| Xi'an is the political, economic and cultural center in northwest China, its urbanization and industrialization has developed rapidly in recent years, Air pollution often appear also. Frequent fog events made people begin to pay attention to PM10 and PM2.5 and understand its harm to life and health. PM2.5 was incorporated into air quality monitoring system by Xi'an, in order to provide data for the research on PM2.5 pollution.Used of particulate monitoring data, the time change characteristics of PM2.5 and PM10 concentration was studied; Combined with meteorological data, the spatial distribution characteristics of PM2.5 and PM10 concentration and the relationship were analyzed.The main conclusions:1. The air quality of Xi'an was poor in 2013. The annual mean of PM2.5 and PM10 was 2.00 times and 1.71 times of the secondary standard of national air environmental quality respectively. Daily mean of PM2.5 and PM10 ranged from 20?g/m3 to 1229?g/m3 and from 10?g/m3 to 749?g/m3 respectively, the biggest overstandard rate of PM2.5 and PM10 was 49.5% and 49.5% respectively, the biggest overstandard multiple of PM2.5 and PM10 was 7.19 times and 8.99 times respectively.2. The time distribution characteristic of particle concentration:winter has the biggest concentration of particulate matter pollution, then spring, autumn and summer.The maximum concentration of PM2.5 was January, the maximum of PM10 was March, the lowest concentration of PM10 and PM2.5was June.3. The spatial distribution characteristic of particle concentration:spatial distribution of PM2.5 was as follows:Grass Land> The City Stadium> High-tech West Region> High Pressure Company> Xingqing District> Wide Shipped Pool> Economic Development Zone>Textile City> Small Village> Changan Area> Qujiang Cultural Group. The monitor point of the highest PM2.5 concentration was Grass Land, the value was 130.52?g/m3, then The City Stadium, the value was116.51?g/m3, the lowest PM2.5 concentration appeared in Qujiang Culture Group, with a mean of 94.60ug/m3.The spatial distribution of PM10:The City Stadium>Grass Land>Xingqing District>High-tech West Region> Small Village>Textile City> Wide Shipped Pool>Economic Development Zone>Changan Area>Qujiang Cultural Group>High Pressure Company. PM10 concentration of The City Stadium is the highest level, with a mean of 224.12?g/m3, then Grass Land, the average concentration was 219.66?g/m3, PM10 mass concentration of High Pressure Company was the lowest level, the value was 193.70?g/m3. Analyzed the spatial distribution characteristic of particle concentration, Grass Land station has the highest PM2.5 concentration in all stations, so the control point should be changed.4.64 days had the index of air quality over 200 in 2013, mainly distributed in January, February, march, October and December. Winter has 45 days. The daily pollution appeared 7 times. Pollution for 2 days and 3 days appeared four times, for 4 days,6 days,8 days,9 days and 10 days appeared each time, the number of consecutive pollution accounted for 65% of the total number of pollution, particle pollution outbreak at the concentrated form. Its outbreak condition was low temperature, low humidity, small wind, no wind and no rain weather characteristics. The mutations of meteorological conditions had significant correlation between period of sustained pollution and the day before and after.5. Analyzed the concentration of PM2.5 and PM10, air quality was priority, when PM2.5/PM10 was less than 50%, and accounted for more than 70%. Air quality became bad, when PM2.5/PM10 was 50%?60%.Air quality became worse, when PM2.5/PM10 is greater than 60%. The maximum value of PM2.5/PM10 appeared in February, and it was 87.3%. The minimum value of PM2.5/PM10 appeared in March, and it was 16.2%, the annual mean is 53.8%. PM2.5/PM10 of Xi'an was 50%-60%, and air quality was poor. PM2.5 and PM10 had correlation.6. Particle concentration correlated with average temperature, wind speed and precipitation, and no obvious correlation with relative humidity. And meteorological conditions with high temperature and high humidity, wind speed in 2.5?3.4 m/s, rainfall greater than 5mm, was advantageous to the dilution and diffusion of particles, particle concentration was low;In low temperature, relative humidity, wind speed and no precipitation, was not conducive to the dilution and diffusion of particulate matter, the particle concentration was higher. |
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