College of Water Sciences, Beijing Normal University, Beijing 100875, China; State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; Engineering Research Center of Groundwater Pollution Control and Remediation, Ministry of Education, Beijing 100875, China.
College of Water Sciences, Beijing Normal University, Beijing 100875, China; Engineering Research Center of Groundwater Pollution Control and Remediation, Ministry of Education, Beijing 100875, China.
Sci Total Environ. 2016 Apr 15;550:768-784. doi: 10.1016/j.scitotenv.2016.01.144. Epub 2016 Feb 2.
It has been proved that groundwater vulnerability assessment is an effective tool for groundwater protection. Nowadays, quantitative assessment methods for specific vulnerability are scarce due to limited cognition of complicated contaminant fate and transport processes in the groundwater system. In this paper, process-based simulation model for specific vulnerability to nitrate using 1D flow and solute transport model in the unsaturated vadose zone is presented for groundwater resource protection. For this case study in Jilin City of northeast China, rate constants of denitrification and nitrification as well as adsorption constants of ammonium and nitrate in the vadose zone were acquired by laboratory experiments. The transfer time at the groundwater table t50 was taken as the specific vulnerability indicator. Finally, overall vulnerability was assessed by establishing the relationship between groundwater net recharge, layer thickness and t50. The results suggested that the most vulnerable regions of Jilin City were mainly distributed in the floodplain of Songhua River and Mangniu River. The least vulnerable areas mostly appear in the second terrace and back of the first terrace. The overall area of low, relatively low and moderate vulnerability accounted for 76% of the study area, suggesting the relatively low possibility of suffering nitrate contamination. In addition, the sensitivity analysis showed that the most sensitive factors of specific vulnerability in the vadose zone included the groundwater net recharge rate, physical properties of soil medium and rate constants of nitrate denitrification. By validating the suitability of the process-based simulation model for specific vulnerability and comparing with index-based method by a group of integrated indicators, more realistic and accurate specific vulnerability mapping could be acquired by the process-based simulation model acquiring. In addition, the advantages, disadvantages, constraint conditions and applying prospects of the quantitative approach for specific vulnerability assessment were discussed.
已证实地下水脆弱性评估是保护地下水的有效工具。由于对地下水系统中复杂污染物归宿和运移过程的认识有限，目前针对特定脆弱性的定量评估方法还很缺乏。本文提出了一种基于过程的特定脆弱性模拟模型，用于评估硝酸盐对地下水的影响。该模型采用一维非饱和带水流和溶质运移模型，为地下水资源保护提供了一种方法。在本案例研究中，以中国东北的吉林市为例，通过实验室实验获得了非饱和带中反硝化和硝化的速率常数以及铵和硝酸盐的吸附常数。将到达地下水位的时间 t50 作为特定脆弱性指标。最后，通过建立地下水净补给量、地层厚度与 t50 之间的关系来评估整体脆弱性。结果表明，吉林市最脆弱的区域主要分布在松花江和磨牛河的泛滥平原上。最不脆弱的区域主要出现在第二阶地和第一阶地的背面。低、中、高脆弱性的总面积占研究区的 76%，表明遭受硝酸盐污染的可能性相对较低。此外，敏感性分析表明，非饱和带特定脆弱性的最敏感因素包括地下水净补给率、土壤介质的物理性质和硝酸盐反硝化的速率常数。通过验证基于过程的特定脆弱性模拟模型的适用性，并与一组综合指标的基于指数的方法进行比较，可以通过基于过程的模拟模型获得更真实和准确的特定脆弱性图。此外，还讨论了特定脆弱性定量评估方法的优缺点、约束条件和应用前景。
