| 摘要: |
| 鄱阳湖作为中国最大的淡水湖,2000年后其水系和湖体水质总体都呈下降趋势.以鄱阳湖流域内的典型流域——乐安河流域为例,初步分析了流域内面源污染的主要影响因素、主要污染成分及其对污染程度的影响.研究表明,氮比磷对水质影响更明显,氮的3种物质形态中硝态氮(NO3--N)含量最高,对水质影响也最大.根据总氮和NO3--N浓度差异可将流域内的水质分为4个区域,从上游到下游富营养化程度不断升高,最上游为Ⅱ类水质,而最下游的总氮浓度接近Ⅳ类水标准.3年监测期内降雨量和强度的变化导致氮、磷浓度的巨大差异,林地对面源污染物有较好的消减作用,而农田的氮、磷流失是营养物产生的主要来源,人类活动特别是农事活动对土壤氮、磷的干扰是导致氮、磷浓度年内变化的主要原因.因此,削减流域内营养盐的产生、减少入湖河流携带污染物总量是改善鄱阳湖水质的重要途径. |
| 关键词: 鄱阳湖流域 乐安河流域 农业面源污染 富营养化 |
| DOI：10.18307/2015.0212 |
| 分类号: |
| 基金项目:江西省科学合作计划项目(20142BDH80016)和江西省主要学科学术和技术带头人培养计划专项(20123BCB22008)联合资助. |
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| Nutrient loading and its controlling factors in Le'an River watershed, Lake Poyang basin |
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]XIA Yu1,2, YAN Bangyou3, FANG Yu2
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1.School of Science, Nanchang University, Nanchang 330031, P. R. China;2.Office for Mountain-River-Lake Development and Management Committee of Jiangxi Province, Nanchang 330046, P. R. China;3.Department of Science and Technology, Jiangxi Province, Nanchang 330046, P. R. China
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| Abstract: |
| Le'an River, located in the northeast of Jiangxi Province (southeast China), is a tributary of China's largest freshwater lake, Poyang Lake, which drains directly into the Yangtze River. The watershed covers an area of app. 8000 km2, with an average annual precipitation between 1687-1870 mm. There is no huge settlement in the watershed, of which forest and farmland accounts for 95% in the area. According to the historical data, the water quality is much worse in wet seasons than in dry ones, so it is believed that mainly diffuse pollution, especially caused by agriculture, influences the water quality. Based on data from 17 monitoring stations within Le'an River watershed from 2009 to 2011, major influence factors, ingredients of diffuse pollution, and the extent of pollution have been analyzed. The main conclusions of this paper are:1) NO3--N has the highest content and most important influences on water quality among the 3 physical forms of nitrogen. TP has a comparably minor influence on water quality. The whole watershed can be divided into 4 districts according to the cluster analysis. The water quality remains to be type Ⅱ in the upstream area with at least 90% forest coverage. Eutrophication increases from upstream to downstream along with an increasing share of farmland, illuminating that anthropogenic induced land use change is the major factor of diffuse pollution. 2) The amount and intensity of precipitation play a significant role on nutrient concentration. Rainfall could increase surface runoff instantly, introducing abundant pollutant into the water body and leading to rapidly increasing in nutrient concentration. 3) Except in major flood period of the year, the maximum volume of water body could dilute nutrients greatly. In a year with regular or high rainfall, water quality appears fine with ample water volume, but it turns bad in a year or season with less water. Moreover, with soaring frequency of extreme meteorological events caused by global climate change and the construction of large-scale hydro-power project in the Yangzi River basin, Lake Poyang's water shortage will become regular, the water volume will decrease continuously, as well as the lake's self-purification capacity, therefore positive and effective countermeasures should be taken to improve the watershed sustainability. 4) Although the present water quantity of Lake Poyang is good, there are still pressures caused by economic development and climate change, which is threatening the watershed sustainability. Stakeholders and decision-makers shall work more effectively on environment conservation in the upstream area in particular with high attention to reasonable landuse plan, improving soil quality, and enhancing watershed environment capacity. |
| Key words: Lake Poyang watershed Le'an River watershed diffuse pollution eutrophication |
