Heavy Metals, Phosphorus and Some Other Elements in Urban Soils of Hangzhou City, China

Health implications of inhaling and/or ingesting dust particles with high concentrations of heavy metals from urban soils are a subject of intense concern. Understanding the geochemistry of these metals is key to their effective management. Total concentrations of heavy metals,phosphorus (P) and 8 other elements from topsoil samples collected at 82 locations in Hangzhou City were measured to:a) assess their distribution in urban environments; and b) understand their differentiation as related to land use. Metal mobility was also studied using a three-step sequential chemical fractionation procedure. About 8.5%,1.2%,3.6%,11.0% and 30.3% of the soil samples had Cd,Cr,Cu,Pb,and Zn concentrations,respectively,above their allowable limits for public and private green areas and residential use. However,in commercial and industrial areas,most samples had metal concentrations below their allowable limits. Statistical analyses revealed that the 16 measured elements in urban soils could be divided into four groups based on natural or anthropic sources using a hierarchical cluster analysis. Additionally,Cu,Pb,and P showed similar spatial distributions with significant pollution in commercial zones,suggesting vehicle traffic or commercial activities as dominant pollutant sources. Also,Cd,Co,Cr,Ni,Zn,Mn and Fe had the highest concentrations in industrial locations,signifying that industrial activities were the main sources of these seven metals. Moreover,the data highlighted land-use as a major influence on heavy metal concentrations and forms found in topsoils with large proportions of soil Cd,Co,Cr,and Ni found in residual fractions and soil Cu,Pb and Zn mainly as extractable fractions.

Chemical Criteria to Assess Risk of Phosphorus Leaching from Urban Soils

Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P concentrations using water, sodium bicarbonate and citric acid. Meanwhile the soils were artificially leached in columns and P concentrations in the leachates were determined. With linear regression a two-stage linear relationship was found to exist between concentrations of P in the leachates …

RELATIONSHIPS BETWEEN FRACTIONATIONS OF Pb, Cd, Cu, Zn AND Ni AND SOIL PROPERTIES IN URBAN SOILS OF CHANGCHUN, CHINA

An extensive soil investigation was conducted in different domains of Changchun to disclose the fractionations of Pb, Cu, Cd, Zn and Ni in urban soils. Meanwhile correlation analysis and multiple stepwise regressions were used to define relationships between soil properties and metal fractions and the chief factors influencing the fractionation of heavy metals in the soils. The results showed that Pb, Ni and Cu were mainly associated with the residual and organic forms; most of Cd was concentrated in the residual and exchangeable fractions. Zn in residual and carbonate fraction was the highest. The activities of the heavy metals probably declined in the following order: Cd, Zn, Pb, Cu and Ni. The chemical fractions of heavy metals in different domains in Changchun City were of significantly spatial heterogeneity. Soil properties had different influences on the chemical fractions of heavy metals to some extent and the main factors influencing Cd, Zn, Pb, Cu and Ni fractionation and transformation were apparently different.

Distribution of Cu and Pb in particle size fractions of urban soils from different city zones of Nanjing, China

Soil samples from 4 defined city zones of Nanjing were randomly collected at 0-5 cm and 5-20 cm intervals and size fractions of soil particles were separated from undisturbed bulk soils by low energy dispersion procedure. The total contents of Cu and Pb in the different particle size fractions of the urban soils were analyzed by HNO3-HF-HClO4 digestion and flame atomic absorption spectrophotometer determination. The total content of Cu and Pb in soil particle size fractions varied with their size and with city zones as well. Both the content and variation with the size fractions of Pb was bigger than of Cu supporting our previous finding that there was Pb pollution to different degrees in the urban soils although the two elements were generally enriched in clay-sized fraction. Contaminated Pb tended to be preferentially enriched in the size fraction of 2000-250 μm and clay-sized fraction. While the size fractions of the soils from newly developed and preserved area contained smaller amount of Cu and Pb, the partitioning of them in coarse and fine particle size fractions were insignificant compared to that from inner residence and commercial area. The very high Pb level over 150 mg/kg of the fine particle fractions from the soils of the inner city could be a cause of high blood Pb level reported of children from the city as acute exposure to Pb of fine particles of the urban soil might occur by soil ingestion and inhalation by young children. Thus, much attention should be paid to the partitioning of toxic metals in fine soil particles of the urban soils and countermeasures against high health risk of Pb exposure by soil ingestion and dust inhalation should be practiced against the health problem of blood Pb for young children from the cities.

