Determination Volatile Organic Compounds Of Soils And Sediments

The methods of treatment technology of volatile organic compounds (VOCs) in soil and sediment samples are reviewed. The main methods have mentioned as follows: extraction, static headspace, purge and trap, membrane introduction, with the principles and applications of all methods are discussed in detail, as well as the introduction of the technology of sampling and preservation. This paper studies the followings:(1)A method for the determination of trace volatile thioether in waters,has been developed with purge and trap pre-concentration followed by GC-MS analysis in SIM mode. The ideal experimental conditions were as follows:purge time of 10 min,desorb time of 3 min,desorb temperature of 225℃, purge temperature of 30℃. Under these conditions, the linear responses were observed for DMS, EMS and DES in the ranges of 0.8~27.0,0.8~27.0 and 0.8~26.0μg/L, with correlation coefficients(r) of 0.9998,0.9 999 and 0.9999,respectively.The relative standard deviations(n=6) were all below 6.0%. The detection limits of the method were 0.31,0.15 and 0.21μg/L for DMS, EMS and DES, respectively. The recovery was between 90.7%~104.7%.(2)The volatile thioether in sediments were determined by water leaching supernatant-purge and trap-gas chromatograph-mass spectrometry. Experimental parameters impacting the performance, such as the mass of sediment, the pH and concentration of supernatant solution, were investigated. Under the optimized conditions, the relative standard deviations of DMS, EMS and DES were 5.46%~7.31%, the recovery was between 86.36%~101.25%.(3) The volatile organic compounds(halohydrocarbon, benzenes and chlorobenzenes) in soil/sediments were determined by water leaching supernatant-purge and trap-gas chromatograph-mass spectrometry. Experimental parameters impacting the performance ,such as the mass of sediment, the pH and concentration of supernatant solution, were investigated. Under the optimized conditions, the relative standard deviations of VOCs were 2.63%~11.63%, the recovery was between 66.53%~90.77%, which may relate to the kind of soil/sediments.(4)Adsorption and desorption characteristics of low concentrations volatile organic compounds(VOCs) on soils and sediment surfaces were investigated at natural condition.The result revealed that, adsorption and desorption isotherm of VOCs on soils and sediment can be described by linear and freundlichb models.The results of adsorption indicated that the adsorption process cann't find competitive adsoption of different organic compounds , adsorption process also belong to physical adsorption. The results of desorption indicated that the hystersis phenomena appeared during the desorption process,and the hystersis coefficients of the herbicides in soils and sediments are greatly different.