Spatiotemporal Variation Of PM_2.5 Concentration In Guangdong Hong Kong Macao Bay Based On MODIS And Surface Monitoring

On February 18,2019,the Central Committee of the Communist Party of China and the State Council issued the outline of development planning of Guangdong Hong Kong Macao Bay area,One belt,one road,is the key to the development of the world.The plan is based on the outline of the plan.The Great Bay area of Guangdong,Hong Kong and Macau should not only build a dynamic world-class city group,an international technological innovation center,an important support for the construction of the"one belt and one road",and a demonstration area for the deep cooperation between the mainland and Hong Kong and Macao,but also create a quality life circle suitable for livable industries and become a model for high-quality development.It marks that the development of Guangdong,Hong Kong and Macao Bay area has become a national development strategy.During the 13th Five Year Plan period,a number of major industrial projects were successively arranged and put into production,and industrial upgrading and upgrading were continuously promoted,which will bring greater pressure on the ecological environment security of Dawan district.Air pollution has strong regional and complex characteristics.PM_2.5 has the characteristics of small particle size,large area,strong activity,easy to absorb toxic and harmful substances,and can stay in the atmosphere for a long time for long-distance transmission.The study of PM_2.5 concentration characteristics and mechanism is related to the health and well-being of the people in the bay area and atmospheric environment quality.Based on the hourly PM_2.5 concentration data of the sub stations of the regional air monitoring network of Guangdong,Hong Kong and Macao,using multiple regression model,GIS technology and statistical methods,this study systematically studied the temporal variation characteristics,spatial distribution simulation and influencing factors of the concentration in the study area.The main results are as follows:?1?In four years,the annual average concentration of PM_2.5 in Dawan District decreased by 5.27?g·m^-3,with a decrease rate of 15.04%.The seasonal variation of PM_2.5 concentration in Dawan district is obviously different,and the seasonal variation trend between years is basically the same.The curve shows a relatively symmetrical"U"shape,and the monthly average concentration curve shows the characteristics of monthly peak and valley bottom.The highest peak appears in January or December,October is the second highest peak of mass concentration,and the second peak appears in March or April.From June to August,most of them are U-shaped bottoms.The days of concentration exceeding the standard shall be 2016 at least and 2017 at most.The time of PM_2.5 pollution exceeding the standard is concentrated in January,October,November and December,but it generally lasts for a few days each time,and the space quality quickly returns to"excellent"or"good".?2?The spatial difference of PM_2.5 concentration value in the four seasons in the monitoring sub region is obvious,showing a significant northwest southeast three-level decline and differentiation as a whole.The PM_2.5 quality concentration in the north,northwest Guangzhou,Foshan and Zhaoqing is higher,followed by Dongguan,Zhongshan and Jiangmen,Huizhou,Shenzhen,southern Zhuhai and southeast.In the winter,the concentration difference among the monitoring areas is the most obvious.In the study period,the maximum number of days reaching the standard is 364?Huizhou,2015?,and the minimum number of days reaching the standard is 332?Zhaoqing,2015?.The total number of days reaching the standard is more than 332,and the 24-hour concentration reaching rate of the whole year is more than 91.20%,with a high reaching rate.?3?The error between AOD and standard value is 14.14%,which does not exceed the upper error limit.The data reliability meets the research requirements.The maximum value of AOD in pollution period is generally lower than 0.45,and the proportion distribution shows a single peak type.The proportion change of each interval increases first and then decreases,which is similar to a single peak.The high value areas of AOD are mainly located in the south of Guangzhou,Foshan,the north of Zhongshan,Dongguan and the northwest of Shenzhen,while there is no obvious high value of AOD in Hong Kong and Macao.?4?The spatial pattern of PM_2.5 concentration in the simulated pollution period shows that the typical area of the high concentration concentration concentration area is the Guangfo junction,and gradually evolved into high concentration,micro high concentration and low concentration.There are 13 grids with"excellent"concentration,accounting for 2.26%,548 grids with"good"concentration,accounting for 95.13%,and 15 grids with"light pollution",accounting for 2.61%.The variables AOD,mean air pressure and mean relative humidity have positive effects on the interpreted variables.