Lead content of urban soils in China

This paper presents the background value of Pb content in soils from Wuhan,Lanzhou,Changchun andQingdao cities in China,the soils were contaminated by either of smelter,automo- bile,chemical industries,and traffic road. The degree of Pb pollution in the four cities is different,Wuhan >Qingdao > Changchun>Lanzhou. The heavier pollution is where it is nearer to the pollution source. The Pb pollution in Wuhan,Qingdao and Changchun is similar to that of Ber- mingham.

Competitive adsorption and mobility sequence of heavy metals in urban soils of southeastern China

Heavy metals can be introduced into urban soils at the same time. Therefore, their selective retention and competitive adsorption by the soils become of major importance in determining their availability and movement throughout the soil. In this study, the availability and mobility of six heavy metals in eight urban soils collected from different cities of Zhejiang Province, southeastern China were assessed using distribution coefficients（Kd） and retardation factor（Rf）. The results showed that there were great differences in the Kd and Rfamong the tested soils. The adsorption sequences were Cr〉Pb〉Cu〉Cd〉Zn〉Ni, and the Kd decreased with increasing levels of metal addition. Ni generally has the lowest Rf values followed closely by Cd, and Zn whereas Cr and Pb reached the highest values. The results suggest that Ni and Zn have the highest mobility associated to the lowest adsorption, Cr and Pb present the opposite behavior. Correlation analysis indicates that soil pH, CaCO3 content, and cation exchange capacity （CEC） are key factors controlling the solubility and mobility of the metals in the urban soils.

Ecological Risk Assessment of Combined Pollution of Heavy Metals and Pesticides in Urban Soils

Urban soil is the main component of urban ecological systems and the key risk receptor from urbanization. Heavy metal and green pesticide pollutions in urban soils have been widely reported with the expanding of urbanization. Since urban soil pollution comes from various resources, application of integrated thinking and methods is needed in ecological risk assessment of urban soil pollution. This paper synthetically reviewed the combined pollution of heavy metals and pesticide, and ecological risk assessment, and then proposed some research trends and areas in the future that are required to carry out intensively according to the present situation of environmental pollution and international research fronts.

Spatial distribution and pollution assessment of heavy metals in urban soils from southwest China

To identify the concentrations and sources of heavy metals, and to assess soil environmental quality, 63 soil samples were collected in Yibin City, Sichuan Province, China. Mean concentrations of As, Pb, Zn, and Cu were 10.55, 61.23, 138.88 and 56.35 mg/kg, respectively. As concentrations were comparable to background values, while Pb, Zn, and Cu concentrations were higher than their corresponding background values. Industrial areas exhibited the highest concentrations of As, Pb, Zn, and Cu, while the lowest concentrations occurred in parks. Statistical analysis was performed and two cluster groups of metals were identified with Pb, Zn, and Cu in one group and As in the other. Spatial distribution maps indicated that Pb, Zn, and Cu were mainly controlled by anthropogenic activities, whereas As could be mainly accounted for by soil parent materials. Pollution index values of As, Pb, Zn, and Cu varied in the range of 0.24-1.93, 0.66-7.24, 0.42-4.19, and 0.62-5.25, with mean values of 0.86, 1.98, 1.61, and 1.78, respectively. The integrated pollution index （IPI） values of these metals varied from 0.82 to 3.54, with a mean of 1.6 and more than 90% of soil samples were moderately or highly contaminated with heavy metals. The spatial distribution of IPI showed that newer urban areas displayed relatively lower heavy metal contamination in comparison with older urban areas.

