An Analysis on Water Quality and Eutrophication in the Coastal Area of Qinzhou Bay

Water quality was monitored in the coastal area of Qinzhou bay,Qinzhou,Guangxi,southern China in May,2012.The results showed that all of the basic parameters such as water temperature,salinity,pH and dissolved oxygen in this coast were suitable for the growth and breeding for all kinds of living beings in subtropical oceans during this period.Dissolved inorganic nitrogen and activated SiO2-3-Si appeared over-abundant in the coastal area,but the dissolved inorganic phosphorus had a feature of low content,the higher N /P ratio means that PO3-4-P might become a potential factor to limit phytoplankton growth.COD appeared the phenomenon of exceed standard in some stations.The results of pollution index A and single factor pollution index Piindicated that there was two grade pollution degree in the whole survey region,which belongs to just beginning pollution,and 30% of these stations were polluted by organic aerobic organisms at different degree.The result of eutrophication index suggested that it has not been achieved eutrophication status to the whole study area,but there has been an eutrophication condition for some regions.The mean( range) value of contribution to the eutrophication was 72.46%( 67.36%-83.96%).COD has become an important factor for the contribution of eutrophication in the study area.