Air-Soil Exchange of Organochlorine Pesticides in a Traditionally Agricultural Region in China: Base on the Bark/Air Partitioning Model

Abstract

Willow barks were collected for OCP analyses in the middle reach of the Huaihe River (MRHR), China. ∑OCPs in the tree barks were 16.00-50.35 ng g -1 (mean: 27.60±7.48 ng g -1 , dry weight). HCHs were the dominant OCPs in the bark samples. The historical usage of technical HCH and DDT considerably impacted the HCHs and DDTs in the barks. Heptachlor, Aldrin, Isodrin, etc., have never been used in China, but they were frequently detected in the barks, indicating their unknown usage or atmospheric transportation from other source regions. Volumetric air concentrations of OCPs were estimated using a model for bark/air partitioning. Calculated air concentrations of ΣDDTs and ΣHCHs were 0.16±0.04 and 10.38±4.13 ng m -3 , respectively. The results of air-soil exchange were: HCB, HCHs, and Heptachlor presented net volatilization; DDTs preferred net deposition; Endosulfan-I and Endosulfan-II might be in equilibrium or presented a weak trend of deposition; and Aldrin was in equilibrium.