Speciation and phytoavailability of heavy metals in sediments in Nanjing section of Changjiang River

Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium (Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations of tested metals. The highest range was for Cu (38.8–120.4 mg kg⁻¹), followed by Cr (74.4–120.0 mg kg⁻¹), Zn (80.9–121.1 mg kg⁻¹), Ni (26.0–55.5 mg kg⁻¹), Pb (15.8–46.7 mg kg⁻¹) and Cd (0.28–0.48 mg kg⁻¹). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according to the release curve showed significant relativity with the total Cd concentration in the sediment.     

Mobility and ecological risk assessment of heavy metals in surface sediments of Xiamen Bay and its adjacent areas,China

Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12 samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr, and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg⁻¹), followed by Pb (27–71 mg kg⁻¹), and lower concentrations were found for Cd (42–1,913 μg kg⁻¹) and Hg (0–442 μg kg⁻¹). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent areas.     

Geochemical and statistical approach to evaluate background concentrations of Cd,Cu, Pb and Zn (case study: Eastern Poland)

An attempt was made to evaluate background concentrations of Cd, Cu, Pb and Zn by means of geochemical and statistical approach. As many as 753 samples taken from 51 profiles located in Eastern Poland were analysed. For the estimation of geochemical background values, direct geochemical methods and a statistical analysis for the whole population of samples were applied. Average values of heavy metal concentration in loess sediments (bedrock) as well as in profiles not affected by human activity were measured. The iterative 2σ technique and calculated distribution function were chosen as statistical methods. The resulting values (background concentrations range) were as follows: Cd 0.5–0.9 mg kg⁻¹, Cu 5–16 mg kg⁻¹, Pb 12–26 mg kg⁻¹ and Zn 31–47 mg kg⁻¹. All the methods applied gave similar results. The highest deviation of the background was noted for Cu and the lowest for Zn. The lowest values of background were obtained for loess sediments and the highest in the case of the multiple 2σ method.     

Heavy metals pollution in the soil of an irregular urban settlement built on a former dumpsite in the city of Tijuana, Mexico

The aim of this study was to evaluate soil pollution by heavy metals in an irregular settlement built on a dumpsite. The soil samples were analyzed for Cd, Cr, Cu, Pb and Ni. None of the concentrations found for the heavy metals analyzed were higher than the established Mexican official standards for contaminated soils. The mean concentrations found for the analyzed metals were as follows: 1.4 mg kg⁻¹ for Cd, 4.7 in mg kg⁻¹ for Cr, 304 mg kg⁻¹ for Cu, 74 mg kg⁻¹ for Pb and 6 mg kg⁻¹ for Ni. The results of the geoacummulation index values show that the site was very polluted with Cu and Pb (class 7), polluted to strongly polluted with Ni (class 4); moderately polluted to polluted with Cd (class 3), and moderately polluted with Cr (class 1). The correlation analysis shows a high correlation between Pb and Cu (r ² = 0.98), which would be explained if the main source of the polluting heavy metals was the result of electrical wire burning to recover Copper. Principal component analysis shows three principal components. The first main component (PC1) encompasses Cr, Cd, Pb and Cu. These heavy metals most likely have their origins from the open burning of municipal solid waste, tires and wire. The other two components are encompassed by Cr (PC2) and Ni (PC3). The sources of these pollutants are more likely related to the corrosion of junk metal objects and automobile use.     

Hyperaccumulation of lead,zinc, and cadmium in plants growing on a lead/zinc outcrop in Yunnan Province,China

A field survey was conducted to identify potential hyperaccumulators of Pb, Zn or Cd in the Beichang Pb/Zn mine outcrop in Yunnan Province, China. The average total concentrations of Pb, Zn, and Cd in the soils were up to 28,438, 5,109, and 52 mg kg⁻¹, respectively. A total of 68 plant species belonging to 60 genera of 37 families naturally colonizing the outcrop were recorded. According to metal accumulation in the plants and translocation factor (TF), Silene viscidula was identified as potential hyperaccumulator of Pb, Zn, and Cd with mean shoot concentrations of 3,938 mg kg⁻¹ of Pb (TF = 1.2), 11,155 mg kg⁻¹ of Zn (TF = 1.8) and 236 mg kg⁻¹ of Cd (TF = 1.1), respectively; S. gracilicanlis (Pb 3,617 mg kg⁻¹, TF = 1.2) and Onosma paniculatum (Pb 1,837 mg kg⁻¹, TF = 1.9) were potential Pb hyperaccumulators. Potentilla griffithii (Zn 8,748 mg kg⁻¹, TF = 1.5) and Gentiana sp. (Zn 19,710 mg kg⁻¹, TF = 2.7) were potential Zn hyperaccumulators. Lysimachia deltoides (Cd 212 mg kg⁻¹, TF = 3.2) was a potential Cd hyperaccumulator. These new plant resources could be used to explore the mechanisms of Pb, Zn and/or Cd hyperaccumulation, and the findings could be applied for the phytoremediation of Pb, Zn and/or Cd-contaminated soils.     

