A new study of an international research group is questioning the widely accepted "free ion activity model" FIAM that assumes that the free metal ion activity reflects the chemical reactivity of the metal, i.e., the extent to what the metal reacts with binding sites on the cell membrane surface, and hence its bioavailability and toxicity. According to the results of this new study, humic acids increase dissolved lead bioavailability for marine invertebrates.
Background:
An important goal in aquatic ecotoxicology is to predict the bioavailability of dissolved metals as a function of their speciation in the environment. The widely used models, FIAM and BLM (biotic ligand model) were developed to address this challenge. According to these models, the presence of dissolved organic matter (DOM), as humic acids (HA), in natural waters is assumed to decrease dissolved metal bioavailability by binding metal ions and, therefore, decreasing the free ion concentration in solution. Although these models have been widely used in bioavailability studies, there are also a number of studies showing deviating results and questioning their general applicability to natural waters.
The new study:The new study performed by Paula Sanchez-Marín from the University of Viego, Spain, and her co-workers aimed at testing the applicability of FIAM to dissolved Pb in the presence of DOM in marine systems. Pb complexation by HA in artificial seawater was checked by means of square wave anodic stripping voltammetry (SWASV). Uptake and toxicity of this metal in the absence and presence of HA was tested using excised gills of Mytilus edulis and the Paracentrotus lividus embryo-larval bioassay respectively. Both Pb uptake by mussel gills and Pb toxicity to sea urchin larvae increased in the presence of HA, and this increase was higher at higher HA concentrations.
The original study
Paula Sánchez-Marín, J. Ignacio Lorenzo, Ronny Blust, Ricardo Beiras,
Humic Acids Increase Dissolved Lead Bioavailability for Marine Invertebrates, Environ. Sci. Technol., 41/16 (2007) │5679-5684.
DOI: 10.1021/es070088h
Related studies S.N. Luoma, G.W. Bryan,
Factors controlling the availability of sediment-bound lead to the estuarine bivalve Scrobicularia plana, J. Mar. Biol. Assoc. UK, 58 (1978) 793-802. DOI:
10.1017/S0025315400056769 H.E. Allen, R.H. Hall, T.D. Brisbin,
Metal speciation. Effect on aquatic toxicity, Environ. Sci. Technol., 14/4 (1980) 441-443.
DOI: 10.1021/es60164a002 M.L. Freedman, P.M. Cunningham, J.E. Schindler, M.J. Zimmerman,
Effect of lead speciation on toxicity, Bull. Environ. Contam. Toxicol., 25/1 (1980) 389-393.
DOI: 10.1007/BF01985543 H. Babich, G. Stotzky, Influence of chemical speciation on the toxicity of heavy metals to the microbiota, in: J.O. Nriagu (ed.), Aquatic toxicology, John Wiley & Sons, New York, 1983, pp. 1-46.
T.M. Florence, G.F. Batley,
Chemical Speciation and Trace Element Toxicity, Chem. Aust., 55 (1988) 363.
C. B. Dissayanake,
Humic substances and chemical speciation - implications on environmental geochemistry and health, Int. J. Environ. Stud., 37/4 (1991) 247-258.
DOI: 10.1080/00207239108710637 M. Zhang, J. Wang, J. Bao,
Study on the relationship between speciation
of heavy metals and their ecotoxicity. I. Toxicity of copper, cadmium,
lead and zinc in the presence of different complexation agents, Chin. J.
Oceanol. Limnol., 10/3 (1992) 215-222.
S. Jonnalagadda,
Toxicity, bioavailability and metal speciation, Comp. Biochem. Physiol. C, 106/3 (1993) 585-595.
DOI: 10.1016/0742-8413(93)90215-7 K. Hughes, M.E. Meek, R. Newhook, P.K.L. Chan,
Speciation in Health Risk Assessments of Metals: Evaluation of Effects Associated with Forms Present in the Environment, Regul. Toxicol. Pharmacol., 22 (1995) 213-220.
DOI: 10.1006/rtph.1995.0003 B. Corain, G.G. Bombi, A. Tapparo, M. Perazzolo, P. Zatta,
Aluminium toxicity and metal speciation: established data and open questions, Coord. Chem. Rev., 149 (1996) 11-22.
DOI: 10.1016/S0010-8545(96)90006-5
H.E. Witters, Chemical speciation dynamics and toxicity assessment in aquatic systems, Ecotoxicol. Environ. Safety, 41/1 (1998) 90-95.
DOI: 10.1016/S0141-1136(00)00097-0 Takashi Kunito, Kazutoshi Saeki, Hiroshi Oyaizu, Satoshi Matsumoto,
Influences of Copper Forms on the Toxicity to Microorganisms in Soils, Ecotoxicol. Environ. Safety, 44 (1999) 174-181.
DOI: 10.1006/eesa.1999.1820
L. Guo, B. Hunt, P.H. Santschi, S.M. Ray,
Effect of dissolved organic matter on the uptake of trace metals by american oysters, Environ. Sci. Technol., 35 (2001) 885-893.
DOI: 10.1021/es001758l
L.V. Ginneken, L. Bervoets, R. Blust, Bioavailability of Cd to the common carp, Cyprinus carpio, in the presence of humic acid, Aquat. Toxicol., 52 (2001) 13-27.
DOI: 10.1016/S0166-445X(00)00134-X M.J. Gardner, E. Dixon, I. Sims, P. Whitehouse,
Importance of Speciation in Aquatic Toxicity Tests with Aluminum, Bull. Environ. Contam. Toxicol., 68 (2002) 195-200.
DOI: 10.1007/s001280238 K. Fent,
Ecotoxicological effects at contaminated sites, Toxicology, 205 (2004) 223-240.
DOI: 10.1016/j.tox.2004.06.060 J.I. Lorenzo, O. Nieto, R. Beiras,
Effect of humic acids on speciation and toxicity of copper to Paracentrotus lividus larvae in seawater, Aquat. Toxicol. , 58 (2002) 27-41.
DOI: 10.1016/S0166-445X(01)00219-3 H. Ma, S.D. Kim, H.E. Allen, D.K. Cha,
Effect of Copper Binding by Suspended Particulate Matter on Toxicity, Environ. Toxicol. Chem., 21 (2002) 710-714.
DOI: 10.1002/etc.5620210404 Simon C. Apte, G.E. Batley, K.C. Bowles, P.L. Brown, N. Creighton, L.T. Hales, R.V. Hyne, M. Julli, S.J. Markich, F. Pablo, N.J. Rogers,
A Comparison of Copper Speciation Measurements with the Toxic Responses of Three Sensitive Freshwater Organisms, Environ. Chem., 2/4 (2005) 320-330.
DOI: 10.1071/EN05048 Pietro Apostoli,
Rita Cornelis, John H. Duffus, P. Hoet, D. Lison, D. Templeton,
Elemental Speciation in Human Health Risk Assessment,
Environmental Health Criteria #234, WHO, Geneva, 2006.
Related EVISA Resources
Brief summary: Speciation and Toxicity
Related EVISA News (newest first)
last time updated: August 29, 2024
