Accumulation and sources of heavy metals in urban topsoils: a case study from the city of Xuzhou, China

The knowledge of the variability, the anthropogenic versus natural origin and corresponding environmental risk for potentially harmful elements in urban topsoils is of importance to assess human impact. The aims of the present study were: (1) to assess the distribution of heavy metals (Sn, Li, Ga, Ba, Fe, Mn, Co, Be, Ti, Al, Hg, Cr, Sb, As, Bi, Pd, Pt, Au, Ni, Cd, Zn, Cu, Pb, Se, Mo, Sc and Ag) in urban environment; (2) to discriminate natural and anthropogenic contributions; and (3) to identify possible sources of pollution. Multivariate statistic approaches (principal component analysis and cluster analysis) were adopted for data treatment, allowing the identification of three main factors controlling the heavy metal variability in Xuzhou urban topsoils. Results demonstrate that Hg, Cr, Sb, As, Bi, Pd, Pt, Au, Ni, Cd, Br, Zn, Cu, S, Pb, Se, Mo, Sc and Ag could be inferred to be tracers of anthropogenic pollution, whereas Al, Ti, Ga, Li, V, Co, Pt, Mn and Be were interpreted to be mainly inherited from parent materials. Iron, Ba, Sn, Pd and Br were interpreted to be affected by mixed sources.     

Correlation between magnetic susceptibility and heavy metals in urban topsoil: a case study from the city of Xuzhou, China

Anthropogenic influence, mainly due to urban and industrial activities and traffic exhaust, may affect urban topsoil via atmospheric contamination and solid waste. Magnetic susceptibility measurements were conducted on 21 urban topsoil samples from the city of Xuzhou, China. High intensities of magnetic susceptibility were detected in the majority of the samples. SEM analysis shows that magnetic minerals are in the form of spherules and mainly due to anthropogenic inputs. The heavy metals Pb, Cu, Zn, Se, Sc, Mo, Fe, and Bi show strong correlations with magnetic susceptibility, and Ag, Ba, Cd, Ni, Cr, Sb, and Sn, on the other hand, show a weak correlation with magnetic susceptibility. Whereas, of these metals studied, only Hg has no significant correlation with the susceptibility. The Tomlinson pollution load index (PLI) also shows significant correlation with the susceptibility (χ). The present study shows that magnetic susceptibility is a fast, inexpensive, and non-destructive method for the detection and mapping of contaminated soils.     

Assessment of heavy metal pollution in urban topsoils from the metropolitan area of Mexico City

This study reports the degree of heavy metal pollution (Cr, Cu, Ni, Pb, Zn and V) in 135 urban topsoil samples from the metropolitan area of Mexico City. Pollution indices (PI) were calculated to identify the metal accumulation with respect to the background values. The levels of heavy metals in the analyzed samples show a wide range of variation. Lead, Zn and Cu are the elements most enriched in the analyzed area, presenting pollution indexes of up to 23.8, 21.6 and 12.4, respectively. Geochemical maps were produced to assess the spatial distribution of pollution index. It is concluded that emissions from vehicles may be the major source of Pb urban contamination; furthermore, other small or large factories are possible sources for soil pollution (Cu, Zn). The concentration of Cr, Ni, and V in most of the analyzed samples do not appear to reach pollution levels. The assessment of the soil environmental quality in the metropolitan area Mexico City in terms of PI can be used as the basis for a regular monitoring program for implementing suitable pollution control measures.     

Spatial distribution of metals in urban topsoils of Xuzhou (China): controlling factors and environmental implications

The contamination of soils by metals from various sources is a subject of increasing concern in recent times. Twenty-eight elements (Fe, Ti, Cr, Al, Ga, Pb, Sc, Ba, Li, Cd, Be, Co, Cu, Mn, Ni, V, Zn, Mo, Pt, Pd, Au, As, Sb, Se, Hg, Bi, Ag and Sn) have been analyzed from urban topsoil from the city of Xuzhou. The concentrations of these analyzed elements have been correlated to some soil parameters such as organic matter, pH, cation exchange capacity, carbonate content, and granulometric fractions (clay, silt and sand). Results of the statistical analysis show a large variety and complexity in these relationships. The spatial distributions of these metal concentrations were also constructed using geographical information system. The spatial distribution patterns of the elements analyzed show that traffic and industrial activities are the principal anthropogenic pollutant sources.     

