Dichlorodiphenyltrichloroethane (DDT) was a commonly used pesticide from World War II through the 1960’s. DDT is generally used to control mosquito populations and as an agricultural insecticide. The pesticide and its degradation products (DDD and DDE) can bioaccumulate within ecosystems having negative implications for animal and human health. Consequently, DDT usage was banned in the United States in 1973. In a contaminant study performed in Escambia Bay, Florida, in 2009, DDT was present in 25% of study sites, most of which were located in the upper bay wetlands. Concentrations were well above the Florida Department of Environmental Protection's (FDEP) Probable Effect Level (PEL) and ratios of DDT and its metabolites indicated a recent introduction to the system. Spring 2017 sampling showed no DDT, DDE at five of six sampling sites and DDD at two of the six sites. Preliminary results for spring of 2018 showed evidence of DDT, DDD and DDE when extracted using EPA methods 3540c and 3620c. Additionally, a solid-phase microwave extraction (EPA methods 3051a and 3546) was run in parallel to compare the results from the two methods. Extracts were analyzed using a gas chromatograph with electron capture detection (GC-ECD) as per EPA method 8081c. Results show the presence of DDE at all five sites tested, DDD at four sites (each method tested positive for three sites, one of the sites differed in each method), and DDT remaining at one site (detected by both methods at one site and only by microwave at second site). Of the five tested sites, three sites exhibited decreasing contamination with increased depth and two sites exhibited generally increasing concentrations. A comparison of methods using a relative percent difference suggests error in one or both analytical methods, with average differences of 76% and 97% for DDE and DDD, respectively. The microwave extraction resulted in a higher concentration of contaminants in over two-thirds of the contaminated samples.

DDT extraction and analysis: A comparison of methods

2019 Spring National Meeting

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