矿井水排放湖泊沿岸土壤氮素空间分布规律的研究——以宁夏灵武园疙瘩湖为例

Spatial distribution of soil nitrogen along a mine water discharge lake:Taking Yuangeda Lake in Lingwu City,Ningxia Province

为探明湖泊滨岸对矿井水中氮素的截留与缓冲作用及其与滨岸土壤氮素空间分布间的关系,以宁夏灵武市羊场湾煤矿矿井水排放湖泊——园疙瘩湖为研究对象,测定了该湖水滨区域、近岸陆域和自然区域土壤中8种氮素的含量和土壤酶的活性,分析了水滨区域和近岸陆域与自然区域相比的土壤氮素变化系数及其随距矿井水排放口距离远近的变化规律。结果表明:园疙瘩湖滨岸土壤氮素空间分布存在异质性;相比较而言,水滨区域与周边自然区域的土壤氮素分布特征差异较大,而近岸陆域与周边自然区域的差异较小;相较于无机态氮,有机态氮的空间异质性更强;各有机氮形态中,颗粒物有机氮多被截留于离岸最近的水滨区域,而氨基酸氮和可溶性有机氮则需要更为宽阔的截留区域;水滨区域对颗粒物有机氮的截留效应随着距矿井水排放口距离的增加而降低;水滨区域和近岸陆域对氨基酸氮的截留效应在1400 m内逐渐降低,而在1400 m后趋于稳定;水滨区域和近岸陆域对可溶性有机氮的截留效应与其离矿井水排放口的距离无关,这可能是因为可溶性有机氮的易溶解特性使其随水体的迁移性较强,滨岸带土壤虽在吸附和缓存可溶性有机氮中发挥了一定的作用,但其较强的迁移性致其在滨岸带土壤中的分布较为均一;滨岸土壤氮素的空间异质性与土壤酶活性无关。综上可知,湖泊滨岸土壤对矿井水中有机态氮具有截留作用,且该截留作用多发生在距矿井水排放口1400 m的滨岸带内,滨岸土壤对矿井水中氮素的截留作用亦是滨岸土壤氮素空间分布异质性的主导因素。本研究结果可为指导矿井水排放路径的设计及矿井水资源的合理开发与利用提供指导。

The nitrogen content,nitrogen variation coefficient,and soil enzyme activity along the waterfront,coastal land,and natural areas of Yuangeda Lake were assessed.Yuangeda is a drainage lake that collects effluent from Yangchangwan mine in Lingwu City,Ningxia Hui Autonomous Region.Spatial variation in the nitrogen interception effect along the waterfront and coastal area with increasing distance from the drainage outlet was also analyzed.The main objectives of this study were to explore the spatial distribution of nitrogen in the river and lake bank and examine the interception and buffering effects of the river and lake shores on mine water nitrogen.The spatial distribution of nitrogen in coastal soils was heterogeneous.The soil nitrogen distribution characteristics varied between the waterfront area and the surrounding natural area,whereas the coastal land area and the surrounding natural area were similar.The soil organic nitrogen exhibited stronger spatial heterogeneity than inorganic nitrogen.Among the various organic nitrogen forms,particulate organic nitrogen was mostly confined to the waterfront area close to shore,while amino acid nitrogen and soluble organic nitrogen required a wider interception area.The particulate organic nitrogen retention effect in the waterfront area decreased with distance from the mine water discharge port.The amino acid nitrogen interception effect in the waterfront area and the coastal land area gradually decreased up to 1400 m and then stabilized.The soluble organic nitrogen interception effect observed in the waterfront area and coastal land area was independent of the distance from the mine water outlet,which can be attributed to the high mobility of soluble nitrogen in water.Although riparian soils contributed to the absorption and buffering of soluble organic nitrogen,its high mobility resulted in a more uniform soil distribution.The spatial heterogeneity of riparian soil nitrogen was unrelated to soil enzyme activity.In summary,the waterfront soil has an interception effect on organic nitrogen in the mine water,which mostly occurs in the coastal zone<1400 m from the discharge outlet.The coastal soil interception effect on mine water nitrogen was the dominant factor in the spatial distribution of nitrogen.The results of this study could provide guidance for the design of mine water discharge routes and the development and utilization of mine water resources.