Many studies have been conducted on heavy metal concentrations in urban outdoor dust in China,showing that differences exist in the metal concentrations of different cities. However, no report has studied the distribu...Many studies have been conducted on heavy metal concentrations in urban outdoor dust in China,showing that differences exist in the metal concentrations of different cities. However, no report has studied the distribution of heavy metals across Chinese cities. This work presents the spatial distribution of heavy metals in urban outdoor dust in Chinese cities and discusses the causes for the differences in heavy metal levels across cities by analyzing and summarizing data for 20 provincial capitals from the published scientific literature. The results show that the geometric mean values of Ni and Cr in urban dust of China are lower than or comparable to crustal levels, whereas levels of Cd, Cu, Pb, and Zn are significantly greater than crustal levels. The spatial distributions of Cu, Pb, and Zn in urban dust all exhibit a pattern in which heavy metal levels are greater in cities located in the south of China than in the north. Commercial areas and residential-education areas accumulate more Cd in their dust than industrial areas and traffic areas, and industrial areas and residential-education areas accumulate more Pb than commercial areas and traffic areas. The Zn level in dust from industrial areas is significantly greater than in other areas, and Cu exhibits no significant difference between different functional areas. A positive correlation exists between Cd and Zn in urban dust and population density. Urban dust Pb in Chinese cities is lower than the world average as calculated using data for thirteen cities in different countries. Cd, Cu, and Zn levels in China are close to world averages.展开更多
Support vector regression(SVR) method is a novel type of learning machine algorithms,which is seldom applied to the development of urban atmospheric quality models under multiple socio-economic factors.This study pres...Support vector regression(SVR) method is a novel type of learning machine algorithms,which is seldom applied to the development of urban atmospheric quality models under multiple socio-economic factors.This study presents four SVR models by selecting linear,radial basis,spline,and polynomial functions as kernels,respectively for the prediction of urban dust fall levels.The inputs of the models are identified as industrial coal consumption,population density,traffic flow coefficient,and shopping density coefficient.The training and testing results show that the SVR model with radial basis kernel performs better than the other three both in the training and testing processes.In addition,a number of scenario analyses reveal that the most suitable parameters(insensitive loss function ε,the parameter to reduce the influence of error C,and discrete level or average distribution of parameters σ) are 0.001,0.5,and 2000,respectively.展开更多
The total concentrations of Cd,As,Pb,Cr,Ni,Co,Zn,Cu,Ag,Hg,and Mo were determined in the atmospheric dust of the city of Yerevan by atomic absorption spectrometry(AAnalyst PE 800).Heavy metal pollution levels were eval...The total concentrations of Cd,As,Pb,Cr,Ni,Co,Zn,Cu,Ag,Hg,and Mo were determined in the atmospheric dust of the city of Yerevan by atomic absorption spectrometry(AAnalyst PE 800).Heavy metal pollution levels were evaluated by calculating geo-accumulation(I_(geo)) and summary pollution(Z_c) indices.Potential human health risk was assessed using the United States Environmental Protection agency's human health risk assessment model.The results show that mean contents of all elements tested except Ni and Cr were substantially higher than local geochemical background values.According to the I_(geo),Yerevan territory is strongly-to-extremely polluted by As,Ag,Hg,Mo,and Cd.The Z_c assessment indicated that very high pollution was detected in 36%of samples,high in 32%,average in 12%,and low in 20%.The health risk assessment revealed a noncarcinogenic risk(HI >1) for children at 13 samplings sites and for adults at one sampling site.For children the risk was due to elevated levels of Mo,Cd,Co,and As,while for adults,only Mo.Carcinogenic risk(>1:1,000,000) of As and Cr via ingestion pathway was observed in 25 and 14 samples,respectively.This study,therefore,is the base for further detailed investigations to organize problematic site remediation and risk reduction measures.展开更多
Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijin...Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijing(China),primarily due to haze and dust events(15–30 April 2012).Of particular interest were relevant vertical variations within the lower urban boundary layer(UBL).First,the haze and dust events were characterized by different atmospheric conditions,as quite low wind speed and high humidity are typically observed during haze events.In addition,for the description of stability conditions,the bulk Richardson number(RiB) was calculated for three different height intervals: 8–47,47–140,and 140–280 m.The values of RiB indicated an apparent increase in the occurrence frequency of stably-stratified air layers in the upper height interval—for the 140–280-m height interval,positive values of RiB occurred for about 85% of the time.The downward turbulent exchange of sensible heat was observed at 280 m for the full diurnal cycle,which,by contrast,was rarely seen at 140 m during daytime.These results reinforce the importance of implementing high-resolution UBL profile observations and addressing issues related to stably-stratified flows.展开更多
