PH11 Bioaccumulation and Biotransformation of POPs
Exhibit Hall
8:00 AM - Thursday, 13 November 2003
(PH116) Analytical Uncertainty and bioavailability of pesticides in Lake Apopka Restoration Area soils.
Richter, S1, Schell, J2, 1 St. Johns River Water Management District, Palaka, FL, USA2 BBL Sciences, Tallahassee, FL, USA
ABSTRACT- As part of an on-going state-wide wetlands restoration program, the St. Johns River Water Management District converts former agricultural lands back to their natural state. In 1998, at a restoration area on the north shore of Lake Apopka, the conversion resulted in a large influx of migratory birds to recently flooded fields. Over a 4-month period in the winter of 1998-1999, hundreds of fish-eating birds died, primarily white pelicans. Given the historic agricultural use of persistent chlorinated pesticides, these compounds were investigated as a possible causal agent. Due to reported discrepancies in the analysis of these compounds in bird tissues, particularly toxaphene, an inter-laboratory round-robin program was initiated for soil. Six labs analyzed an Apopka soil sample (TOC about 38%). Five labs used sonication extraction following EPA Method 8081. One lab used a Soxhlet extraction procedure with a non-standard solvent that was developed many years ago and used routinely for soil analysis. Except for cleanup, all other analytical conditions were consistent among the labs. Unexpectedly, the Soxhlet toxaphene results were about 5 times higher than the sonication values (e.g., 150 ppm vs. 30 ppm). To try to understand these findings, an extraction study was undertaken using 30 Apopka soil samples with varying levels of organochlorine pesticides and organic carbon. Soxhlet extraction consistently gave results that were 3 to 5 times higher than sonication. These data provide interesting findings regarding appropriate analytical methodologies for these areas including: the dramatic impact TOC has on the extractability of chlorinated organic compounds from sediments, and the uncertainty inherent in analytical results used to estimate potential environmental bioavailability and ecological risks. These uncertainties may result in overestimates or underestimates of risks, depending upon the analytical method used.
Key words: bioaccumulation, Apopka, sediments, toxaphene