Organochlorine pesticide contamination of ground water in the city of Hyderabad

摘要

Organochlorine pesticides are ubiquitous and persistent organic pollutants used widely throughout the world. Due to the extensive use in agriculture, organic environmental contaminants such as HCH, DDT along with other organochlorine pesticides are distributed globally by transport through air and water. The main aim of present study is to determine contamination levels of organochlorine pesticides in the ground water of Hyderabad City. Water samples were collected from 28 domestic well supplies of the city. For this study, random sampling technique was applied, all the samples were collected in high purity glass bottles and refrigerated at 4℃ until analysis. Solid Phase Extraction (SPE) is used for the extraction of organochlorine pesticide residues in water sample. The collected water samples were pre-filtered through a 0.45 μg glass fiber filter (Wattman GF/F) to remove particulate matter and were acidified with hydrochloric acid (6N) to pH 2.5. Methanol modifier (BDH, for pesticide residue analysis, 10 mL) was added to water sample for better extraction. SPE using prepacked reversed phase octadecyl (C-18 bonded silica) contained in cartridges was used for sample preparation. Prior to the extraction, the C-18 bonded phase, which contains 500 mg of bonded phase, was washed with 20 mL methanol. The sample was mixed well and allowed to percolate through the cartridges with flow rate of 10-15 mL/min under vacuum. After sample extraction, suction continued for 15 min to dry the packing material and pesticides trapped in the C-18 bonded phases were eluted by passing 10 mL hexane and fraction was evaporated in a gentle steam of Nitrogen. In all samples pesticide residues were analyzed by GC (Chemito-8510) with Ni~(63) ECD detector. Helium was used as carrier gas and nitrogen was used as make up gas. The injection technique was split/split less. All the samples analyzed were found to be contaminated with four pesticides i.e. DDT, β-Endosulfan, α-Endosulfan and Lindane. DDT was found to range between 0.15 and 0.19 μg L~(-1), β-Endosulfan ranges between 0.21 and 0.87 μg L~(-1), α-Endosulfan ranges between 1.34 and 2.14 μg L~(-1) and Lindane ranges between 0.68 and 1.38 μg L~(-1) respectively. These concentrations of pesticides in the water samples were found to be above their respective Acceptable Daily Intake (ADI) values for Humans.