Air Pollutant Emissions From Ships In Xiamen Port And The Impacts On The Surrounding Air Quality

In recent years,Xiamen’s shipping industry has maintained a steady upward trend,and the shipping industry has become an important engine driving Xiamen’s urban development.The changes in the spatial distribution of pollutants such as SO2,NO2,CO,PM10 and PM2.5 in 2017 and 2020 confirmed the impact of changes in ship source emissions on the air quality of the port and its surrounding areas.Therefore,it is urgent to analyze the characteristics of ship emissions in Xiamen,and clarify the impact of ship-sourced air pollutants emissions on the air quality of the Xiamen Bay.Based on the AIS(Automatic Identification System)data dynamic method,this study established the 2017 and 2020 ship emission inventory,and entered the WRF-CALPUFF(Weather Research and Forecasting Model-California PUFF Model)to calculate the smoke emission from the ship.The distribution of the mass concentrations of pollutants diffused into the atmosphere,and the feasibility of the model has been verified through the actual measurement and analysis of PM2.5 samples at Haitian Port and Songyu Port.Based on the 2017 and 2020 emission inventories of ships,the total emissions of SO2,NOx,CO,PM10,PM2.5,HC and VOCs in the typical months of 2017(January,April,July and November)were 8300 t,6753 t,577 t,757 t,662 t,255 t and 260 t,respectively,and the emissions of SO2,NOx,CO,PM10,PM2.5,HC and VOCs in the same period in 2020 were 2783 t,1125 1t,996t,318t,274t,435t and 445 t,respectively.Affected by the use of low-sulfur oil,SO2,PM10 and PM2.5 emissions were decreased by 65.8%,57.3%and 58.0%in 2020.The WRF-CALPUFF coupling model was used to simulate the concentration distribution of air pollutants emitted by ships.In order to verify the feasibility of the meteorological model,the WRF output meteorological parameters were compared with the measured values of the weather station.And it was found that the temperature,air pressure,wind speed,wind direction and other meteorological factors have a good time matching consistency with the measured values,and the simulated pressure values were consistent with the measured values.The value correlation was generally greater than 0.90(P<0.01),the temperature correlation was between 0.64-0.93(P<0.01),and the wind speed was between 0.52-0.82(P<0.01).It had a good simulation effect,and the simulation effect of wind speed in autumn and winter was better than spring and summer.PM2.5 samples were collected at Xiamen Haitian Port and Songyu Port in July,September,November and December 2020.Since V and Ni are chemical trace elements that indicate heavy oil combustion,the V and Ni of PM2.5 samples were determined experimentally.It was found that when the ship’s source emission was in the upwind direction,V and Ni often had high values,which verified the tracer effect of V and Ni on the ship’s source.So it was mainly based on the V concentration to reverse the contribution of the ship’s PM2.5 in the two terminal monitoring stations.The verification found that the calculated value based on the V element is significantly related to the simulated value of the CALPUFF model.The correlation between the calculated value and the simulated value at Haitian Port and Songyu Port was 0.43-0.61(P<0.05)and 0.43-0.78(P<0.05),respectively,indicating the credibility of the CALPUFF simulation results.Comparing the results of ship source diffusion in 2017 and 2020(before and after the use of low-sulfur oil),it could be concluded that the average contribution rate of SO2 emissions from ships to Xiamen had dropped from 40.5%-50.3%in 2017 to 39.6%44.5%in 2020,but still maintained a high level.Due to the increase in NOx emissions from ships,its contribution to the Xiamen had changed from 25.6%-31.9%in 2017 to 24.23%-44.86%in 2020,and the contribution in summer has increased.CO emissions were relatively small,and most of the contribution to the site was below 1%.So the source of CO from ships could be neglected.The contribution rate of PM2.5 emissions from ships to Xiamen decreased from 7.9%-10.7%in 2017 to 5.5%-6.0%in 2020,and the overall impact had been reduced.When the southwest wind and northeast wind prevail,the diffusion direction of the pollutant concentration of ships was obviously different.In the summer(southwest wind prevails),the contribution of ships in Xiamen was significantly higher than that in autumn and winter(northeast wind prevails).Quanzhou was only affected when southwest winds prevailed.Based on ship emission inventory in November 2020,the impact of shore power usage on the contribution of ships were analyzed.Assuming that pollutant emissions are reduced by 70.0%when the ship is parked(the shore power policy will be tightened in 2022),SO2,NOx,CO,PM10 and PM2.5 total emission reduction rates are 42.0%,29.0%,26.9%,35.1%and 33.6%,respectively.Under the same meteorological conditions,the reduction rate of SO2,NO2,CO and PM2.5 was 36.6%-68.9%,52.5%80.8%,t 50.2%-59.0%,and 56.5%-65.5%,respectively,indicating that shore power promotion was effective in reducing ship proliferation.Finally,the current development of reduction measures(alternative use of clean energy and terminal treatment technologies)and existing problems were summarized.We suggest the Xiamen government improving relevant laws and regulations as soon as possible to ensure the supply and circulation of high-quality low-sulfur oil on the market,accelerating the deployment and promotion of shore power,increasing funding subsidies for shore power use,encouraging and supportting innovative enterprises,and developing the end treatment equipment that has economic and environmental effects.