Occurrence and sources of selected organochlorine pesticides in the soil of seven major Indian cities: Assessment of air-soil exchange.

India is an agricultural country and organochlorine pesticides (OCPs) accounts for nearly three fourth of the annual pesticide consumption. Selected OCPs were therefore quantified in 81 soil samples along urban-suburban-rural transect from New Delhi and Agra in the north, Kolkata in the east, Mumbai and Goa in the west and Chennai and Bangalore in the southern part of India. ΣOCPs ranges from 2 to 410 ng/g dry weight (Mean, 35) with dominance of endosulfan sulfate in the rural sites. Urban centers and suburbs reflects OCP usage for vector control. Lower winter temperature in New Delhi favored site-specific deposition of most OCPs in soil. Volatilization of OCPs from soil occurred in the Indian cities having higher ambient temperature. Due to the compounded impact of past and ongoing usage of selected OCPs like DDT, a sporadic cycle of emission and re-emission from Indian soil is expected to continue for many more years to come.