1.Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences;2.Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment
【研究目的】氯代烃、苯系物等有机污染物对我国地下水水质造成重要威胁，监控自然衰减技术在场地污染修复中发挥着重要作用，研究监控自然衰减技术，有利于推动场地污染控制与修复技术发展。【研究方法】本文通过对某化工污染场地地下水中1,2,3-三氯丙烷（TCP）和苯3年的长期监测，对地下水污染物浓度、氧化还原电位（ORP）、硝酸盐浓度的变化及微生物多样性进行分析，研究了场地不同含水层TCP和苯的自然衰减特征，并采用一级衰减动力学方程，计算了污染源区TCP和苯自然衰减能力。【研究结果】结果表明：研究区地下水存在不同程度的TCP和苯的自然衰减；潜水及承压含水层地下水ORP值分别为-225~-57 mV和-182~-3 mV，为中-强还原环境，具备有机污染物厌氧生物降解基础环境条件；与非污染源区、承压含水层相比，污染源区、潜水含水层地下水微生物自然衰减作用更强，其中，污染源区MMW02监测井潜水含水层地下水TCP和苯的降解率分别为80.00% 和77.88%；潜水含水层TCP和苯的衰减速率分别为0.0018 d-1和0.0016 d-1，承压含水层TCP和苯的衰减速率分别为0.001 d-1和0.0015 d-1。【结论】有机污染场地地下水中存在明显的微生物自然衰减作用，但衰减速率较低，场地单纯依靠监控自然衰减的修复时间可能需要数十年甚至更长，因此需要与其他修复技术相结合建立地下水有机污染修复体系。
[Objective] Organic pollutants, such as chlorinated hydrocarbons and BTEX, have a major threat to the groundwater quality in our country. Natural attenuation monitoring plays an important role in the remediation technologies of contamination sites. The study of natural attenuation monitoring will be conductive to promoting the development of contaminated site control and remediation. [Methods]In order to study the natural attenuation of 1,2,3-trichloropropane (TCP) and benzene in different aquifers groundwater, the 3-year monitoring data of TCP, benzene, oxidation reduction potential (ORP), nitrate (NO3-) and biodiversity in an organic contaminated site has been collected and analyzed. Natural attenuation capacity of the pollution source area of the site was calculated using first order decay dynamics equation. [Results]The results showed that the natural attenuation of TCP and benzene occurred in the aquifer, and ORP values of phreatic and confined aquifer groundwater were -225~-57 mV and -182~-3 mV, respectively, which meant medium-high reducing environment, and anaerobic biodegradation of organic pollutants could be happened. Moreover, the effect of micro-biological degradation was stronger in the pollution source area and phreatic aquifer groundwater than that in non-pollution source area and confined aquifer, and the degradation rates of TCP and benzene in the phreatic aquifer of MMW02 monitoring well were 80.00% and 77.88%, respectively. The attenuation rate of TCP and benzene were 0.0018 d-1 and 0.0016 d-1 in phreatic aquifer, and 0.001 d-1and 0.0015 d-1 in confined aquifer. [Conclusions] Natural attenuation by microorganisms exists obviously in the groundwater contaminated by organic pollutants, but the decay rate is lower. The remediation time of the site will be longer by natural attenuation simply. Therefore, the effective remediation system for organic contamination in the groundwater should be established by the combination of natural attenuation with other technologies.