Concentration and spatial variability of mercury and other heavy metals in surface soil samples of periurban waste mine tailing along a transect in the Almadén mining district (Spain)

Mercury (Hg) is one of the elements with increasing environmental significance. A total of 22 samples (soils, rocks and gels) were collected along a 6 km transect around the Valdeazogues River valley in the southwest of the Iberian Peninsula (Almadén, Spain). Samples were characterized by different soil types of depositional sequences associated with mining tailings, type and system tracts: 15 surface soil samples included in the transect; 3 of a Haploxerept soil profile developed on slates; 2 of quartzite and slates rocks (reference rocks in the area). Moreover, two of a gel substance (in the lower tract of the river). Soil samples were analyzed for Hg, Cu, Ni, Cr, V, Pb, Cd and As, as well as for organic matter, pH abrasion and calcium carbonate content. All samples were collected from the Almadén mining district. The level of occurrence of the elements (especially Hg) and the effect of some properties on its concentration distributions were investigated. The total mercury contents varied in the range 7,315–3.44 mg kg⁻¹. The mean concentration of total mercury in soils and rocks was 477.03 mg kg⁻¹dry mass. This value is very high compared to the regional background value of other areas. Only rarely is it higher than 1%: in one sample (7,315 mg kg⁻¹) it was almost eight times in comparison with the affected zones, with a high value of 1,000 mg kg⁻¹. Significant differences between samples were found in the total content of mercury. A large percentage of the samples registered detectable levels of V, Cr, Ni, Pb, As and Cu. Cd readings were below the detectable range for all samples tested. Cr mean concentration was 216.95 mg kg⁻¹ (minimun concentration 86, maximun 358); V mean concentration was 119.09 mg kg⁻¹ (minimun concentration 69, maximun 1,209); As mean concentration was 51.24 mg kg⁻¹ (minimun 13.3 and maximun 319.4); Ni mean concentration was 45.64 mg kg⁻¹ (minimun concentration 21.2 and maximun 125.6); Cu mean concentration was 33.25 mg kg⁻¹ (minimun concentration 19.3 and maximun 135); Pb mean concentration was 15.19 mg kg⁻¹ (minimun 1.12 and maximun 1013). Metal distribution generally showed spatial variability ascribed to significant anthropogenic perturbation by mining tailing type. Hg showed vertical profile characterized by surface enrichment, with concentrations in the upper layer (93.7–82.2 mg kg⁻¹ in front of 3.4 of the rock value) exceeding, in several occasions, the background value. The results obtained denote a potential toxicity of some heavy metals in some of the studied samples. Water-soluble mercury could enter the aquatic system and accumulate in sediments. Mercury and other heavy metals contamination depended on the duration and intensity of mining activities.     

Trace metals (Cd,Pb, Cu,Zn and Ni) in sediment of the submarine pit Dragon ear (Soline Bay,Rogoznica, Croatia)

Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06–0.12 mg kg⁻¹, Pb: 28.5–67.3 mg kg⁻¹, Zn: 17.0-65.4 mg kg⁻¹, Cu: 21.1–51.9 mg kg⁻¹, Ni: 27.8–40.2 mg kg⁻¹) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.     

Environmental geochemistry of toxic heavy metals in soils around Sarcheshmeh porphyry copper mine smelter plant,Rafsanjan, Kerman,Iran

