| Since we followed the policy of reform and opening in Xi’an, the urbanization and industrialization have been developing rapidly, while environmental problems emerged with the development of the economy, especially the atmospheric pollution problems was serious, and inhalable particles became the primary pollutants. To better reveal the characteristics and laws of concentration variation of atmospheric particulate matter, and provided the scientific basis for pollution prevention and controlled measures in south of Xi’an, it was necessary to study on PM10 temporal and spatial variation.Through 4 times’ high resolution day and night observation of 70m height building in Chang’an University community in May 2013, and 3 times the same work in 52m height building of Shaanxi Normal University in April 2014 we studied PM10 temporal and spatial variation feature、rule、influencing factors, evaluated air quality levels of PM10 concentrations in the southern region. The main conclusions were as follows.(1) In May 2013, the day and night variation trend of PM10 concentrations from the ground to 70m height was consistent, which totally indicated bimodal distribution, and reached two peaks at 12:00 and 22:00. According to diurnal variation of PM10 concentrations, they could be divided into five stages. The first stage was 8:00～10:00 AM, at this stage, the PM10 concentration was relatively low. The second stage was the highest stage, which emerged from 12:00 AM to 14:00 PM. The third stage was 16:00～18:00PM, the PM10 concentrations was in the middle.The forth stage was 20:00～22:OOPM, the PM10 concentrations was relatively high. The fifth stage was 0:00～6:00AM, the stage was the lowest. In April 2014, the PM10 concentrations in the range from ground to 52m height could be divided into four stages. The first stage was 8:00～12:00 AM, the PM10 concentrations was lowest. The second stage was 14:00～18:00PM, the PM10 concentrations was relatively low. The third stage was 20:00～0:00PM, at this time PM10 concentrations reached the highest stage. The fourth stage was 2:00～6:00AM, the PM10 concentrations were relatively high.(2) Vertical variation of PM10 concentrations could be divided into three types in south 2nd ring of XI’an in May 2013. The first type appeared in the 10:00～12:00 AM and 20:00PM, the main characteristics of the PM10 concentration increased as altitude increased, with an average increase rate of 0.048ug/m. The second type took mainly in 8:00 AM,14:00～18:00 PM and 22:00-0:00 PM, the main characteristics of PM10 concentration increased with height increased and increased to the maximum, with an average increase rate was 0.065ug/m. The third type occurred mainly in 2:00～6:00 AM, at that time,the PM10 concentration showed minimal increases with height increasing, and the rate was 0.013ug/m. April 2014 vertical variation of PM10 concentrations can be divided into four types. The first type appeared at 12:00AM,14:00 and 18:00PM, as high-altitude increaseed, PM10 concentrations showed a slowly increasing trend, the average increase rate was 0.25ug/m. The second type occurred mainly in 8:00AM and 16:00PM, the main characteristics of PM10 concentration was that it remained stable or showed a slowly decreasing trend, decline rate was -0.096ug/m. The third type appeared at 20:00-22:00PM and 6:00AM, the main characteristics were presented PM10 concentration rapidly decreased with the increasing height, and the decline rate was-7.7ug/m. The fourth trend occured mainly in 10:00AM and 2:00～4:00AM, the main characteristics of PM10 showed a slow decreasing trend with the increasing height, and the average decline rate was -0.064ug/m.(3) The PM10 concentration had a negative relationship with temperature and wind speed in May 2013 and April 2014, at the same time it showed a positive relationship with humidity and air pressure.(4) In May 2013, the main remote pollutants sources were from industries in developed southern cities of our country and also from the dry climate area, where have low vegetation coverage and more dust. In April 2014, the main remote pollutants source of contaminants was low vegetation coverage area and desertification regions. At April 17, the 100m height’s remote pollutants source comes from Shanghai.(5) According to the observational data of PM10 concentration in April 2014 and May 2013, and used API index to evaluate atmospheric environmental quality in two areas. In May 2013, the air quality was good, and in April 2014, air quality was mainly dominated by good, also showed a slight pollution.(6) Through using multivariate linear regression model to predicted PM10 concentrations, we got the regression equations, it was Y=0.88+0.005XT+0.003XRH-0.010Xws-0.007Xp, and the forecast results showed that this model could be a good response to vertical changes in PM10 concentrations, with availability. |
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