挥发性有机物污染土壤样品采样方法比较

以苯系物污染土壤样品的采集为例,比较了4种不同采样方法导致样品检测结果的差异。其中,方法 1将样品装填至广口瓶内并压实密封,方法2采用非扰动采样器采集10 g样品后转移至加有10 mL甲醇保护剂的Vial瓶中密封,方法 3用非扰动采样器采集10 g样品后直接将其密封于采样器内,方法 4用Encore采样器采样后将其密封于采样器内。结果表明,方法 2采集样品的检出率最高,其余3种方法的差异不明显,方法 2采集样品的检出结果 71%以上都大于其余3种方法。而且,对于挥发性较强的苯与甲苯,以方法 2采集的样品91%以上都大于其余3种方法,最大及平均检出浓度高出2~3个数量级。5种不同土质样品检测结果表明,对于有机质含量较低的细砂,方法2的最高及平均检出浓度均高于其余3种方法 1~3个数量级,差异随土壤有机质含量的升高而降低。可见,对于苯系物及挥发性强于苯系物的其他挥发性有机物污染土壤样品的采集,方法 2效果最优,可指定为VOCs污染场地土壤样品的采样方法。

Comparison of Different Sampling Methods for Soil Contaminated by VOCs

Taken soil contaminated by BTEX as an example, the difference among analysis results brought out by 4 different sampling methods were compared. For method 1, contaminated soil was filled into jar manually and compacted until the jar was full and then sealed. For method 2, about 10 g soil was collected with a common core sampler without any disturbance to the soil sample and then transferred and sealed into a Vial where 10 mL methanol was added in advance. For method 3, the soil sample was sealed in the sampler used in method 2 immediately after it was collected. And for method 4, a specific sampler named Encore was used to collect the sample without any disturbance and the sample was also sealed in the sampler immediately. The analysis results reveal that the detection rate for method 2 is the highest, while there is no obvious difference among the other three. More than 71% percent of samples collected using method 2 is higher than the samples collected using the other three methods in analysis results. Furthermore, for benzene and toluene, which are much more volatile, more than 91% percent of samples collected using method 2 are higher in analysis results than the samples collected by the other threes methods. And, the highest and average concentration analyzed for the two contaminants are higher by 2-3 orders. For the 5 different soil textures investigated in the paper, the highest and average concentration detected in samples collected by method 2 are higher by 1-3 order in sandy soil, and the difference will become less obvious as the organic carbon content in soil increase. Therefore, it can be concluded that method 2 is the most appropriate sampling method for BETX and some other more volatile organic contaminants, and can be recommended as the designated method used to sample soil polluted by VOCs during contaminated site investigation.