| China has suffered from severe particulate matter(PM)pollution in recent years.Both pollution areas and levels are increasing gradually.The PM pollution episodes not only occur in the traditional developed areas like the Beijing-Tianjin-Hebei(BTH)and the Yangtze River Delta(YRD)region,but also frequently happen in the key regions of China.There have been more severe PM2.5 pollution problems,especially in the autumn and winter season.It is very urgent that people’s desire to improve the environment,and beside to provide a healthy living environment,the actions of improving air quality can also help human better cope with climate change.In order to decrease the PM2.5 concentration and improve the air quality the Chinese government released a series of environmental policies since 2013.From the perspective of observation in recent years,the overall environmental air quality in the country has been improved.The contributions of weather condition change and emission reduction activities play a key role.However,the air pollution situation in autumn and winter is still grim,and the problem of regional pollution transmission is significant.Under such a background,it is particularly important to determine the main drivers of air quality improvement,clarify the sources of pollutants,and provide advice on the governance of air pollution is particularly important.In this study,multi-source data such as ground monitoring PM2.5 concentration,meteorological observation data and reanalysis data,as well as anthropogenic source emission inventories were used to analyze the temporal and spatial variation characteristics of PM2.5 concentration in recent years and the variation characteristics of daily average concentration in winter 2013.The multivariate linear regression model was used to quantitatively analyze the relationship between the daily average PM2.5 pollution change and meteorological conditions in winter 2013.With the help of WRFCMAQ regional air quality model,assuming the same emission from January to February 2018,the spatial and temporal variation characteristics of PM2.5 pollution were quantitatively evaluated,and the impact of meteorological conditions on the change of PM2.5 pollution in different regions were quantified.Furthermore,a method for quikly distinguishing the influence of regional emission changes and meteorological conditions on PM2.5 concentration in different regions was proposed,and the weather and emission changes in different regions are calculated respectively.Using this method,it was quantitatively revealed that the dominant factors leading to the change of PM2.5 pollution in the key regions of China during winter.The main results and conclusions of the paper are summarized as follows.1)Study on the temporal and spatial variation characteristics of PM2.5 pollution in key regions in winter and statistical regression relationship with weather conditionsAt present,the whole focus key regions of China is affected by PM2.5 pollution.PM2.5 pollution not only occurs in traditional areas of concern(such as the BeijingTianjin-Hebei region and the Yangtze River Delta region),but also has an impact on other regions.The most polluted areas are located in the southwestern part of Hebei Province and the western part of Shandong Province.The PM2.5 pollution in coastal cities is relatively mild.The concentration of PM2.5 in most parts of China,including the study area,showed a downward trend between 2013 and 2017.Through correspondence analysis of daily average PM2.5 concentration distribution and daily average weather conditions,it is shown that severe PM pollution corresponded with stable weather conditions,i.e.,small Sea Level Pressure gradient,lower Planetary Boundary Layer(PBL)height and weaker winds.Statistics showed that the changes of the mean PM2.5 concentration over the key regions lagged behind the variations in the PBL height and wind speeds by about 12-18 h,and the variations in weather conditions could explain about 71%(R2)of the overall changes in PM2.5 concentrations,indicating that regional PM2.5 pollution was dominated by weather conditions in the study area.2)Study on the influence of weather conditions on the change of PM2.5 concentration in recent yearsThe decline in PM2.5 concentrations is conducive to the combined effects of weather conditions and emission reduction activities,and the contribution of emission reduction activities is even greater.Compared the PM2.5 pollution in 2017 with that in 2013,the contribution of emission reduction activities was 22.8%and 34.1%,accounting for 56.2%and 81.2%of the total contributions,respectively.For the BTH and YRD regions,other factors(such as emission reduction activities)in recent years have played an important role in reducing the concentration of PM2.5,especially in the YRD region,the contributions of emission reduction activities are basically greater than the contribution of weather conditions during the same period.For both the two regions,the contribution of emission reduction activities exceeded 50%.Take the BTH and YRD as a whole,the contribution of emission reduction activities to the reduction of PM2.5 concentration accounted for 76%,while the contribution of weather conditions for 24%.The impact of meteorological conditions on the concentration of PM2.5 in different regions such BTH and YRD is different,which is more favorable to the decrease of PM2.5 concentration in BTH region.3)Study on quickly quantitatively distinguishing the impact of changes in emissions and weather conditions on PM2.5 concentration in different regionsA method for quickly distinguishing the impacts of different regional emission changes and weather conditions on PM2.5 concentration is proposed,and the actual PM2.5 emissions in October-December 2013 and October-December 2017 are optimized,and the PM2.5 concentrations are simulated at the same period.The results showed that compared with 2013,in 2017,the concentration of PM2.5 in the regions,including the southern part of BTH,the western Shandong province,and the southern part of Jiangsu province and Shanghai,decreased significantly due to the better weather conditions,and the decline was obvious,basically exceeding 10 μg m-3.In the other hand,in the southern part of the key regions,such as Zhejiang,the PM2.5 concentration increased slightly.Compared the period of October-December 2017 with the same period of 2013,the actual PM2.5 emissions in the study area decreased significantly.In 2017,the contribution of local emission reduction to local PM2.5 concentration reduction is close to or exceed 50%,with a peak value of 78%appeared in the southern part of BTH and northern Zhejiang.In summary,from the short-term scale(such as winter),PM2.5 concentration changes are mainly dominated by weather conditions,on the other hand,from a longterm scale,weather conditions and anthropogenic emissions are the main reasons for the change of PM2.5 concentration.In recent years,the decrease of PM2.5 concentration and the change of weather conditions play a certain role,but it is the emission reduction activities that play a leading role. |
PDF Full Text Request