通风速率对汽油污染土壤通风效率的影响及修复时间的预测

Effects of Airflow Velocity on the Venting Efficiency of Gasoline Polluted Soil and the Estimation of Remediation Time

原位通风处理土壤石油烃污染对于土壤和地下水的有机污染控制具有极其重要的现实意义。本文以实地砂土,通过土柱试验研究了不同通风速率对土壤中汽油烃的去除效率,并通过土壤汽油烃含量和土壤挥发性有机物的监测数据估计了通风修复时间。结果表明,真空抽提通风速率越大,土壤中的汽油烃去除速率越快,但通风速率由400mL·min-1提高到800mL·min-1,土壤污染物修复效果差异不太明显,最佳的土壤通风速率为400mL·min-1。土壤汽油烃监测数据的指数拟合曲线和土壤挥发性有机物监测数据进行的对数拟合曲线都能反映土壤污染物的衰减情况,二者分析得到的污染物通风修复时间有一定相关性。因为土壤挥发性有机物易于监测,可以以土壤气体中总挥发性有机物(TVOC)来估计土壤中污染物的衰减和估计土壤通风净化时间,并在实际土壤通风修复过程中通过土壤气体中TVOC的监测反映土壤污染修复状况,当TVOC浓度降低到10mL·m-3以下时,修复过程基本可以结束。

In situ remediation of petroleum hydrocarbon has significance to the organic pollution control of soil and groundwater. The influence of air extracting velocity on the efficiency of soil venting was studied with column test using the field sand. And the remediation time was estimated by numerical fitting results based on the data of total petroleum hydrocarbons （TPH） in soil and that of the total volatile organic compounds （TVOCs） monitored during the soil venting process. The results showed that the greater the soil venting velocity, the faster the gasoline pollutant was removed from sand column. But when the venting velocity rose from 400 mL·min^-1 to 800 mL·min^-1, the remediation time changed little. So the optimal venting velocity was 400 mL·min^-1 There was certain correlation between the estimated result of remediation time based on the exponential/logarithm numerical fitting of TVOCs in soil gas and that of the exponential numerical fitting of TPH in soil. And these two monitoring indexes both could indicate the attenuation of the gasoline in soil. But as TVOCs in soil was easy to be monitored, it could be used to estimate the remediation time of soil venting based on the numerical fitting and be used to monitor the remediation status in real venting remediation process. When the value of TVOCs was lower than 10 mL·m^-3, the soil venting process could be closed.