Pollution Characteristics And Source Apportionment Of Ambient Particulate Matter In Hangzhou,Yangtze River Delta Of China

As the host city of the 19th Asian Games in 2022,air pollution control is one of the core tasks in Hangzhou,on the basis of creating the"Asian Games Blue",the more so as to realize the long-term management of the "West Lake Blue".Understanding the pollution characteristics and source apportionment of ambient particulate matter in Hangzhou area,especially fine particles(PM_2.5),is of great significance for air pollution control policy decision-making,when the source apportionment of ambient particulate matter can reflect the control point of industries and regions.In order to recognize and analyze the pollution characteristics and source apportionment of ambient particulate matter,it can be cut from the following aspects:What are the pollution characteristics of ambient particulate matter?What are the methods for analyzing the source apportionment of ambient particulate matter?And which source analysis methods are suitable for this study?Based on the analysis of the pollution characteristics of ambient particulate matter,this study established a set of PM_2.5 source apportionment system integrated Chemical Mass Balance Model?CMB?and TrajStat software,and the local emission sources and regional potential source areas were obtained.The main research contents are as follows:?1?To indentify the pollution characteristics of ambient particulate matter comprehensively in Hangzhou,including spatial and temporal variations of particulate matter and its relation to other factors?such as other atomospheric pollutants and meteorological factors?and chararcterization of chemical compositions in atmospheric particles,hourly concentrations of PM₁?PM_2.5 and PM₁0 in urban Hangzhou during 2015-2016 and offline PM_2.5 samples chemical composition data in urban Hangzhou and Lin'an background during 2014-2015 were analyzed,using statistical analysis.?2?To indentify the key sources of PM_2.5 from aspects of local emission and regional transportation pollution,CMB tool and TrajStat software were applied.The main results are as follows:?1?Compared with November 2014 to July 2015,PM_2.5 concentration decreased from 72±34?g/m³ to 56±40?g/m³ during September 2015 to August 2016.However,concentration of PM₁0?86±51?g/m³?and PM_2.5 were still 1.2 times and 1.6 times respectively that of the Class ? standard(PM₁0:70?g/m³?PM_2.5:35?g/m³)of China ambient air quality standards?GB3095-2012?.At the same time,the contribution of PM₁?32×20?g/m³?to particulate air pollution could not be neglected,accounting for 58%of PM_2.5.?2?PM₁ was the main atmospheric particulate matter from anthropogenic emission during rush hours and peak hours,while the form of PM_1-2.5 and PM_2.5-10 was less.The formation of PM,was dominated by a single discharge at one time.However,during the period of 10:00-16:00 with strong photochemical activity,gas-particle secondary conversion became an important source of PMi.In addition,meteorological conditions such as boundary layer height,relative humidity,wind speed and wind direction affected the generation and diffusion of atmospheric particles.?3?The secondary inorganic particles(SO₄^2-NO₃^-?NH₄⁺)were rich chemical species of PM_2.5 in Hangzhou,totally accounting for about 45%.There was a strong secondary conversion process of SO₂ to SO₄^2-?NO₂ to NO₃^-revealed by the high sulfur oxidation rate SOR?0.32?and the nitrogen oxidation rate NOR?0.12?.The organic matter was one of the main chemical species of PM_2.5??28%?,which was the highest proportion of identifiable substances among the individual components,with little difference between urban and suburban.The percentage of minerals dust in PM_2.5 was about 8%,2 times of that in North Amercia,reflecting a different pollution characteristic of fine particulate matter.The concentrations of chemical species in PM_2.5 increased with the increase of pollution levels?L₁?L₂?L₃?L₄?in winter,especially the proportion of secondary inorganic particles(SO₄^2-NO₃^-?NH₄⁺)increased significantly,indicating that the secondary conversions made a significant contribution on the raise of PM_2.5 concentration during the pollution period.?4?The concentration of PM_2.5 in Hangzhou was affected both by local emission sources and regional transportation pollution.Sulfates?21.5%??nitrates?19.4%??vehicle exhaust dust?18.2%??fugitive dust?14.1%?and coal combustion dust?10.7%?were the five main local emission sources.Besides,the impact of regional transportation pollution had a seasonal variation.Northern Zhejiang province and southeast Anhui province were the main potential source areas in spring,summer and autumn,contributing about 20?40?g/m³ to the average daily PM_2.5 concentration.In winter,southern Shandong province was also the main potential source areas in addition to the surrounding cities of Hangzhou,lhich coLtributed about 60?g/m³ to the average daily PM_2.5 concentration.