赣江流域土地利用方式对无机氮的影响

赣江无机氮是鄱阳湖氮素输入的主要来源,查明流域土地利用方式对赣江无机氮的影响对鄱阳湖的富营养化防治具有重要意义.基于2013年1月和6月对赣江干流和主要支流NO-3-N和NH+4-N的浓度测定,通过不同空间尺度和土地类型等级划分,利用相关分析和冗余分析研究土地利用方式对赣江无机氮浓度的影响.结果表明,不同空间尺度的子流域划分方式对赣江流域土地利用类型与无机氮浓度的相关性有较大影响.与NO-3-N相比,选择更小的子流域划分尺度有助于分析土地利用方式对NH+4-N浓度的影响;在温度较高、微生物活动强烈的季节,也应选择更小的子流域划分尺度研究土地利用方式对无机氮浓度的影响.一级土地利用分类下,赣江流域水田、水域对NO-3-N起"源"作用,林地、草地起"汇"作用;居民建设用地对NH+4-N起"源"作用,林地起"汇"作用.二级土地利用分类下,水田中丘陵水田是赣江NO-3-N浓度的主要来源,其次为平原水田,山区水田最小.居民建设用地中的城镇用地和其它工矿建设用地是赣江NH+4-N的主要污染来源,农村用地是NO-3-N的主要污染来源.

Investigation of the impacts of land use on inorganic nitrogen in the Ganjiang River

Identifying the influence of land use on inorganic nitrogen in the Ganjiang River has great significance for eutrophication control in the Poyang Lake. Based on the investigation of NO₃^--N and NH₄⁺-N concentration in the mainstream and major tributaries of the Ganjiang River in January and June of 2013, we analyzed the influence of land use on inorganic nitrogen by correlation analysis and redundancy analysis through different spatial scales and classification levels of land use. We found that different spatial scales of sub-basin division had great impacts on the correlation between land use patterns and inorganic nitrogen concentration. Compared to NO₃^--N, a smaller spatial scale of sub-basin was more helpful to investigate the influence of land use on NH₄⁺-N concentration. In addition, a smaller spatial scale of sub-basin was also helpful to analyze the influence of land use on inorganic nitrogen concentration in high temperature season with intensive microbial activity. Under the first level of land use classification, paddy field and water area was a source of NO₃^--N, while forest and grass land was a sink; Residential construction land was a source of NH₄⁺-N, while forest land was a sink in the Ganjiang River. Under the second level of land use classification, among the paddy field, hill paddy field was the main source of NO₃^--N, followed by plain paddy field and mountain paddy field. Among the residential construction land, urban land and industrial and mining land were the main source of NH₄⁺-N, while rural land was the main source of NO₃^--N in the Ganjiang River.