Study on Dissolved Inorganic Nitrogen Distributions and Eutrophication in the Jiaozhou Bay

Based on the monthly observed hydrochemical data in the Jiaozhou Bay in the period from January to December,2003,the distributional characteristics and space-time variations of dissloved inorganic nitrogen(DIN) in the sea area were analyzed,and the eutrophication conditions were assessed. It is shown from the analysis results that the annual mean DIN concentration in the area is 17.70 μmol/dm~3,and(NO_3-N) is the main component of DIN with a concentration accounting for 58.2 % of DIN concentration on an average.In autumn,the NO_3-N concentration is the highest,and accounts for 64.74 % of DIN concentration.The DIN contration is the highest in the northeastern Jiaozhou Bay and decreases gradualy to wards the inner bay and bay mouth.The annual mean dissolved inorganic phosphorus(DIP) concentration in the area is only 0.49 μmol/dm~3,and the annual mean ratio of DIN to DIP in the surface seawater is(39.41),so DIP in the area is deficient relative to DIN.It is shown from the nutritional condition index distributions that the northeast coastal area belongs to eutrophic area,and the red tide may constitute a serious threat to the sea area in summer and autumn.