Study On The Level, Distribution And Source Apportionment Of Main Metal Elements In Atmospheric Particles In Changsha

Atmospheric particle is a class of major air pollutants in Changsha. Atmosphericparticle has adverse effect on human health and it can adsorb heavy metals to increaseits toxicity. Thus, it is necessary to study the level, distribution and sourceapportionment of main metal elements in atmospheric particles to understand theregional and city air pollution status and particle pollution control.This paper collected samples of total suspension particle (TSP) in12ponits inChangsha, including Railway station, Shida, Dongtang, Tianxin, Yuhua and Wujialinget al., in June,2011to December,2012. The concentrations of17kinds of mainmetals (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mn, Ni, Pb, Ti, V, Zn) wereanalyzed with inductively coupled plasma optical emission spectrometer (ICP-OES)and microwave-assisted digestion. Pollution characteristics, source apportionment andseasonal variation of the mass concentration of particles were discussed. Combiningthe local meteorological background, particulate pollution and back trajectory intypical haze weather were also analyzed. Meanwhile, the dust fall samples of14points were collected with dust fall sampling device in December,2011. The dust fallsamples were continuously collected in Changsha Railway Station from June toAugust in2011. Current pollution status and pollution characteristics of metals wereanalyzed, including the spatial variations and source apportionment. The results werelisted as follows:(1) The17kinds of metals in TSP ranged from0.0023to6.036μg/m3. Theconcentration of the main mental elements follows the decreasing order of Ca＞Fe＞Al＞K＞Zn＞Pb＞Ba＞Mn＞Cu＞Ti＞V＞Ni＞Cr＞As＞Cd＞Co＞Hg. Theproportion of crustal elements was higher than anthropogenic elements. Comparedwith other cities in China, the pollution level of metals in TSP was at medium level.The distribution characteristics showed that the concentrations of metals in industrialareas and business districts were higher than those in suburbs. Yuhua district is one ofthe heaviest pollution districts in Changsha. Based on the data obtained from twotypical sampling points from June to December,2011, the seasonal variation showedthat metal concentrations in summer were clearly lower than those of winter in TSPsamples. Correlation analysis showed that Al, Ti, K, etc in TSP mainly came from thesoil, and As, Ca, Cr, Cu, Fe, Hg, Mn, Ni, Pb, etc. were related to human activities. Enrichment factor analysis showed that the enrichment degree of Ba, Ca, Cu, Hg, Pb,Zn, Ni, etc was high, which was mainly affected by anthropogenic sources, Cd and Cahad severe enrichment in the whole city. Principal component analysis showed thatthe sources of main metal elements in TSP were very complex,4kinds of pollutionsource were the main sources of atmospheric TSP in Changsha. The contribution ratewas as follows: the industrial emissions accounted for34.34%, construction dust andsoil dust accounted for25.14%, motor vehicle emissions account for15.74%, coalaccounted for13.23%. In addition, weather conditions had a significant influence onthe concentration of pollutant. Mass concentrations of particulate in haze weatherwere significantly higher than the annual averages. Backward air mass trajectoryanalysis showed that, in addition to the local emissions, the transportation fromregional air pollution in the middle-east cities was an important source leadingparticle pollution in Changsha.(2) The concentration of the main metal elements in dust fall in Changsharanged in6.0to31470mg/Kg, following the decreasing order of Ca＞Fe＞K＞Al＞Zn＞Mn＞Ba＞Ti＞Pb＞Cu＞Ni＞Cr＞V＞Co＞As＞Se＞Cd. Because of thecomplexity of regional pollution, the spatial distribution of quality concentrations of17main metal elements in dust fall was large different in different regions inChangsha. Enrichment factor analysis showed that enriched elements in dust fall ineach measuring point drop were mainly Cd, Ca, Zn, Se, Pb, Cu, Ni, etc. In addition tosoil sources, Mn, K, As, Cr, Ba, etc may be overlapped to source of industrialpollution. Principal component analysis showed that4pollution sources of main metalelements in dustfall in Changsha were as follow in turn: coal combustion andindustrial emissions accounted for36.22%, motor vehicle exhaust emissionsaccounted for21.99%, accounting for19.27%of soil dust. Construction dustaccounted for12.36%.