A meta-analysis of heavy metals pollution in farmland and urban soils in China over the past 20 years

A total of 713 research papers about field monitor experiments of heavy metals in farmland and urban soils in China,published from 2000 to 2019,were obtained.A meta-analysis was conducted to evaluate the level of China's heavy metal pollution in soils,mainly focusing on eight heavy metals.It was found that the average concentrations of cadmium(Cd),lead(Pb),zinc(Zn),copper(Cu),mercury(Hg),chromium(Cr),nickel(Ni),and arsenic(As)in China were 0.19,30.74,85.86,25.81,0.074,67.37,27.77 and 8.89 mg/kg,respectively.Compared with the background value(0.097 mg/kg),the Cd content showed a twofold(0.19 mg/kg)rise in farmland soils and a threefold(0.29 mg/kg)rise in urban soils.The decreasing order of the mean Igeo was Cd(1.77)>Pb(0.62)>Zn(0.60)>Cu(0.58)>Hg(0.57)>Cr(0.54)>Ni(0.47)>As(0.28).Nearly 33.54%and 44.65%of sites in farmland and urban soils were polluted with Cd.The average concentrations of eight heavy metals were not sensitive change in recent two decades in farmland and urban soils.The average P_n values for urban(2.52)and farmland(2.15)soils showed that heavy metal pollution in urban soils was more serious than that in farmland,and the middle Yangtze River regions,where industrial activity dominates,were the most polluted.The meta-analysis comprehensively evaluated the current pollution situation of soil heavy metal,and provided important basis for soil management and environment prevention in China.

Determining the influence of the physicochemical parameters of urban soils on As availability using chemometric methods：A preliminary study

An initial exploration was conducted using mathematical and statistical methods to obtain relevant information about the determination of the physicochemical parameters capable of controlling As uptake by ryegrass grown on contaminated topsoils.Concentrations of As in the soils were from 10 to 47 mg/kg,mainly in the As（V） form（57%–73%）.Concentrations of As in water extracts were very low（61–700 μg/kg）.It was suggested that As（Ⅲ） was mainly in the uncharged species and As（V） in the charged species.Chemometric methods revealed that the values of the ratio As（Ⅲ）/As（V） depended on the assimilated-phosphorus,the pseudo-total and water-extractable Fe contents and the soil p H.Arsenic concentrations measured in ryegrass shoots ranged from 119 to 1602 μg/kg.Positive linear correlations were obtained between As in ryegrass shoots and water extractable-As.The transfer coefficient of As correlated well with the ratio assimilated-phosphorus/Fe-oxides.As（Ⅲ）uptake by the shoot of ryegrass was controlled by the organic matter and Fe-oxide contents.

Heavy metal contamination of urban topsoil in a petrochemical industrial city in Xinjiang, China

Heavy metal pollution is a widespread phenomenon in many countries of the world. In this study, we conducted a field investigation to assess the status of heavy metal pollution in urban soils of Dushanzi, a district of Karamay city in Xinjiang, China. A total of 56 soil samples in the topsoil layer of 0-15 cm were collected within the urban area and seven elements （Cu, Zn, Cd, Pb, Cr, As and Ni） were analyzed. The mean concentrations of these metals were all higher than their corresponding background values of soils in Xinjiang. We used the pollution index and ecological risk index to assess the degree of heavy metal pollution and the potential ecological risk of urban soils. The pollution index values of Cu, Zn, Cd, Pb, Cr, As and Ni were 1.81, 1.35, 4.64, 1.27, 1.80, 1.39 and 1.22, respectively; and the potential ecological risk index values for them were 12.03, 1.79, 185.05, 8.39, 4.78, 18.44 and 1.79, respectively. These results indicated that urban soils in Dushanzi were polluted by heavy metals to some extent and demonstrated a high ecological risk, as influenced by industrial activities. Cd was the key element for the metal pollution of urban soils in the study area. Correlation analyses, principal component analysis coupled with the spatial distribution maps of element concentrations further soils can be mainly attributed to petrochemical commercial activities. revealed that heavy metal pollution of urban ndustry, coal chemical industry, traffic and