The Sarcheshmeh copper mine smelter plant is one of the biggest copper producers in Iran. Long-time operation of about 25 years of the smelter plant causes release of potentially toxic heavy metals into the environment. In this paper, geochemical distribution of toxic heavy metals in 28 soil samples was evaluated around the Sarcheshmeh smelter plant. Soils developed over the nonmineralized and uncontaminated areas have an average background concentration of 41.25 mg kg⁻¹ Cu, 26.6 mg kg⁻¹ As, 12.7 mg kg⁻¹ Pb, 0.9 mg kg⁻¹ Sb, 1.9 mg kg⁻¹ Mo, 1.7 mg kg⁻¹ Sn, 0.2 mg kg⁻¹ Cd, 0.15 mg kg⁻¹ Bi, 235 mg kg⁻¹ S and 73.4 mg kg⁻¹ Zn, respectively. As a result of smelting process, the upper soil layers (0–5 cm) were polluted by Cu (>1,397 mg kg⁻¹), Cd (>3.42 mg kg⁻¹), S (>821 mg kg⁻¹), Mo (>10.3 mg kg⁻¹), Sb (>11.7 mg kg⁻¹), As (>120.6 mg kg⁻¹), Pb (>83.8 mg kg⁻¹), Zn (>214.9 mg kg⁻¹), and Sn (>3.7 mg kg⁻¹), respectively. These values are much higher than the normal concentration of the elements in the uncontaminated soil layers. The elemental values decrease with distance travelled away of the smelter plant, especially at minimum wind direction. Furthermore, high contaminated values of Cu (8,430 mg kg⁻¹), As (500 mg kg⁻¹), Pb (331 mg kg⁻¹), Mo (61 mg kg⁻¹), Sb (56.2 mg kg⁻¹), Zn (664 mg kg⁻¹), Cd (17.2 mg kg⁻¹), Bi (13.4 mg kg⁻¹), and S (3,780 mg kg⁻¹) were observed in the upper soil layers close to the smelting waste dumps. Sequential extraction analysis shows that about 270 mg kg⁻¹ Cu, 28 mg kg⁻¹ Pb, 50.33 mg kg⁻¹ Zn, and 47.84 mg kg⁻¹ As were adsorbed by Fe and Mn oxides. The carbonate phases include 151 mg kg⁻¹ Cu, 28 mg kg⁻¹ Pb, 25 mg kg⁻¹ Zn, and 32.99 mg kg⁻¹ As. Organic matter adsorbed 314.6 mg kg⁻¹ Cu and 29.18 mg kg⁻¹ Zn.     

Spatial variability of heavy metals in soils across a valley plain in Southeastern China

An investigation was carried out to survey the magnitude and spatial distribution of heavy metals, as well as their relation with soil series, in a valley plain in Southeastern China. Soil was sampled at 159 sites by combining a squared grid and nested sampling strategies along the transect perpendicular to the Qujiang River in Zhejiang Province, China. Total concentrations of six metals, namely Cu, Fe, Mn, Ni, Pb and Zn, were measured. Classical statistics and geostatistics were used to quantify their spatial characteristics. There was a considerable variation in many of these parameters. The total concentrations ranged from 6.8 to 29.3 mg kg⁻¹ for Cu, 6,784 to 18,678 mg kg⁻¹ for Fe, 94 to 385 mg kg⁻¹ for Mn, 6.1 to 20.3 mg kg⁻¹ for Ni, 25.0 to 49.5 mg kg⁻¹ for Pb, and 12 to 160 mg kg⁻¹ for Zn. Pearson correlation coefficients among total metal concentrations and selected soil properties showed a number of strong associations. By virtue of analysis of variance, a predominant influence of soil series on the spatial variability of metal concentrations was observed. All metals were spatially correlated. The semivariograms of Cu, Fe, Mn, Ni and Zn were dominated by short range correlation (600 or 700 m), and that of Pb by long range (1200 m). Block kriging maps of total metal concentrations and soil properties showed strip distributions, perpendicular to the river, in the manner similar to the soil series. Principal component analysis was run to identify common distribution patterns of heavy metals and soil properties. These results illustrate that soil series information of valley plain may be useful for developing management zones for site-specific agriculture.     

Immobilization of heavy metals in a contaminated soil in Iran using di-ammonium phosphate,vermicompost and zeolite

Fractionation of heavy metals (HMs) in amended soils is needed to predict elemental mobility in soil and phytoavailability to plants. A study was conducted to determine the effects of different amendments on HMs availability and their redistribution among soil fractions. A contaminated soil was selected from around a Zn mine and amended with 0, 2, 4, and 6 g kg⁻¹ of vermicompost (VC), zeolite (ZE), and di-ammonium phosphate (DP) and incubated at field moisture. The amounts of Cd, Pb, Zn, and Cu were determined from the soil after 6 months of incubation time using DTPA and sequential extraction procedures. The total concentrations of Cd, Pb, Zn, and Cu were 41, 3,099, 1,997, and 83 mg kg⁻¹ of soil, respectively. All amendments decreased significantly [probability (p) ≤ 0.05] DTPA-extractable Cd, Pb, and Cu, but not Zn, in the soil. For instance, DTPA-extractable Cd, Pb, and Cu decreased by 40, 290, and 20%, respectively, and that of Zn increased by 18% with DP₁ (2 g kg⁻¹ of di-ammonium phosphate) application. The concentrations of Pb and Cd decreased mainly in the specifically sorbed (SS) but increased in the amorphous Fe oxide (AFeO) fraction with DP application, indicating redistribution of Pb and Cd in the fractions with less mobility. Lead immobilization by DP was mainly attributed to the P-induced formation of chloropyromorphite, which was identified in the DP treatment using X-ray diffraction technique. It was concluded that DP was the most effective amendment in immobilizing Pb and Cd, though it increased Zn mobility.     

