Discussion On Extraction Methods Of Total Volatile Organic Compounds In Soil

With the quick development of Agriculture & Industry, the output of harmfulwastes is increasing steadily, with the growing pollution area and pollution grade. Atpresent, TVOCs(total volatile organic compounds) were the most common pollutantsin groundwater. Study on the migration and transform of TVOCs from the surface togroundwater is valuable and meaningful. So, we conducted a method of extract thevolatile organic compounds from soil. Directly extraction is more convenience thanother extractions, using less time, less workloads and testing more samples one timethan soxhlet method.The pretreatment methods and extraction reagents were mainly studied in thispaper. Four volatile halohydrocarbons ( chloroform, carbon tetra- chloride,trichloroethylene, tetrachloroethylene)and six volatile benzene compounds(benzene,toluene, ethyl benzene, p-xylene, m-xylene, o-xylene) were taken as the targetcompounds. They were determined by gas chromatography with automatic headspacesampler. Three pretreatment methods (ambient shake, shake at 40℃ ,shake useultrasound)and ten extraction solutions(water, methanol, cyclohexane, hexane,diethyl ether and five different ratios of cyclohexane and diethyl ether) were studied.The travel form of TVOCs in soil consists of adsorption, diffusion, degradationand so on. Adsorption is a important form, so we will discuss it as a most major aim.The result of compare of three pretreatment methods and ten extraction reagents isjust like below: Diethyl ether and methanol can extract in a higher extraction, and thetime lasts just about 12~24 hours;Shake at 40 ℃ and shake use ultrasound canprovide a warm and catalyze surrounding, which can increase the volatilization andcracking of object pollutant;When the concentration of original dunking is 300mg/L,with shake at 40℃ and shake use ultrasound, the result maybe very high with3351.41μg/L, also maybe very low with 2.24μg/L, putting up an extremely unstablechange.In the experiments of different original concentration of aim pollutant inmethanol with 50mg/L~400mg/L, the extraction percentage of halohydrocarbons is0.85%～3.40%, and the extraction percentage of benzene series is 35.2%～89.3%.The precision is not good with the infection of volatilization loss.In this experiment, the volatile and crack reduce the precision of extractionresults.