Acute Toxicity of Sediment-Sorbed Endrin, Methoxychlor, and Endosulfan to Hyalella azteca and Chironomus tentans

摘要

Although once widely used, most organochlorine pesticides (OCs) have been de-registered in the United States for 20-30 years. Due to their hydrophobic nature, OCs tend to accumulate and persist in sediments. Currently, sediment residues of OCs are still routinely found in aquatic environments and depending on their availability to aquatic organisms, they may pose a significant threat (You et al. in press). In our previous study (Weston et al. 2004), 70 sediments samples were collected and toxicity evaluated from a 10-county area in the agriculturally dominated Central Valley of California. In this study, pyrethroids were determined to be the main contributor to the observed toxicity of the collected sediments; however, residues of OCs including endrin, methoxychlor and endosulfan were detected routinely and may be responsible for the toxicity found at several sites. Endrin has been banned for agricultural use for more than two decades, while endosulfan and methoxychlor are currently being applied for a variety of agricultural activities. To assess the toxicity data in our previous study (Weston et al. 2004), an extensive literature review was performed of 10-d sediment LC50 values of OCs for H. azteca and C. tentans. However, the information on the acute lethality of endrin, endosulfan and methoxychlor in sediments to these two aquatic organisms was lacking. Therefore, the objectives of this study were to fill data gaps by conducting 10-d sediment toxicity tests with endosulfan (the alpha- isomer, beta-isomer and endosulfan sulfate compounds individually), endrin and methoxychlor to H. azteca and C. tentans. In addition, the relative sensitivity of the selected OCs also was compared between the two species.