Contamination assessment of copper,lead, zinc and chromium in dust fall of Jinan,NE China

To assess the pollution of heavy metal in dust fall, nine dust fall samples were collected during the heating period and non-heating period from Jinan, a city in northeastern China. The samples were analyzed for Cu, Pb, Zn and Cr and the contamination level of heavy metals was assessed on the basis of the geo-accumulation index (I _geo). The results indicated that all of the four investigated metals accumulated significantly in the dust fall of Jinan, and the metal concentrations were much higher than background values. During the heating period, the mean values for Cu, Pb, Zn and Cr in the dust fall were 354.9, 688.5, 2,585.5 and 478.6 mg kg⁻¹. During the non-heating period, the mean values for Cu, Pb, Zn and Cr in the dust fall were 228.2, 518.2, 1,933.9 and 96.3 mg kg⁻¹, respectively. The I _geo values calculated based on background values revealed that the contamination level of heavy metal in the dust fall ranges from moderately contaminated to heavily contaminated, and it mainly originates from traffic and industry. In this work, the dust fall residue compared to the standard reference was also chosen as the background value to calculate the I _geo value. This method is useful for situations in which the background value is difficult to obtain.     

Quantitative spatial characteristics and environmental risk of toxic heavy metals in urban dusts of Shanghai,China

Associated with the rapid urbanization and industrialization, most of the urban parks and recreational areas in Shanghai are built close to major roads or industrial areas, where they are subject to many potential pollution source, including automobile exhaust and factory emissions. Urban dusts, containing many toxic heavy metals such as Pb, Cr, Cd, Hg and As, are one of main contributors for environmental pollution. In this study, 261 dust samples were collected from two different localities (streets and parks) in the urban area of Shanghai, China. Pb and Cr concentrations of all samples were determined by atomic adsorption spectrophotometer analyzer, and Cd, As and Hg concentrations in 74 samples by atomic fluorescence spectroscopy. The mean concentrations of Pb, Cr, Cd, As and Hg are 287, 157, 1.24, 8.73 and 0.16 mg kg⁻¹, respectively. Each heavy metal shows a wide range of concentration values. In comparison with heavy metal background values of soil in Shanghai, urban dusts have elevated metal concentrations as a whole, except those of As. The concentrations of Pb, Cr, Cd, As and Hg are 11.3, 2.1, 10.3, 0.997, 1.7 times of the soil background values, respectively. Compared with the global mean concentrations, Cr concentration in urban dusts is slightly higher. Pb, Cr and Hg show normal distribution after logarithmic transformation. Pb, Cr, Cd, As and Hg have second-order variation trends of the spatial distribution. The spatial distribution features of five toxic heavy metals, in general, illustrate relatively high levels within the regions of the inner-city ring highway and southwestern Shanghai. Cr and Cd are higher in Baoshan industrial park and the shipbuilding industries regions. The order of environmental risk is Pb > Cd > Cr > Hg > As. Pb and Cd have the highest risk for environment pollution and human health among the five metals. The pollutant sources of toxic heavy metals in Shanghai urban dusts are preliminarily concluded as follows: As may have mainly a natural source. Burning of coal has become the main source of Hg pollution. Pb, Cr and Cd have three sources, traffic, building construction, and weathering corrosion of building materials.     

Background levels and baseline values of available heavy metals in Mediterranean greenhouse soils (Spain)

This study determines extractable levels of Cd, Cu, Pb, Zn, Ni and Co in western Almería (Spain) greenhouse surface soil horizons using EDTA solution, which is identified as the fraction available for organisms and plants. It also establishes background levels, geochemical baseline concentration and reference values (RV), and investigates the possible relationships between soil properties and elemental concentrations. The results show that the soil concentration of these extractable heavy metals was high as those reported by other authors for Spanish agricultural soils. The available RV concentrations obtained (mg kg⁻¹) were: Cd 0.17, Cu 1.6, Pb 13.8, Zn 5.0 Ni 1.7 and Co 2.9. Using the upper baseline criterion, 95% of greenhouse soils present a relatively higher content of extractable heavy metals given their Cd and Cu concentration. Significant correlations between total and EDTA-extractable metal levels were found for Zn, Pb, Cu, Cd and Ni. Soil properties also related to heavy metals content, suggesting that Cd, Cu, Pb and Zn are of similar origin and relate to anthropic activities, and implies the same interactions and/or relationships among these metals.     

