[关键词]
[摘要]
开展地下水水化学特征及成因分析是地下水资源评价的基础。本文以内蒙古乌拉盖地区地下水为研究对象,综合利用水化学计量分析、多元统计分析、空间统计分析及氧化还原分析等,开展区域地下水水化学特征及成因研究。结果表明研究区地下水水化学特征存在显著的空间分区特征。水岩作用是控制研究区水化学演化的主要因素,蒸发浓缩及离子交换作用次之。水岩作用中硅酸岩风化作用是主控作用,碳酸盐岩溶解次之,蒸发岩影响较为微弱,这与区域地质背景相匹配。部分地下水存在的硝酸盐污染,空间分析表明区域分散的农牧业及人类活动成为地下水硝酸盐污染的重要来源。氧化还原分析表明区域存在潜在的反硝化趋势,但是电子供体及受体分析无法确定地下水硝酸盐的环境行为,需要引入稳定同位素分析进一步确认区域地下水反硝化是否存在。本研究结果为干旱及半干旱区地下水资源可持续开发利用提供科学依据及技术支撑。
[Key word]
[Abstract]
The sustainable use of groundwater in arid and semi-arid regions was related to regional ecological security and food security. However, with the rapid development of social and economic construction, the exploitation of groundwater resources had increased, which had made the already severe water supply shortage more tense. And the water resource problem caused by the water quality crisis was more serious than the reduction of water quantity. Carrying out research on groundwater chemistry in arid and semi-arid areas not only had important academic significance for clarifying the origin and formation of groundwater, but also had important value for scientific and reasonable regional groundwater development and protection of groundwater resources. This research took groundwater in the Wulagai area of Inner Mongolia as the research area, comprehensively utilized water stoichiometric analysis, multivariate statistical analysis, spatial statistical analysis and redox analysis to carry out regional groundwater hydrochemical characteristics and causes. The results showed that the groundwater hydrochemical characteristics in the study area had significant spatial zoning characteristics. There were certain differences in the water chemistry types of deep and shallow groundwater in different regions. The shallow groundwater in Zone 1 was mainly Ca-HCO3 pattern (40%), and the deep groundwater was mainly Ca-HCO3 (38%) and Na-HCO3 patterns (38%); shallow groundwater in Zone 2 was also mainly Ca-HCO3 pattern (57%), and deep water chemistry patterns had changed, mainly Ca-HCO3 (54%) and Na-HCO3 patterns (45%); The types of water chemistry in Zone 3 were relatively diverse. The shallow groundwater was mainly Ca-Mg-Na-HCO3 pattern (37%), other types were also distributed, and the deep groundwater is mainly Ca-Na-HCO3 pattern (29%). Water-rock interaction was the main factor controlling the evolution of water chemistry in the study area, and there were still certain differences in different regions and stratifications. Among them, zone 3 was also affected by evaporation and concentration and ion exchange. The weathering of silicate rock was the main controlling effect in the water-rock interaction, followed by the dissolution of carbonate rock, and the influence of evaporite was relatively weak, which matched the regional geological background. Furthermore, factor analysis showed that human activities were also an important factor affecting the hydrochemical characteristics of groundwater. There was a certain amount of nitrate pollution in groundwater in the study area. Spatial analysis showed that the spatial distribution of nitrate in the whole area was a typical random distribution pattern, and there was no discrete and aggregation effect at the pollution point, which indicates that the regional dispersion of agriculture, animal husbandry and human activities become an important point source of groundwater nitrate pollution. Redox analysis showed that there was a potential denitrification trend in the area, but electron donor and acceptor analysis could not determine the environmental behavior of groundwater nitrate. It was necessary to introduce stable isotope analysis to further confirm the existence of regional groundwater denitrification. The results of this study provided scientific basis and technical support for the sustainable development and utilization of groundwater resources in arid and semi-arid areas.
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[基金项目]
国家重点研发项目2019YFC1805300,国家自然科学42077154