Soil In Shanghai Research Articles

Occurrence, Distribution and Risk Assessment of Mercury in Multimedia of Soil-Dust-Plants in Shanghai, China.

The urban environment is a complex ecosystem influenced by strong human disturbances in multi-environmental media, so it is necessary to analyze urban environmental pollutants through the comprehensive analysis of different media. Soil, road dust, foliar dust, and camphor leaves from 32 sample sites in Shanghai were collected for the analysis of mercury contamination in soil–road dust–leaves–foliar dust systems. Mercury concentrations in surface soils in Shanghai were the highest, followed by road dust, foliar dust, and leaves, successively. The spatial distribution of mercury in the four environmental media presented different distribution patterns. Except for the significant correlation between mercury concentrations in road dust and mercury concentrations in leaves (r = 0.56, p < 0.001), there was no significant correlation between the other groups in the four media. Besides this, there was no significant correlation between mercury concentrations and land types. The LUR (Land use regression) model was used to assess the impact of urbanization factors on mercury distribution in the environment. The results showed that soil mercury was affected by factories and residential areas. Foliar dust mercury was affected by road density and power plants. Leaf mercury was affected by power plants and road dust mercury was affected by public service areas. The highest average HI (Hazard index) value of mercury in Shanghai was found in road dust, followed by surface soil and foliar dust. The HI values for children were much higher than those for adults. However, the HI values of mercury exposure in all sampling sites were less than one, suggesting a lower health risk level. The microscopic mechanism of mercury in different environmental media was suggested to be studied further in order to learn the quantitative effects of urbanization factors on mercury concentrations.

Improved heavy metal mapping and pollution source apportionment in Shanghai City soils using auxiliary information

Soil heavy metal pollution can be a serious threat to human health and the environment. The accurate mapping of the spatial distribution of soil heavy metal pollutant concentrations enables the detection of high pollution areas and facilitates pollution source apportionment and control. To make full use of auxiliary soil properties information and show that they can improve mapping, a synthesis of the Bayesian Maximum Entropy (BME) theory and the Geographically Weighted Regression (GWR) model is proposed and implemented in the study of the Shanghai City soils (China). The results showed that, compared to traditional techniques, the proposed BME-GWR synthesis has certain important advantages: (a) it integrates heavy metal measurements and auxiliary information on a sound theoretical basis, and (b) it performs better in terms of both prediction accuracy and implementation flexibility (including the assimilation of multiple data sources). Based on the heavy metal concentration maps generated by BME-GWR, we found that the As, Cr and Pb concentration levels are high in the eastern part of Shanghai, whereas high Cd concentration levels were observed in the northwestern part of the city. Organic carbon and pH were significantly correlated with most of the heavy metals in Shanghai soils. We concluded that Cd pollution is mainly the result of agricultural activities, and that the Cr pollution is attributed to natural sources, whereas Pb and As have compound pollution sources. Future studies should investigate the implementation of BME-GWR in the case of space-time heavy metal mapping and its ability to integrate human activity information and soil category variables.

The Mechanical Properties of Naturally Deposited Soft Soil under True Three-Dimensional Stress States

Abstract Foundation instability and collapse accidents often occur during construction in soft soil regions. The mechanical properties of naturally deposited soft soil in Shanghai were discussed in light of experimental observations from a series of major principal strain-controlled true triaxial undrained shearing tests performed on cubical undisturbed soft soil specimens. The results show that the three-dimensional stress state has a strong influence on the stress and pore pressure properties of soft soil. The initial gradients of deviator stress–strain curves and strength of soft soil obviously increase with the increasing intermediate principal stress and confining pressure. The measured mechanical responses of soft soil are subject to the influence of stress path effects, changes in the initial mean effective stress, and relative magnitudes of intermediate principal stress b. The effective stress paths are manifested by concave or convex shape caused by excess pore pressure, which increases with the increasing b value. The failure envelopes in the p′- q space are a series of straight lines with various slopes at various b values that intersect at the same point in the p′-axis. Considering the effects of the intermediate principal stress and structural characteristics, the failure function with a shape function g(b) for Shanghai soft soil is presented. The results calculated by the equation g(b) presented are in good agreement with experimental data.

