Comparison of Soil VOCs measured by soil gas, heated headspace, and methanol extraction techniques

Comparisons of soil volatile organic compound (VOC) measurement techniques and soil properties expected to influence these measurements were performed at two dissimilar sites. A total of 41 soil gas, 52 heated headspace, and 51 methanol extraction/purge‐and‐trap measurements were obtained on collocated samples. Contaminants present at both sites included cis‐1,2‐dichloroethene, 1, 1, 1‐trichloroethane, trichloroethene, and tetrachloroethene. Heated headspace offered the highest sensitivity, as indicated by the greatest percentage of detections per number of analyses. The statistical regression between headspace concentrations and methanol extraction concentrations was highly significant (p < 0.001) with r2 = 0.53. Headspace concentrations (range, 7 to 4250 ng/g) ran approximately 20 to 30% of the methanol extraction concentrations (range, 260 to 7300 ng/g), indicating that the methanol was able to extract significantly more of the chlorinated hydrocarbons (CHCs) than the headspace extraction, even in soil...