Optimal Design Of Monitoring Network And Comprehensive Assessment Of The Seawater Quality In China Seas

Marine environment is facing increasing pressure in China. The basis of the assessment and management of marine environment is to monitor marine environment effectively, especially in the costal areas. How to effectively design marine environmental network in order to assess and monitor marine environment become a hot topic in the study of marine environment.On the basis of the existing monitoring sites and elements of marine environment, this thesis proposed Seawater Environmental Quality Index to evaluate the quality of the marine environment. On this basis, Ordinary Kriging Variance Analysis method was applied in the optimization of the monitoring sites in the study area. In addition, statistics method was used in the frequency optimization of marine environment. The marine environment could be assessed comprehensively and accurately by these methods, which can provide the theoretical basis and technical support for the monitoring and management of our country's marine environment quality. Taken North Sea, South Sea, and East Sea as examples, the comprehensive assessment of seawater quality and the optimization of monitoring sites and frequency are as follows.1. The quality of marine environment is clean in the center of Bohai Sea. The analysis of environmental quarter monitoring elements of Bohai Sea in 2011 shows that the monitoring elements concentrations are highest in August, followed by October, the lowest in May. The seawater quality of Liaodong Bay, sea area near Dalian City and Bohai Bay is slightly polluted, while the quality is good in the Laizhou Bay. The seawater quality in the center of Bohai Sea is excellent. According to the total potential ecological risk of the trace metal pollutants, the pollution of Bohai Sea is relatively low. Based on the average values of environmental elements of seawater from 2004 to 2010 in Bohai Sea, Seawater Environmental Quality Indices of 38 monitoring sites are extracted to represent the pollution level of this area. The quality of existing monitoring network is analysed through ordinary kriging variance analysis method. The optimised monitoring network of 42 monitoring sites is proposed, which can improve the monitoring precision. Based on low, medium and high budget analysis,163 monitoring sites from 2009 to 2010 in Bohai Sea has been optimized.2. The assessment of seawater environmental quality in the northern of the Yellow Sea shows that inorganic nitrogen, oil, mercury, and lead in the coastal area are in the III seawater quality index and slightly polluted. The pollution is from shore factories, surface runoff, marine transportation, oil well exploration and atmospheric deposition, combining with warm current, coastal stream and cold water mass in the center of the Yellow Sea. Based on the average values of environmental elements of seawater from 2004 to 2011 in the northern of the Yellow Sea, Seawater Environmental Quality Indices of 206 monitoring sites are extracted to represent the pollution level of this area. The existing estimation error standard deviation is 0.2199. Considering the current marine environmental quality, the monitoring network of 213 monitoring sites is proposed by variance reduction method.3. The seawater quality of Shanghai seas is severely polluted. The main pollutants of study area are inorganic nitrogen, phosphate, oil, copper and lead.The pollution of south branch is more serious than north branch's. Based on the seawater environmental quality index and the mean values of environmental elements of seawater from 1985 to 2006, seawater environmental quality index is proposed to characterize the pollution level in this study. On this basis, kriging variance analysis method is applied in the optimization of marine monitoring network in order to get more accurate and abundant information of the marine environment. SEQI of 42 monitoring sites is extracted to describe the pollution level of this area. Combining the average standard error of the monitoring network and the marine environment pollution level, the number of monitoring sites is increased from 42 to 59 by kriging variance analysis method. The whole seawater quality of Xiangshan Harbour is severely polluted and the pollution extent becomes more and more serious from the outer of the Harbor to the inner. Combing with monitoring conditions and requirements, the monitoring sites of Xiangshan Harbor are optimized by variance reduction method. The optimized monitoring network comprised by 50 monitoring sites is proposed.4. In the coastal area of the South China Sea, the seawater quality of the Pearl River Estuary is severely polluted, and the eastern of Zhanjiang seas is moderately polluted. The seawater quality of the Beibu Gulf is slightly polluted, while the quality is good at eastern of Guangdong seas and Hainan Island. The seawater quality of the offshore area outside the Beibu Gulf and the northern of the South China Sea are good, while the quality is moderately polluted in the central and southern regions by the land-based sources by neighboring countries. Through ordinary kriging variance analysis method, the monitoring sites of coastal and southern area of the South China Sea have been designed, which can improve the quality of monitoring network.5. Based on statistical method analysis, monitoring frequency of the monitoring elements in the North Sea, Xiangshan Harbor and Hong Kong seas are optimized. Because there is a certain range of variation of the designed monitoring frequency in the study area, the maximum value is chosen as the optimal monitoring frequency for the continuity and integrity of the monitoring data. The monitoring frequency of pH values, dissolved oxygen, salinity and chemical oxygen demand is smaller, while the frequency of nitrate, nitrite, ammonium, phosphate and oil are higher.