Transformation of Chlorpyrifos and Chlorpyrifos-Methyl in Prairie Pothole Porewaters

Tuesday, 16 December 2014
Rachel May Anderson and Yu-Ping Chin, Ohio State University Main Campus, Columbus, OH, United States
The prairie pothole region (PPR) extends over approximately 700,000 km2 in the Great Plains region in United States and Canada and is a critical breeding ground for migratory waterfowl, as well as an important ecosystem for diverse invertebrates and aquatic plants (van der Valk, 2003). Consisting of up to 12 million permanent and temporary depressional wetlands, the PPR is negatively impacted by non-point source pesticide pollution due to extensive agricultural development in the region. Recent studies have shown that high (mM) levels of sulfate in the pothole lakes are capable of abiotically reducing dinitroaniline and chloroacetanilide pesticides (Zeng, 2011; Zeng, 2012). In this study the transformation of the organophosphorus pesticide chlorpyrifos (CP) and its analog chlorpyrifos-methyl (CPM) was studied using pore waters sampled from two pothole lakes. CP and CPM have been found to react in the laboratory with sulfur species via a SN2 mechanism, with degradation by sulfur compounds occurring faster than hydrolysis at high pH (Wu, 2006). To date the reaction of CP and CPM in natural environments with sulfur species has not been studied. Chlorpyrifos-methyl underwent rapid degradation in the presence of reduced sulfur species in pore water, while chlorpyrifos degradation occurred at significantly slower rates. Both CP and CPM degradation occurred at comparable rates to what has been previously observed in the laboratory (Wu, 2006).


van der Valk, Arnold G., and Roger L. Pederson. "The SWANCC decision and its implications for prairie potholes." Wetlands 23.3 (2003): 590-596.

Wu, Tong, Qiu Gan, and Urs Jans. "Nucleophilic Substitution of Phosphorothionate Ester Pesticides with Bisulfide (HS-) and Polysulfides (Sn2-)." Environmental science & technology 40.17 (2006): 5428-5434.

Zeng, Teng, et al. "Pesticide processing potential in prairie pothole porewaters."Environmental science & technology 45.16 (2011): 6814-6822.

Zeng, Teng, Yu-Ping Chin, and William A. Arnold. "Potential for abiotic reduction of pesticides in prairie pothole porewaters." Environmental science & technology 46.6 (2012): 3177-3187.