| Liaodong Bay is a semi-closed sea area.Affected by special geographical environment its selfpurification ability was poor.Pollutants were drained in large quantities through industrial outlets,rivers,urban domestic sewage pipelines,offshore oil fields,ships,aquaculture and so on,in which made the area around Liaodong Bay nearshore contaminated by eutrophication,petroleum hydrocarbons and heavy metals to varying degrees.The ecosystem of Liaodong Bay had been affected,which was mainly reflected in the deteriorating fishery resources,the increase of biological diseases in mariculture,and the increase of mortality rate,the occurrence of red tide disasters has become more frequent,and the scale and duration of red tide disasters have been expanding day by day.Based on the 3-year monitoring data from 2015 to 2017,this paper investigated and studied the seawater quality in Yingkou and Panjin inshore of Liaodong Bay.Based on the systematic theory,scientific methods were used to comprehensively and objectively describe the water quality of Yingkou and Panjin offshore waters of Liaodong Bay Spatial and Seasonal Distribution of Inorganic Nitrogen,Active Phosphate,COD,Petroleum and Chlorophyll-a in Water.The eutrophication index method and the ratio of nitrogen and phosphorus were used to evaluate the eutrophication status and nutrient structure in the sea area,and environmental protection countermeasures and environmental planning suggestions were put forward in view of the existing problems in Yingkou and Panjin coastal areas of Liaodong Bay.The main results of this thesis are as follows:1.Through the analysis of single factor standard index method,it was concluded that the main pollutants in the investigation area were inorganic nitrogen and active phosphate.The content of inorganic nitrogen was the lowest in August each year,with the exception of individual stations that meet the first class of seawater quality standards,the rest are exceeded.The content of active phosphate was the lowest in May,the highest in October,The average value of the every stations data throughout the year of active phosphate showed the lowest rate of over-standard in 2016,30%;in 2017,it was the highest,reaching 60%.The year with heavy COD pollution is 2016 and only a few stations in 2015 did not meet the first-class seawater water quality standard,and in 2017,they all met the first-class seawater water quality standard.The pollution of petroleum was more serious in 2015.Compared with 2015,the content of petroleum in 2016 was obviously reduced.The oil content in the sea area monitored in 2017 was in accordance with the first-class standard of seawater quality.Through the analysis of comprehensive index evaluation method,it was concluded that the pollution grade of the monitored sea area in the past three years is 4 grades,which belonged to the serious polluted area.Inorganic nitrogen and active phosphate were the main pollution factors.2.Based on the monitoring data of 2015,2016 and 2017,seasonal distribution characteristics of inorganic nitrogen and active phosphate,The results showed that the contents of inorganic nitrogen were lower in August and higher in March,May and October.The contents of active phosphate were lower in May and August and higher in March and October.Analysis of inorganic nitrogen and active phosphate level distribution by monitoring data of 2016 and 2017,showed that the contents of inorganic nitrogen and active phosphate in the monitored sea area in 2017 were higher than those in 2016.The horizontal distribution showed that the concentration of estuarine and coastal was higher in the northern part of the monitored sea area than in the central and southern part.(Away from estuaries and coastal waters)The characteristic of low content.3.Based on the monitoring data of 2016 and 2017,COD,petroleum seasons and horizontal distribution were analyzed,which showed the COD content in the sea area monitored in 2017 was significantly lower than that in 2016,and the COD content in March was the highest in four monitoring months.The horizontal distribution of COD showed the characteristics of high concentration in the northern estuaries and coastal areas of the monitoring area.The content of petroleum in 2017 was obviously lower than that in 2016.The horizontal distribution of petroleum showed the characteristics of high concentration in estuaries and coastal areas of the monitoring area,but the seasonal distribution was not obvious.Based on the monitoring data of May,August and October2017,the seasonal and horizontal distribution of chlorophyll a in the monitored sea area was analyzed.The results showed that the chlorophyll-a content distribution in the monitored sea area had obvious seasonal variation characteristics,which showed as follows: summer > spring > autumn.In summer,the content of chlorophyll-a in seawater was about 2 times of that in autumn,but the horizontal distribution of chlorophyll-a level was not obvious.4.According to the analysis of eutrophication of seawater in the four monitoring months of 2016 and 2017,the eutrophication degree of seawater in March and May2016 was higher than that in August and October,and the eutrophication degree of sea water was the lowest in October.In August 2017,the degree of seawater eutrophication was the lowest,and the degree of seawater eutrophication was still high in March and May.The eutrophication degree was the highest in October,All the monitoring stations were in eutrophication state,mainly mild and moderate eutrophication,Mainly affected by active phosphate.Compared March 2017 with March 2016,the number of stations in severe eutrophication increased by 5,mainly due to inorganic nitrogen.In May 2017,the eutrophication state of seawater was better than that of May 2016,and the eutrophication state of August 2017 was better than that of August 2016.The eutrophication of seawater in October 2017 was the heaviest in two years.According to the eutrophication analysis of the whole year of 2016 and 2017,the degree of eutrophication of seawater has little change in 2016 and 2017.The eutrophication sea area was mainly concentrated in the central and northern part of the monitoring area.The higher eutrophication level was the partial station at the estuary of the river.5.Compared with 2016,PN / ratio of Yingkou and Panjin coastal monitoring stations decreased slightly in 2017,especially in August and October.The main reason was that in August 2017 the content of inorganic nitrogen was lower,but in October the content of active phosphate was higher.In March May and August2017,the nutrient structure of the sea area was not balanced,but better in October.The larger PN / of the station was still far from the coast,mainly because the concentration of N,P and other elements gradually became smaller with the distance from shore,but the range of inorganic nitrogen was smaller than inorganic phosphorus,so the PN / became higher.Two years of data analysis showed that phytoplankton growth in the sea area has been in the state of phosphorus limitation.By comparing the PN / changing curve and eutrophication curve,the PN / changing curve and eutrophication curve showed the opposite trend on the whole,when the eutrophication index was higher,the PN / was lower.6.Based on the investigation,analysis and research on the marine environmental quality of Yingkou and Panjin coastal areas,the countermeasures and environmental planning suggestions for the marine environmental protection in Yingkou and Panjin coastal areas were put forward.Improve the relevant laws and regulations for marine environmental protection and formulate the corresponding environmental protection policies.Formulate the allowable discharge standards of nitrogen and phosphorus concentrations according to the functions of the coastal waters of Yingkou and Panjin in Liaodong Bay.Strengthen planning guidance,optimize industrial structure and layout.Because there were many monitoring departments,the responsibilities of monitoring were duplicated,and even restrict each other,it was necessary to set up an effective coordination mechanism as soon as possible,and establish a high-level organization to coordinate the various departments.Establish the marine ecological compensation mechanism,clarify the legal status of marine ecological compensation,and provide clear legal support for the implementation of marine ecological compensation in practice.Speed up the implementation of the marine ecological red line system,establish a new management model of marine ecological environment protection and management based on the red line system,and promote the marine ecological environment to gradually improve. |
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