HP7 Pyrethroids, Chemistry, Toxicity, and TIE Methods
Room 18C/D, Level 4
2:10 PM - 5:30 PM, Thursday, 13 November 2003
Chair: Lydy, Michael ,
Co-chair: Weston, Don ,
(613) Pyrethroid concentrations and sediment toxicity in agriculture-dominated waterbodies of California.
Weston, D1, You, J2, Lydy, M2, 1 University of California, Berkeley, CA, USA2 Southern Illinois University, Carbondale, IL, USA
ABSTRACT- Approximately 50,000 kg of pyrethroids are used in agriculture within the watersheds of the Sacramento and San Joaquin Rivers (California), yet until recently there had been no data on levels of pyrethroids in aquatic sediments of the region, and sediment toxicity testing had been minimal. Our study examined the sediment chemistry and toxicity at approximately 35 stations distributed across 10 California counties that tended to use the greatest amounts of pyrethroid pesticides. The stations were generally located in waterbodies receiving either runoff or irrigation return flow from agricultural lands, and all stations were sampled twice with sampling timed to target peak pyrethroid use and/or times of expected greatest concentrations. Pyrethroids were measurable in the majority of sediments tested with a detection threshold of 1 ng/g dry sediment. Permethrin was found at the greatest concentrations, with lesser amounts of lambda-cyhalothrin, esfenvalerate, and bifenthrin. Concentrations were usually less than 10 ng/g, though levels as high as 500 ng/g were detected. The same sediments were tested with Hyalella azteca and Chironomus tentans, using both 10-d survival and 10-d growth endpoints. Mortality in excess of controls was seen in about 15% of the 140 tests (35 sites times two sampling events per site times two test species). In a minority of these cases, pyrethroids were present in relatively high concentrations (>100 ng/g) and may have been responsible for the toxicity. In the case of most toxic sediments however, pyrethroid levels were quite low and the causes of toxicity were unknown, though organochlorines (endosulfan, DDT and metabolites) were present and may have been contributing factors.
Key words: sediment toxicity, pyrethroids, Hyalella azteca, Chironomus tentans