[Characteristics and Genesis of NO₃ Type Water in Shallow Groundwater in Liujiang Basin]

In recent years, groundwater nitrate pollution has become more and more severe. Anthropogenic activities have become more significant, not only causing pollution, but also changing the hydrochemical type of groundwater and leading to the emergence of NO₃ type groundwater. This study focuses on the Liujiang Basin. The characteristics and influencing factors of NO₃ type water in shallow groundwater are analyzed, and the significance of NO₃ type water is discussed. Results show that shallow groundwater in the Liujiang Basin is of poor quality and nitrate pollution is severe. NO₃ type water comprises 20.9% of all effective data for the area and is mainly distributed in the southeast and a few parts of the northern mountainous area. Based on the characteristics of NO₃ type water, this can be classified as high TDS NO₃ type water or low TDS NO₃ type water. TDS and total hardness concentration values of high TDS nitrate type water are high and the concentration range is wide. Conversely, TDS and total hardness concentration and the concentration range of low TDS NO₃type water are both low. The formation of NO₃ type water is mainly driven by human domestic sewage, agricultural fertilization, and septic tank and landfill leachate infiltration, among others. The pollution load of high TDS NO₃ type water is generally higher than that of low TDS NO₃ type water. Analysis of NO₃ type water makes it possible to prevent and control groundwater pollution when there is an increasing pollution trend but pollution is not yet severe.