Enrichment and sources of trace metals in roadside soils in Shanghai, China: A case study of two urban/rural roads

The road traffic has become one of the main sources of urban pollution and could directly affect roadside soils. To understand the level of contamination and potential sources of trace metals in roadside soils of Shanghai, 10 trace metals (Sb, Cr, Co, Ni, Cu, Cd, Pb, Hg, Mn and Zn) from two urban/rural roads (Hutai Road and Wunign-Caoan Road) were analyzed in this study. Antimony, Ni, Cu, Cd, Pb, Hg and Zn concentrations were higher than that of soil background values of Shanghai, whereas accumulation of Cr, Co and Mn were minimal. Significantly higher Sb, Cd, Pb contents were found in samples from urban areas than those from suburban area, suggesting the impact from urbanization. The concentrations of Sb and Cd in older road (Hutai) were higher than that in younger road (Wunign-Caoan). Multivariate statistical analysis revealed that Sb, Cu, Cd, Pb and Zn were mainly controlled by traffic activities (e.g. brake wear, tire wear, automobile exhaust) with high contamination levels found near traffic-intensive areas; Cr, Co, Ni and Mn derived primarily from soil parent materials; Hg was related to industrial activities. Besides, the enrichment of Sb, Cd, Cu, Pb and Zn showed a decreasing trend with distance to the road edges. According to the enrichment factors (EFs), 78.5% of Sb, Cu, Cd, Pb and Zn were in moderate or significant pollution, indicating considerable traffic contribution. In particular, recently introduced in automotive technology, accumulation of Sb has been recognized in 42.9% samples of both roads. The accumulation of these traffic-derived metals causes potential negative impact to human health and ecological environment and should be concerned, especially the emerging trace elements like Sb.

An improved method to calculate the vertical earth pressure for deep shield tunnel in Shanghai soil layers

Previous studies on field monitoring data indicate that vertical earth pressure would be overestimated by the Terzaghi theory for a deeply buried shield tunnel, which is widely adopted in tunnel design. A kinematic mechanical model was proposed to evaluate its influence on vertical earth pressure and implementation into the finite element program in this paper. To investigate the vertical earth pressure, a numerical study using the commercial software of PLAXIS was conducted on the vertical earth pressure distribution on a single shield tunnel, considering different tunnel diameters and burial depths in sandy and clay layers, such as Shanghai soil strata. Based on finite element model results, the existing problems such as soil displacement around tunnel, earth pressure distribution, collapsed soil mass width and sliding friction in the Terzaghi loosening earth pressure formula for a sand layer were discussed. Then, a feasible calculation method for vertical earth pressure on the tunnel lining was proposed. Through comparisons between calculated results and field measurements, the improved formulas were verified, providing a reference for future designs of deep underground structures in Shanghai Soil Layers.

Recent Advances in Horizontal Jet Grouting (HJG): An Overview

This paper discusses recent advances in the implementation of horizontal jet grouting (HJG) for the ground improvement of soft soil. Field trials of HJG were undertaken in soft soils in Shanghai, and the research is reported and discussed in this paper. Particular emphasis was placed to study the hardening process in non-cohesive soils. The recent innovations in HJG were found to arise principally from challenges in implementing jet grouting in sandy soil and also from the harmful effects on the surrounding caused by the traditional implementation process. Accordingly, the recently developed composite jet pipe, pressure-control jet grouting and control discharge horizontal jet grouting methods have been successfully implemented to mitigate the ground upheaval and displacements. Moreover, the characteristics of the jet grout columns obtained with these methods were found as a rule to perform beyond expectations. It was also found that the newly developed horizontal twin-jet grouting technology, underpinned by an instant-solidification mechanism, overcame challenging issues such as mixing uniformity, loss of admixture and hardening. The characteristics of hardening in particular have initiated new perspectives, given that a better acquaintance of the mechanisms of hardening and ground displacements is bound to play an important role in the future practice and the development of the jet grouting process. Interestingly, smoothed particle hydrodynamics technique was found to be suited for modeling jet grouting mechanisms.

