高原河谷城市浅层地下水铁锰分布特征、影响因素及其对生态环境的影响——以西宁市为例

Distribution characteristics,influencing factors and impacts on ecological environment of Fe and Mn in shallow groundwater of Plateau Valley-City:A case study of Xining City

【研究目的】高原河谷城市因受地形条件限制,生态环境脆弱,强烈的人为活动已对地下水产生剧烈影响。铁锰离子已成为典型高原河谷城市西宁市浅层地下水中超Ⅲ类地下水的主要贡献指标,威胁着当地生态环境安全及居民身体健康。深入探究高原河谷城市浅层地下水中铁、锰的分布特征和影响因素,以期为该区提出地下水污染防治措施及缓解供水水质安全问题提供技术支持。【研究方法】本文以西宁市144组浅层地下水样品水化学组分测试结果为依据,结合研究区地质、地貌、土地利用类型、水文地质调查资料与人类活动影响,研究了西宁市浅层地下水中铁锰分布特征及影响因素。【研究结果】研究区浅层地下水中铁、锰超标率分别为20.98%和9.79%,对超Ⅲ类地下水的贡献率排名较2012年分别上升2名和3名。建设用地中浅层地下水铁锰超标率比其他土地利用类型用地分别高出1.4倍和3.47倍;研究区浅层地下水水化学类型有36种,建设用地中地下水化学类型多达21种,高铁锰地下水主要富集于HCO_(3)–Ca·Mg型水、HCO_(3)·SO_(4)–Ca型水中。地下水中铁锰离子的迁移和富集,除了与上覆盖层性质、地面污染、地下水径流条件有关外,主要受控于氧化还原环境,与酸碱条件无明显相关。【结论】研究区地下水中铁锰含量升高主要是受原生沉积环境所致,而局部建设用地中浅层地下水铁锰含量升高则是受原生沉积环境和人类活动共同影响所致,因此有必要对建设用地中的地下水铁锰含量进行长期监测,制定相应的管理措施,防止未来研究区浅层地下水中铁锰含量进一步升高。

This paper is the result of hydrogeological survey engineering.[Objective]Due to the limitation of terrain conditions,the ecological environment of plateau valley cities is fragile,and the strong human activities have had a severe impact on groundwater.Iron and manganese ions have become the main contribution index of super−class III groundwater in shallow groundwater in Xining,a typical plateau valley city,which seriously threatens the local ecological environment security.and the health of residents.The distribution characteristics and influencing factors of iron and manganese in shallow groundwater in plateau valley cities are deeply explored in order to provide technical support for the prevention and control measures of groundwater pollution and the alleviation of water quality safety problems in this area.[Methods]Based on the test results of hydrochemical composition of 144 groups of shallow groundwater samples in Xining city,combined with the geology,landform,land use type,hydrogeological investigation data and the influence of human activities,this paper studies the distribution characteristics and influencing factors of Fe and Mn in shallow groundwater in Xining city.[Results]The over−standard rates of Fe and Mn in shallow groundwater in the study area are 20.98%and 9.79%.Compared with 2012,the contribution rate of Fe and Mn ions to ClassⅢgroundwater increased by 2 and 3,respectively.The excess rate of Fe and Mn in shallow groundwater of construction land is 1.4 times and 3.47 times higher than that of other land use types,respectively.There are 36 hydrochemical types of shallow groundwater in the study area,and 21 hydrochemical types of groundwater in construction land.Groundwater with high Fe and Mn is mainly enriched in HCO_(3)–Ca·Mg type water and HCO_(3)·SO_(4)–Ca type water.The migration and enrichment of Fe and Mn ions in groundwater are mainly controlled by oxidation−reduction environment,and have no obvious correlation with acid−base conditions,except for the properties of overburden,ground pollution,groundwater runoff conditions.[Conclusions]The increase of Fe and Mn content in groundwater in the study area is mainly caused by the primary sedimentary environment,while the increase of Fe and Mn content in shallow groundwater in local construction land is caused by the primary sedimentary environment and human activities.Therefore,it is necessary to monitor the Fe and Mn content in groundwater in construction land for a long time and formulate corresponding management measures to prevent the increase of Fe and Mn content in shallow groundwater in the future.