Numerical Approaches to Identification of Characteristic Soil Layers in an Urban Environment

Pedogenetic soil horizons are one of the fundamental building blocks of modern soil classification; however, in soils of urban areas which are often strongly disturbed by human activities, horizons are difficult to distinguish but substitutive morphological layers may be identified. To identify the characteristic soil layers in an urban environment, 224 soil layers of 36 in-situ pedons were examined and described in urban and suburban Nanjing, and 27 variables were extracted for multivariate analysis. Three groups and six subdivisions were identified by TwoStep cluster analysis combined with hierarchical cluster analysis based on factor scores. Soil forming factors and soil forming processes could be interpreted from the principal component analysis （PCA） of variables, cluster analysis of soil layers, and discriminant analysis of soil layer groups and their subdivisions. Parent materials, moisture regimes, organic matter accumulation, and especially nutrient accumulation were the main causes of characteristic soil layer formations. The numerical approaches used in this study were useful tools for characteristic soil layer identification of urban soils.

Polycyclic aromatic hydrocarbon in urban soil from Beijing, China

Polycyclic aromatic hydrocarbons （EPA-PAHs） in the urban surface soils from Beijing were determined using gas chromatography and mass spectrometry （GC-MS）. It is significantly complementary for understanding the PAHs pollution in soil of integrated Beijing city on the basis of the information known in the outskirts. The total concentration of 16 EPA-PAH was from 0.467 to 5.470 μg/g and was described by the contour map. Compound profiles presented that the 4-, 5- and 6-ring PAHs were major compositions. The correlation analysis showed that PAHs have the similar source in the most sampling sites and BaP might be considered as the indicator of PAHs. Characteristic ratios of anthracene （An）/（An＋ phenanthrene （Phe））, fluoranthene （Flu）/（Flu/ pyrene （Pyr）） and benzo[a]pyrene （BaP）/laenzo[g,h,i]perylene （BghiP） indicated that the PAHs pollutants probably mainly originated from the coal combustion and it was not negligible from vehicular emission. The level of PAHs in our study area was compared with other studies.

Content and densities of soil organic carbon in urban soil in different function districts of Kaifeng

Urban soil, forming along with the development of city, has unique properties of soil organic carbon. On the basis of field investigation and laboratory analysis, soil organic carbon （SOC） of Kaifeng city was studied, and the results showed that the characteristics of SOC were different not only among function districts in urban area, but also between urban area and suburbs. The order of SOC in topsoil was industrial district 〉 recreational district 〉 traffic district 〉 cultural/educational district 〉 residential/administrative district. The density of soil organic carbon （SOCD） in both topsoil and profile followed the orders of recreational district 〉 industrial district 〉 traffic district〉cultural/educational district 〉 residential/adminis-trative district, and cultural/educational district 〉 traffic district〉industrial district〉recreational district 〉 administrative/residential district, respectively. SOCD in both topsoil and profile decreased along the transection line from urban area to suburbs and urban area had 2.53-fold more SOCD in topsoil and 1.56-fold more SOCD in profile than suburbs, respectively. SOC decreased with the depth and was mainly distributed within the scope of 0-30 cm. The variances of SOC in urban area were more complicated than that in suburbs.