Magnetic evidence of anthropogenic dust deposition in urban soils of Shanghai, China

The magnetic particulates from anthropogenic activities can be detected by magnetic methods rapidly and cost-effectively. This study focused on the investigation of vertical variations in magnetic properties in soil profiles and magnetic enhancement originating in Baoshan, Shanghai. Also the feasibility of using arable and urban park soils as a new context for magnetic monitoring was explored. A combination of magnetic and scanning electron microscopic (SEM) techniques was applied to three soil profiles. Non-pedogenic magnetic enhancement in topsoil was recorded at all three sites accompanied by coarsening of magnetic grain size. The dominant magnetic properties reflect multi-domain (MD) and pseudo-stable single domain (PSD) ferrimagnetic minerals. Both of magnetic concentrations and grain size decrease with the depth, depending on the pollutant input, soil type and degree of vertical mixing. SEM images confirmed the presence of anthropogenic particulates fly-ash. It was concluded from this study that topsoil magnetic enhancement arising from atmospheric contaminants was readily identifiable in both arable fields and urban parks, thus broadening the scope of magnetic research on urban and industrial pollution.

Orthogonal test and regression analysis of the strain on silty soil in Shanghai under metro loading

Cyclic triaxial test by means of the geotechnical digital system is conducted for the soil near the Guoquan Road Station of Metro Line 10 in Shanghai to analyze the strain characteristics and the variation law of saturated silty soil under subway loading. Orthogonal design method is used to arrange the experiment, considering the following factors: frequency ratio f R, cyclic stress ratio σ R, vibration time ratio N R, and the interaction function among them. Results show that the cyclic stress ratio σ R, the frequency ratio f R, the vibration time ratio N R, and the interaction between the cyclic stress ratio σ R and the vibration time ratio N R have a significant effect on the axial strain of the subway tunnel. The effect of the interaction between the cyclic stress ratio σ R and the vibration time ratio N R is also significant. From the analysis of variance and regression theory, the nonlinear regression equation of the cumulative plastic strain of silty soil under subway loading is established. Residual analysis proves that the equation is ideal and credible. The results have important value for the design of subway tunnels.

Occurrence, homologue patterns and source apportionment of short- and medium-chain chlorinated paraffins in suburban soils of Shanghai, China

In order to systematically investigate the spatial distribution, homologue profiles, and sources of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in suburban soils in Shanghai, SCCPs and MCCPs in soils were analyzed using gas chromatography coupled with low resolution mass spectrometry in electron capture negative ion (ECNI) mode (GC-ECNI-MS). The CP concentrations in soils were between not detected (ND) – 697 ng g−1 with a median value of 3.52 ng g−1 for SCCPs, and ND – 666 ng g−1 with a median value of 15.3 ng g−1 for MCCPs, respectively. The concentrations of MCCPs in most soils were higher than that of SCCPs. The total CP concentrations (sum of SCCPs and MCCPs) in soils varied from ND to 964 ng g−1 with a median value of 20.5 ng g−1. The concentration of MCCPs was higher than that of SCCPs in most soils. The levels of SCCPs and MCCPs in suburban soils in Shanghai were at the medium level when compared to other areas around the world. No significant correlation was observed between soil CP concentrations and total organic carbon contents (p > 0.05). For different use type of soils, the median concentrations of CPs in soils were found higher in greenland than that in other areas probably due to busy traffic, sewage sludge application and/or wastewater irrigation. All soils were divided into two groups by hierarchical cluster analysis (HCA) both for SCCPs and MCCPs. Three discharge sources of CPs in suburban soil of Shanghai were identified by PMF model.

