Abstract

After the application of a pesticide, only a part of it has an effect on the target, while other part of the pesticide circulates in different environments turning into an environmental risk. In Chile, one of the pesticides widely used is chlorpyrifos (CLP), where the highest percentage is traded at the VI Region. The objective of this study was to quantify the biodegradation of CLP in two Soil Series (Fluventic Haploxerolls) from the VI Region, using a labeled chlorpyrifos with 14Carbon (14C-CLP) in the molecular structure. The biodegradation of CLP was measured for a soil incubation period of 69 days for the Serie O'Higgins (S1), and 57 days for Serie Rancagua (S2). Every three days the 14Co2produced was quantified, also the total 14C-CLP bound and extractable residues in the soil were measured during the process. The results showed that 50 % of the biodegradation was attained after 40 days of incubation for S1, and 24 days in S 2, while at the end of the total period 59.5 % and 61.3 % of pesticide were biodegraded for S1 and S2, respectively. As an approach the GUS index was assessed assuming the 50 % of the CLP biodegradation as the CLP half life, representing a value of 1.38 for S 1 and 0.79 for S2. These indexes indicate CLP as a non leachable product and a low potential risk of groundwater contamination.