Characteristics Of Organic Phosphorus Pollution Of East Plain Region And Its Effects On Lake Eutrophication

Nowadays, lake eutrophication is becoming a serious eco-environmental problem in our world and an important water pollution problem in our country. The most sever lake eutrophication in our country is in the east plain region, and in this region most lakes are facing serious eutrophication problems. Phosphorus in sediments is an important source and sink of phosphorus in lake water, and is tightly related to lake eutrophication, therefore, it is considered as an main factor in causing lake eutrophication. Up to date, researches focused on inorganic phosphorus in lake sediments, however, limited literatures studied on organic phosphorus, which is another important components of Phosphorus in lake sediments. Thus, it is necessary to investigate the biogeochemical characteristics and bioavailability of organic phosphorus in lake sediments.This study is one of the important parts of "lake sediment investigation in east plain region" foundation project. The biogeochemical characteristics of organic phosphorus in sediments were studied, containing organic phosphorus combined forms, distribution, composition and bioavailability. The main results are summarized as follows:1.In our study region, the content of total phosphorus of the sediments were 327-1929 mg/kg, and in general the content of total phosphorus in different types of lakes from big to small in turn:urban lakes>lakes for culture>large lakes in natural. The content of organic phosphorus of the sediments were 65.2-539.2 mg/kg, which account for 19.9%-40.6% of total phosphorus. The variety of organic phosphorus and total phosphorus content have the similar trend in lake sediments with different pollution levels.2.The organic phosphorus in the sediments existed mainly in the form of moderately labile and nonlabile organic phosphorus. Organic phosphorus content in all forms increased as lake pollution degree increased, and varied in different types of lakes in the order of urban lakes> lakes for culture> large lakes in natural.Nonlabile organic phosphorus was the main form of urban lakes and lakes for culture, while the bioavailable organic phosphorus(labile organic phosphorus + moderately labile organic phosphorus) was the main form of large lakes in natural.3.HCl-Po is a main component of moderately labile organic phosphorus and showed remarkably differences in sediments of lakes with different pollution degree. HCl-Po had a significant positive correlation with water TP, TN, chla, CODMn, and significantly associated with TP,LOP and MLOP of lake sediments.it proved that the HCl-Po of lake sediments may be an important source of water phosphorus.4.The contents of DOP in sediments were 2.34-23.35 mg/kg, account for 0.7-1.88% of TP in sediments.The contents of DOP increased following sediments pollution degree increased, and higher in heavy polluted lakes than in light polluted lakes.DOP was positively correlated with DIP, TP, CEC and OM. Soluble phosphate monoester content in sediments werer 0.148-0.945 mg/kg, account for 14.3% of DOP, while soluble phosphodiester content in sediments were 0.041-0.246 mg/kg, account for 4.5% of DOP. Soluble phosphate monoester and phosphodiester average content in sediments was higher than in soils and water. The index kinetics model (lnq=b+klnt) can be used to fit the phosphate release kinetics characteristics of these studied sediments, The release amount of phosphorus in sediments was closely related to the nutrition content in sediments.5.31P NMR analysis results revealed that lake sediments from east plain region main contain six kinds of phosphorus compounds shown as orthophosphate, orthophosphate monoester, orthophosphate diester, pyrophosphate, polyphosphate, Phosphonate. Orthophosphate is the biggest component of phosphorus compounds, and it is accounts for 12.1-27.1% of TP in sediments. Monoester and Diester are two important components of OP in sediments, and they are account for 1.4-5.2% and 0.8-3.4% of TP in sediments, respectively. There are little Pyrophosphate existed which account for only 0.1-0.7% of TP in sediments, and Polyphosphate and Phosphonate are obtained in individual lake sediments. Orthophosphate had a significant positive correlation with water TP and chla, furthermore, Monoester and Diester have the same significant positive correlation, it proved that Monoester and Diester have the upper potential Bioavailability, and should be regarded as important to further research.