Assessment of heavy metals contamination in urban topsoil from Changchun City,China

Due to the rapid urbanization and industrialization that has occurred in China over the last few decades, metals have been continuously emitted into the urban environment and now pose a serious threat to human health. Indeed, there is a growing concern over the potential for pollution of urban soils with heavy metals. Therefore, an extensive soil survey was conducted in urban areas of Changchun, China, to evaluate the current status of heavy metal contamination in soils and to evaluate its potential sources. A total of 352 samples of urban soils were collected from urban areas of Changchun using a systematic sampling strategy in which one sample per km² was taken (0 ~ 20 cm). The levels of Cu, Pb, Zn and the major elements (Mn, Al₂O₃, CaO, Fe₂O₃, MgO, SiO₂, K₂O and NaO) were then determined by X-Ray fluorescence spectrometry (XRF), while the level of Cd was determined by graphite furnace atomic absorption spectrometry (GF-AAS), and the Hg and As concentrations were determined by atomic fluorescence spectroscopy (AFS). The results indicated that, when compared with the background values of topsoil in the Changchun region, the topsoil in urban areas were enriched with metals, particularly Cu, Cd, Zn, Pb and Hg. The results of correlation coefficient analysis showed that Hg, As, Cd, Cu, Pb and Zn were significantly positive correlated with each other, while Cr and Mn formed another group. Moreover, significantly positive correlations were observed between pH and Zn, Pb, Cu, Cd, As and Hg, indicating that pH influences the distributions of these metals in urban soils in Changchun. Principal component analysis (PCA) was conducted to identify sources of heavy metals and the results revealed distinctly different associations among the trace metals and the major elements in the urban soils. The concentration of Cr appeared to be controlled by the parent material (natural sources), while Cu, Pb and Zn were mainly from vehicle emissions, with Zn primarily coming from vehicle tires. Additionally, Hg and As primarily originated from coal combustion, while Cd was mainly associated with industrial sources. According to the pollution index (PI) of each metal, the overall levels of metal pollution were not especially high, but there were clearly contaminated sites concentrated in the central and northeast portion of the studied region. The Nemerow integrated pollution index (NIPI) of the seven metals also indicated that urban soils in Changchun city were classified as having low level of pollution.     

Magnetic signature of heavy metals pollution of sediments: case study from the East Lake in Wuhan,China

Detailed magnetic measurements and geochemical analyses were performed on 114 sediment samples collected from the East Lake, Wuhan city, China, to establish a possible link between the enhanced concentration of anthropogenic magnetic particles and heavy metals with known sources. Relatively higher magnetic susceptibility values (mass-specific, χ, >150 × 10⁻⁸ m³ kg⁻¹) were observed for samples near the pollution sources: e.g. the Wuhan Iron and Steel Company (WISC), the Qingshan Thermal Power Plant (QTPP), the banks (driveways) of the lake and near the sightseeing route of yachts on the lake. Moreover, χ is positively correlated to the concentration of Pb (correlation coefficient r = 0.682), but negatively or weakly correlated with both Zn and Cu. In contrast, anhysteretic remanent magnetization (ARM) is significantly correlated with these major heavy metals (r = 0.645 for Zn–ARM, 0.699 for Pb–ARM and 0.841 for Cu–ARM, respectively), which indicate that ARM serves a better indicator for the pollution of heavy metals in this lake. Thermomagnetic analysis combined with magnetic hysteresis measurements revealed that magnetites in the pseudo-single-domain/multidomain grain-size regions are dominant. Scanning electron microscopy and energy dispersive X-ray examinations of the magnetic extracts showed that these Fe-rich particles have different morphologies: orange-peel structure, hollow structure with adhered smaller particles, Zr-rich melted-like irregular particles, pear-shaped spherules and spherules with slick surfaces. These features are typical for particles produced by anthropogenic activities. Because of the genetic relationship between the environmental setting of the East Lake and the nearby pollution sources, this study suggests that in situ magnetic surveys are sensitive to evaluate the environmental pollution on the lake bottom.     