Laboratory study on impulse current characteristics of clay

Lightning is recognised as one of the most detrimental natural disasters. While numerous research studies were carried out on the lightning impulse characteristics of the grounding system and the critical breakdown characteristics of soil, little attention was paid to the impulse current characteristics of soils when lightning strikes. In this study, the performance of typical soft soil in Shanghai under the action of lightning is analyzed. Different factors, including the impulse current waveforms, the front time and half peak time of impulse current, the quantity of electric charge and absorption of unit heat, have been studied by performing a series of laboratory tests. The test results show that the variation of impulse current due to lightning strike is time dependent. The higher the soil temperature, the larger the peak impulse current produced during lightning strike. The value of the front time decreases exponentially, while the value of the half peak time decreases linearly with the rise of soil temperature. Novel empirical relationships between the impulse current characteristics of soil and soil temperature are proposed, with the aim of providing useful practical references for the design of a grounding system for lightning strikes.

Heavy metals pollution assessment in correlation with magnetic susceptibility in topsoils of Shanghai

This study investigated the heavy metal accumulation, magnetic susceptibility, and their correlation in urban soils of Baoshan District, Shanghai. A total of 127 topsoil samples were collected from industrial (n = 28), roadside (n = 38), residential (n = 21), and agricultural (n = 40) areas. The absolute concentration of heavy metals: lead (Pb), zinc (Zn), chromium (Cr), nickel (Ni), cadmium (Cd), and copper (Cu), was measured using an atomic absorption spectroscopy (AAS). Nemerow pollution index was applied to estimate the pollution level in respective areas. The results showed an excess of heavy metals in the urban topsoil of Baoshan District, among which, Pb, Zn, and Cd were most prominent. The average values of Pb, Zn, and Cd were obtained as 118.5, 228.6, and 0.56 mg kg−1, respectively, which are 5.6, 3.0, and 2.8 times higher than the Shanghai soil background values. Kriging interpolation was employed (according to the pre-evaluated fitted model variogram values of nugget, sill, and range) to assess the spatial distribution of heavy metals. Kriging interpolation depicted that the industrial sites were heavy metal-centric locations. Complimentary to AAS detection method, magnetic susceptibility tool was also applied to evaluate the presence of magnetic particles and their correlation with heavy metals. The magnetic susceptibility of the topsoil in Baoshan District was 148 × 10−8 m3 kg−1, which is ~5 times higher than the background value of Shanghai soil (29.1 ± 9.8 × 10−8 m3 kg−1). In most of the samples, the percentage frequency-dependent magnetic susceptibility (χ fd%) values in the topsoil of Baoshan District were less than 4%, suggesting the absence of pedogenic ultrafine superparamagnetic grains and the presence of anthropogenic multidomain and stable single domain grains. A significantly positive correlation (industrial: r = 0.81, P < 0.01; roadside: r = 0.65, P < 0.01; residential: r = 0.56, P < 0.01; agricultural: r = 0.6, P < 0.01) was found between magnetic susceptibility and heavy metal pollution irrespective of the type of anthropogenic activities at a particular land. The results suggested the reliability of magnetic susceptibility measurement to interpret the heavy metal pollution of the soils.

Spatial distribution of organic carbon fractions and δ13C in urban soils, Shanghai, China

Urban areas are characterized by diverse land-use patterns and are strongly influenced by anthropogenic activities. However, few studies have examined the effects of urbanization on concentrations of soil organic carbon (SOC) and its various components or δ 13C in urban soils. The aim of this study was to assess the spatial distribution of SOC fractions and δ 13C signatures of urban soils in Shanghai, China. The results showed that SOC fractions and δ 13C compositions differ over a range of spatial scales. The concentrations of SOC, readily oxidizable organic carbon (C), black carbon (BC) and δ 13C in surface soils (0–20 cm) were 10.5, 3.5, 6.9 g kg–1 and –24.9%, respectively, and the corresponding concentrations in deep soils (20–100 cm) were 8.4, 2.8, 6.0 g kg–1 and –23.9%. In urban soils, BC accounted for a higher proportion of the SOC pools. Concentrations of SOC, readily oxidizable organic C and BC were higher, whereas the 13C ratio was much lower in the city centre. The effects of carbon isotope fractionation were also more evident in the central urban area. The results also indicated that not only the concentrations of readily oxidizable organic C and BC but also the δ 13C values were related to the time since the soils were converted to urban use. Differences in the time since urbanization and the severity of the associated environmental impacts can be assessed using SOC fractions and δ 13C isotopic compositions because observed changes in these quantities can be attributed to the strong influence of anthropogenic activities.

