1,2-二氯乙烷自然衰减过程中模拟饱和含水层的氧化还原条件变化

Dynamics of Redox Environment during Natural Attenuation of 1,2-Dichloroethane in a Laboratory Aquifer Column

为研究自然条件下饱和含水层中1,2-DCA(1,2-二氯乙烷)的自然衰减过程及该过程中含水层氧化还原环境的变化特征,利用室内连续水流土柱模拟饱和含水层,研究生物降解作用对1,2-DCA自然衰减的贡献以及饱和含水层环境条件的动态变化规律.初始ρ(1,2-DCA)为50 mg/L,模拟地下水流速为450μL/min,模拟试验连续进行30 d,分别监测ρ(1,2-DCA)和水环境指标.结果表明,1,2-DCA自然衰减的一级速率常数为0.068 9 d-1,其中生物降解作用的贡献率为6.34%.1,2-DCA自然衰减过程中,NO3-首先充当生物降解的电子受体,随后Fe3+、SO42-依次发生反应,土柱内部不同高度出现了氧化还原分带,分别是硫酸盐还原带、铁盐还原带、硝酸盐还原带.

Redox condition in saturated aquifers is one of the significant factors influencing natural attenuation of 1,2-Dichloroethane （1, 2-DCA）. In order to investigate the natural attenuation process of 1,2-DCA and its related redox environment variation in a saturated aquifer, a continuous-flow simulation column system was operated in the laboratory. The contribution of biodegradation and the dynamic variation of the redox conditions in the aquifer were studied. The initial concentration of 1,2-DCA was set to 50 mg/L. The velocity of groundwater flow was simulated at a rate of 450 μL/min. A 30 day simulation was conducted, with samples taken every seven days to monitor variation of pollutant concentrations and various redox indicators in the aquifer. The results showed that the estimated first-order decay constant was 0. 0689 d-1, and the contribution of biodegradation to natural attenuation was 6.34%. During the natural attenuation process, NO3 - was first taken as the dominant electronic aeceptor, followed by Fe3＋ and SO42- . Sequential redox zones （sulfate-reducing zone, iron-reducing zone and nitrate-reducing zone, respectively） were observed in the aquifer columns at different distances from the water inlet.