STP921

    Methodology for determining the Relationship Between Toxicity and the Aqueous Speciation of a Metal

    Published: Jan 1986


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    Abstract

    Over the last decade, numerous investigators have tried to determine the link between the aqueous speciation of a metal and the metal's toxicity to aquatic organisms. The high collinearity between the calculated activities of the aqueous chemical species as well as the underdetermined nature of many of the toxicity data sets have made identification of particular toxic species for a metal very difficult and quantification virtually impossible. The original investigators have only applied qualitative techniques, using single species or very small groups of subjectively selected chemical species, to determine the relationship between toxicity and the speciation. Although useful in advancing our general understanding of the relationship between toxicity and the speciation of a metal, these qualitative techniques do not permit simultaneous consideration of the quantitatively important species nor the complex interactions between species.

    In a recent paper, we suggested an approach for determining the toxic chemical species of a metal and for determining and quantifying the relationship between a toxicity measure and the chemical speciation of a metal. Briefly, the approach consists of first computing the aqueous speciation of the metal using the geochemical model, MINTEQ, with a thoroughly reviewed and partially-validated thermodynamic data base. Finally, advanced statistical methods, which were determined to be stable when applied to collinear data and underdetermined systems, are applied to the thermodynamic activities of the metal species and toxicity measures to determine and quantify the relationship between the speciation and toxicity. To test the validity of this methodology, we have applied it to four copper toxicity data sets from the literature for which the primary toxic species have been tentatively identified by the original authors using qualitative techniques. The results of applying the methodology to these studies indicate that the primary toxic chemical species are the free copper ion and the hydroxide species and that the carbonate species are nontoxic. These findings largely confirm the results of previous qualitative analyses of the copper toxicity literature.

    Keywords:

    toxicity, copper, chemical speciation, ridge regression, factor analysis, multivariate statistics, aquatic toxicology


    Author Information:

    Cowan, CE
    Research scientist, senior staff scientist, and senior research scientist, Pacific Northwest Laboratory, Richland, WA

    Jenne, EA
    Research scientist, senior staff scientist, and senior research scientist, Pacific Northwest Laboratory, Richland, WA

    Kinnison, RR
    Research scientist, senior staff scientist, and senior research scientist, Pacific Northwest Laboratory, Richland, WA

    WATER Resources Center, Desert Research Institute, Las Vegas, NV


    Paper ID: STP29046S

    Committee/Subcommittee: E47.10

    DOI: 10.1520/STP29046S


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