[Distribution and enrichment of nutrients in superficial sediment in Tianjin typical waters]

Concentrations of organic matter (OM), total nitrogen (TN), total phosphorus (TP) and bioavailable phosphorus (BAP) were determined in superficial sediment (0-25 cm) collected from 4 selected typical waters (Yuqiao reservoir, Haihe River, Haihe estuary and Bohai Bay) in Tianjin, China. Pollution index (P(i)) and enrichment factors (EF) were taken to analyze nutrients enrichment and dynamic characteristic. The results show that 4 typical waters are polluted by anthropogenic source and much higher than the permissible limits which most benthos can bearing, the concentrations of OM, TN, TP and BAP are decreasing progressively by the order: Haihe River > Haihe estuary> Bohai Bay Tianjin Sea Area. EF for OM, TN, TP and BAP reaches 1.6-6.5, 0.9-2.7, 0.9-2.6 and 4.4-9.2, respectively. The concentrations of BAP in different waters are inconsistent with those of TP, the ratio of BAP to TP in Yuqiao reservoir is the biggest, 16.3%, which shows endogenous source release is serious and eutrophication is the key problems of water pollution. The concentrations of OM and BAP increase in large scale between 1988 and 2005, TP basically keeps unchanging and TN slightly increases. Around Haihe River sediment dredging, nutrient concentrations (OM, TN and TP) of superficial sediments in Haihe River reduce to 57.7%, 82.8% and 85.2% of original concentration, respectively. And sediment dredging plays a positive role in nutrients removal.