Use of multivariate statistical analysis to determine the relationship between the magnetic properties of urban topsoil and its metal, S, and Br content

Multivariate statistical analysis has been used for detailed examination of the relationship between the magnetic properties of Xuzhou urban topsoil, for example concentration-dependent properties (mass magnetic susceptibility (χ), susceptibility of anhysteretic remanent magnetization (χ _ARM), saturation isothermal remanent magnetization (SIRM), soft remanent magnetization (SOFT), and frequency-dependent magnetic susceptibility (χ _FD)) and feature-dependent properties (S _{−100 mT} ratio, SIRM/χ ratio and F _{300 mT} ratio), and the concentrations of metals (Ti, Fe, Cr, Al, Ga, Pb, Sc, Ba, Li, Cd, Be, Co, Cu, Mn, Ni, V, Zn, Mo, Pt, Pd, Au, As, Sb, Se, Hg, Bi, Ag, and Sn), S, and Br in the soil. The results show that SIRM/χ ratios correlate best with the heavy metals (Hg, Cr, Sb, As, and Bi) which are mainly derived from coal-combustion emissions whereas χ _FD correlates best with the metals (Al, Ti, V, Be, Co, Ga, Mn, and Li) which principally originate from soil parents. Concentration-dependent magnetic properties (χ _ARM, χ, SIRM, and SOFT) correlate well with elements (Se, Pb, Cu, Zn, Fe, Ag, Sc, Ba, Mo, Br, S, Cd, Ni, etc.) which are mainly derived from road-traffic emissions. For the same chemical element, χ _ARM, SIRM, and SOFT values are frequently better correlated than χ values, and χ _ARM values are the best indicators of the concentrations of these elements associated with traffic emissions in this study area. In addition, S _{−100 mT} ratios significantly correlate positively with Se, Sc, Pb, Cu, Zn, Mo, and S whereas F _{300 mT} ratios only correlate positively with Pt and negatively with Fe. These results confirm the suitability of different magnetic properties for characterizing the concentrations of heavy metals, S, and Br in Xuzhou urban topsoil.     

Historical changes in heavy metals in the Yangtze Estuary, China

A 6-m-long core was used to examine historical changes in heavy metals on tidal flats in the Yangtze Estuary, China. Over the last 100 years, human impact was minimal. However, over the last few decades, vertical metal concentrations have been affected by human activities such as local industrialization, urbanization and construction of major sewage outlets. Copper, lead and arsenic were identified as contaminants in the Yangtze Estuary on the basis of national pollution standards and a comparison of metals in the upper core with those in the lower core.     

Spatial distribution of heavy metals in soils: a case study of Changxing,China

Six hundred and sixty-five soil samples were taken from Changxing County in Zhejiang Province, China, to characterize the spatial variability of Hg Cd, Pb, Cu, As and Cr. The geostatistics and geographic information system (GIS) techniques were applied, and the ordinary kriging and lognormal kriging were used to map the spatial patterns of the six heavy metals. Hg, Pb, Cu and As were fitted to the spherical model with a range of 85.75, 82.32, 86.10, and 23.17 km, respectively. Cr was fitted to the exponential model with a range of 6.27 km, and Cd was fitted to the linear model with a range of 37.66 km. Both Pb and Cu had strong spatial dependence due to the effects of natural factors including parent material, topography and soil type. Hg, Cd, Cr and As had, however, moderate spatial dependence, indicating an involvement of human factors. Meanwhile, based on the comparison between the original data and the guide values of the six metals, the disjunctive kriging technique was used to quantify their pollution risks. The results showed that only Cd and Hg exhibited pollution risks in the study area. The pollution source evaluated was closely corresponded with the real discharge of industrial production and the application of organomercury pesticides. The results of this study provide insight into risk assessment of environmental pollution and decision making for agricultural production and industrial adjustment of building materials.     

