| The development of shipping industry has promoted the economic development of our country.However,the ship emissions bring great pressure and challenges to the regional air quality.Ship exhaust is one of the main sources of marine pollution,including sulfur oxide,nitrogen oxide and particulate matter.As a very important trace gas in the atmosphere,the amount of SO2 is an important indicator to measure the degree of air pollution and one of the important sources of acid rain.High concentration of SO2 even directly harms human health,destroys plant growth and seriously affects the balance of ecosystem.In order to control the emission of pollutants from ships effectively,the Ministry of transport set up 3 ship emission control areas in December 2015,which significantly reduced the emissions of sulfur oxides,nitrogen oxides and particulate matters from ships.Bohai Sea is one of the three major ship emission control areas in China,including Tianjin port,Dalian port and other large ports.In order to analyze temporal and spatial variation and the effect of SO2 emission reduction around Bohai Sea,the OMI(Ozone Monitoring Instrument)gas-tracing data product OMSO2 carried on Aura satellite was selected,the level-2 data was preprocessed by VISAN software,and the column value of SO2 was extracted.Through comparing the four algorithms,select the appropriate algorithm-BRD based on OMI data for the retrieval of the atmospheric SO2 data and obtain the SO2 column value distribution map in the study area.Then the Bohai Sea was analyzed by spatial analysis method based on the analysis of the seasonal and inter-annual variation characteristics of SO2 distribution.This paper discusses SO2 column change since the establishment of the marine emission control area around the Bohai Sea and the reasons of temporal and spatial variation.The main research results are as follows:(1)Based on the analysis of the change of SO2 column value in 2017,the results show that:the seasonal change of SO2 distribution in the emission control area around the Bohai Sea is very obvious,and the SO2 column volume in spring and winter is significantly higher than that in other seasons.The highest value of SO2 column volume in the study area appears in November,and the lowest value appears in May and August.The monthly average column volume of the whole year presents a "V" shape,which firstly decreases and then increases.(2)The analysis of SO2 concentration in 2016-2018 shows that the annual change is obvious.Since 2016,the peak value of total SO2 column value has decreased year by year,and the high value area has gradually decreased,and low value area has gradually increased since 2017.Among three years,the annual average column volume gradually decreased by 43%and 20%respectively.During 2016-2017,the column value of SO2 changed significantly,and high value area decreased significantly.The column value area of less than 0 increased between 2018-2019 shows the continuous and stable reduction of SO2. |
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