郑州市中心城区浅层地下水“三氮”分布特征及其影响因素分析

Analysis on the Distribution Characteristics and Influencing Factors of “Three Nitrogen” in Shallow Groundwater in the Central Urban Area of Zhengzhou

郑州市中心城区地貌类型分为黄河冲积平原和山前冲洪积平原、黄土丘陵,不同地貌类型具有不同的水文地质特征,依据3种地貌类型及其污染源分布特征设置地下水采样点,研究了浅层地下水中“三氮”[硝酸盐氮(NO_(3)-N)、氨氮((NH_(3)-N))和亚硝酸盐氮(NO_(2)-N)]质量浓度与污染源分布、地下水位埋深及包气带岩性以及水化学环境等因素的关系。结果表明,郑州市中心城区地下水水质受NO_(3)-N和NH_(3)-N影响较大,受NO_(2)-N影响较小;2023年ρ(NO_(3)-N)超标的区域范围较2020年明显减小,ρ(NH_(3)-N)出现局部增大的现象,黄河冲积平原地区“三氮”质量浓度尤其是ρ(NH_(3)-N)变化应引起重视;地下水酸碱环境及氧化还原环境的变化在一定程度上可以引起地下水中“三氮”质量浓度的变化,当地下水处于氧化环境时,地下水中ρ(NO_(3)-N)增加而ρ(NH_(3)-N)降低。

The landform types in the central urban area of Zhengzhou are divided into Yellow River alluvial plain,mountain front alluvial plain,and loess hills.Different landform types have different hydrogeological characteristics.Based on the distribution characteristics of three landform types and their pollution sources,groundwater sampling points are set up to study the relationship between the“three nitrogen”content in shallow groundwater and the distribution of pollution sources,the depth of groundwater level,the lithology of the aeration zone,and the hydrochemical environment.The results show that the groundwater quality in the central urban area of Zhengzhou is greatly affected by the content of nitrate nitrogen and ammonia nitrogen,and is less affected by the content of nitrite nitrogen.The range of nitrate nitrogen content exceeding the standard in 2023 has significantly decreased compared to 2020,and there has been a local increase in ammonia nitrogen content.The changes in“three nitrogen”content,especially ammonia nitrogen content,in the Yellow River alluvial plain area should be taken seriously.The changes in the acid-base and redox environments of groundwater can to some extent cause changes in the“three nitrogen”content in groundwater.When groundwater is in an oxidizing environment,the nitrate nitrogen content in groundwater increases while the ammonia nitrogen content decreases.