Yang Yang, Li Juan, Xi Beidou, Wang Ying, Tang Jun, Wang Yue, Zhao Chuanjun
School of Environment, Beijing Normal University, Beijing, 100875, China; State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
J Environ Manage. 2017 Dec 1;203(Pt 1):114-122. doi: 10.1016/j.jenvman.2017.07.068. Epub 2017 Aug 3.
Contaminant spills in vadose zone are frequently encountered in winter, and the temperature at such times is often under 0 °C. Soil vapor extraction (SVE) is typically effective for the removal of volatile contaminants from vadose zone, but temperature influences its effectiveness. A sandbox laboratory evaluation and a TMVOC numerical model were used to investigate BTEX migration that occurred during SVE remediation processes under low temperatures. The simulation results were consistent with the experimental data obtained in the present study, and the following three conclusions were drawn. (i) The SVE removal rates of benzene, toluene, ethylbenzene, and o-xylene were 89.8%, 71.3%, 29.7%, and 14.4%, respectively. (ii) In two extraction processes, the masses of benzene and toluene in the gas-aqueous-NAPL phases decreased by approximately 20%:70%:10%, with the greatest reduction occurring in the aqueous phase. During the period between these two extraction processes, benzene and toluene migrated from the NAPL phase to the gas and aqueous phases, and their fractions were approximately 30%:70%. (iii) The results proved that under low-temperature conditions, namely -10-5 °C, the SVE removal ratio for benzene was highest among the four tested contaminants. It was therefore determined that TMVOC can provide scientific guidance for determining whether to optimize or terminate SVE operations under low-temperature conditions.
包气带中的污染物泄漏在冬季经常发生，此时的温度通常低于0°C。土壤气相抽提（SVE）通常对从包气带中去除挥发性污染物有效，但温度会影响其效果。利用一个沙箱实验室评估和一个TMVOC数值模型来研究低温下SVE修复过程中发生的BTEX迁移。模拟结果与本研究获得的实验数据一致，并得出以下三个结论。（i）苯、甲苯、乙苯和邻二甲苯的SVE去除率分别为89.8%、71.3%、29.7%和14.4%。（ii）在两次抽提过程中，气-水-NAPL相中的苯和甲苯质量减少了约20%:70%:10%，其中水相减少最多。在这两次抽提过程之间，苯和甲苯从NAPL相迁移到气相和水相，其比例约为30%:70%。（iii）结果证明，在-10-5°C的低温条件下，苯的SVE去除率在四种测试污染物中最高。因此确定TMVOC可以为低温条件下确定是否优化或终止SVE操作提供科学指导。
