Spatial distribution, ecological risk evaluation and potential sources of organochlorine pesticides from soils in India

This study was conducted in an attempt to unravel the concentration level, distribution pattern and potential sources of organochlorine pesticide (OCP) residues in the soil samples from northwestern part of Hyderabad city, India. Soil samples were extracted for pesticide residues using Soxhlet extraction procedure. The sample extracts were analyzed by gas chromatograph coupled with quadruple mass spectrometry (GC-qMS). The results reveal that the delta-HCH, p,p'-DDE, endrin ketone and endosulfan sulfate were most frequently detected, while Heptachlor epoxide and p,p'-DDD were least identified pesticides. The total concentrations of organochlorine pesticides in soils vary from 129 to 1,001 mu g kg(-1)-dry weight. The ratio of (DDD + DDE)/DDT in the soils range from 0.74 to 7.81 which indicates the usage of DDT in the recent past. However, the ratio of DDD/DDE in the soils is < 1, which implies that the primary source of p,p''-DDE was probably from DDT. The average ratios of alpha-/gamma-HCH are lower than 1, which suggest that the lindane has been used recently in the soils of the study area. Also, the total organic carbon shows significant positive correlation with the total concentration of OCPs. This study provides a first time systematic baseline data on OCPs in the soils that could be useful to evaluate the impact on the groundwater as well as risk assessment on human health.