论文部分内容阅读
Lake eutrophication, which could be reversed by the establishment of nutrient criteria and control standards, is of great concern to the Chinese government and limnologists.The historical and present levels of nitrogen and phosphorus in the 28 lakes of China suggested that the nutrient concentrations in the lakes of Xinjiang and Jiangsu (e.g., macrophyte-dominated Lake Gucheng and Lake Shijiu) and the deep lakes in Yunnan Province (Lake Fuxian and Lake Lugu) were relative low while they were high in the other lakes.Furthermore, nitrogen and phosphorus concentrations are still increasing in most of the lakes except Lake Taihu and Lake Xuanwu.A comparison between the cyanobacteria and macrophyte dominated eutrophication indicated that total phosphorus (TP) concentration was always in high levels throughout the year in cyanobacteria dominated lakes (regions).Based on the kinetics results of cyanobacterial decomposition and phosphorus release, the phosphorus flow rates in the ecosystems were relatively fast, which resulted in the high dissolved phosphorus concentration, i.e., the ratios of TDP/TP were all above 30% in different cyanobacteria dominated lakes (regions).The relatively low phosphorus concentrations appeared during the growth of macrophyte and extremely high TP levels when they were decomposed.The relationship between TP and the primary productivities in the lake ecosystems could be simulated with the equation Rmax =k0/(1-η) (Rmax represents the capacity of changing TP into the actual primary productivity (Chl-a), k0 is the slope of linear regression between TP and Chl-a for the standing crop of the 28 lakes examined, and η means the phosphorus transfer efficiency in the lake ecosystem).Then the equation Rmax=e0.000728*Tem was used to describe the relationship between Rmax and the accumulated temperature (Temp).The phosphorus flows in aqueous ecosystems are slow if Temp is lower than 3400 oC·d, and become fast when Tem is above 4730 oC·d.28 lakes are geographically categorized into several groups as Xinjiang lake regions, Inner Mongolia lake regions, northeast plain/mountainous lake regions, eastern plain lake regions and Yun-Gui plateau lake regions in China.These lakes can be classified as fast, intermediate and low flow ecosystems based on their phosphorus flow rates.The TP criteria and the corresponding control standards were relationship with the phosphorus flows rate in aqueous ecosystems.Accordingly, the TP criterion and control standard were 0.08 and 0.20 mg.L-1 for Lake Hulun, 0.03 and 0.06 mg·L-l for Lake Taihu, 0.08 and 0.15 mg·L-1 for Lake Dianchi, respectively.This study provides important theoretical foundation for the establishment of the different lake ecoregions as well as the formulation of nutrients criteria and standards.