Effect of water and salinity on soil behaviour under lightning

The east coast of China, in particular Shanghai, is frequently exposed to lightning, and the resulting annual loss approaches US$30 million. All kinds of protection devices transfer the lightning current and the energy into the ground. In this study, the characteristics of the typical soft soil in Shanghai with different values of water content and salinity under the action of lightning shock have been analysed by an impulse current generator and a self-designed test equipment. The test results show that the current waveform from the impact of lightning in soils has a steep rise and a slow fall. At the same lightning intensity, higher water content or salinity leads to (a) shorter peak time, (b) larger peak current waveform, (c) quicker release speed and (d) larger lightning impulse response. The test results are valuable in guiding the design and the reformation of lightning protection and grounding systems.

Seasonal variations in concentrations, distributions, and air-soil exchange fluxes of dioxin-like polychlorinated biphenyls in Shanghai, China.

Dioxin-like polychlorinated biphenyl (dl-PCB) concentrations in ambient air and soil in Shanghai, China, were measured to allow seasonal and spatial differences in the dl-PCB concentrations, profiles, distributions, fugacity fractions, and air-soil fluxes to be determined. The toxic equivalent (TEQ) DL-PCB concentrations in the air were higher in summer (mean 9.46 fg m(-3), range 1.32-26.3 fg m(-3)) than in winter (mean 4.57 fg m(-3), range 1.55-10.9 fg m(-3)). The DL-PCB concentrations in air were different in different areas, and the concentrations decreased in the order industrial areas > commercial and residential areas > suburban areas > rural area. The mean DL-PCB concentration in soil was 0.25 pg TEQ g(-1) dry weight (dw) and the range was 0.05-0.90 pg TEQ g(-1) dw. The highest DL-PCB concentration in soil was found in a sample from a commercial/residential area. The DL-PCB fluxes were negative (-216 pg m(-2) h(-1) in summer and -41.1 pg m(-2) h(-1) in winter), and the fugacity fractions were below 0.5, indicating that dl-PCBs in Shanghai are deposited from the air to the soil in all seasons. The net fluxes were higher in summer than in winter, and the deposition fluxes were higher in industrial areas than in other areas in both summer and winter.

Abundance and diversity of polycyclic aromatic hydrocarbon degradation bacteria in urban roadside soils in Shanghai.

Understanding the impact of polycyclic aromatic hydrocarbons (PAHs) on soil environments is of increasingly important concern. Therefore, the microbial degradation of PAHs in soils has drawn considerable attention, but little is known about the PAH degradation genes in urban soils. In this study, we examined the diversity and abundance of the PAH degradation bacteria and evaluated whether the specific bacteria can reflect PAH contents in the soils from urban roadsides directly receiving traffic emission. The results of phylogenetic analysis indicated that low PAH degradation bacterial diversity occurred in the urban roadside soils, only including Mycobacterium sp., Terrabacter sp., and one novel cluster. The community composition diversity of PAH degradation bacteria did not show a significant difference across the sampling sites. The abundance of PAH degradation genes ranged from 5.70 × 10(6) to 6.44 × 10(7) gene copies g(-1) dry soil, with an average abundance of 1.43 × 10(7) gene copies g(-1) dry soil, and their spatial variations were related significantly to PAH contents in the soils. The Mycobacterium sp. was the most widely detected and estimated to occupy 65.9-100 % of the total PAH degradation bacteria at most of the soil samples, implying that the Mycobacterium sp. might play a primary role in degrading PAHs in the contaminated urban soil environments.