Soil and groundwater pollution of an urban catchment by trace metals: case study of the Addis Ababa region, central Ethiopia

Analysis of the total heavy metal (Cr, Cd, Pb, As, Cu, Ni, Zn, Co) concentration was performed on 33 soil samples taken from different profiles and soil types in a highly urbanized and industrial sector of Addis Ababa, central Ethiopia. They were analyzed using aqua regia extraction coupled with a four-stage sequential extraction (SE) procedure. The objectives of the analysis were to investigate the degree of soil heavy metal contamination, its binding forms, mobility and the implications for the groundwater resource. The results show a relatively high content of the analyzed trace metals in the soil attributed to anthropogenic and geogenic sources. Although most of the trace metals are found in the upper few centimeters of the residual soils, because of churning processes within the black cotton soils, vertical distribution of the trace metals is complex. According to the heavy metal SE analysis, the major heavy metal contribution is from the residual followed by the hydroxide phases. Groundwater heavy metal contamination is present with more than 90 and 50% of the analyzed groundwater samples exceeding WHO guidelines for Cr and Cd, respectively. Since the degree of soil heavy metal contamination has apparently not surpassed the soil’s buffering capacity, it appears that the transport path of these toxic metals to the groundwater is through fractures, joints, and related preferential flow paths.     

Heavy meals in urban roadside soils, part 1: effect of particle size fractions on heavy metals partitioning

Urban roadside soils are important environmental media for assessing heavy metal concentrations in urban environment. However, among other things, heavy metal concentrations are controlled by soil particle grain size fractions. In this study, two roadside sites were chosen within the city of Xuzhou (China) to reflect differences in land use. Bulk soil samples were collected and then divided by particle diameter into five physical size fractions, 500–250, 250–125, 125–74, 74–45, < 45 μm. Concentrations of metals (Ti, Cr, Al, Ga, Pb, Ba, Cd, Co, Cu, Mn, Ni, V, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) were determined for each individual fraction. These metals could be roughly classified into two groups: anthropogenic element (Pb, Ba, Cd, Cu, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) and lithophile element (Ti, Cr, Al, Ga, Co, Mn, Ni, V) in terms of values of enrichment factor. As expected, higher concentrations of anthropogenic heavy metals (Cu, Zn, Mo, As, Hg, Bi, Ag) are observed in the finest particle grain size fraction (i.e. < 45 μm). However, heavy metals Se, Sb and Ba behave independently of selected grain size fractions. From the viewpoint of mass loading, more than 30% of the concentrations for all anthropogenic heavy metals are contributed by the particle grain size fractions of 45–74 μm at site 1 and more than 70% of the concentrations for all heavy metals are contributed by the particle grain size fractions of 45–74 and 74–125 μm at site 2. These results are important for transport of soil-bound heavy metals and pollution control by various remedial options.     

The distribution of heavy metals in an abandoned mining area; a case study of Strauss Pit, the Drake mining area, Australia: implications for the environmental management of mine sites

Surface water samples from the Drake mining area show elevated metal concentrations, notably cadmium, iron and zinc. A detailed study of a sphalerite /quartz vein from Strauss Pit and chalcopyrite and pyrite from the Adeline mine and Strauss Pit indicate that micro-scale analyses of ores are necessary for environmental management of mine sites. Analyses show that Cd is elevated, up to 2.1 % by weight, and is associated with sphalerite, replacing Zn, or to a lesser extent replacing Pb within small galena grains. High concentrations of Cu are also associated with the Strauss Pit ore as small chalcopyrite grains along the margins of the sphalerite vein, within the central quartz zone of the vein system, and as replacement rims on sphalerite grains. Chalcopyrite from the Adeline mine area, is by comparison, metal poor, but still contains elevated heavy metal concentrations. Whereas, pyrite and chalcopyrite, from Strauss Pit have variable heavy metal concentrations, with chalcopyrite from within sphalerite veins having higher Cd and Zn concentrations than chalcopyrite distal to the veins. Cadmium and other heavy metals within the ores are mobilised during sulphide weathering and enter the drainage network; precipitation of secondary oxidation minerals act as temporary stores for many heavy metals. The complexity of the mineral and heavy metal associations at Strauss Pit suggest that a detailed knowledge of these associations and distributions within ore bodies, and associated waste rocks, are needed by environmental managers of mine sites because the presence of havy metals may greatly affect the decision making process, and management strategies employed. Received; 14 July 1999 · Accepted: 17 August 1999     

