| Particulate organic matter has a wide variety and complex structure and its different in physicochemical properties.These characteristics leads to limited research on its concentration level,chemical composition and source analyses,etc.Therefore,the in-depth study of particulate organic matter is one of the main difficulties in improving China's ambient air quality.It is of great significance to study the particulate organic matter in the North China Plain,to master the pollution characteristics,chemical composition and main pollution sources of particulate organic matter,and to understand the causes of aerosol pollution in the North China Plain,so as to improve the air quality and achieve the PM2.5.5 standard in the North China Plain.In this study,PM2.5.5 samples of a regional site of North China Plain?suburban point?in winter were collected and analyzed by field observation,laboratory analyses and model simulation.During the observation period,the average mass concentration of PM2.5.5 at the regional site of North China Plain?suburban point?was 100.69±42.59?g/m3,which indicated that the air pollution in this area was serious during the observation period.Organic carbon?16.62%?and SNA?35.6%?are important components of PM2.5.And the proportion of SNA in PM2.5.5 is getting higher and higher,which indicates that the secondary pollution of particulate matter at the regional site of North China Plain?suburban point?is aggravating in winter.The concentrations of organic carbon and elemental carbon in PM2.5.5 were 16.74±8.00?g/m3 and 5.78±2.69?g/m3,respectively.It was found that biomass combustion and motor vehicle emissions were the main sources of OC and EC emissions during the observation period,and coal combustion also contributed to some extent.Secondary organic carbon estimated by EC tracer OC/EC method showed that SOC is an important component of OC in winter at a regional site of North China Plain?suburban point?.Sooner or later,due to the impact of local biomass combustion,the proportion of SOC decreases.The effects of ozone,relative humidity,water content and acidity on the formation of SOC are analyzed.The results showed that the liquid-phase acid catalysis may played an important role in SOC under the condition of high water content and high H+concentration.The particulate organic matter in winter at a regional site of North China Plain?suburban point?was analyzed and studied.Totally 150 organic compounds were analyzed.The results showed that the main species of particulate organic matter are carbohydrates,n-alkanes and dicarboxylic acids.The concentration of carbohydrate in the area was significantly higher than that of other organic substances,indicating that biomass combustion had a significant impact on air pollution.Comparing the maximum carbon index and dominant carbon index of n-alkanes,it is found that the regional point is mainly affected by anthropogenic sources and biogenic particulates.For PAHs and hopanes,which are mainly from anthropogenic sources,the distribution of PAHs and hopanes is characterized by the contribution of motor vehicle emissions to particulate organic matter.Analytical methods of secondary organic tracers from biological and anthropogenic sources were studied based on GC-MS.The concentrations of three kinds of tracers and one kind of human tracers are analyzed.The concentration levels of biogenic and anthropogenic SOA in winter at a regional site of North China Plain?suburban point?were estimated by using tracer yield method.The concentrations of isoprene,?-pinene,?-syringene and toluene as precursors of SOA were 0.45±0.25?g/m3,1.32±0.72?g/m3,3.00±1.78?g/m3 and 2.20±1.32?g/m3,respectively.The source of particulate matter was analyzed by chemical mass balance model.The results of source analyses showed that biomass combustion?36.3%?and vehicle emissions?17.9%?are important sources of particulate organic matter at a regional site of North China Plain?suburban point?,indicating that there are many biomass combustion phenomena in winter,and the increase of vehicle ownership aggravates the contribution of vehicle emissions to air pollution.The analytical results of CMB model and tracer yield method can account for 89.6%of the measured OC.About 10.4%of OC can not be resolved,which may be discharged by other primary and secondary sources. |
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