Comparison on Soil Carbon Stocks Between Urban and Suburban Topsoil in Beijing, China

The urban population and urbanized land in China have both increased markedly since the 1980 s. Urban and suburban developments have grown at unprecedented rates with unknown consequences for ecosystem functions. In particular, the effect of rapid urbanization on the storage of soil carbon has not been studied extensively. In this study, we compared the soil carbon stocks of different land use types in Beijing Municipality. We collected 490 top-soil samples(top 20 cm) from urban and suburban sites within the Sixth Ring Road of Beijing, which cover approximately 2400 km2, and the densities of soil organic carbon(SOC), soil inorganic carbon(SIC), and total carbon(TC) were analyzed to determine the spatial distribution of urban and suburban soil carbon characteristics across seven land use types. The results revealed significant differences in soil carbon densities among land use types. Additionally, urban soil had significantly higher SOC and SIC densities than suburban soil did, and suburban shelterbelts and productive plantations had lower SIC densities than the other land use types. The comparison of coefficients of variance(CVs) showed that carbon content of urban topsoil had a lower variability than that of suburban topsoil. Further findings revealed that soil carbon storage increased with built-up age. Urban soil built up for more than 20 years had higher densities of SOC, SIC and TC than both urban soil with less than 10 years and suburban soil. Correlation analyses indicated the existence of a significantly negative correlation between the SOC, SIC, and TC densities of urban soil and the distance to the urban core, and the distance variable alone explained 23.3% of the variation of SIC density and 13.8% of the variation of TC density. These results indicate that SOC and SIC accumulate in the urban topsoil under green space as a result of the conversion of agricultural land to urban land due to the urbanization in Beijing.

Toxic metal enrichment characteristics and sources of arid urban surface soil in Yinchuan City, China

To investigate the environmental quality of the urban surface soil in Yinchuan City, the capital of Ningxia Hui Autonomous Region （Ningxia）, China, we sampled surface soil and measured the concentrations of 8 toxic metals （Pb, Cr, Cu, Zn, Co, Bi, Ni and V） using X-ray fluorescence spectrometry. The enrichment characteristics and sources of these toxic metals in the soil were analyzed by the enrichment factor （EF） and multivariate statistical analysis. The results showed that the mean concentrations of these toxic metals in the soil samples were 25.0, 109.1, 16.8, 26.0, 37.2, 2.7, 25.3 and 59.9 mg/kg for Pb, Cr, Cu, Zn, Co, Bi, Ni and V, respectively, which were 1.2, 1.8, 0.8, 0.4, 3.2, 8.7, 0.7 and 0.8 times of the corresponding background values of Ningxia soil, respectively. The variations of Pb, Zn, Co, Bi and Ni concentrations in the surface soil of Yinchuan were larger than those of the other metals. Our results also showed that the toxic metals investigated in the soil had different enrichment levels. Both Co and Bi were significantly enriched, whereas Cr was only moderately enriched in the soil. There was a deficiency or minimal enrichment of the other toxic metals in the soil. Source analysis results based on the concentration, enrichment characteristics and multivariate statistical analysis indicated that Cr, V and Ni originated from a combination of fossil fuel combustion, traffic pollution and natural occurrence. Pb, Cu and Zn were predominantly derived from natural and traffic sources, while Co and Bi primarily originated from construction sources.

Effects of Urbanization,Soil Property and Vegetation Configuration on Soil Infiltration of Urban Forest in Changchun,Northeast China

Urban forest soil infiltration, affected by various factors, is closely related with surface runoff. This paper studied the effect of urban forest types, vegetation configuration and soil properties on soil infiltration. In our study, 191 typical plots were sampled in Changchun City, China to investigate the soil infiltration characteristics of urban forest and its influencing factors. Our results showed that the steady infiltration rates of urban forest soil were highly variable. High variations in the final infiltration rates were observed for different vegetation patterns and compaction degrees. Trees with shrubs and grasses had the highest infiltration rate and trees with bare land had the lowest infiltration rate. In addition, our results showed that the soil infiltration rate decreased with an increase in the bulk density and with a reduction in the soil organic matter content and non-capillary porosity. The soil infiltration rate also had significantly positive relationships with the total porosity and saturated soil water content. Urban soil compaction contributed to low soil infiltration rates. To increase the infiltration rate and water storage volume of urban forest soil, proper techniques to minimize and mitigate soil compaction should be used. These findings can provide useful information for urban planners about how to maximize the water volume of urban forest soil and decrease urban instantaneous flooding.

