Characterizing Distribution Of Air Pollutants And Influences Factors In The Key Part Of The Silk Road Over China

At present,more than half of the world's people live in the cities;they face air pollution which brought about by the use of large amounts of inefficient energy caused by the progress of the urbanization process,the rapid population growth,especially the rapid economic development.All these air pollutants,including fine particles,SO₂,NO₂ and O3,have more significant harm to human health.Therefore,it is very important to analyze the concentration and source of urban air pollutants.This paper collected the real-time concentration data of six air pollutants in Lanzhou,Jinchang and Jiayuguan during 2014,and then analyzed the spatialtemporal distribution characteristics of air pollutants in three cities.The PM_2.5,NO₂,SO₂ and CO concentrations in Lanzhou,Jinchang and Jiayuguan in 2014 showed a trend of high winter and low summer,and the seasonal variation of ozone concentration was opposite to other pollutants.The high value appeared in the most photochemical reaction in summer,the low value appeared in the weakest photochemical reaction in winter.By the influence of sand and dust weather in the Hexi corridor,the PM₁₀ concentration in three cities showed high value in spring.Human activitiescoupled with changes in meteorological conditions,make significant changes in atmospheric pollutants.The diurnal variation of particulate matter,NO₂ and CO concentration varied bimodal,SO₂ and O3 were single peak type due to human travel and motor vehicle exhaust emission.In the analysis of the ratio of PM_2.5 and PM₁₀ in three cities throughout the year,it was found that the PM_2.5 and PM₁₀ concentrations in the spring pollution events?dust storms?were significantly lower than those in the normal weather conditions,while PM_2.5 and PM₁₀ concentration ratio was significantly higher than the normal weather conditionsin episode days during winter,indicating that there are significant differences in the source of pollutants in different seasons.In addition,we also analyzed the impact of meteorological factors on the distribution of pollutants.The concentration of particulate matter in three cities was negatively correlated with temperature,relative humidity and precipitation,and positively correlated with wind speed.NO₂,SO₂,CO negatively correlated with temperature and precipitation;O3 was positively correlated with temperature,but not correlated with precipitation.For Lanzhou and Jinchang,relative humidity and SO₂ have the strongest negative correlation,NO₂ follows,and CO and ozone basically have nocorrelation.There was no significant correlation between NO₂,SO₂ and CO and relative humidity in Jiayuguan,and the ozone concentration and relative humidity showed weak correlation.In addition,the four air pollutants were negatively correlated with wind speed.The relationships between local meteorological elements and PM concentrations suggest a clear association between the highest PM concentrations,with T? 7?,and strong winds?3-4 scale?,but the effect of relative humidity is relatively complicated,with more PM₁₀ and PM_2.5 exceedances being registered with relative humidity less than 40% and 40-60% in Lanzhou,while the higher exeedances in Jinchang appeared in 80-100%.This paper analyzes the six air pollutants in three cities during 2014 and calculates the contribution rate of each pollution source to pollutants.The study shows that sources of pollutants in the Jinchang and Jiayuguan areas including dust storms,industrial production and heating,automobile exhaust,in which dust storms are the main source of particulate matter,and the contribution of dust storms to coarse and fine particles is 90% and 60%,respectively.SO₂ and NO₂ mainly from industrial production and heating and automobile exhaust emissions,CO and O3 is mainly from the car exhaust.For Lanzhou,during the normal weather conditions,the source of air pollutants,including industrial production and heating,automobile exhaust,which particulate matter and SO₂ are the industrial production and heating and other coal combustion process of major pollutants,NO₂,CO and O3 are mainly from vehicle exhaust.During dust sorm,the sources of air pollution in Lanzhou are divided into natural and anthropogenic sources.More than 85% of the particulate matter comes from natural sources?dust storms?,NO₂,SO₂,CO and O3 are mainly derived from anthropogenic sources.