This paper presented chemical characteristics of wetland inflow diffuse dust and dirt. Single land use impervious areas (parking and roads) were observed and analyzed in commercial and residential areas for organic ma...This paper presented chemical characteristics of wetland inflow diffuse dust and dirt. Single land use impervious areas (parking and roads) were observed and analyzed in commercial and residential areas for organic matters, phosphorus and heavy metals. The buildup data were collected for approximately six months from December to June. The frequency of monitoring was observed daily for the first two months, twice a week for the next two months and once a week for the last two months. The results indicated significant variations in the organic matters and heavy metals strength and total accumulation among the observed areas. High pollutants strength was associated with smaller dust and dirt (DD) particles. Concentrations of phosphorus varied between 5.1 μg/g and 8.3 μg/g in DD particle less than 75 μm and account for 35%-60% of the total phosphorus. The organic matter accumulation rate associated with particles less than 600 μm and greater than 600 μm was 0.1-1 g·(curb-m) -1 ·d -1 and 0.1- 1.5 g·(curb-m) -1 ·d -1 , respectively. DD particles greater than 600 μm consist of 70%-90% of leaves and other plant residues. The strength of heavy metals was more at road compared to parking areas both in commercial and residential areas. Percentage of Zn, Cu and Pb attached with particles less than 200 μm were in the range of 50%-70% in parking, 45%-90% on smooth roads and 30%-80% on rough roads. All the dust and dirt exhibited rising trend with time. Dust and dirt buildup data follow a non-linear accumulation function and can be presented better either by an exponential or power function.展开更多
文摘Many studies have been conducted on heavy metal concentrations in urban outdoor dust in China,showing that differences exist in the metal concentrations of different cities. However, no report has studied the distribution of heavy metals across Chinese cities. This work presents the spatial distribution of heavy metals in urban outdoor dust in Chinese cities and discusses the causes for the differences in heavy metal levels across cities by analyzing and summarizing data for 20 provincial capitals from the published scientific literature. The results show that the geometric mean values of Ni and Cr in urban dust of China are lower than or comparable to crustal levels, whereas levels of Cd, Cu, Pb, and Zn are significantly greater than crustal levels. The spatial distributions of Cu, Pb, and Zn in urban dust all exhibit a pattern in which heavy metal levels are greater in cities located in the south of China than in the north. Commercial areas and residential-education areas accumulate more Cd in their dust than industrial areas and traffic areas, and industrial areas and residential-education areas accumulate more Pb than commercial areas and traffic areas. The Zn level in dust from industrial areas is significantly greater than in other areas, and Cu exhibits no significant difference between different functional areas. A positive correlation exists between Cd and Zn in urban dust and population density. Urban dust Pb in Chinese cities is lower than the world average as calculated using data for thirteen cities in different countries. Cd, Cu, and Zn levels in China are close to world averages.
基金Projects(2007JT3018, 2008JT1013, 2009FJ4056) supported by the Key Project in Hunan Science and Technology Program, ChinaProject(20090161120014) supported by the New Teachers Sustentation Fund in Doctoral Program, Ministry of Education, China
文摘Support vector regression(SVR) method is a novel type of learning machine algorithms,which is seldom applied to the development of urban atmospheric quality models under multiple socio-economic factors.This study presents four SVR models by selecting linear,radial basis,spline,and polynomial functions as kernels,respectively for the prediction of urban dust fall levels.The inputs of the models are identified as industrial coal consumption,population density,traffic flow coefficient,and shopping density coefficient.The training and testing results show that the SVR model with radial basis kernel performs better than the other three both in the training and testing processes.In addition,a number of scenario analyses reveal that the most suitable parameters(insensitive loss function ε,the parameter to reduce the influence of error C,and discrete level or average distribution of parameters σ) are 0.001,0.5,and 2000,respectively.
