| Nitrogen input and accumulation caused by human activities potentially influences the regional environment, especially the water environment. This paper introduces the concept of “net anthropogenic nitrogen accumulation”, NANA and defines it as the difference between N input and N output caused by human activities, which are estimated from the accumulation in atmospheric N deposition, N fertilizer use, N accumulation of human food and animal feed, N fixation and riverine N accumulation. It is found in the study that NANA in Beijing has a downward trend from 12557 kg·(km2·a)-1 in 2003 to 11606 kg·(km2·a)-1 in 2007, but still 2-5 times that of other countries. The distribution of NANA is closely associated with the population distribution and land use type. The change of NANA is mainly related to the population density and the amount of applied fertilizer. As to the whole Beijing area, atmospheric N deposition is the largest source of N, accounting for 51% of NANA, which is followed by fertilizer use of 37.4％ and human food and animal feed of 16.6％. The population density and the amount of applied fertilizer are main factors affecting NANA. The accumulated N is mainly distributed in soil, water system, body of animal and plant as well as the atmosphere. The effect of N on the environment can be effectively prevented by controlling the sources and proliferation of N. |
