Study On Chemical Characteristics And Source Of Particulate Matter And Heavy Pollution Analysis In Heating Season, Taiyuan

Atmospheric PM2.5 and PM10 samples were sampled in December,2014. 18 kinds of elements 、 9 kinds of water-soluble ions and 2 kinds of carbon components were analyzed to obtain the chemical composition characteristics of PM2.5 and PM10. Enrichment Factor（EF）and Factor Analysis（FA） were applied for source apportionment.Then, using HYSPLIT trajectory Model, I discussed the possible reason of heavy pollution weather found in sampling period.For Taiyuan In 2014, heavy pollution process（class Ⅴ and Ⅵ） throughout the year was all found in the heating season, and the primary atmospheric pollutants were mainly PM2.5 and SO2. Main chemical components of PM2.5 and PM10 during the observation were OC>EC>SO₄^2->NH⁴⁺>Cl^->NO₃^->Si>Ca and OC > EC > SO₄^2-> Ca > NH⁴⁺> Cl^- > NO₃^-> Si, respectively. Carbonaceous materials, water-soluble ions and elemental components account 43.6%, 42.7%, 13.7% for the total mass concentration of PM2.5 respectively, and 38.9%, 38.7%, 22.4% of PM10.SO₄^2-, NH⁴⁺, Cl^-, NO₃^- and Ca²⁺ were the top 5 ions measured in mass concentration, while high mass concentration of Cl^- is a significant characteristic compared to other cities. Ionic equilibrium analysis showed a overall alkaline environment in atmospheric particulates during the observation, with the excess NH⁴⁺, which is the control factor of the formation of secondary inorganic aerosols; ratio of [NO₃^-]/[SO₄^2-] was 0.47, which less than 1, illustrate the stationary sources was the main source and coal-burning pollution was still a prominent characteristic of the air pollution in Taiyuan. OC and EC were mainly gathering in fine particulate matter, with OC and EC in PM2.5 accounted 87.9% and 78.5% for that in PM10. OC/EC analysis, correlation analysis and regression analysis were conducted, pointing out that the direct emission of coal-burning and its incomplete combustion were the vital reasons for high mass concentration of carbonaceous components in the heating season.Enrichment factor analysis showed that the EF value of As、Cu、Zn、Pb、Cd were more than 100,especially for Pb（355.6） and Cd（1494.8）, indicated that the heavy metal elements in the atmosphere were influenced by human activities strongly.The results of source apportionment for PM2.5 using factor analysis were:（1） coal-burning-based combustion source, 24%.（2） dust（soil and construction）, 23%.（3） secondary inorganic aerosols（SIA）, 17%.（4） industrial activities, 13%.（5） vehicles, 9%.（6） other sources, 14%. The results of source apportionment for PM10 using factor analysis were:（1） dust（soil and construction） and industrial fly-ash, 34%.（2） secondary inorganic aerosols（SIA） and biomass burning, 25%.（3） coal burning and vehicles, 16%.（4） other sources, 25%.The chemical composition of atmospheric particulates changed dramatically when the heavy pollution process occurred: mass percentage of water-soluble ions rose from 24.6% up to 45.3% while the mass percentage of earth crust elements dropped from 24.95% to 9.3% in PM2.5, however, the mass percentage of carbonaceous materials maintained stability,indicated that earth crust elements contributed little to the formation of heavy pollution, while secondary inorganic aerosols（SIA） generated rapidly and heavily was the chemical essence of heavy pollution process. The emission of human activities like coal combustion, industrial activities and vehicles were the internal cause of heavy pollution, while static stability meteorological environment with high relative humidity and atmospheric inversion were the crucial inducements, which exacerbated the atmospheric secondary reaction, manifested as the augment of the mass percentage of water-soluble ions. Wind maybe the important mechanism of the removal of heavy air pollution.Backward trajectory model showed a changing direction of airflow with the speed slowing down before the formation of heavy pollution process, which may bring the air pollutants in the adjacent region to Taiyuan, aggravating the air quality; however, air pollutants were diluted and blew away when the cold airflow from Siberia went through Taiyuan quickly, manifested as the drop of air temperature and humidity, the increase of wind speed, the rapidly improvement of air quality, as well as the rise of mass percentage of earth crust elements with respect to the chemical composition of atmospheric particulates.