| PM2.5?particulate matter 2.5,particulate matter 2.5 micron in diameter?in the atmosphere has an important impact on air visibility,climate change and human health.It has become an inevitable requirement to clarify the characteristics of PM2.5in air-polluted areas,its spatial distribution and source analysis.It is of great significance to reduce PM2.5 concentration,reduce haze pollution and improve local air quality in these areas.In this paper,five cities in North China?Beijing,Nanjing,Wuhan,Taiyuan and Guangzhou?in the central and eastern part of China were selected as the research objects by chemical analysis from December 2016 to November 2017.Water-soluble inorganic ions and carbon components in the fine particles were continuously observed in order to better understand the current situation of regional atmospheric fine particulate pollution.The specific conclusions are as follows:?1?The temporal and spatial variations of PM2.5 were studied by collecting and observing PM2.5 in five selected cities in central and Eastern North China.Considering the average concentration of PM2.5,the distribution characteristics of different pollution levels and the annual over-standard rate,the order of PM2.5pollution from strict to light is Nanjing,Taiyuan,Wuhan,Beijing and Guangzhou.?2?The concentration levels of nine water-soluble inorganic ions(F-,Cl-,SO42-,NO3-,Na+,NH4+,K+,Mg2+,Ca2+)in PM2.5 of five cities were studied and analyzed by ion chromatography.The temporal and spatial variation characteristics of water-soluble inorganic ions in PM2.5,the acidity and alkalinity of PM2.5 and the chemical forms of main ions were studied and analyzed,and the fixed pollution sources were determined by NO3-/SO42-ratio.The relative contribution of coal-fired and mobile pollution sources?motor vehicle exhaust?to PM2.5 pollution was preliminarily analyzed.?3?The concentration levels of elemental carbon?EC?and organic carbon?OC?in PM2.5 of Beijing,Taiyuan,Wuhan and Guangzhou were analyzed by thermo-optical reflection method.In addition,the spatial and temporal variations,correlation and OC/EC ratio characteristics of EC and OC were also studied.?4?In order to explore the sources of water-soluble inorganic ions and carbon components in PM2.5 and estimate the contribution rate of each pollution source,principal component analysis?PCA?was used.It is found that the carbon components of PM2.5 in Beijing,Wuhan,Taiyuan and Guangzhou are mainly affected by biomass combustion,motor vehicle exhaust,coal combustion and other factors,and the total efficiency is more than 80%.Through the study of air pollution in five cities in the central and Eastern North China region,it is expected to provide some reference for pollution prevention and control measures in the central and Eastern North China region. |
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