加油站油类污染物自然衰减现场试验研究

利用自行设计制作的一套土壤气体取样监测装置,在北京地区某加油站开展了包气带内石油类污染物自然衰减的现场试验研究.在现场对包气带内的土壤气体样本进行采集,并对样本中的VOC含量及O2、CO2含量进行了检测分析.2个阶段的检测结果表明,经过381 d的自然衰减,污染点位的TVOC浓度减少了99.2%,BTEX的气相浓度占TVOC的比例由17.0%降至12.1%;O2和CO2含量在G3点位呈现出随着土壤深度的增加,O2含量逐渐减少、CO2含量逐渐增加的变化趋势.通过对试验结果的分析得出以下结论:①第一次检测结果表明G3点位附近存在一定的土壤污染,经过381 d的自然衰减,G3点位土壤中的BTEX含量已降至保护环境的标准以下,该污染现场的环境监控措施可以解除;②对造成该点污染的原因进行推断,可以判定污染为短期污染源导致,不存在持续的泄漏源;③自然衰减能够有效清除土壤中污染物,可以作为北京市同类污染场地有效的治理手段加以考虑;④检测污染土壤中O2和CO2含量的变化是判断有机污染物需氧降解的有效手段.

In situ Experimental Research on Natural Attenuation of Oil Pollutants in a Gas Station

The natural attenuation rules of oil pollutants are investigated by carrying out a field experiment in a gas station in Beijing, using a set of soil gas sampling and monitoring device designed independently. The samples of soil gas were collected in the field and tested to examine the content of O₂, CO₂and VOCs in the unsaturated zone. The results show that after 381 days' natural attenuation, the concentration of the contaminants at the polluted point deceased by 99.2%, while the ratio of BTEX to TVOC decreased from 17.0% to 12.1%. Moreover, the content of O₂ decreased while that of CO₂ grew as the soil depth increases at G3 point. Further theoretical analysis indicated that:1The test results of first-step experiment show that there was a certain level of contamination in G3 area. And after 381 days' natural attenuation, the content of the BTEX at G3 point fell below the environmental standard level, which means the control measures could be removed. 2The origin of the contamination was proved as short-term sources, and no long-term sources of leakage existed. 3An effective removal of contaminants in the soil was found under the influence of the natural attenuation. This method could be applied in long-term monitoring for similar contaminated sites.4The test of O₂and CO₂contents was proved to be an effective approach to determine if the aerobic degradation happens.