Studies on the Behavior of 14C-chlorpyrifos in a Model Rice Ecosystem

Fate of ¹⁴C-chlorpyrifos was studied in a model rice ecosystem. The level of ¹⁴C-residues in floodwater showed initially a rapid decline in first 10 days. These residues were observed till 30 days. The insecticide residues in soil did not show any appreciable build-up, thereby indicating that the residue levels of this insecticide may not be significant. Extractable residues were formed up to 10–13% of the applied ¹⁴C-activity during the period of 136 days, while the bound fraction of ¹⁴C-residues reached a maximum of 2.9% after 92 days. Algae and rice plants showed ¹⁴C-residues to the extent of only 0.01% of the applied ¹⁴C-activity. Rice grains did not show any residues at all. These results indicate that chlorpyrifos undergoes considerable degradation in rice soils and does not leave residues, which may be of environmental concern.