Ambient Temperature Modulates Dissipation and Redistribution of Chlorpyrifos and 3,5,6-Trichloro-2-Pyridinol in Paddy Field

Abstract

ABSTRACT Chlorpyrifos is an extensively used insecticide in the agriculture worldwide and was often detected in both surface waters and groundwater, posing threats to local residents’ health. Temporal changes and environmental fate of chlorpyrifos and 3,5,6-trichloro-2-pyridinol (TCP; the main degradation product of chlorpyrifos) were studied in field paddy lysimeters. On the other hand, batch sorption tests of both chlorpyrifos and TCP and dissipation test of chlorpyrifos under submerged condition were conducted for the paddy soil in the laboratory. Following field application, concentration of chlorpyrifos in the floodwater decreased rapidly by >90% of the initial concentration in the first two days. Higher temperature during the daytime, as compared to the nighttime, could not only lead to larger dissipation rates of chlorpyrifos and TCP in the floodwater in the first two days, but also cause greater release of TCP into the soil pore water for more days. A rain event at an early time (i.e., day 2) caused a transient peak release of chlorpyrifos and TCP into the soil pore water; however, no such changes occurred upon later rain or irrigation event(s). In future studies, due attention should be paid to the risk of the runoff and leaching of the weakly sorbing TCP.