柳江盆地浅层地下水硝酸型水特征和成因分析

Characteristics and Genesis of NO_3 Type Water in Shallow Groundwater in Liujiang Basin

近年来地下水硝酸盐污染状况越来越严重,人类活动对地下水的影响加剧,不仅造成污染,甚至改变了地下水的水化学类型,出现了硝酸型地下水.本研究以柳江盆地为例,分析了该地区浅层地下水中硝酸型水的特征和影响控制因素,探讨了硝酸型水的研究意义.结果表明,柳江盆地浅层地下水中硝酸盐污染严重;在全区211组有效数据中,硝酸型水占比20.9%,主要分布在研究区东南部,北部山区分布较少且零散;根据硝酸型水的特征可将其划分为高TDS硝酸型水和低TDS硝酸型水,高TDS硝酸型水的TDS和总硬度浓度均较大,且浓度范围较广,低TDS硝酸型水的TDS和总硬度浓度值和浓度范围均较小;硝酸型水的形成主要受人类生活污水、农业施肥、化粪池和垃圾渗滤液下渗等影响,其中,高TDS硝酸型水的污染负荷通常高于低TDS硝酸型水;通过对硝酸型水的分析研究,能够尽早发现污染并不严重但已有污染趋势的区域,以便及时进行地下水的污染防治,避免水质进一步恶化.

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 NO_3 type groundwater. This study focuses on the Liujiang Basin. The characteristics and influencing factors of NO_3 type water in shallow groundwater are analyzed,and the significance of NO_3 type water is discussed. Results show that shallow groundwater in the Liujiang Basin is of poor quality and nitrate pollution is severe. NO_3 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 NO_3 type water,this can be classified as high TDS NO_3 type water or low TDS NO_3 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 NO_3 type water are both low. The formation of NO_3 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 NO_3 type water is generally higher than that of low TDS NO_3 type water. Analysis of NO_3 type water makes it possible to prevent and control groundwater pollution when there is an increasing pollution trend but pollution is not yet severe.