鄱阳湖流域浅层地下水硝酸盐氮时空分布特征与来源

Spatial and Temporal Distribution Characteristics and Source Analysis of Nitrate in Shallow Groundwater of the Poyang Lake Region

以鄱阳湖流域为研究区,以区内浅层地下水作为研究对象,对浅层地下水硝酸盐氮分布特征和时空变化规律进行研究并分析来源。浅层地下水中硝酸盐氮浓度在0.5~21.6 mg/L范围内,平均值为7.0 mg/L。丰水期和枯水期,硝酸盐氮浓度分别为0.7~21.6和0.5~15.7 mg/L。高浓度硝酸盐氮主要出现在流域内典型农灌区。水体氢氧同位素特征显示,地表水主要来源为大气降水,受其他补给来源及蒸发作用的混合影响;地下水主要来源为当地大气降水,与地表水发生混合作用,受蒸发作用影响较小。硝酸盐氮氧同位素结果显示降雨、灌溉、土地利用类型、肥料施用是影响研究区浅层地下水中硝酸盐氮浓度及分布的主要因素。贝叶斯模型计算结果显示,土壤氮对地下水硝酸盐氮的贡献率最大,平均贡献率为44.6%;大气降水的贡献率仅次于土壤氮,平均贡献率为28.2%;氮肥,污水和粪便的贡献率分别为19.4%和7.8%。

This study took the Poyang Lake Region as the research area and the shallow groundwater was selected as the research object.The distribution characteristics and temporal and spatial variation of nitrate in shallow groundwater in the Poyang Lake Region were studied and source of nitrate in groundwater was analyzed.Nitrate concentration in shallow groundwater was between 0.5-21.6 mg/L with an average of 7.0 mg/L.In the wet and dry seasons,nitrate concentration was 0.7-21.6 mg/L and 0.5-15.7 mg/L,respectively.Groundwater with high concentration of nitrate was mainly found in the typical agricultural irrigation area.The hydrogen and oxygen isotopic characteristics of water samples showed that surface water was mainly from meteoric precipitation,and influenced by other recharge sources and evaporation.Shallow groundwater was mainly recharged by local meteoric precipitation and was mixed with surface water,less affected by evaporation.The results of nitrogen and oxygen isotopic composition of nitrate showed rainfall,irrigation activities,land use type and fertilizer application were major factors affecting the concentration and distribution of nitrate in shallow groundwater in the study area.The calculation results using Bayesian model showed that soil nitrogen had the maximum contribution rate to nitrate in groundwater,with an average contribution rate of 44.6%.Atmospheric precipitation had a secondary contribution rateto nitrate in groundwater with an average contribution rate of 28.2%.The contribution rates of nitrogen fertilizer,sewage and feces were 19.4%and 7.8%,respectively.