Contamination,bioaccessibility and human health risk of heavy metals in exposed-lawn soils from 28 urban parks in southern China's largest city,Guangzhou

The total concentrations and oral bioaccessibility of heavy metals in surface-exposed lawn soils from 28 urban parks in Guangzhou were investigated, and the health risks posed to humans were evaluated. The descending order of total heavy metal concentrations was Fe > Mn > Pb > Zn > Cu > Cr > Ni > Cd, but Cd showed the highest percentage bioaccessibility (75.96%). Principal component analysis showed that Grouped Cd, Pb, Cr, Ni, Cu and Zn, and grouped Cr and Mn could be controlled two different types of human sources. Whereas, Ni and Fe were controlled by both anthropogenic and natural sources. The carcinogenic risk probabilities for Pb and Cr to children and adults were under the acceptable level (<1 × 10⁻⁴). Hazard Quotient value for each metal and Hazard Index values for all metals studied indicated no significant risk of non-carcinogenic effects to children and adults in Guangzhou urban park soils.     

Multivariate techniques as alternative statistical tools applied to magnetic proxies for pollution: a case study from Argentina and Antarctica

Several statistical analyses—as alternative tools—were applied to magnetic monitoring studies. Magnetic and chemical data from two environments have been gathered from previous papers and studied separately. Univariate and multivariate analyses were first examined, revealing a link between magnetic and chemical variables. The latter analyses, in particular, canonical correlation analysis, showed very good canonical correlations: R = 0.950 (Antarctica) and R = 0.891 (Argentina). On the other hand, in order to classify the data according to the degree of contamination, principal coordinates and discriminant analyses, as well as the comparison of several multivariate means were performed. Three groups were distinguished in both case studies, which were well classified at a low margin of error and quite different from each other at a significant level: 0.01 (Antarctica) and 0.05 (Argentina). The joint use of these statistical analyses also showed, in agreement with previous studies, that the relevant variables in order to identify atmospheric pollution are: magnetic susceptibility, saturation of isothermal remanent magnetisation, anhysteric susceptibility/magnetic susceptibility, remanent coercivity, and copper, lead, zinc and chromium contents.     

Pt and Pd concentrations and source in urban roadside soils from Xuzhou,China

This investigation represented the preliminary study to characterize Pt and Pd concentrations and enrichment ratios in urban roadside soils. Roadside soil samples were analyzed by ICP-MS. Data from 21 roadside topsoil samples show medians of Pt and Pd concentrations are 2.9 and 2.8 ng g⁻¹, respectively. These values are higher than those of upper crust that average 0.4 and 0.4 ng g⁻¹, respectively. The relatively lower Pt and Pd concentrations are expected due to recent introduction of catalysts to China compared to the prolonged use of catalysts in Europe. Hierarchical clustering analysis indicates that Pt and Pd in Xuzhou urban roadside soils were mainly from the traffic emissions. Computation of enrichment ratios using the upper crust values as background levels suggests that the roadside soils had enrichment medians of 6.4 for Pt (range 2.5–11.75) and of 6.75 for Pd (range 2.75–9.25). Lower Pt/Pd ratios (range 0.35–2.86) in relation to similar studies in other countries were observed due to the different automobile catalytic converters. In general, fine fraction (<250 μm) contains higher Pt and Pd concentrations compared to the coarse fraction (250–500 μm).     

