关键词: 海洋化学, 龙江, 营养盐, 富营养化, marine chemistry, Longjiang Estuary, nutrient, eutrophication

Abstract: Based on the data from water surveys in 2012 and 2013, the distribution, composition and eutrophication of nitrogen and phosphate in Longjiang Estuary were studied. The results indicated that the DIN and PO4-P concentrations ranged from 0.808 ~ 5.285, 0.610 ~ 5.383 mg/L and 0.028 ~ 0.324, 0.096 ~ 0.643 mg/L, respectively, and showed varying degrees of excessive status and rising trend. There was a pronounced decreasing trend of N and P concentrations from riverine to marine regions because of the dilution by relative oligotrophic coastal waters, and N and P values in the seawater were high in winter/spring festival and low in summer/autumn festival due to the impact of reduction in surface runoff during the dry season. NH4-N ratios in DIN were as high as 51.15% ~ 63.25% and 43.88% ~ 69.39% during two years, dominating the state of pollution of DIN in the estuary. The N/P ratios ranged from 10.83 ~ 13.12 and were closed to Redfield value（16:1）, based on this nutrient conditions, it may suitable for phytoplankton bloom. The potential eutrophication assessment indicated that the stations in Longjiang Estuary were at the stage of eutrophication, Longjiang Estuary may have faced with more serious threat such as red tide by eutrophication because of the high absolute concentrations of nitrogen and phosphorus.