中国主要湖泊营养氮沉降临界负荷的研究

水体营养氮沉降临界负荷是不致使水体产生富营养化的最高氮沉降量。文中探讨了一种依据湖泊氮质量平衡原理计算营养氮沉降临界负荷的方法。用该方法计算表明 ,我国主要湖泊的营养氮沉降临界负荷比较低 ,大部分小于 1keq· hm- 1 · a- 1 ,部分已为目前的氮沉降量或者两者相当接近 ,意味着只接受氮沉降也能导致这些湖泊产生富营养化。但实际统计结果表明 ,氮沉降在导致受工农业生产和生活影响很大的城市和郊区湖泊的水质富营养化的所有氮污染源中所占比例较低 ,而其它来源的氮输入如河道入湖、工业生活废水和农田径流等才是导致富营养化的最主要因素 ,它们的量已远远超过了这些水体可随最高允许氮负荷。因此 ,对控制这些湖泊的水质富营养化而言 ,控制氮沉降并不是目前最紧迫的任务 ,而其它人为污染源的控制才是最急需的。但氮沉降临界负荷在湖泊富营养化的中长远控制中仍具有十分重要的意义。

On critical loads of nutrient nitrogen deposition for some major lakes in China

Critical load of nutrient nitrogen deposition for surface water is the highest nitrogen deposition never causing water eutrophication. A method to calculate the critical load of nutrient nitrogen deposition was proposed in the paper according to the nitrogen mass balance within the lake catchment. Results based on this method show that for most of the major lakes in China, critical loads of nutrient nitrogen deposition are quite low, most of which are lower than 1 keq\5hm\+\{-1\}\5a\+\{-1\}, and some are exceeded or approached by present nitrogen deposition. It means that eutrophication will occur for these lakes even under nitrogen deposition. Nevertheless, statistical data indicate that nitrogen deposition only accounts for a small part of the total nitrogen pollution sources resulting in water eutrophication for those lakes affected by industrial and agricultural actions, while other sources such as wastewater of industry and domestic and agricultural runoff account for the larger proportions. Nitrogen input from these sources is much more than the permitted nitrogen loads which will not induce the lakes to suffer from eutrophication. As a result, to control water eutrophication of these lakes, it is not most urgent to control nitrogen deposition but to control the other sources of nitrogen pollution mentioned above. However, critical loads of nutrient nitrogen deposition for lakes still have significant importance in the long\|term controlling of water eutrophication.