Characteristics Of PM_2.5 In Guiyang And Its Source Apportionment

Atmospheric particulate matter pollution has become an important issue of air pollution and its source is very extensive. It is a huge number, complicated composition, diverse property, the most harmful urban air pollutant, and a primary pollutants of urban air quality. In particular the enrichment of toxic ingredients are great harm to human health. Therefore, pointing out the particulate source and the proportion of each source of the city is a very important and complex issue for the prevention of particle pollution, and is also one of important particulate matter research of the atmosphere in china and abroad over the past decade.In this paper, The 357 of particulate matter(PM2.5) samples were continuous collected in Guiyang city from May 2013 to June 2014. The influence of the level of atmospheric concentration of particulate matter, the characteristic of the seasonal distribution and the meteorological conditions on the particles were studied by the national standard gravimetric method. The trace elements As, Hg, Mn, Cu, Zn, Cr, Cd, Pb of particulate matter were measured by ICP-MS, the major elements K, Ca, Na, Mg, Al, Fe, Mn were measured by ICP-OES, the Pb isotope was measured by MC, the concentrations of total Hg(THg) in PM2.5 samples were measured by using Lumex with a Zeeman atomic absorption spectrometer(ZAAS), and the morphology and particle sources were studied by Tecnai G2F20 S-TWIN transmission electron microscope and PMF model. Results were as follows:The concentration of Guiyang PM2.5 was ranging from 4μg/m3 to 193μg/m3 with an average of 70±33 μg/m3. An obvious seasonal variations was observed: winter>autumn>spring>summer. In winter, the reasons of the increase of atmospheric particulate matter concentration were that the coal sources rised and inversion weather appeared frequentiy. In summer the atmosphere particle concentration was low.The elemental concentrations characteristic was Na > Ca > Al > K > Mg > Fe > Cu > Zn > Mn > Pb > Ba > Mg > Cr > Ni > Sr > As > Zr > W > Rb > Ga > Bi > Ge > Co >U and Na, Ca, Al, K passed1000ng/m3, Mg, Fe, Cu, Zn, Mn were between 1000 and 100ng/m3, other element were under 100ng/m3. The Pb isotopic(204Pb, 206 Pb, 207 Pb, 208Pb) content were analyzed. The results showed that the ratio of 206Pb/207 Pb was ranged from 1.17 to 1.21.The ratio indicated that Pb in atmospheric particulate matter was origined from coal and industrial emissions. The concentrations of THg in PM2.5 ranged from 11 to 2560 pg/m3 with an average of 104±85 pg/m3. An obvious seasonal variations was observed: winter > spring > autumn > summer. Comparedwith investigated results of other cities, the present study shows lower level of particulate mercury pollution in Guiyang city.The TEM analysis indicated that the component of PM2.5 were constituted by soot aggregates, fly ash, mineral particles, sulfate particles and organic particles in Guiyang and the fine particles and ultrafine particles were aggregated easily.The PMF model run results showed that factor 1 representing coal source contained Ca, K, Na, Fe, Cu, Zn, Pb, Mn, Cr, Cd elements, factor 2 representing building cement contained Na, Ca, Al, Fe, K, Mg elements and Ca, Al, Fe as building cement identify the element were more than 70%; factor 3 representing biomass combustion contained K, Al, Mn, Cr, Mo elements and K, Mn is the identification element of biomass combustion; factor 4 representing traffic source contained Na, Ca, Al, Mg, Fe, Cu, Zn, Pb, Mo elements and Fe, Mo related with heavy-duty diesel combustion; factor 5 representing soil dust contained Ca, Al, Fe, K, Mg elements; and factor 6 representing oil combustion and industrial mixed sources emissions contained Ni, Cr elements and Ni, Cr are residual oil burning and metal smelting logo elements and the importance of Ni is nearly 80%.The results of sources apportionment by PMF model showed that six pollution sources of Guiyang PM2.5 were coal, building cement, biomass combustion, traffic, soil dust, oil combustion and industrial mixed sources emissions, and their contributions were 46.6%, 9.0%, 21.7%, 14.8%, 6.2%, 1.7%. The contribution of coal-fired source,biomass combustion sources and traffic sources for PM2.5 were up to 83.1%,and it was very important with the lives of residents, industry and terrain in Guiyang City.