| In recent years, aerosol pollution has been a hot topic in air quality monitoring and research. Lots of researches show that aerosols will not only reduce the visibility and change the climate of a city, but also contain many poisonous and harmful substances which can do harm to both human health and ecological environment. What's worse, it is the carrier of other pollutants and reaction bed. Aerosols in different areas have different physicochemical properties, and the natural environment in Chongqing is very special, so that the air pollution treatment in Chongqing should depend on the research of local monitoring. Jinyun Mountain is a state-level scenic, however, the rapid development of urbanization in Beibei increases the dust emission sources, such as traffic, construction, etc. The deeper development of tourism of Jinyun Mountain leads to an increase of automobiles and travelers on holidays. Therefore, the air quality in Jiny Mountain troubles the local citizens.This research on aerosol monitoring to Jinyun Mountain lasts for 13 months, from January, 2010 to January,2011, aiming to learn about the environmental background of aerosol in the whole Chongqing area based on the analysis of mass concentration of TSP and PMjo of local aerosols, and the study of water soluble ion concentration and seasonal variation. Moreover, the analysis of the relationship between the source of water-soluble components contained in aerosols and meteorological condition, and the control of the natural and artificial sources of aerosol particles in Jinyun Mountain provide basic data and reasonable suggestions for Chongqing air quality assessment.The main conclusions of this paper are:(1) The overall situation of air quality in Jinyun Mountain is good:in rainy season, the average mass concentration of TSP is 103.6μg·m-3, meeting the national 1-grade air quality standard; but in dry season, it is 158.4μg·m-3, lower than the national 2-grade air quality standard. In TSP and PM10, average values of water soluble ion concentration are 60.0μg·m-3 and 52.4μg·m-3, which are 47% and 52% of particulate matter. Compared with a decade ago, both the water-soluble components content and proportion have increased significantly, and have been the major components of atmosphere TSP and PM10. And SO42- has been the first among the anion in proportion, and then NO3 takes the second place; Ca2+has been the first among the kation. Consequently, the main air pollution type in Jinyun Mountain is CaSO4.(2) After analyzing the source of water soluble ions in aerosol, we can find that, under normal conditions, F-,Cl-,Na+, K+, Mg2+, etc, chiefly come from natural sources. That is to say, ecological environment in Jinyun Mountain is good, and its self-purification of pollutants is very strong, and SO42-, NO3-, Ca2+ are mainly from artificial sources, which are affected by climate and seasons change.(3) In the natural condition, the mass concentration of aerosol particles and water-soluble components are mainly controled by the process of precipitation and fog weather. Temperature and humidity are the main vital meteorological factors that influence the concentration of aerosols. Based on the above conditions, aerosol particles experience a series of complicated physical and chemical change from birth to death, which depends on the double action of accumulation and scavenging process of aerosol particles.(4) Atmospheric precipitation is one of the most significant wet scavenging process. For one thing, atmospheric precipitation has a strong capacity of scouring the large particles. On the other hand, the water-soluble components of aerosols can be dissolved into cloud or rain, and then they drop down on the ground with the atmospheric precipitation. In summer and fall, wet scavenging process is predominant; therefore both aerosol particles and water-soluble components will be decreased.(5) During the late winter and early spring, because of the little atmospheric precipitation, and the relative humidity is low, the wet scavenging process is reduced. While in Chongqing, there is much radiation fog in this season when the air is very stable stratification and it is easier for pollutant accumulation. In winter, the temperature in Jinyun Mountain is lower than that in Beibei downtown area, the air flow sinks down, and it becomes cold high pressure near ground, while in the air, it becomes low pressure. As a result, the warm lighter air flows upward Jinyun Mountain with the pollutants from the downtown and makes the air pollution heavier. It calls the accumulation process of aerosols.(6) During summer, the hot weather in Chongqing is unbearable. As a result, SO2 and NOx in atmosphere may take the chemical reactions easier, and produce SO42- and NO3-. If there is no rainfall, part of these SO42- and NO3- will exist in aerosol particles. Since aerosol particles in the atmosphere has shorter life span than the acid gas, it will be scavenged with the dry and wet deposition; when it rains, SO42- and NO3-, soluble in water, will be down to the ground through wet scavenging process. This phenomenon can be regarded as a game playing between the accumulation process and the wet scavenging process. (7) Meteorological factors have a great effect on secondary ions. According to the influence of temperature to SO42- and NO3-, when the average daily temperature is higher than 27 degrees Celsius, which exist in gaseous forms; when the average daily temperature is between 15 and 27 degrees Celsius, SO42- and NO3- exist in both gaseous forms and solid forms. When relative humidity is between 65～75%, the average concentration of SO42-is the highest. The aerosols are dominanted by solid-state sulphate particles. Above this humidity range, the air tends gradually saturated, SO2 and sulphate particles are easy to cause homogeneous chemical reactions with the precipitation and water droplets in clouds, and then cleared with precipitation. And below this range, the evaporation of chemical reaction does not occurred to strengthen that part of SO2 criterion with gaseous state back in the atmosphere; and below this range, the evaporation starts to strengthen, one part of the SO2 which hasn't occurred chemical reaction, returns to atmosphere with gaseous state.(8) SO2 and NOx are easy to occur homogeneous chemical reactions with the precipitation and water droplets in clouds, then cleared with precipitation, or directly forms acid rain. When it is thick fog, a higher relative humidity can speed up the transformation of second components like sulfates and nitrates, increasing the level of air pollution. Sand aerosol is high effect to air pollution, the concentration of SO42- and cationic increases multiples. The particle size and shape are obviously different with fog weather.(9) The artificial source of aerosols mainly comes from the burning of fossil fuel, automotive emission and the dust from construction sites and cement factories. The ratio of NO3-/SO42- in TSP of Jinyun Mountain is 0.33(0.06～1.53), which means the fixed emissions source (fossil fuel burning) is still the main source of water soluble ions in local TSP. the source of SO42- is industrial coal burning in central towns, and the produced SO2 was sent there through elevated sources and tele-transmitting.10 years ago, the ratio of NO3-/SO42- in TSP of Jinyun Mountain was 0.1, which means the pollution source of second aerosol almost comes from industrial coal burning. And now, the contribution of mobile emission source also can not be ignored. The environment has certain self-purification capability. Usually pollutants can spread and be swept away by atmospheric circulation, but with the terrain occlusion of Chongqing, the pollutants can be easily accumulated to high concentration, and atmospheric circulation will take the pollutants to the clean areas in suburb and pollute it. Therefore, it is particularly important for the Chongqing government to strengthen the comprehensive treatment of atmospheric environment.
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