[Spatial distribution characteristics of surface sediments nutrients in Lake Hongze and their pollution status evaluation].

In order to illuminate nutrient spatial distribution characteristics in surface sediment of Lake Hongze, sediment samples at 10 representative sampling stations were collected in June of 2008, and concentrations of organic matter, total nitrogen, organic nitrogen, ammonia nitrogen, nitrate, total phosphorus, inorganic phosphorus, Al-Phosphorus, and calcium-Phosphorus in sediment of each station were measured. Analyze showed that: organic matter and total nitrogen are significantly correlated, and organic nitrogen occupies 90% of total nitrogen, which means that carbon and nitrogen were from the same source; Inorganic phosphorus is the majority (70%) of total phosphorus, and the calcium-Phosphorus accounts for a large percentage of inorganic phosphorus; The spatial distribution pattern of organic matter in the lake is very similar with that of total nitrogen, organic nitrogen and total phosphorus, which belongs to a typical sediment distribution pattern called Turbidity Flood Model. The C/N analysis showed that the main sources of organic matter in surface sediments are from the sedimentation of biomass in its water column. By organic matter index evaluation standards and organic nitrogen evaluation standards, the pollution levels of sediment at each sampling stations in the lake were evaluated at clean category, except that at north part of Longji, which was polluted by organic nitrogen.