| This paper took the Pearl River Delta cities?Guangzhou City,Shenzhen City,Dongguan City,Foshan City,Zhongshan City and Huizhou City?as the study area.Urban dust samples in four functional zones?Residential zone,Commercial zone,Industrial zone and Traffic zone?were collected in each city.The concentrations of Pb,Cr,Cd,As,Hg,Cu,Zn and Ni were measured,then the seasonal and spatial distributions of heavy metals in urban dust were studied.On this basis,the pollution levels,potential ecological risk and human health risk of heavy metals in urban dust were evaluated.BCR sequential extraction was used to extract the chemical forms of heavy metals?Pb,Cr,Cu,Zn and Ni?,and their mobilities were estimated.The main conclusions were as follows:?1?The average concentrations of Cd,Cu and Zn in urban dust are higher in the six cities.Compared with the average concentrations of heavy metals in urban dust of the six cities and the order of the average concentrations of heavy metals from high to low is Foshan City,Guangzhou City and Shenzhen City where the average concentrations of heavy metals are higher.The average concentrations of Pb,Cr,Cd,As,Hg,Cu,Zn and Ni in urban dust are 166.25,248.27,0.74,13.87,0.11,203.82,968.29 and 65.98 mg·kg-1?Foshan City?,184.81,122.47,0.73,15.04,0.11,181.10,775.48 and 40.48 mg·kg-1?Guangzhou City?and 122.02,143.60,0.56,8.28,0.16,143.97,681.96 and 41.95 mg·kg-1?Shenzhen City?,respectively.?2?In general,the average concentrations of heavy metals in urban dust of the commercial zone are the highest in Guangzhou City,Dongguan City,Zhongshan City and Huizhou City,the industrial zone for Shenzhen City and the residential zone for Foshan City.The average concentrations of Pb,Cr,Cd,As,Hg,Cu,Zn and Ni in these functional zones are 188.00,137.81,0.84,18.62,0.13,180.59,1048.08 and 46.91 mg·kg-1?Guangzhou City?,98.64,128.64,0.89,12.53,0.13,126.80,1122.46 and 38.16 mg·kg-1?Dongguan City?,112.43,151.89,0.47,9.18,0.07,216.48,573.36 and 45.32 mg·kg-1?Zhongshan City?,62.75,90.35,0.32,7.82,0.03,64.04,292.92 and 18.80 mg·kg-1?Huizhou City?,236.57,273.73,0.83,9.77,0.12,317.55,1424.31 and 78.37 mg·kg-1?Shenzhen City?and 176.00,258.38,0.80,12.22,0.17,218.10,1174.15 and 87.14 mg·kg-1?Foshan City?,respectively.?3?The concentrations of Cd in urban dust is greatly influenced by seasonal change in Guangzhou City,Hg for Shenzhen City,Zhongshan City,Dongguan City and Huizhou City and Pb for Foshan City.The ratioes?winter/summer?R of the average concentrations of heavy metals in winter and summer are 1.62?Guangzhou City?,2.46?Shenzhen City?,1.42?Zhongshan City?,1.64?Dongguan City?,0.36?Huizhou City?and 1.58?Foshan City?,respectively.The concentrations of heavy metals in urban dust of the traffic zone and the commercial zone are greatly influenced by seasonal change in Guangzhou City and Dongguan City,the residential zone and the commercial zone for Shenzhen City and Huizhou City,the residential zone and the traffic zone for Foshan City,the residential zone and the industrial zone for Zhongshan City.The R are 1.60,1.31?Guangzhou City?,1.30,1.44?Dongguan City?,1.56,1.52?Shenzhen City?,0.70,0.83?Huizhou City?,1.41,1.32?Foshan City?and 1.31,1.25?Zhongshan City?,respectively.?4?Pb and Cu in urban dust are mainly in the reducible fraction and residual fraction,the residual fraction for Cr and Ni,the mild acido-soluble fraction for Zn in Guangzhou City.Pb in urban dust is mainly in the reducible fraction,the residual fraction for Cr and Ni,the reducible fraction and the oxidisable fraction for Cu,the mild acido-soluble fraction for Zn in Shenzhen City and Dongguan City.Pb and Cu in urban dust are mainly in the reducible fraction,the residual fraction for Cr and Ni,the mild acido-soluble fraction for Zn in Foshan City,Zhongshan City and Huizhou City.The mobility for heavy metals in urban dust of Guangzhou City and Zhongshan City is in order of:Zn>Ni>Pb>Cu>Cr,Zn>Ni>Cu>Pb>CrforShenzhenCity,DongguanCityandHuizhouCity,Zn>Cu>Ni>Pb>Cr for Foshan City.?5?Geoaccumulation pollution index was used to estimate the pollution levels of heavy metals in urban dust of the Pearl River Delta.The pollution degrees of Zn,Cd and Cu in urban dust of the six cities are more serious during winter and summer.The indexes are 3.39,3.11,2.83?the winter of Guangzhou City?,2.81,2.42,2.31?the summer of Guangzhou City?,3.23,2.66,2.43?the winter of Shenzhen City?,3.18,2.02,2.23?the summer of Shenzhen City?,3.18,2.56,2.00?the winter of Dongguan City?,2.62,2.18,2.33?the summer of Dongguan City?,3.73,3.12,3.02?the winter of Foshan City?,3.19,2.68,2.61?the summer of Foshan City?,2.57,2.54,2.34?the winter of Zhongshan City?,2.56,2.22,2.26?the summer of Zhongshan City?and 1.54,2.00,1.11?the winter of Huizhou City?,1.72,1.83,1.27?the summer of Huizhou City?,respectively.The pollution degree of the heavy metals in different functional zones was not the same.?6?The heavy metals in urban dust of the Pearl River Delta cause a certain level ecological risk.Thereinto,Cd,Hg and Cu have the highest ecological risk in all six cities during winter and summer.The potential ecological risk indexes Ei are 389.73,55.46,53.27?the winter of Guangzhou City?,242.41,52.26,37.80?the summer of Guangzhou City?,306.70,85.03,48.18?the winter of Shenzhen City?,188.84,35.20,36.97?the summer of Shenzhen City?,286.61,49.24,32.17?the winter of Dongguan City?,204.91,28.61,38.40?the summer of Dongguan City?,399.11,57.35,61.21?the winter of Foshan City?,291.96,94.10,46.57?the summer of Foshan City?,266.52,32.88,39.94?the winter of Zhongshan City?,218.30,24.10,37.21?the summer of Zhongshan City?and 182.15,10.48,16.29?the winter of Huizhou City?,162.06,28.58,18.52?the summer of Huizhou City?,respectively.And the comprehensive potential ecological risk indexes of all the functional zones reach a potential ecological risk level of middle-up.?7?The heavy metals in urban dust cannot cause non-carcinogenic risk for the adults of six cities during winter and summer.And Cr,Cd,As and Ni do not have the carcinogenic risk.The integrated index?HI?indicated that the non-carcinogenic risk is showed for the children in the residential zone?1.01?,commercial zone?1.18?,traffic zone?1.05?of winter and the commercial zone?1.07?of summer in Guangzhou City,the industrial zone?1.45?of winter in Shenzhen City,the industrial zone?1.17?of summer in Dongguan City,the residential zone?1.34?,commercial zone?1.04?,industrial zone?1.44?,traffic zone?1.48?of winter and the residential zone?1.01?,industrial zone?1.42?,traffic zone?1.15?of summer in Foshan City and the commercial zone?1.01?of summer in Zhongshan City.So people should pay enough attention to these functional zones. |
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