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Effects of dilution on the exposure in sediment toxicity tests—buffering of freely dissolved concentrations and changes in mixture composition
Author(s) -
ter Laak Thomas L.,
Mayer Philipp,
Klamer Hans J. C.,
Hermens Joop L. M.
Publication year - 2007
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/07-113r.1
Subject(s) - dilution , sediment , environmental chemistry , chemistry , contamination , matrix (chemical analysis) , toxicity , environmental science , chromatography , geology , ecology , paleontology , physics , organic chemistry , biology , thermodynamics
Some sediment toxicity tests, such as the Microtox® test, are conducted by diluting either contaminated sediment or an aqueous phase with clean water. The present study aims to clarify how the dilution procedure affects the exposure of organisms. It is shown that freely dissolved concentrations of hydrophobic compounds are buffered by desorption from the sediment matrix when sediment is diluted with water. The buffering depends on the properties of the sediment matrix and contaminant. Consequently, the composition of a contaminant mixture changes with dilution, and the exposure in a sediment dilution toxicity test is poorly defined. This questions the application and subsequent assessments of such tests. Additionally, the often‐observed higher toxicity in sediment dilution tests relative to elutriate dilution tests is not sufficient to claim direct contact exposure, because the enhanced sensitivity in sediment dilution tests also can be explained by buffering from the sediment matrix. In applying these tests, one should be aware of the fundamental differences between the sediment dilution strategy and the dilution of an aqueous phase and of the consequences it has for the outcome of the test.