Nitrogen distribution in the lakes and lacustrine of China

China has numerous lakes within its territory. According to geographical location, genesis and topography, China can be divided into five lake regions: 1, East China plain lake region; 2,Yungui plateau lake region; 3, Monxin lake region; 4, North-east lake region; and 5, Qin-zan plateau lake region. Geographical location and environmental conditions exert an important effect on the nitrogen distribution in lakes. The lakes with serious pollution and eutrophication have a higher content of nitrogen, about 1.8 to 3.8% of the total nitrogen in water and 0.4–0.9% of the nitrogen in sediment. and the lakes that are closed or semi-closed or located in an arid or semi-arid area also have more nitrogen content (0.91% of nitrogen in water and 0.216% of nitrogen in sediment in Erhai lake). Four sources of nitrogen are contained within the lake sediment: 1, from terrestrial sources by erosion from the basin; 2, from pollution by the industry and waste water of urbanization; 3, by autochthonous plankton and algae and 4, from chemical deposition in a drought zone. The sediments derived from terrestrial plants have a high nitrogen content but also have a high C/N ratio, while nitrogen sources from autochthonous plankton have a high nitrogen content but have a low C/N ratio, as some lakes located near cities are eutrophied or hypertrophied.