Study On The Pollution Of Heavy Metals And Polycyclic Aromatic Hydrocarbons On The Surface Dust In Baotou City

In recent decades,with the acceleration of urbanization and industrialization,the problem of urban environmental pollution had increased obviously.Urban surface dust is an important carrier of all kinds of pollutants in the environment,which plays an indicative role in the monitoring of urban environmental.Among all kinds of pollutants,heavy metals and polycyclic aromatic hydrocarbons(PAHs)cause the greatest harm to human health and urban environmental system.Heavy metals in urban surface dust can enter the human body through respiratory inhalation,skin contact and hand mouth intake,which cause serious harm to human health,especially to the elderly and children.The study found that heavy metals accumulated in humans can lead to respiratory diseases,kidney diseases,cancer,child growth retardation and many other adverse health.Polycyclic aromatic hydrocarbons(PAHs)are toxic,carcinogenic and mutagenic,and are harmful to human health.Polycyclic aromatic hydrocarbons(PAHs)with higher rings will have a greater impact on human health,such as gene mutations and cancer.BaP,one of the most dangerous polycyclic aromatic hydrocarbons(PAHs),is listed by EPA as a possible human carcinogen.Therefore,the study of heavy metals and PAHs pollution in urban surface dust is of great significance to understand the change of urban environmental.At present,most of the researches on heavy metals and polycyclic aromatic hydrocarbons(PAHs)in surface dust are carried out in large cities from developed or developing countries(such as Beijing,Shanghai,Nanjing and Xi 'an).However,small and medium-sized cities with rapid industrialization and urbanization have carried out a small amount of research,especially in arid and semi-arid areas of northwest China.However,because of the lack of environmental protection awareness and pollution treatment technology in these areas,there is less research on small and medium-sized industrial cities.Environmental problems are more serious than big cities.In recent years,there is a serious environmental pollution problem in Baotou city,however,the research on the surface dust that more likely to be in contact with the human body and is more harmful to the environment,is not reported and which cannot reflected The environmental pollution in Baotou city comprehensively,accurately,especially the study of the polycyclic aromatic hydrocarbon in the dust is not reported in the relevant literature.Therefore,in this paper,12 kinds of heavy metals and 16 kinds of PAHs in the surface dust of Baotou city were studied,and the contents of heavy metals and polycyclic aromatic hydrocarbons(PAHs)in the surface dust of Baotou city were analyzed.The environmental pollution degree and health risk of heavy metals and PAHs in surface dust of Baotou city were evaluated,the possible sources of heavy metals and PAHs in surface dust were identified and their contribution to each element by qualitative and quantitative methods were identified.Finally,the compound pollution characteristics of heavy metals and PAHs in surface of Baotou city were summarized.The main contents of the study are as follows:(1)The average content of heavy metal Ni,V and As in the surface dust in Baotou city is less than or close to the soil background value of the Hetao plain,while the average content of Ba,Co,Cr,Cu,Mn,Pb,Zn,Cd and Hg is higher than the soil background value of the Hetao plain.The concentration of Co,Cr,Pb,Cd and Hg in the dust is obvious,and attention should be paid to the treatment.The content of Ba,Pb,Zn and Hg in the commercial area is the highest,and the content of Cr,Cu,Mn,Ni,V,Cd and As is the highest in the industrial area,and the content of Co is the highest in the main road.The spatial distribution of the content of Ni,Mn and Cr is similar,from the east to the west,the content Gradually decrease and the spatial distribution of the other heavy metals is different.The heavy metal content of the surface dust in 2012 and 2014 shows that the heavy metal Ba,Co,Mn,Pb,V and Zn have a downward trend.Cr,Cu and Ni have a tendency to increase,and the change of Cr is the most.The mean geo-accumulation index(Igeo)values of heavy metal in surface dust of Baotou was in the order of Co>Cr>Hg>Cd>Pb>Cu>Ba>V>Zn>Mn>Ni>As,indicating the heavy metals are seriously polluted with Cr,Cd and Hg in the surface dust of Baotou City.The pollution load index(PLI)of heavy metals in surface dust of Baotou City ranged from 0.87 to 4.38,with an average of 1.76,belonging to moderate pollution.The overall pollution level decreased gradually from west to east,and the pollution was the most serious in the western Hexi industrial park of the study area.Jiuyuan District and the vicinity of the Saihantara park are less polluted,even no pollution.The potential ecological risk index of each functional area was in the order of business district>cultural district>industrial zone>residential area>main road>park square.The commercial district is the strong potential ecological risk,the cultural and educational district,the industrial district,the residential area and the main road are the strong potential ecological risk,and the park