石灰岩含水介质中苯系物(BTEX)生物可降解性判识

Potential Biodegradability of BTEX in the Aqueous Solution Containing Limestone

岩溶含水系统遭受石油烃污染的环境问题十分普遍。相对于多孔含水介质,石油烃BTEX在石灰岩含水介质中的生物可降解性还不确定。为此,本研究开展了BTEX在石灰石和岩溶地下水介质中的静态微元体实验。经过77天的实验检测分析,结果表明:(1)BTEX化合物在可利用电子受体溶解氧或硝酸盐存在条件下具有生物可降解性;(2)向系统中补充电子受体硝酸盐,具有促进生物降解的作用,其对BTEX的去除率可高达94%;(3)未发现补充硫酸盐能够促进BTEX生物可降解性;(4)甲苯和二甲苯容易被生物降解,但苯的去除具有一定的难度。

Currently, karst groundwater contaminated by petroleum hydrocarbons is increasingly common, but few researches focus on such contamination especially in karst subterranean river. In such cases, perhaps biodegradation is a good way to remove contaminants. However, there is few experimental evidences to support this method. To better understand the biodegradation of BTEX compounds that are greatly concerned among petroleum contaminants, a microcosm experiment was performed to examine the BTEX biodegradability in limestone aqueous medium, using limestone and fresh karst groundwater. Four groups including control, nitrate amendment, sulfate amendment and free amendment cases were designed. In the control group （P0）, concentrations of nitrate and sulfate had no change during the period from day 7 to day 77, but concentrations of dissolved oxygen had obvious changes due to incomplete sterilization. In nitrate-amended group （P1）, the amendments of nitrate stimulated the BTEX attenuation in concentration from 2.085 mg/L to 0.129 mg/ L. Nitrite as an intermediate was first accumulated and then disappeared. In sulfate-amended group （P2）, concentrations of both sulfate and BTEX were basically stable, indicating that no enhancement occurred in the groups. In no addition group （P3）, the removal rate of BTEX was 15% （excluding the value in P0 group）. Our data shows that ： （1） BTEX compounds have biodegradability in the presence of available electron acceptor like dissolved oxygen or nitrate; （2） amendment of nitrate can enhance the BTEX biodegradation to reach a removal rate of 74%; （3） amendment of sulfate has no effect on the BTEX biodegradation; （4） methylbenzene and xylene are readily biodegraded, but benzene is difficulty.