Assessing environmental fate of β-HCH in Asian soil and association with environmental factors.

Chinese Gridded Pesticide Emission and Residue Model was applied to simulate long-term environmental fate of β-HCH in Asia spanning 1948-2009. The model captured well the spatiotemporal variation of β-HCH soil concentrations across the model domain. β-HCH use in different areas within the model domain was simulated respectively to assess the influence of the different sources of β-HCH on its environment fate. A mass center of soil residue (MCSR) was introduced and used to explore environmental factors contributing to the spatiotemporal variation of β-HCH soil residue. Results demonstrate that the primary emission dominates β-HCH soil residues during the use of this pesticide. After phase-out of the pesticide in 1999, the change in β-HCH soil residues has been associated with the Asian summer monsoon, featured by northward displacement of the MCSR. The displacement from several major sources in China and northeastern Asia shows a downward trend at a 95% confidence level, largely caused by environmental degradation and northward delivery of β-HCH under cold condition in northern area. The MCSRs away from the India and southern and southeastern Asia sources show a rapid northward displacement at a 99% confidence level, featuring the cold trapping effect of the Tibetan Plateau.