基金implemented in the frames of a theme "Studying geochemical stream of elements in atmospheric air of Yerevan"(No 13-1E220,2011) under agreement-based(thematic) financial support of the State Committee of Science to the Ministry of Education and Sciences RA
文摘The total concentrations of Cd,As,Pb,Cr,Ni,Co,Zn,Cu,Ag,Hg,and Mo were determined in the atmospheric dust of the city of Yerevan by atomic absorption spectrometry(AAnalyst PE 800).Heavy metal pollution levels were evaluated by calculating geo-accumulation(I_(geo)) and summary pollution(Z_c) indices.Potential human health risk was assessed using the United States Environmental Protection agency's human health risk assessment model.The results show that mean contents of all elements tested except Ni and Cr were substantially higher than local geochemical background values.According to the I_(geo),Yerevan territory is strongly-to-extremely polluted by As,Ag,Hg,Mo,and Cd.The Z_c assessment indicated that very high pollution was detected in 36%of samples,high in 32%,average in 12%,and low in 20%.The health risk assessment revealed a noncarcinogenic risk(HI >1) for children at 13 samplings sites and for adults at one sampling site.For children the risk was due to elevated levels of Mo,Cd,Co,and As,while for adults,only Mo.Carcinogenic risk(>1:1,000,000) of As and Cr via ingestion pathway was observed in 25 and 14 samples,respectively.This study,therefore,is the base for further detailed investigations to organize problematic site remediation and risk reduction measures.
基金funded by the National Basic Research Program of China (Grant No.2014CB447900)Xiaofeng GUO acknowledges the support of the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences (Grant No.LAPC-KF-2009-02)
文摘Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijing(China),primarily due to haze and dust events(15–30 April 2012).Of particular interest were relevant vertical variations within the lower urban boundary layer(UBL).First,the haze and dust events were characterized by different atmospheric conditions,as quite low wind speed and high humidity are typically observed during haze events.In addition,for the description of stability conditions,the bulk Richardson number(RiB) was calculated for three different height intervals: 8–47,47–140,and 140–280 m.The values of RiB indicated an apparent increase in the occurrence frequency of stably-stratified air layers in the upper height interval—for the 140–280-m height interval,positive values of RiB occurred for about 85% of the time.The downward turbulent exchange of sensible heat was observed at 280 m for the full diurnal cycle,which,by contrast,was rarely seen at 140 m during daytime.These results reinforce the importance of implementing high-resolution UBL profile observations and addressing issues related to stably-stratified flows.
文摘This paper presented chemical characteristics of wetland inflow diffuse dust and dirt. Single land use impervious areas (parking and roads) were observed and analyzed in commercial and residential areas for organic matters, phosphorus and heavy metals. The buildup data were collected for approximately six months from December to June. The frequency of monitoring was observed daily for the first two months, twice a week for the next two months and once a week for the last two months. The results indicated significant variations in the organic matters and heavy metals strength and total accumulation among the observed areas. High pollutants strength was associated with smaller dust and dirt (DD) particles. Concentrations of phosphorus varied between 5.1 μg/g and 8.3 μg/g in DD particle less than 75 μm and account for 35%-60% of the total phosphorus. The organic matter accumulation rate associated with particles less than 600 μm and greater than 600 μm was 0.1-1 g·(curb-m) -1 ·d -1 and 0.1- 1.5 g·(curb-m) -1 ·d -1 , respectively. DD particles greater than 600 μm consist of 70%-90% of leaves and other plant residues. The strength of heavy metals was more at road compared to parking areas both in commercial and residential areas. Percentage of Zn, Cu and Pb attached with particles less than 200 μm were in the range of 50%-70% in parking, 45%-90% on smooth roads and 30%-80% on rough roads. All the dust and dirt exhibited rising trend with time. Dust and dirt buildup data follow a non-linear accumulation function and can be presented better either by an exponential or power function.
