DDT, Chlordane, and Hexachlorobenzene in the Air of the Pearl River Delta Revisited: A Tale of Source, History, and Monsoon

Although organochlorine pesticides (OCPs) have been banned for more than three decades, their concentrations only decreased gradually. This may be largely attributable to environmental persistence, illegal application, and exemption usage. study assessed the historic current regional context dichlorodiphenyltrichloroethane (DDT), chlordane, hexachlorobenzene (HCB), which were added Stockholm Convention in 2001. An air sampling campaign was carried out 2018 nine cities of Pearl River Delta (PRD), where historical OCP application most intensive China. Different seasonalities observed: DDT exhibited higher summer winter; chlordane showed less seasonal variation, whereas HCB winter. The unique coupling monsoon with DDT-infused paint usage, winter HCB-combustion emission, local emission jointly presents a dynamic picture these OCPs PRD air. We used BETR Global model back-calculate annual emissions, accounted insignificant contributions nationally documented production (<1‰). Local emissions main sources p,p'-DDT while ocean limited (<4%). shows that geographic-anthropogenic factors, including source, history, circulation pattern, combine affect fate compounds.