Characteristics of Nutrients and Eutrophication Assessment of the Laoshan Bay,Qingdao

SUN Wei; TANG Xianchun; XU Yandong; LIU Yuanjin; MA Jianxin; ZHANG Huanjun

Abstract：According to four cruises in the Laoshan Bay,Qingdao,in May、August and November 2014,and in March 2015,including Dissolved Inorganic Nitrogen(DIN),Orthophosphate(PO4-P)and Chemical? Oxygen? Demand(COD),nutrients characteristics in concentration and structure were studied,and the eutrophication degree of the Laoshan Bay was assessed by single factor index,eutrophication index and grey clustering analysis.The results showed that DIN was the principal contamination parameter of water quality of the Laoshan Bay.The concentrations of DIN,PO4-P and COD were slightly higher in the mouth and central bay than the offshore area.The concentrations of nutrients were higher in the summer cruises,and the concentration of COD was slightly higher in the winter cruises.The N∶P ratio in average rate of a year was 68.35,the structure of nutrients was characterized by phosphoruslimitation in the Laoshan Bay.The eutrophication index in average rate of a year was 1.34.The results of grey clustering analysis showed that the proportions of mid-eutrophic (Ⅱ) and eutrophic (Ⅲ) stations were 92.86％ and 0％ respectively in spring,64.29％ and 21.43％ respectively in summer,92.86％ and 7.14％ respectively in autumn,100％ and 0％ respectively in winter.Grey clustering analysis was more applicable eutrophication level evaluation in Bay.