Supplemental References on the BLM and Related Topics
Bibliography
Cited and Supplemental References on the BLM and Related Topics
Chapman, G.A., S. Ota and F. Recht, January “Effects of Water Hardness on the Toxicity of Metals to Daphnia magna,” a USEPA project status report.
City of San José Development of a site-specific water quality criterion for copper in South San Francisco Bay. San José/Santa Clara Water Pollution Control Plant, San José, CA. 171 pp.
Cusimano, R.F., D.F. Brakke and G.A. Chapman Effects of pH on the toxicities of cadmium, copper and zinc to steelhead trout (Salmo gairdneri). Can.J.Fish.Aquat.Sci. 43(8):
Davis, A. and D. Ashenberg The aqueous geochemistry of the Berkeley Pit, Butt, Montana, U.S.A. Appl. Geochem. 4:23-36.
Dunbar, L.E., 1996b. “Derivation of a Site-Specific Dissolved Copper Criteria for Selected Freshwater Streams in Connecticut,” Falmouth MA, Connecticut DEP, Water Toxics Program, Falmouth, MA. (excerpt from an uncited report that was received from author)
Erickson, R.J., D.A. Benoit and V.R. Mattson, “A Prototype Toxicity Factors Model For Site-Specific Copper Water Quality Criteria,” revised September 5, 1996, United States Environmental Protection Agency, Environmental Research Laboratory-Duluth, Duluth, MN.
Erickson, R.J., D.A. Benoit, V.R. Mattson, H.P. Nelson Jr. and E.N. Leonard, “The Effects of Water Chemistry on the Toxicity of Copper to Fathead Minnows,” Environmental Toxicology and Chemistry, 15(2):
MacRae, R.K., December, “The Copper Binding Affinity of Rainbow Trout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis) Gills,” a thesis submitted to the Department of Zoology and Physiology and The Graduate School of the University of Wyoming in partial fulfillment of the requirements for the degree of Master of Science in Zoology and Physiology.
MacRae, R.K., D.E. Smith, N. Swoboda-Colberg, J.S. Meyer and H.L. Bergman, “Copper Binding Affinity of Rainbow Trout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis) Gills: Implications for Assessing Bioavailable Metal,” Environmental Toxicology and Chemistry, 18(6):
Meyer, J.S., R.C. Santore, J.P. Bobbitt, L.D. DeBrey, C.J. Boese, P.R. Paquin, H.E. Allen, H.L. Bergman and D.M. DiToro, “Binding of Nickel and Copper to Fish Gills Predicts Toxicity When Water Hardness Varies, But Free-ion Activity Does Not,” Environmental Science and Technology, 33(6):
Pickering, Q.H., and C. Henderson, “The Acute Toxicity of Some Heavy Metals to Different Species of Warmwater Fishes,” International Journal of Air and Water Pollution, 10:
Playle, R., L. Hollis, N. Janes and K. Burnison, August 6-9, “Silver, Copper, Cadmium, Dissolved Organic Carbon, and Fish,” extended abstract in Transport, Fate and Effects of Silver in the Environment, 3rd International Conference Proceedings of Argentum, an International Conference, Washington, DC.
Schubauer-Berigan, M.K., J.R. Dierkes, P.D. Monson and G.T. Ankley, “pH-Dependent Toxicity of Cd, Cu, Ni, Pb and Zn to Ceriodaphnia dubia, Pimephales promelas, Hyalella azteca and Lumbriculus variegatus,” Environmental Toxicology and Chemistry, 12:
Stephan, C.E., D.I. Mount, D.J. Hansen, J.H. Gentile, G.A. Chapman and W.A. Brungs, January “Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses,” USEPA Office of Research and Development, Environmental Research Laboratories: Duluth, Minnesota; Narragansett, Rhode Island and Corvallis, Oregon, 98 pp.
WQSA: Introduction to the BLM