华北平原典型剖面地下水三氮污染时空分布特征

华北平原地下水氮元素污染的时空分布特征鲜有报道,本文结合华北平原水文地质条件,从山前平原至中部平原选取两个剖面,四次采集地下水样品并测定三氮含量,调查评价典型剖面上三氮污染状况并深入分析其时空分布特征。结果表明:华北平原典型剖面上地下水的三氮中超标最为严重的是氨氮;三氮总量整体上随时间呈上升趋势;硝态氮、氨氮、亚硝态氮含量的空间分布不尽相同,前两者在山前平原的含量高于中部平原;第三者则呈相反趋势;从垂直方向上看,三氮含量随地下水埋深增加而减小。在不同的水井类型中,灌溉井和监测井中三氮的含量普遍较高,而在饮用水井中氨氮污染相对严重,会对人类健康造成一定风险。

Temporal and Spatial Distributions of Nitrogen Contamination in Groundwater along the Typical Cross-sections of the North China Plain

Temporal and spatial distributions of nitrogen contamination in groundwater of the North China Plain are unclearly known. The nitrogen pollution assessment and analysis of its pollution distribution pattern in this area is needed. According to the hydrogeologic conditions of the North China Plain, we selected two geologic across-sections in this region from the piedmont plain to the central plains to obtain the nitrogen contents in groundwater samples four times, The data of nitrogen contents for four times from 2010 to 2013 in groundwater samples along two geologic across-sections were estimated and the nitrogen pollution status was analyzed systematically. The results showed that along the typical geologic cross-sections of the North China Plain, ammonia exceeded most seriously that in drinking water standard, among ammonia, nitrate, and nitrate in groundwater, the total amount of ammonia, nitrate, and nitrate concentrations increased with time for those 3 years overall. Spatially, the average concentrations of nitrate and ammonia in the piedmont plain were higher than those in the central plains, while the average concentrations of nitrite in the piedmont plain were far lower than those in the central plains. Furthermore, in the vertical direction, the concentrations of ammonia, nitrate, and nitrate in groundwater decreased generally with depth. Finally, total nitrogen concentrations in groundwater in different types of wells varied while they were higher in those irrigation and monitoring wells, and, however, the ammonia contamination in the drinking wells was relatively serious, which would bring about a risk to human health.