| China’s aquaculture industry develops rapidly and provides a large number of high quality animal protein to people.The problem of eutrophication caused by aquaculture is becoming more serious because of the high density culture and feeding too much and waste water discharging lacks management;on the other hand,The quality and safety of aquatic products has been a serious threat by the pollution outside.The north of Zhejiang province is one of the traditional areas and the most developed areas of freshwater aquaculture in China.To find out the situation of eutrophication pollution and heavy metal pollution in this area,and provide basic data for the future,we carry out this investigation.We chose Huzhou City and Jiaxing City of North Zhejiang and investigated by random sampling for two years.We investigated the water and its pond of 35 farms for the eutrophication.Ion chromatography analyzer,visible spectrophotometer and total organic carbon analyzer were used to detect six eutrophic pollution parameters.They are ammonia nitrogen,nitrate nitrogen,nitrite nitrogen,permanganate index,chemical oxygen demand,total organic carbon.The results tell me that the pollution parameters of aquaculture water without treatment are obviously higher than the water supply except nitrite nitrogen.The exceed standard rate of permanganate index and chemical oxygen demand over the third levelis higher than 50%.Most of the aquaculture water return to the outside without treatment,so it will cause the eutrophication pollution of water outside by the current aquaculture mode.We collected 181sediment samples included river sediment for the investigation of heavy metal pollution.We use atomic absorption spectrophotometer and atomic fluorescence spectrophotometer to analyze the Cu,Zn,Cr,Pb and Cd of the samples had been digested by microwave digestion instrument.We evaluated data by Nemerow index and potential ecological risk index.It tell me that the heavy metal content in most of the samples is in the level of light pollution,even in some areas even have already been medium or severe pollution levels.The level of Cd pollution in river sediments is the highest of all.Considering the maximum value of the pollution index on soil environment,the safety range of Nemerow index is more narrow than potential ecological risk index. |
