某石油污染含水层降解能力地球化学评估

Geochemical evaluation of biodegradation capacity in a petroleum contaminated aquifer

含水层降解能力是石油类污染场地监控自然衰减需获取的重要参数.通过测定某石油污染场地地下水电子供体(苯系物﹑化学耗氧量)和电子受体/产物(DO﹑NO_3^-﹑Mn^(2+)﹑Fe^(2+)﹑SO_4^(2-)和HCO_3^-)等地球化学指标,分析了电子供受体分布规律,确定了电子受体背景值,采用传统地球化学评估法,计算了所有单井降解能力;在此基础上,引入累积概率曲线法,更科学的评估了场地含水层降解能力,结合地下水更新能力,估算了污染物降解速率;同时,划分了含水层降解能力强弱区.结果显示:该场地单井降解能力为36.49～70.05mg/L,其累积概率拟合曲线符合F(x)=0.008e^(0.07x)指数模型,以此评估含水层降解能力为57.83mg/L.以径流量132m^3/d估算地下水更新能力,估算污染物降解速率为2790kg/a;强降解能力区位于下游源区,面积约为5100m^2,占场地总面积的5.3%;地下水中硫酸盐﹑硝酸盐消耗严重,强化硫酸盐还原和反硝化作用可能是该场地管理修复的一个有效方法.

It is essential to determine the biodegradation capacity when monitoring or enhancing natural attenuation of petroleum in contaminated aquifers.Here,the concentrations of typical electron donorcontaminants(benzene,toluene,ethylbenzene,and xylene,and chemical oxygen demand)and electron acceptors and byproducts(dissolved oxygen,NO3?,Mn2+,Fe2+,SO4 2?and HCO3?)in a petroleum-contaminated aquifer were determined.The background electron acceptor/byproduct concentrations were determined from the electron donor concentrations,and the acceptor/byproduct distributions were characterized.The biodegradation capacity at each well was estimated using a general geochemical evaluation method.The cumulative probability curve method was used withthe general method to evaluate the biodegradation capacities in the aquifer.The biodegradation rates were determined from the biodegradation capacities and groundwater renewal rates,and different biodegradation zones were identified from the biodegradation rates.The biodegradation capacities of the wells were 36.49~70.05mg/L,and the biodegradation capacity cumulative probability curve for each well fitted the exponential equation F(x)=0.008e0.07x.The whole-aquifer biodegradation capacity(determined using the probabilities for the different aquifer parts)was 57.83mg/L and the whole-aquifer biodegradation rate(calculated defining the groundwater renewal rate as the groundwater runoff rate,132m3/d)was 2790kg/a.The downstream source zone was found to have a strong biodegradation capacity.It was concluded that petroleumcontaminants were mainly degraded by the electron acceptors SO4 2?and NO3?reduction.Enhancing SO4 2?and NO3?reduction may be a promising way of managing and remediating the study site.