Assessment, Composition and Possible Source of Organochlorine Pesticides in Surface Soils from Ürümqi, China

Abstract

Twenty–eight surface soil samples from 5 functional zones (park, traffic roadside, business/residential area, rural area, and industrial area) of Ürümqi, China were collected and analyzed for the concentrations of 14 organochlorine pesticides (OCPs), such as 3 isomers of hexachlorocyclohexane (HCHs) (α–HCH, β–HCH, and γ–HCH), 4 dichlorodiphenyltrichloroethanes (DDTs) (p, p′–DDT and its metabolites p, p′–DDD (1,1–dichloro–2,2–bis(p–chlorophenyl)ethane) and p, p′–DDE (1,1–dichloro–2,2–bis(4–chorophenyl)ethylene), and o, p′–DDT), and methoxychlor, aiming to survey the residue levels and compositions of these 14 OCPs, to identify possible sources of the OCPs, and to assess their potential risks to human health and the environment in surface soils of Ürümqi. The concentrations ranged from non–detected to 30.86 μg kg−1 for HCHs (sum of α–, β–, and γ–HCH), from non–detected to 40.03 μg kg−1 for DDTs (sum of p, p′–DDT, p, p′–DDD, p, p′–DDE, and o, p′–DDT), and from non–detected to 11.95 μg kg−1 for methoxychlor. The total concentrations of the OCPs ranged from 16.40 to 84.86 μg kg−1, with a mean of 41.89 ± 16.25 μg kg−1. According to the measured concentrations and occurrence rates of the 14 OCPs, DDTs, HCHs, and methoxychlor were the most dominant compounds. Among the 5 functional zones, the total concentration of OCPs was in the order of rural area > traffic roadside > park > business/residential area > industrial area. The different compositions of DDTs and HCHs indicated that the residues of these compounds in most soil samples originated from historical application, besides slight recent introduction at some sampling sites. The results of Pearson correlation analysis showed that soil total organic carbon played an important role in the residue levels of HCHs, but such relationships were not found with DDTs or other OCPs. The soil quality of Ürümqi was classified as Class I based on the guidelines of the Chinese Environmental Quality Standard for Soil (GB15618–1995), indicating that the residue levels of OCPs have little risks to the environment and human health in the study area.