RELATIONSHIPS BETWEEN ORGANIC MATTER IN SEDIMENTS AND INTERNAL NUTRIENT LOADINGS IN SHALLOW LAKES IN HUBEI PROVINCE OF CHINA

Eutrophication of Lake is attributable to the burgeoning human population in its watershed. In this study, comparative investigations have been conducted to study the nutrient distribution pattern、physical and chemical properties of sediments in different areal lakes. Sediment samples have been collected during the period from 2002 to 2004 in seven shallow lakes (Lake Yue hu, Longyanghu, Houguanhu, Liangzihu, Niushanhu, Baoanhu and Luhu) in Hubei Province for analysis of organic matter(OM), total nitrogen (TN), total phosphorus (TP) in surface sediments. The grain size of sediment in Lake Yuehu,Longyanghu and Baoanhu was also determined. In addition, Vertical profiles of OM, TN and TP in sediments were described in Lake Yuehu and Lake Longyanghu. For organic matter in surface sediments, urban lakes like Yuehu and Longyanghu showed not only significantly higher contents, but also a spatial heterogeneity with littoral zones being more abundant. Thus external discharge was its main source and accelerated the process of eutrophication. Furthermore, OM significantly related with TN and TP vertically and spatially, but the relationship between OM and TN was better than the relationship between OM and TP. As in the case of carbon, a dominant proportion of the nitrogen found in the sediments is organically bound. For phosphorus, on the other hand, a dominant proportion is inorganically bound. Grain size was also closely connected with OM and TN, respectively. But there was no correlation between TP and grain size. It may be interpreted by the diversity of Phosphorus forms. In short, OM may act as an important factor accelerating the process of eutrophication in urban lakes.