Signatures of Indian endosulfan usage in China's environment.

Endosulfan, as an organochlorine pesticide (OCPs), was widely used in agriculture. As the largest endosulfan user country in the world and adjacent to China, it is interesting to know to what extent the endosulfan usage of India could affect the environment in China. In this study, we established gridded endosulfan usage, atmospheric emission, and soil residue inventories in 2010 based on its application in different crops in China and India. We employed an atmospheric transport model CanMETOP to simulate atmospheric and soil concentrations, as well as dry and wet deposition flux of α- and β-endosulfan. Results were used to assess the signatures of Indian endosulfan usage in the China's environment. In 2010, endosulfan usage, atmospheric emissions, and highest soil residue in China were 3083.9, 1312.7, and 587.5 tonnes, and 3204.8, 1441.4, and 463.7 tonnes in India, respectively. The spatial distribution of modeled atmospheric and soil concentrations, and dry deposition fluxes of endosulfan were in line with its usage but wet deposition fluxes were mainly identified in Southern China and Sichuan basin with heavy rainfall, especially for α-endosulfan. Endosulfan tended to transport from India to Tibetan plateau, Yunnan-Kweichow Plateau, and some provinces in southern China under the Indian Summer Monsoon regime. Due to its stronger volatility, α-endosulfan posed a more significant impact on China's environment via the atmospheric transport from India compared to β-endosulfan. Although rainfall during Indian Summer Monsoon reduced endosulfan levels in the air during its journey from India to China, it was observed that Indian endosulfan usage in 2010 contributed more than 50% of atmospheric concentrations and 30% of soil concentrations of α-endosulfan in some regions in Tibetan plateau.