State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum-Beijing, Beijing, 102249, China.
State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum-Beijing, Beijing, 102249, China.
Chemosphere. 2024 Aug;361:142551. doi: 10.1016/j.chemosphere.2024.142551. Epub 2024 Jun 7.
The fate of volatile organic compounds (VOC) vapors in the unsaturated zone is the basis for evaluating the natural attenuation potential and vapor intrusion risk. Microcosm and column experiments were conducted to study the effects chemical speciation and soil types/properties on the fate of petroleum VOCs in unsaturated zone. The biodegradation and total attenuation rates of the seven VOCs obtained by microcosm experiments in black soil and yellow earth were also generally higher than those in floodplain soil, lateritic red earth, and quartz sand. The VOC vapors in floodplain soil, lateritic red earth, and quartz sand showed slow total attenuation rates (<0.3 d). N-pentane, methylcyclopentane, and methylcyclohexane showed lower biodegradation rates than octane and three monoaromatic hydrocarbons. Volatilization into the atmosphere and biodegradation are two important natural attenuation paths for VOCs in unsaturated soil columns. The volatilization loss fractions of different volatile hydrocarbons in all five unsaturated soils were generally in the order: n-pentane (93.5%-97.8%) > methylcyclopentane (77.2%-85.5%) > methylcyclohexane (53.5%-69.2%) > benzene (17.1%-73.3%) > toluene (0-45.7%) > octane (1.9%-34.2%) > m-xylene (0-5.7%). The fractions by volatilization into the atmosphere of all seven hydrocarbons in quartz sand, lateritic red earth, and floodplain soil were close and higher compared to the yellow earth and black soil. Overall, this study illustrated the important roles chemical speciation and soil properties in determining the vapor-phase transport and natural attenuation of VOCs in the unsaturated zone.
挥发性有机化合物（VOC）蒸气在非饱和带中的命运是评估自然衰减潜力和蒸气入侵风险的基础。本文通过微宇宙和柱实验研究了化学形态和土壤类型/性质对非饱和带中石油 VOC 命运的影响。还通过微宇宙实验研究了黑土和黄土中七种 VOC 的生物降解和总衰减速率，结果表明，黑土和黄土中七种 VOC 的生物降解和总衰减速率通常高于冲积土、红壤和石英砂中的。冲积土、红壤和石英砂中的 VOC 蒸气表现出缓慢的总衰减速率（<0.3 d）。正戊烷、甲基环戊烷和甲基环己烷的生物降解率低于正辛烷和三种单环芳烃。挥发进入大气和生物降解是非饱和土壤柱中 VOC 的两种重要自然衰减途径。五种非饱和土壤中不同挥发性烃类的挥发损失分数通常为：正戊烷（93.5%-97.8%）>甲基环戊烷（77.2%-85.5%）>甲基环己烷（53.5%-69.2%）>苯（17.1%-73.3%）>甲苯（0-45.7%）>正辛烷（1.9%-34.2%）>间二甲苯（0-5.7%）。在石英砂、红壤和冲积土中，所有七种烃类通过挥发进入大气的分数与黄土和黑土相比接近且更高。总体而言，本研究说明了化学形态和土壤性质在确定非饱和带中 VOC 的气相传输和自然衰减中的重要作用。
