赣江流域土地利用方式对河流水质的影响

赣江是鄱阳湖的最大支流,是鄱阳湖水污染物的主要来源,查明流域土地利用方式对赣江水质的影响和鄱阳湖的水环境保护具有重要意义。基于2012年对赣江7个主要支流NH+4-N、TP、CODMn和DO浓度的每月测定结果,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流域河流水质的影响。研究结果表明,子流域的土地利用方式对TP的影响大于缓冲区;对CODMn的影响在丰水期大于缓冲区,在枯水期小于缓冲区;对NH+4-N的影响在丰水期与缓冲区接近,在枯水期小于缓冲区;DO受土地利用方式的影响较小。水田中的丘陵水田是赣江水体TP和丰水期CODMn的主要来源;平原水田是枯水期CODMn的主要来源。居民建设用地中的城镇用地是赣江水体TP、NH+4-N和丰水期CODMn的主要来源,农村用地是CODMn的主要来源。水域中的水库坑塘是赣江水体TP和丰水期NH+4-N、CODMn的主要来源。

Influence of land use on river water quality in the Ganjiang basin

The global transition from undisturbed to human-dominated landscapes has impacted river water quality worldwide and made the quantification of land use a valuable indicator of water pollutant. The Ganjiang River, as the largest tributary of the Poyang Lake Basin, is the main pollution source of the Poyang Lake. Identifying the influence of land use on water quality in the Ganjiang River has great significance for water environment protection in the Poyang Lake. In this study, we investigated the monthly concentration of NH₄⁺-N, TP, COD_Mn and DO in seven major tributaries of the Ganjiang River in 2012 and analyzed the influence of land use on river water quality by the methods of correlation analysis and redundancy analysis. Two spatial scales, the sub-basin and buffer zone, and two levels of land use classification were considered. The first level of land use classification was paddy field, dry farm, forest land, grass land, water area, resident construction land and unused land, resulting from remote sensing image interpretation. The second level of land use classification was obtained from the first level based on different geomorphology, canopy density, grass coverage and other factors. The results showed that forest was the largest land use pattern in the study area, followed by paddy field and dry farm. The concentration of TP had a significant positive correlation with NH₄⁺-N in wet season, while NH₄⁺-N had a significant negative correlation with DO in dry season. The pollution sources of TP both in wet season and dry season were from hill paddy field, urban land, reservoir and pond. The pollution sources of COD_Mn were from paddy field, urban land, reservoir and pond, and rural residential land in wet season, while from plain paddy field and rural residential land in dry season. The pollution sources of NH₄⁺-N were from urban land, reservoir and pond in wet season, while from urban land, mountainous dry farm, riparian forest land and low coverage grassland in dry season. Additionally, different spatial scales of land use had different impacts on water quality indicators. The land use in sub-basin had more influence on TP and wet seasonal COD_Mn than that in buffer zone, while it had less influence on dry seasonal COD_Mn than that in buffer zone. For NH₄⁺-N, the land use in sub-basin had similar influence as that in buffer zone in wet season, while less influence than that in buffer zone in dry season. The impact of land use on DO was not significant. Moreover, we found that it was more helpful to study the source of the river water pollutant based on the second level of land use classification than the first level of land use classification. Among the paddy field, hill paddy field was the main source of TP and wet seasonal NH₄⁺-N; while plain paddy field was the main source of dry seasonal COD_Mn. Among the residential construction land, urban land was the main source of TP, NH₄⁺-N, and wet seasonal COD_Mn, while rural residential land was the main source of COD_Mn. Among the water area, reservoir and pond were the main source of TP, wet seasonal NH₄⁺-N and wet seasonal COD_Mn.