Study On The Characteristics Of Eutrophication In Different Areas Of Dianchi Lake

Lake Dianchi watershed is located in the southwest of Kumming of Yunnan province, which is a typical plateau freshwater lake watershed in China. In recent years, there have been a lot of researchers to study the problem of the eutrophication of Lake Dianchi. At present, the major foucus of the research is on the Lake Dianchi watershed, or the nutrient in the sediment, instead of nutrient and sediment organic matter through the Yunnan comprehensive tracer lake eutrophication. Molecular markers, distribution characteristics of n-alkanes can indicate source of organic matter. Therefore, based on four types of typical into rivers, water nutrient spatial variation characteristics analysis, sediment organic matter in different time and space distribution characteristics in Lake Dianchi, the paper analyzes the different lake eutrophication of in Lake Dianchi source condition.At first, we analyze spatial distribution rules of nitrogen and phosphorus nutrient, COD and Lake Dianchi sediment source of organic matter of four types of typical rivers into the lake of Lake Dianchi (urban rivers, urban-rural fringe rivers,farmland river, river village). Then, we utilize nitrogen and phosphorus than (TN/TP)to analyze four river summer nutrition status of water quality. Next we use the 210Pbex to determine the sequence of the Lake Dianchi sediment samples. On this basis, combining sediment nutrient (TOC,TN, TP), carbon molecules corresponding normal alkanes, and various environmental parameters, we comprehensively discuss the Lake Dianchi watershed environmental evolution and human activities,which provides scientific data basis about the relationship between the phenomenon of eutrophication of Lake Dianchi watershed scale in one hundred and the reason of the bad ecological environment.Through the above research, we can drw the following conclusions:(1) The Lake Dianchi sedimentary environment features:Sediments 210Pbex specific activity with depth is not present attenuation index model. Dating results show that sediment s span is 1877～2014, the deposition rate of 0.09 g (cm2·a)-1 on northern Lake Dianchi. Dating results show that sediment span is 1860～2014, the deposition rate of 0.11 g· (cm2 · a)-1 on northern Lake Dianchi.Deposition .rate as the changes of the s characteristics,is related into the lake in the specific historical events.(2) alkanes to organic matter source resolution in the sediments in Lake Dianchi:Carbon number distribution range is: the corresponding normal alkanes was C12～C34, Lake Dianchi sediment parameters recorded nC27/nC31 ratio and the corresponding normal alkanes was Paq and CPI. This indicates that the Lake Dianchi sediments from down to up herbs and woody plants change alternately, and the high carbon number of organic matter in sediments mainly from Lake Dianchi endogenous submerged floating and large plants. C/N ratio and distribution characteristics and the corresponding normal alkanes showed that the Lake Dianchi sediment organic matter source is different: north of Lake Dianchi sediment organic matter mainly comes from the human endogenous plant and terrestrial organic matter source; Lake Dianchi south of the organic matter in sediments mainly comes from internal large aquatic plants and terrigenous higher plants mixed source.Therefore, in the future study of organic matter and sediments in the Lake Dianchi,the researchers should strengthen the research of the Lake Dianchi different organic matter.(3) water nutrient characteristics of The Lake Dianchi watershed:In summer, four kinds of typical rivers of Lake Dianchi watershed are seriously polluted in terms of Yunnan total nitrogen (TN), total phosphorus (TP), nitrate nitrogen and ammonia nitrogen. Besides, it is obvious to find the increase of TN and TP from upstream to downstream so as to cause nitrogen and phosphorus nutrient constantly enrichment along the river. The order of the average concentration of TN, TP, COD is that formland-type rivers (Da river) > towns and villages type river(Chai river) > integrated urban and rural type river (Baoxiang river) > urban rivers carrying type (panlong river). Especially, the pollution of farmland river (Da river)is most serious, in terms of TN, NH3-N, NO3-N TP and COD. In Summer of rivers into the lake Lake Dianchi, TN, NH3-N,NO3--N and TP concentration of the southern is higher than that of northern rivers into the lake, which is opposed to that in internal TN,NH3-N、NO3--N and TP pollution distribution of Lake Dianchi.,We hypothesized that the mojor factor is the internal release. Therefore,in the future study of Dianchi eutrophication, the reserchers should strengthen the research of Dianchi endogenous.(4) Nutrient characteristics of The Lake Dianchi sediments of:With the increase of sediment depth, since the 1970s, TOC and TN, TP in theDianchi sediments gradually increases, Lake Dianchi primary productivity rises ceaselessly, which show the Lake Dianchi watershed environment began to degenerate.