河套灌区浅层地下水NO3--N时空变化及驱动因素

为探明河套灌区地下水硝酸盐污染现状、时空演变特征和主要影响因素，选择乌拉特灌域为研究区，采用统计分析、 Piper三线图、相关分析和离子比值等方法，探究了该地区地下水硝酸盐质量浓度时空变化格局和主要驱动因素.结果表明，乌拉特灌域地下水氮素主要以NO^-₃-N为主，ρ（NO^-₃-N）存在极高值(60.00 mg·L^-1),超标率达10.50%;时间分布：8月地下水ρ（NO^-₃-N）最高(平均值为6.61 mg·L^-1), 10月(6.22 mg·L^-1)和11月(6.25 mg·L^-1)次之，3月(平均值为1.77 mg·L^-1)最小，土壤中NO^-₃-N在降雨和灌溉驱动作用影响下，下渗至地下水，呈现出丰水期和灌溉集中期高于其它时期的特征；空间分布：灌域西南部(8.87 mg·L^-1)&g...

Temporal and Spatial Variation Characteristics and Driving Factors of Nitrogen of Shallow Groundwater in Hetao Irrigation District

As an important food production area in the north of China, the Hetao plain is extremely vulnerable to nitrate pollution caused by agricultural production activities and additional factors. Thus, it is of great significance for the environmental protection and rational use of groundwater to detect the current situation of groundwater nitrate pollution, temporal and spatial evolution characteristics, and main influencing factors in the Hetao irrigation district. We selected the Wualte irrigation area as the study area, and the characteristics of temporal and spatial changes in groundwater nitrate concentration and the main influencing factors in this area were explored. We used statistical analysis to analyze the nitrogen content of groundwater in the study area, and the Piper three-line diagram was used to explore the characteristics of chemical composition and evolution; furthermore, we used ion ratio and correlation analysis methods to explore the source of NO₃^--N in groundwater. The results showed that NO₃^--N was the main existing form of nitrogen in the Wulate irrigation area, and its concentration varied from 0.01 to 60.00 mg·L^-1, with an exceeding standard rate of 10.50%. In terms of time, the characteristic of time change was that the NO₃^--N concentration in August of groundwater was the highest (average 6.61 mg·L^-1), followed by that in October (6.22 mg·L^-1) and November (6.25 mg·L^-1), and that in March (average value of 1.77 mg·L^-1) was the lowest. With the influence of rainfall and irrigation, the NO₃^--N in the soil was infiltrated into the groundwater, showing the characteristic that wet season and concentrated irrigation periods were higher than those in other periods. Spatially, it appeared as southwest (8.87 mg·L^-1)>northwest (4.25 mg·L^-1)>east (0.89 mg·L^-1), mainly due to the original geological conditions, land use, and domestic waste stacking. In addition, the concentration of NO₃^--N of groundwater in the study area was closely related to the depth of groundwater and redox conditions but was relatively less affected by the concentration of water chemical ions. Therefore, identifying the temporal and spatial distribution characteristics and main sources of groundwater nitrogen pollution can provide a scientific basis for scientific fertilization, groundwater nitrate pollution control, and water safety.