Occurrence, sources and health risk assessment of polycyclic aromatic hydrocarbons in urban (Pudong) and suburban soils from Shanghai in China

A comprehensive investigation was conducted to the urban (Pudong) and suburban soils in Shanghai. A total of 154 soil samples were analyzed for 26 PAHs including highly carcinogenic dibenzopyrenes (DBPs). The total concentrations ranged from 25.8 to 7380μgkg−1 for Σ26PAHs and 18.8 to 6320μgkg−1 for 16 USEPA priority PAHs (Σ16PAHs), respectively. The BaP toxic equivalent (BaPeq) concentrations were between 6.41 and 2880μgkg−1 for Σ24PAHs, 1.11 and 620μgkg−1 for Σ16PAHs and 2.72 and 2250μgkg−1 for Σ4DBPs. The high PAH contamination in green land soils might originate mainly from local road traffic and industrial activities, and sewage sludge application or waste water irrigation for soil. Seven sources of soil PAHs in Shanghai were identified by positive matrix factorization (PMF) model. The mean risk quotient (m-RQ) values indicated that there were medium to high ecological risks in 9.10% of soil samples, pyrene (Pyr), benzo[b]fluoranthene (BbF) and benz[a]anthracene (BaA) were the major ecological risk drivers under agricultural use. The cancer risk (CR) values were within the acceptable range at 35.7%, 35.1% and 31.2% of sampling sites for children, youths and adults, respectively. The total lifetime carcinogenic risk (TLCR) values at 57.8% of sampling sites were within the acceptable range. Overall, cancer risks of soil PAHs in all sampling sites in the studied area were below the highest acceptable risk, suggesting that soil PAHs are unlikely to pose a significant cancer risk for population based on ingestion, dermal contact and inhalation exposure pathways.

Black carbon in soils from different land use areas of Shanghai, China: Level, sources and relationship with polycyclic aromatic hydrocarbons

Black carbon (BC) in soils plays a key role of carrying hydrophobic pollutants like polycyclic aromatic hydrocarbons (PAHs). However, little is known about the spatial distribution, sources of BC and its relationship with PAHs in urban soils. We studied BC, total organic carbon (TOC) and PAHs concurrently in 77 soils collected from downtown area, suburban and rural area and industrial area of Shanghai, China. BC was determined by both chemical oxidation (dichromate oxidation, BCCr) and chemo-thermal oxidation (CTO-375, BCCTO). BC sources were identified qualitatively by BC/TOC concentration ratios and BC-cogenerated high molecular weight (HMW) PAH isomer ratios and quantitatively by principal component analysis followed by multiple linear regression (PCA-MLR). Results showed that BCCr concentration (4.65g/kg on average) was significantly higher than BCCTO (1.91g/kg on average) in Shanghai soils. BCCr concentrations in industrial area were significantly higher than those in other two. Stronger correlation was found between PAHs and TOC, BCCr than that between PAHs and BCCTO, which indicates the possibility of PAHs being carried by charcoal and other organic matters thus negating its exclusive dependence on soot. Charcoal was therefore suggested to be taken into account in studies of BC and its sorption of PAHs. BC/TOC ratios showed a mixed source of biomass burning and fossil fuel combustion. PCA scores of BC-cogenerated HMW PAHs isomer ratios in potential sources and soil samples clearly demonstrated that sources of BC in urban soils may fall into two categories: coal and biomass combustion, and traffic (oil combustion and tire wear). PCA-MLR of HMW PAHs concentrations in soil samples indicated that coal and oil combustion had the largest contribution to BC in urban soils while tire wear and biomass combustion were important in downtown and rural area, respectively, which indicated they were main sources of HMW PAHs and presumably of BC.

