长江和长江口高含量无机氮的主要控制因素

THE DOMINANT CONTROLLING FACTORS OF HIGH CONTENT INORGANIC N IN THE CHANGJIANG RIVER AND ITS MOUTH

根据 1 997— 1 998年长江和长江口河水和雨水的现场调查、历史资料以及相关文献 ,定量分析长江流域无机氮的主要来源和输送通量。估算表明 ,降水无机氮、农业非点源氮 (化肥和土壤流失的氮 )和点源污水氮的输入分别占长江口无机氮输出通量的 62 .3%、1 8.5 %和1 4.4%。氮的降水输入是长江口高含量无机氮的主要来源 ,进入长江的降水氮仅仅大约占长江流域全部降水氮的 36.8%。降水氮主要受控于化肥气态损失、化石燃料燃烧及动植物过程中释放的物质等。实际上 ,化肥N的气态损失和农业非点源流失大约占长江流域年化肥N使用量的 60 % 。

Based upon the site investigations of river and rain w aters in 1997-1998 in the Changjiang River and its mouth, together with histori cal data including those in the literature, the main sources and transport fluxe s of inorganic N in the Changjiang River catchment were quantitatively estimated . The results show that the inorganic N caming from precipitation, agriculture n on-point sources (lost from fertilizer and soil) and point sources sewages disch arged were about 62.3%, 18.5% and 14.4% of the export flux of inorganic N in the Changjiang River mouth, respectively. The N from precipitation was the main sou rce of the high content inorganic N in the Changjiang River mouth and the precip itation N entering the Changjiang River was only 36.8% of total precipitation N in the Changjiang River catchment. The N in precipitation were mainly controlled by the fertilizer losses, the combustion of fossil fuels and the released subst ances from animals and plants processes and so on. In fact, about 60% of consump t ion of annual fertilizer N were lost from gaseousness and agriculture non-point sources, this is a key factor to control the high content inorganic N in the Cha ngjiang River mouth.