Contamination Characters And Sources Of Heavy Metals In Road Dusts Of Fuzhou City

According to the different land uses,this study taken the transportation hub,urban construction area,industrial area,and residential area as sample areas.Road surface dust and foliar dust(collectively referred to as road dust)samples were collected from these areas of the old urban areas,new urban areas and suburban areas in Fuzhou city respectively.Detailed investigation was conducted to understand the contamination characters and the main sources of these road dusts through the analysis of the particle size,heavy metal content and lead isotopic composition.The contribution of each pollution source was also calculated through Ternary-mixed model.Particle size analysis showed that the road surface dust and foliar dust of the four sample areas in Fuzhou were mainly composed of coarser grit(>63um),accounting for 60.03%and 74.82%of the sample size respectively.The frequency curves of the foliage dust showed asymmetric unimodal and bimodal distribution,and road surface dust showed asymmetric bimodal distribution mainly,indicating multi source of road dust in Fuzhou.Compared with other cities in our country,the particle size of road dust in Fuzhou was generally coarser with poor sorting.The particle size of foliar dust increased from suburban areas,the new urban areas to the old urban areas.The particle size of road surface dust in the new urban areas was the the coarest,that in the old urban areas came second,and the dust in suburban areas was the finest.It was affected mainly by the intensity of human activities.The average particle size of road dust in different lanes was Motor vehicle lane>sidewalk>bicycle Lane,which was mainly caused by human activities and road sweeping.The contents of V,Cr,Mn,Co,Ni,Cu,Zn,Pb,As and Cd were all significantly higher than that those in the background soil of Fuzhou,which reached a certain level of accumulation.The concentration of Cd in foliar dust was the highest,which was 8.63 times of the background value.The distribution of heavy metals in foliar dust did not show obvious characteristics in different sample areas.However,the heavy metal concentrations of road surface dust in different sample areas showed as industrial area>urban construction area>transportation hub>residential area;Heavy metal content of foliar dust and road surface dust in different districts showed as old urban area>new urban area>suburban area;Heavy metal contents of road surface dust in different suburbs behaved differently,those in transportation hub and residential area showed as motor vehicle lane>bicycle lane>sidewalk;Industrial area and urban construction area showed as sidewalk/bicycle lane>motor vehicle lane.All elements expect V,Co,and As in the road dusts had reached varying degrees of pollution status,in which Cd was the most serious.The pollution level in industrial area,was higher than other sample areas.Health risk assessment revealed that ingestion was the main way of exposure,the non-cancer risk of children was greater than that of adult,and the risk value was higher than the safety range,had a non-cancer risk that should be given special attention.The lead in foliar dust mainly originated from coal,with an average contribution rate of 43.73%.Automobile exhaust came second,with a contribution rate of 35.04%.Construction dust and industrial dust provided only a small number of lead,construction dust was the largest contributors of lead in road surface dust with the rate of 34.38%,following 26.18%and 27.16%contribution rates of vehicle exhaust and industrial dust respectively.The coal provide only a small percentage.Combined lead isotope analysis with multivariate statistics,the main sources of heavy metals in the foliar dust in Fuzhou were coal combustion and waste incineration,with a contribution rate of 47.31%,traffic and industrial emissions came second,with a contribution rate of 19.728%.Heavy metals of road surface dust mainly came from industries pollution and traffic emissions,with a contribution rate of 54.32%,followed by urban construction and waste incineration.These indicated that besides the effective control of three traditional pollution sources of coal,industrial and traffic emissions,domestic garbage should be properly treated too,such as centralized collection and disposal.