Short- and medium-chain chlorinated paraffins in urban soils of Shanghai: Spatial distribution, homologue group patterns and ecological risk assessment

Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. Data on the presence of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in urban areas with dense population are still scarce to date. SCCPs and MCCPs were measured in urban soils from Shanghai to comprehensively investigate their levels, spatial distribution, homologue group patterns and ecological risk. The concentrations of CPs in soils varied from ND to 615ngg−1 with a median value of 15.7ngg−1 for SCCPs and from 1.95 to 188ngg−1 with a median value of 7.98ngg−1 for MCCPs, respectively. The concentrations of SCCPs in most soils were higher than those of MCCPs. The total CP concentrations in soil samples were between 4.10 and 625ngg−1 with a median value of 26.4ngg−1. For different functional zones, the median concentrations of soil CPs were found higher in green land including park, greenbelt and campus than those in roadside. The highest concentrations of CPs in soils could be derived from sewage sludge application and wastewater irrigation for green land. Three types of soils were classified by hierarchical cluster analysis (HCA) for SCCPs and MCCPs, the most abundant homologue groups in the bulk of the soil samples were C11Cl5–7 and C13Cl5–7 for SCCPs, and C14Cl7–8 and C15Cl7–8 for MCCPs. Correlation analysis and PCA suggested that SCCPs and MCCPs in soils in the studied area derived from different sources. The preliminary ecological risk assessment indicates that soil CPs at present levels poses no significant ecological risk for soil-dwelling organisms.

Heavy Metal Contamination and Assessment of Roadside and Foliar Dust along the Outer-Ring Highway of Shanghai, China.

Foliar and roadside dust samples were collected from five sites along the outer-ring highway of Shanghai, one of the biggest metropolitan areas of China, to assess heavy/toxic metal contamination. Concentrations of Zn, Cu, Ni, As, and Hg in foliar dust were higher than in roadside dust, whereas concentrations of Pb and Cd were higher in roadside dust. In the roadside dust, average concentrations of all metals except As in foliar and roadside dust samples were significantly above the background values of soil in Shanghai: the ratios between the average of samples and background values of Shanghai were in the order: Cd (25.1) > Zn (12.2) > Cu (6.16) > Pb (5.74) > Ni (5.50) > Hg (5.18) > As (1.05). By using the geo-accumulation index, the pollution grades of seven heavy metals at five sampling sites were calculated. Roadside dust was heavily to extremely contaminated with Cd; moderately to heavily contaminated with Zn; and moderately contaminated with Cu, Hg, Pb, and Ni. Foliar dust was heavily contaminated with Cd; moderately to heavily contaminated with Zn and Cu; and moderately contaminated with Hg, Pb, and Ni. The contamination level of heavy metals in the Puxi area was greater than that in the Pudong area, which might be related to the industrial distribution and land use. Combined with correlation analysis, hierarchical cluster analysis indicated that atmospheric deposition is the main source of Cd, Hg, As, and Pb in dust and that Cu and Zn in dust are mainly from heavy traffic on the highway. A portion of Ni in dust also comes from the parent soil.

Spatial distributions and sources of heavy metals in sediment from public park in Shanghai, the Yangtze River Delta

As one of the largest and most modern cities in China, Shanghai has experienced rapid urban expansion over the last three decades, which may cause environmental pollution. This study collected the surface sediments from 35 lakes in public parks in different areas of Shanghai and explored the relationship between heavy metals (HM; Co, Cr, Ni, Cd, Cu, Pb, and Zn) distribution and city urbanization factors. The concentrations of Co, Cr, and Ni in sediment were similar to those in background soil of shanghai, whereas the levels of Cd, Cu, Pb, and Zn were elevated. Overall, sediments from the central urban core area (CUC; inside the inner-ring highway) contained significantly higher levels of Cd, Cu, Pb, and Zn than those from the developed urban area (DDU; between the inner- and middle-ring highway), the developing urban area (DIU; between the middle- and outer-ring highway), and the suburban area (SU; outside the outer-ring highway), suggesting potentially large contributions from point sources related to human activities in the highly urbanized regions. For Co, Cr, and Ni, no significant differences of concentration and enrichment were found among different areas. The levels of Cd, Cu, Pb, and Zn showed strong associations with density of road network (R2>0.84) in six urban administration districts of Shanghai, quantitatively confirming that these four metals mainly originated from traffic emission. However, the percent of residential and industrial lands had no correlation with HM (Cd, Cu, Pb, and Zn) concentrations in sediment from Shanghai.