Characteristics of Nutrients Distribution from Recent Sediment in Lake Nansihu

Nutrients concentrations in surface and core sediments from Lake Nansihu were investigated. The results showed that sediments from Lake Nanyang had significantly higher TP concentrations than any other area of Lake Nansihu. Lake Dushan suffered from the highest TOC and TN content. Lake Zhaoyang had low TOC, TN and TP concentrations. The method of 137Cs dating was used to derive accumulation rates of 3.5 mm/a for Lake Dushan. The historical profiles of Lake Dushan for nutrients showed that TOC, TN and TP mainly enriched in 0-8 cm, and presented simultaneously changeable trends. The development of society and economy in the Basin had resulted in nutrients release increasing, which made nutrients accumulation in recent sediment. The ratios of C:N varied slightly from 7.6 to 11.4 for the recent core. These characteristics suggested that organic matters in the sediments mainly originated from continental plants without cellulose and reserved variations in ecosystems resulted from continents. The monitored data indicated that the discharge of domestic, industry and agriculture from the lake basin directly into Lake Nanyang was the mainly source that made the enrichment of TOC, TN and TP in Lake Nansihu.