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基于野外原位抽注试验和同位素技术的含水层反硝化速率研究
郇环1, 刘兵2, 朱岗辉1, 刘梦娇1, 刘伟江1, 姜永海3
1.生态环境部土壤与农业农村生态环境监管技术中心;2.防灾科技学院;3.中国环境科学研究院
摘要:
反硝化作用是地下水硝酸盐污染去除最重要的过程。由于水文地质条件和水文地球化学环境的复杂性和不确定性,精准测定含水层反硝化速率是反硝化过程的研究难点。选取潮白河冲洪积扇中部中国环境科学研究院地下水创新野外基地作为研究区,基于野外原位试验和15N同位素示踪法提出一种含水层反硝化速率的测定方法。该方法综合体现了研究区实际水文地质条件和水文地球化学环境对反硝化作用的影响,以及充分考虑了硝酸盐在含水层中稀释弥散作用对计算结果的影响。研究显示:①潮白河冲洪积扇中部某地地下26~28 m处于还原环境,含水介质以粉细砂为主,NO3-N平均值为2.77 mg/L。②该深度反硝化速率(以N计)在 348.81~564.07 μg/(kg?d)之间,平均值为450.20 μg/(kg?d)。通过与研究区含水介质、采样深度和硝酸盐背景值相似的国内外案例对比研究,初步评估结果处于合理区间。③测试结果具有一定不确定性,主要来自忽略中间产物NO2-和NO的计算方法、扰动采样方法、N2O的操作规范程度以及采样频率等方面。研究方法为测定含水层硝酸盐速率研究提供了新的思路,研究结果可为地下水中硝酸盐转化过程机理研究、地下水硝酸盐污染修复及风险管控提供关键的理论支撑数据。
关键词:  地下水  反硝化速率  硝酸盐污染  同位素技术  原位抽注试验
DOI:
分类号:
基金项目:国家自然科学基金项目(No.41602260);国家水体污染控制与治理科技重大专项(No.2017ZX07107-005, 2018ZX07109-003)
Study on denitrification rate in the aquifer based on in-situ pumping/ injecting test and isotope technique
郇环,et al
Abstract:
Denitrification process of nitrate in aquifers is vital because it can dissipate groundwater nitrate pollution. It is very difficult to acquire the accurate denitrification rate in the aquifer due to the complicated hydrogeological conditions and hydrogeochemical environment in the field. A method was proposed for determining the denitrification rate in the aquifer based on in-situ pumping/injecting test and isotope technique. The method was applied in the Groundwater innovation field base of Chinese Research Academy of Environmental Sciences, which was located in the middle of Chaobai River alluvial-proluvial fan. The method integrated the effect of actual hydrogeological conditions and hydrogeochemical environment on the denitrification process, as well as the effect of dilution and dispersion of nitrate in the aquifer. The results showed that the shallow aquifer, which was composed by sandy loam, was in the reducing environments at the depth of 26~28 m of the study area. The average nitrate concentration was 2.77 mg/L. The denitrification rates ranged between 348.81 and 564.07 μg/(kg?d) with the average value of 450.20 μg/(kg?d). The values was preliminarily verified to be reasonable by comparative study of domestic and foreign cases with the study area. The method of ignoring the intermediate products of NO2- and NO, perturbation sampling method, operation specification degree of N2O and sampling frequency can result in the uncertainty of denitrification rates. The method can objectively and quantitatively determine the denitrification intensity in the aquifer as a new idea. The results can provide key data for studying the mechanism of nitrate fate and transport in the aquifer, and remediation and risk control of groundwater nitrate pollution.
Key words:  groundwater  denitrification rate  nitrate pollution  in-situ pumping/injecting test  isotope technique