Pollution Characteristic And Environmental Safety Assessment Of Atmospheric Particulate Matter At The Area Of Hengyang Region

With the rapid development of economic, and with the increase of population density, the pollutant emissions of atmospheric environment are increasing rapidly. Air particulate matter is one of the atmospheric pollutants, its dangers are affected by concentration, particle size and chemical composition of the adsorbed. Heavy metals in particulate matter. The harmful of heavy metals in particulate matter to the human body and the environment can not be ignored. Taking Hengyang as research subjects. From April to May 2014, the sampling points were setted in four typical urban functional areas of Hengyang. Collect the samples of respirable particles, TSP, PM2.5.The article used the gravimetric method to analyze the mass concentration. Flame atomic absorption spectrometry and atomic fluorescence spectrometry were used to analysis the content of heavy metals. Tessier sequential extraction method were used to analyze the distribution of heavy metals. The article used single-factor evaluation method and Nemerow pollution index method and other methods to evaluate its harmfulness. The conclusions were as followed:(1)Average number of particles each cubic meter in the range of 0.500-10.366 um was 152.089. The average mass concentration was 86.81 ug / m3.The mass concentration and quantity of respirable particulate were mainly in the fine particulate matter.(2)The average mass concentration of TSP was 230.8 μg / m3.The sequence of the average concentration of TSP was as follow:industrial zone> commercial district> transportation route> living area.The mass concentration of some sampling points exceeded the daily mean value of the ambient air quality standards(GB3095-2012).The average mass concentration of PM2.5 was 118.9 μg/ m3.The sequence of the average concentration of PM2.5 was as follow:industrial zone> living area > commercial district> transportation route. The mass concentration of 20 samplings of PM2.5 exceeded the daily mean value of the ambient air quality standards(GB3095-2012)(75 μg / m3).Rainfall can make a significant reduction in the concentration of TSP. With the increase of the relative humidity, the mass concentration of PM2.5 will decreases.The mass concentration ratio of PM2.5 and TSP was 51.52%. The suspended particles were mainly in fine particulate matter.(3)The sequence of concentrations of heavy metals(TSP and PM2.5) was as follow: Pb> Cu> As> Cd> Hg. Some samples’ concentrations of As, Cd(TSP and PM2.5)were higher than the daily mean value of the ambient air quality standards( As:0.06 ug/m3,Cd:0.05 ug/m3).Samples exceeded in industrial areas were more than other areas. The content ratio(PM2.5 / TSP) in all the heavy metals was higher than the mass content ratio(PM2.5 / TSP) in atmospheric particulate matter. Heavy metals were easier concentrate in fine particulate matter.(4)The proportion that single pollution index of Four heavy metals exceeded had the same trend:Hg>Pb>Cd>As. The sequence of single pollution index of Four heavy metals in four functional areas was as follow: As>Cd>Pb>Hg. This article evaluated samples by Nemerow pollution index. The proportion of the sample(TSP and PM2.5) which stayed clean or safe were 41.67% and 83.33%. The percent of samples which exceed background values were 50% and 12.5%. There were seldom sample which were moderately polluted or serious polluted. Those were collected from the industrial zone.(5)The results of speciation analysis showed that the content of various heavy metals showed the same trend. They had less impact on the surrounding environment. Pb, Cd, Cu, were mainly in the(F1 + F2 + F3 + F4) and prone to metastasis. Bioavailability of heavy metals(TSP、PM2.5) from strong to weak were as follow:Cd> Pb> Cu> As> Hg. Bioavailability of Cu、Hg in TSP were higher than PM2.5. Bioavailability of Pb、Cd、As in PM2.5 were higher than TSP. Pb, Cd, Cu, were the potential bioavailability elements. Hg were unavailable elements.