Evaluation Of The Physicochemical Environment And Nutrition Status In Danzi Island

Danzi Island is subordinate to Zhifu district, Yantai city. It is located at373420N and1212830E. It lies2.3n mile from the nearest of the coast line and5.6km from Kongdong Island southeast. To know about the situation of the waterquality in this waters, the writer implemented a eighteen-month investigation on thetemperature, salinity, transparency, depth, pH, DO, COD, nitrite, nitrate, ammonianitrogen, reactive phosphate, total nitrogen, total phosphorus, chlorophyll A,chlorophyll B, oils and heavy metal from August2010to January2012in the watersof Danzi island. And the writer analyzed the results and further indicated the changingpattern of each index. The evaluation on the nutritional state was conducted in orderto provide the scientific knowledge on protecting and exploiting the waters in DanziIsland reasonably.During the research, four sampling sites were set up around Danzi Island. Twowater layers were sampled in each site every month. After the samples were gotten,they were filtered by the0.45μm-diameter filter membranes made by Millipore andconserved in low temperature. When the samples were brought to the laboratory, wedetermined DO and COD by titration while determined the nitrite, nitrate, ammonianitrogen, reactive phosphate, total nitrogen, total phosphorus, chlorophyll and oils byspectrophotometric method.During the research, the water temperature in Danzi Island varied seasonally. Thesummer temperature was high and the winter temperature was low. The precipitationin summer and fall was so heavy that the salinity in these seasons was low. Thesalinity in winter was high. On the whole, the changes were seasonal significantly.The transparency and depth have the strong monthly variation. The monthly variationof pH was corresponding fundamentally and went high totally. The average of DO and COD were5.85mg/L and0.64mg/L respectively. The values reached the secondwater quality standard and the first water quality standard respectively. In contrast tothe other bays, DO was low. The concentration of the chlorophyll has the seasonalchange significantly. In fall and winter the values were lower than those in spring andsummer. The results may be related to the growing season of the phytoplankton. Thecontent of oils was low. The average was only0.20mg/L and reached the secondwater quality standard.During the research, the average contents of the inorganic nitrogen and reactivephosphate were0.48mg/L and1.13×10^-2mg/L respectively. Compared with theforeign results, the value of the inorganic nitrogen was low clearly, but it was middlein the domestic rank. The value of the reactive phosphate was low clearly. The twovalues reach the fourth water quality standard and the first water quality standardrespectively. The N-P ratio was more than16and the average was114.48.Approximately, it was as7.16times as the Redfield ratio. This showed the inorganicnitrogen was abundant and the reactive phosphate was very deficient. It became themain restriction factor to the phytoplankton in the waters. According to the potentialeutrophication evaluation model, the nutrition quality index method and the Organicpollution index, the waters belonged to the potential phosphorus limitedeutrophication（ⅥP）and eutrophication level. The Organic pollution degree belongedto level3and indicated the waters was suffered from the light pollution.