Ecological environment response of benthic foraminifera to heavy metals and human engineering: A case study from Jiaozhou Bay,China

The estuary and coastal zone are the key areas for socio-economic development,and they are also the important channels for pollutants transported to the sea.The construction of the Jiaozhou Bay Bridge changed the hydrodynamic condition of the bay,which made the self-purification capacity of the bay weakened and the pollution in the estuary and adjacent coastal zone become more serious.In this study,55 surface sediment samples were collected from the three seriously polluted estuaries and the adjacent coastal zone of Jiaozhou Bay to comprehensively study how the benthic foraminifera response to heavy metal pollution and human engineering,and to assess the ecological risks of the bay.A total of 80 species,belonging to 42 genera,were identified in this study.The results showed that Cu,Pb,Cr,Hg,Zn,and As had low to median ecological risks in the study area which would definitely affect the ecological system.The construction of the Jiaozhou Bay Bridge has resulted in pollutants accumulated at the river mouth of Loushan River,which has adverse effects on the survival and growth of benthic foraminifera.The lowest population density and diversity as well as the highest FAI(Foraminiferal Abnormality Index)and FMI(Foraminiferal Monitoring Index)occurred at Loushan River Estuary which indicated that the ecological environment of the northeastern part of Jiaozhou Bay(Loushan River Estuary)had been seriously damaged.Licun River and Haipo River estuaries and the adjacent coastal zone were slightly polluted and had low ecological risk.As a consequence,it suggested that the supervision of industrial and domestic waste discharge and the protection of the ecological environment in northeast Jiaozhou Bay should be paid more attention.     

Spatial variations in heavy metals on tidal flats in the Yangtze Estuary,China

Surface samples are used to determine onshore-offshore variations in heavy metal concentrations on tidal flats on Chongming and Hengsha Islands in the Yangtze Estuary, China. The Mann-Whitney U-Test suggests that proximity to the estuarine turbidity maximum does not result in significantly higher metal concentrations on tidal flats. Principal Components Analysis shows that grain-size is the primary control on metal concentrations, reflecting the occurrence of salt marsh and mud and sand flats. Sediment quality is comparable to that of pristine estuaries because of dilution by high river sediment loads.     

Dissolved trace elements and heavy metals in the Danjiangkou Reservoir,China

Concentrations of trace elements and heavy metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sr, V and Zn) in the Danjiangkou Reservoir, the water source area of the Middle Route of China’s interbasin South to North Water Transfer Project, were analyzed using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and compared with the national and international standards for drinking water. The results indicated that concentrations of As, Pb, Sb and Se in the Reservoir exceeded the standards and they would pose health risk for residents in the region and the water receiving areas of the interbasin water transfer project. Spatial and temporal variability of the trace elements and heavy metals in the Reservoir implies their mixed sources of natural processing and anthropogenic activities in the upper drainage of the Reservoir. The research results would help develop water resource management and conservation strategy for the interbasin water transfer project.     

Determination of historical emission of heavy metals into the atmosphere: Celje case study

The research shows that in the Celje area (Slovenia), the historical anthropogenical emissions are 1,712 tons of Zn and 9.1 tons of Cd. For Zn, this value represents approximately 0.3% of the total Zn production in that area. Close to the former zinc smelting plant, the “Zn precipitation” has been estimated to be up to 0.036 mm. The 100-year Zn production left behind a heavily contaminated area with maximum concentrations of Zn of up to 5.6% in attic dust and 0.85% in the soil, and 456 mg/kg of Cd in attic dust and 59.1 mg/kg in the soil. The calculation of historical emissions is based on the data of heavy metals concentration in the attic dust at 98 sampling points and on the data from 19 measurement sites of the weight of total monthly air deposit. The main idea behind determining past emissions is that when the weight of the deposited dust on a small area is multiplied by the concentration of the element in that area, the mass of the polluter which has been transported to the place of interest by air can be calculated. If we sum up all the weight over the whole geochemical anomaly, we get the quantity of historical emissions.