The Environment Sedimentological Study of Erhai Lake－Correlation between nutrients and particle size distribution in superficial sediments

Key words: 
• Erhai lake /
• superficial sediments /
• nutrients /
• particle size distribution /
• environmental significance

Abstract: Erhai lake,the second largest lake in the Yunnan Plateau in Southwest China,is located in Dali Prefecture with 25°35'to 25°58'Nin Latitude 100°05'to 100°07'Ein logitude Erhai Lake is a typical rift lake in the Dali Basin developed along the YuaJiang Hoonghe great fault and has been in existence since Later Pliocene.In November 1996(winter),the lake water quality was still in a poor condition,with a low concentration of dissolved oxygen.The lowest Do value was 1.7 mg/L.Results of comprehensive assesment indicate that water quality at most of the sections was grade III,with some of them reaching grade IV.The sudden deterioration of water quality in Lake Erhai has clearly indicated that the lake's water quality is at a critical state.In order to prevent occurrence of more eutrophication in the future,study of nutrient and pollutant emissions from sediment to the lake by environment sedimentology methods would be necessary.By Studying relationship between nutrient and particle size distribution for the Erhai lake's superficial seddiments,the results show that clay mineral is generally positively correlated with total phosphorus,Fe P and O P. The multiple regression results suggest that there are apparently positive correlation among TN,TON(total organic nitrogen),T HN 3,A'% and deris minerals.The TP content is mainly comprised of inorganic posphorus and positively correlated with sediments with higher content of clay minerals and smaller particle size mainly deposited in the lake center in the northern part of Erhai lake.