ter Laak Thomas L, Mayer Philipp, Klamer Hans J C, Hermens Joop L M
IRAS--Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 2, 3584 CM Utrecht, The Netherlands.
Environ Toxicol Chem. 2007 Oct;26(10):2187-91. doi: 10.1897/07-113R.1.
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.
一些沉积物毒性测试，如微毒性测试，是通过用清洁水稀释受污染的沉积物或水相来进行的。本研究旨在阐明稀释过程如何影响生物体的暴露情况。研究表明，当用水稀释沉积物时，疏水性化合物的自由溶解浓度会通过从沉积物基质中的解吸作用得到缓冲。这种缓冲作用取决于沉积物基质和污染物的特性。因此，污染物混合物的组成会随着稀释而变化，并且沉积物稀释毒性测试中的暴露情况定义不明确。这对这类测试的应用和后续评估提出了质疑。此外，在沉积物稀释测试中相对于淘析液稀释测试经常观察到的较高毒性，并不足以声称是直接接触暴露，因为沉积物稀释测试中增强的敏感性也可以用沉积物基质的缓冲作用来解释。在应用这些测试时，应该意识到沉积物稀释策略与水相稀释之间的根本差异以及它对测试结果的影响。