Characterization of Urban Soil with SEM-EDX

The coal is largely used for generation of energy in the India, and their huge exploitations cause contamination of the soil. In the present work, the inorganic contamination of surface soil in the coal basin of the country, Korba is described. The concentration of elements i.e. C, O, S, Cl, Na, Mg, Al, Si, P, K, Ca, Ti, Fe, Mn and Ni in the surface soils (n = 30) was analysed by technique i.e. scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), ranged from 6.6% - 36.4%, 37.8% - 54.3%, 0.07% - 0.39%, 0.03% - 0.25%, 0.10% - 0.39%, 0.12% - 0.49%, 3.7% - 10.3%, 12.2% - 24.4%, 0.11% - 0.60%, 0.68% - 3.22%, 0.8% - 2.7%, 0.25% - 0.61%, 2.3% - 6.4%, 0.08% - 0.22% and 0.04% - 0.16% with mean value (p = 0.05) of 18.8% ± 2.7%, 49.0% ± 1.5%, 0.18% ± 0.03%, 0.11% ± 0.02%, 0.23% ± 0.03%, 0.32% ± 0.03%, 6.1% ± 0.5%, 16.9% ± 0.9%, 0.27% ± 0.04%, 1.6% ± 0.2%, 1.5% ± 0.2%, 0.41% ± 0.03%, 4.3% ± 0.4%, 0.14% ± 0.02% and 0.08% ± 0.01%, respectively. The surface soil morphology, concentration variation of elements, pollution indices and contaminant sources in the soil are discussed.

Hyperspectral Inversion and Analysis of Zinc Concentration in Urban Soil in the Urumqi City of China

Excessive accumulation of zinc(Zn)in urban soil can lead to environmental pollution and pose a potential threat to human health and the ecosystem.How to quickly and accurately monitor the urban soil zinc content on a large scale in real time and dynamically is crucial.Hyperspectral remote sensing technology provides a new method for rapid and nondestructive soil property detection.The main goal of this study is to find an optimal combination of spectral transformation and a hyperspectral estimation model to predict the Zn content in urban soil.A total of 88 soil samples were collected to obtain the Zn contents and related hyperspectral data,and perform 18 transformations on the original spectral data.Then,select important wavelengths by Pearson’s correlation coefficient analysis(PCC)and CARS.Finally,establish a partial least squares regression model(PLSR)and random forest regression model(RFR)with soil Zn content and important wavelengths.The results indicated that the average Zn content of the collected soil samples is 60.88 mg/kg.Pearson’s correlation coefficient analysis(PCC)and CARS for the original and transformed wavelengths can effectively improve the correlations between the spectral data and soil Zn content.The number of important wavelengths selected by CARS is less than the important wavelengths selected by PCC.Partial least squares regression model based on first-order differentiation of the reciprocal by CARS(CARS-RTFD-PLSR)is more stable 2 and has the highest prediction ability(R=0.937,RMSE=8.914,MAE=2.735,RPD=3.985).The CARS-RTFD-PLSR method can be used as a means of prediction of Zn content in soil in oasis cities.The results of the study can provide technical support for the hyperspectral estimation of the soil Zn content.

Effects of urbanization on heavy metal accumulation in surface soils, Beijing

Urbanization processes affect the accumulation of heavy metals in urban soils. Effects of urbanization on heavy metal accumulation in soils were studied using Beijing as an example. It has been suggested that the ecological function of vegetation covers shifting from natural to agricultural settings and then to urban greenbelts could increase the zinc（Zn） concentrations of soils successively. The Zn concentration of urban soils was significantly correlated to the percentage of the impervious land surface at the500 m × 500 m spatial scale. For urban parks, the age or years since the development accounted for 80% of the variances of cadmium（Cd） and Zn in soils. The population density,however, did not affect the heavy metal distributions in urban soils. To conclude, the urban age turned out to be a notable factor in quantifying heavy metal accumulation in urban soils.