Séminaire
Persistent organic pollutants that have accumulated in soils can be re-mobilized by volatilization in response to chemical equilibrium with the atmosphere. Clean air masses from the Indian Ocean, advected with the onset of the summer monsoon, are found to trigger or enhance re-volatilization of the nowadays banned chemicals hexachlorocyclohexane (HCH) and polychlorinated biphenyls (PCBs) from background soils in southern India. The air is polluted during transport by the southwesterly monsoon winds across the subcontinent. For HCH and dichlorodiphenyltrichloroethane (DDT), air-surface exchange has declined since the ban of these substances from agriculture, but re-mobilisation of higher chlorinated PCBs may have reached a historical high, 40 years after peak emission.