Study On Analytical Method Of Volatile Chlorinated Hydrocarbons In Environment And Soil Vapor Extraction For Remediation In A Soil Column

This study aimed at the two most common compounds of volatile chlorinated hydrocarbons TCE and 1,1,1-trichloroethane. In this study, we studied on the Purge-and-Trap gas chromatography in water and soil, and established the gas chromatographic method by the six-way valve quantitative sampling; on the other hand, soil vapor extraction through the one-dimensional soil column experiment on TCE and 1,1,1-trichloroethane contaminated soil was studied. The main results are as follows:(1) Through the orthogonal experiment of the purge flow, purge time and desorption temperature, found that desorption temperature is the most significant affecting factor in the purge and trap process of TCE and 1,1,1-TCA. (2) Optimized purge and trap conditions, purge flow of 50mL/min, purge time of 7min, desorption temperature of 300℃, desorption time of 2min and purge air temperature of 30℃. (3) Established the Purge-and-Trap gas chromatography of the determination on TCE and 1,1,1-TCA in water; the standard working curve of the linear correlation coefficients are 0.9988 and 0.9993, detection limits are 0.75μg/L and 0.10μg/L, and the analysis method is accurate and reliable. (4) Established the Purge-and-Trap gas chromatography of the determination on TCE and 1,1,1-TCA in soil; the standard working curve of the linear correlation coefficients are 0.9944 and 0.9961, detection limit are 0.61mg/kg and 0.41mg/kg, and the analysis method is accurate and reliable. (5) Established the six-way valve gas chromatography of TCE and 1,1,1-TCA in gas; the standard working curve of the linear correlation coefficient of 0.9988 and 0.999, respectively, detection limits are 0.27mg/L and 0.6mg/L, and the analysis method is accurate and reliable. (6) Increasing the air flow of SVE can reduce the remediation time and the total air volume, but the remediation efficiency will be reduced too. (7) Water content on SVE great impact on the remediation process, when the water content increases, TCE, and 1,1,1-TCA decreased the remediation efficiency, but the remediation time also increased, this will tend to increase the cost and time. (8) Increasing soil organic matter will decrease the remediation efficiency, because the organic matter on TCE and 1,1,1-TCA has a high adsorption capacity. (9) Pulsed extraction is more economical than the continuous extraction.