Eutrophication Evaluation And Characteristic Analysis Of Zhelin Bay Based On P-S-R Framework

With the increasing social demand for coastal economic development,the pressure on China's near-shore marine environment will follow.There are still many problems in the offshore waters.For example,local coastal waters are seriously polluted,typical marine ecosystems are in poor health,land-based pollution pressures are higher,marine environmental risks are prominent,local red tides are in a high-occurrence period,and the range of green tides increases.Therefore,this paper uses the second generation of seawater eutrophication evaluation method for reference,uses hyperspectral remote sensing to obtain the spatial data of inorganic nitrogen,inorganic phosphorus,chemical oxygen demand,chlorophyll a,dissolved oxygen,Secci Disk Depth and other water quality indicators,and constructs a seawater evaluation method combining pressure,state and response.Using the constructed evaluation method of seawater eutrophication,the eutrophication degree of Zhelin Bay and its adjacent waters,which often have inferior water quality standards,was evaluated.The conclusions are as follows:(1)Based on the GF-2 image as the data source,combined with the advantages of objectoriented multi-scale segmentation and random forest classifier,by adjusting the optimal segmentation scale and feature space optimization,an automatic interpretation method of near shore water body information based on random forest object-oriented is established.Its interpretation accuracy reaches 94%,which is superior to object-oriented and pixel-based random forest recognition methods.Therefore,this method was used to extract the pond culture area,river and water body in the bay of Zhelin Bay.(2)According to the standards of coastal environmental monitoring in China,the water quality index is selected,the assessment system of seawater eutrophication based on P-S-R framework is established and the "high,medium high,medium,medium low,low" grades were used to assign the value,and they are divided into 1,2,3,4,5.(3)after determining the water quality indicators,by collecting water samples,measuring water spectrum and acquiring synchronous transit satellite images,the optical characteristics of water samples were analyzed,and the remote sensing inversion model of water quality index,such as inorganic nitrogen,inorganic phosphorus,chemical oxygen demand,chlorophyll a,dissolved oxygen,Secci Disk Depth,was constructed.Through comparison of different methods and error analysis to determine the best estimation model,the accuracy is 0.68,0.87,0.8,0.81,0.8 and 0.71.(4)The pressure index,state index and response index are used to evaluate the degree of eutrophication pressure,symptom manifestation and spatial distribution of response effect in Zhelin Bay.The results showed that the eutrophication of Zhelin Bay decreased from the nearshore,the estuary,and the junction of dajinmen and xiaojinmen to the Bay,and the comprehensive evaluation grade of the nearshore pond culture area and the estuary of Huanggang river was poor and inferior.However,the inner bay is in a medium and good state,and the water quality in the deeper part of the bay is better.(5)Using the statistical yearbook data of Raoping County in Chaozhou City from 2013 to 2017,explore the impact of domestic sewage and industrial sewage discharge and marine aquaculture on marine nutrients.The results show that the growth trend of domestic sewage and industrial wastewater discharge and seawater aquaculture industry is the same as the trend of seawater nutrients.To a certain extent,it shows that human activities have a direct impact on the input of seawater nutrients in Zhelin Bay.