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Effect of humic acids on toxicity of DDT and chlorpyrifos to freshwater and estuarine invertebrates

Authors

  • Laurent C. Mézin,

    Corresponding author
    1. College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062-1346, USA
    Current affiliation:
    1. The current address of L.C. Mézin is 100 First Street, Suite 1700, San Francisco, CA 94105, USA
    • College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062-1346, USA
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  • Robert C. Hale

    1. College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062-1346, USA
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Abstract

The effects of dissolved humic acids(HA)on the acute toxicities of the organophosphate pesticide chlorpyrifos and the organochlorine pesticide 4,4′-dichlorodiphenyltrichloroethane (DDT) were assessed by using freshwater crustaceans (Cerio-daphnia dubia) and saltwater crustaceans (Americamysis bahia). The effects of filtered Aldrich HAs (10–100 mg/L) on organism mortality were determined. Humic acids had no effect on mortality of A. bahia for either pesticide at a salinity of 20%, but greatly reduced the mortality of C. dubia for both pesticides in freshwater (0%). In the latter case, the effect was proportional to the HA concentration. The difference in toxicity mitigation as a function of salinity is believed to be due to conformational changes in the HA molecules, which impact pesticide—HA binding, rather than to organismal effects.

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