square is the medium potential ecological risk.The speciation of heavy metal in surface dust of Baotou is different,Co and Zn are mainly extracted by acetic acid,while Cr,Mn,Ni,Cu,Pb,Ba,As,V is residue.Under acidic conditions,Co,Zn and Mn are easy to migrate,which is harmful to the environment.The health risk assessment results of heavy metals in surface dust of Baotou city showed that ingestion of dust particles was the main way of risk of non-carcinogenic exposure to surface dust in Baotou city.In general,health risks from exposure from heavy metals in dust to children are higher than to adults.The largest non-carcinogenic risk index of Ba,Pb,Zn in surface dust is commercial areas,the largest non-carcinogenic risk index of Cr,Cu,Mn,Ni,V,As in the surface dust is industrial zone.Co has the largest non-carcinogenic risk index in the main road,and Cd has the largest non-carcinogenic risk in the surface dust of the Park Square.Hg has the largest non-carcinogenic risk index in surface dust in cultural and educational areas.The results of multivariate statistical analysis and PMF show that the pollution sources of heavy metals in surface dust of Baotou city are mainly natural sources,mixed source,building sources,industrial sources,and so on.Among them,Ni,V and As are mainly natural sources.The contribution rates of natural sources to Ni,V and As were 55.56%,44.48%and 73.55%,respectively.Heavy metal Ba,Cu,Pb,Zn,Cd,Hg is mainly a mixed source of industrial and traffic activities.The contribution of the source to these six elements is 50.93%,60.69%,65.64%,72.21%,46.45%,respectively.40.57%.Co is mainly derived from building construction or decoration,as well as weathering and corrosion of building materials(architectural source),and its contribution is as high as 67.71%.The accumulation of Cr and Mn in dust was mainly influenced by industrial sources,which contributed 50.17%to Cr and 42.28%to Mn,respectively.(2)The average value of BkF is the highest and the mean Ant is the lowest among the 16 kinds of optimal controlled PAHs in Baotou city.The PAHs is dominated by high ring PAHs in dust of Baotou city.NaP,Acy,Phe,Fla,DBA are highest in commercial districts,Ace,Flu,Pyr are highest in industrial areas,Ant,BaA,Chy,BkF,BaP,BghiP,InP were the highest in residential area and BbF was the highest in main road.Compared with the screening value and control value of soil pollution risk in China,the surface dust of residential area and commercial district of Baotou City is seriously polluted by polycyclic aromatic hydrocarbons(PAHs).Compared with the European agricultural soil PAHs pollution standard of Maliszewska,the PAHs pollution in commercial area was the most serious.Compared with Canada's agricultural soil control standards,the surface dust in Baotou has been seriously polluted by PAHs.Compared with the Dutch soil evaluation and control criteria,the surface dust in Baotou city received polycyclic aromatic hydrocarbons(PAHs)pollution in different degrees,especially BkF,Fla and NaP,which had great ecological risk.Nimero composite index showed that the PAHs comprehensive pollution index of surface dust in all functional areas was more than 3,which indicated that the risk grade of PAHs pollution in Baotou city was extremely high,and the relevant departments should pay more attention to it.For the three exposure pathways of PAHs in dust,the exposure pathway of ingestion is the main route of carcinogenic risk of PAHs in surface dust of Baotou city,and the total carcinogenic risk of PAHs to children is higher than that of adults in Baotou city.The results of isomer ratio analysis,multivariate statistical analysis and PMF show that the main source of PAHs in surface dust of Baotou is pyrolysis source,and the PAHs in some areas dust comes from petroleum products and low temperature combustion source of fossil fuel.NaP,Ace,Phe,Ant,BaA,BbF,BkF,BaP,BghiP,InP in the surface dust of Baotou is mainly derived from combustion source,which contributes 68.98%,59.11%,41.91%,44.21%,50.45%,86.93%,75.62%,55.24%,87.41%,81.30%respectively.The second is the contribution of petroleum source toAcy,Flu,Fla,Chy.The contribution rate of petroleum source to DBA is 100%,to Acy for 92.49%,to Pyr for 82.22%,to Fla for 56.63%,to Chy for 51.68%.Other sources contributed only 17.33%to Phe,16.74%to Ant and 12.59%to BghiP in the surface dust of Baotou City.(3)The correlation between heavy metal content and physical and chemical indexes and constant components was high,while the correlation between PAHs content and dust physical and chemical indexes and constant components was lower.In addition,the correlation between heavy metals and polycyclic aromatic hydrocarbons(PAHs)in surface dust of Baotou city was not significant,only a few heavy metals and polycyclic aromatic hydrocarbons(PAHs)showed certain significance.The Bivariable LISA maps of heavy metals and PAHs shows that there are greatly differences on the cluster about High-low,low-high,low-low and non-significant between heavy metals and polycyclic aromatic hydrocarbons(PAHs).However,most of the high concentration areas of heavy metals and polycyclic aromatic hydrocarbons(PAHs)appeared in Hexi industrial park in the west of the study area and the south of Donghe area.