长江上游非点源氮素负荷时空变化特征研究

Temporal-Spatial Changes of Non-point Source Nitrogen in Upper Reach of Yangtze River Basin

利用输出系数模型,结合RS和GIS技术,对长江上游从20世纪60年代到2003年的非点源氮素负荷进行估算,分析了其产生机理和时空变化特征。结果表明,近50a来,长江上游非点源氮素负荷总量呈上升趋势,从1960年的30.69万t上升到2003年的130.34万t。就省份和水系而言,四川一直是氮素负荷总量最大的省区,多年平均负荷贡献率为53.3%;1960—1990年的金沙江水系,1990年后的嘉陵江水系是氮素负荷总量最大的水系,两者的多年平均贡献率分别为25.4%和27.5%。长江上游非点源氮素负荷强度也呈上升趋势,从1960年的0.31t·km-2上升到2003年的1.30t·km-2。就省份和水系而言,重庆一直是氮素负荷强度最高的省区,多年平均负荷强度为1.58t·km-2;1960—1990年的上游干流区间,1990年后的嘉陵江水系,是氮素负荷强度最高的水系,两者的多年平均负荷强度分别为1.46和1.49t·km-2。

Temporal-spatial changes of non-point nitrogen pollution in upper reach of Yangtze River basin over the last 50 years were studied based on the simulation of its load by export coefficient model. The results indicated that, in the recent 50 years, both amount and load intensity of non-point nitrogen increased in the study area. As far as amount was coneemed, it increased from 3.07×10^5 tons in 1960 to1.3×10^6 tons in 2003. Sichuan province was the most important contributor, with an average annual contribute-ratio 53.3%. Jialing River, replacing Jinsha River, had the biggest loading of non-point source nitrogen since 1990. Average annual contribute-ratios of Jinsha River and Jialing River were 25.4% and 27.5% respectively. Non-point nitrogen load intensity increased from 0.31 to 1.30 t· km^-2 from 1960 to 2003. Chongqing was the highest nitrogen load intensity area among various districts, with average annual 1.58 t· km^-2. Jialing River, substituting the main channel region of upper reach, had been the highest nitrogen load intensity water system after 1990. Average annuals of the main channel region in upper reach and Jialing River were 1.46 and 1.49 t· km^-2 respectively.