Mineralogy and geochemistry of the Texeo Cu–Co mine site (NW Spain): screening tools for environmental assessment

The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m³ of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg⁻¹ Cu, 1,100 mg kg⁻¹ As, 549 mg kg⁻¹ Co, and 840 mg kg⁻¹ Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg⁻¹ Cu, 1,373 mg kg⁻¹ As, 685 mg kg⁻¹ Co, and 1,040 mg kg⁻¹ Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l⁻¹ and 240 mg kg⁻¹ in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of these elements are high enough to warrant further investigation.     

Trace elements contamination of agricultural soils affected by sulphide exploitation (Iberian Pyrite Belt,Sw Spain)

Agricultural soils of the Riotinto mining area (Iberian Pyrite Belt) have been studied to assess the degree of pollution by trace elements as a consequence of the extraction and treatment of sulphides. Fifteen soil samples were collected and analysed by ICP-OES and INAA for 51 elements. Chemical analyses showed an As–Cu–Pb–Zn association related with the mineralisation of the Iberian Pyrite Belt. Concentrations were 19–994 mg kg⁻¹ for As, 41–4,890 mg kg⁻¹ for Pb, 95–897 mg kg⁻¹ for Zn and of 27–1,160 mg kg⁻¹ for Cu. Most of the samples displayed concentrations of these elements higher than the 90th percentile of the corresponding geological dominium, which suggests an anthropogenic input besides the bedrock influence. Samples collected from sediments were more contaminated than leptosols because they were polluted by leachates or by mining spills coming from the waste rock piles. The weathering of the bedrock is responsible for high concentrations in Co, Cr and Ni, but an anthropogenic input, such as wind-blown dust, seems to be indicative of the high content of As, Cu, Pb and Zn in leptosols. The metal partitioning patterns show that most trace elements are associated with Fe amorphous oxy-hydroxides, or take part of the residual fraction. According to the results obtained, the following mobility sequence is proposed for major and minor elements: Mn, Pb, Cd, > Zn, Cu > Ni > As > Fe > Cr. The high mobility of Pb, Cu and Zn involve an environmental risk in this area, even in soils where the concentrations are not so high.     

Assessing the concentration and potential dietary risk of heavy metals in vegetables at a Pb/Zn mine site,China

Cd, Pb, Cu and Zn were measured in vegetables in Xiguadi village around Lechang Pb/Zn mine in Guangdong province, South China. The daily intake (DI) of these metals from vegetables by local people was also determined. The respective Cd, Pb, Cu and Zn concentration was 0.05–0.90 (mean 0.25), 1.04–5.82 (2.64), 0.53–7.07 (2.00) and 3.87–25.20 (11.68) mg kg⁻¹, of which Cd concentration in all vegetables exceeded the safe limit given by FAO/WHO. The DI was found to be 49.76, 475.56, 360.36 and 2,102.63 μg, respectively. The present results indicated local mining activity caused vegetable heavy metal contamination and Cd concentration exceeding the stipulated standards for all vegetables indicating potentially serious dietary risks for local people.     

Particulate-associated potentially harmful elements in urban road dusts in Xi’an,China

Sixty five urban road dust samples were collected from different land use areas of ∼240 km² in Xi’an, China. The concentrations of Ag, As, Cr, Cu, Hg, Pb, Sb and Zn were determined to investigate potentially harmful element (PHE) contamination, distribution and possible sources. In addition, the concentrations in different size fractions were measured to assess their potential impact on human health. The highest concentrations were found in the fraction with particle diameters between 80 μm and 101 μm, the finest particles (<63 μm) were not the most important carriers for Ag, As, Cd, Cr, Cu, Hg, Pb and Zn. The percentages of these elements in particles with diameters less than 63 μm (PM₆₃) and less than 101 μm (PM₁₀₁) were in the range of 7–15%, and 30–55%, respectively. Three main factors influencing element distributions have been identified: (a) industrial activities; (b) prior agricultural land use; and (c) other activities commonly found in urban areas, such as traffic, coal combustion, waste dumping, and building construction/renovation. The highest concentrations were found in industrial areas for As (20 mg kg⁻¹), Cr (853 mg kg⁻¹), Cu (1071 mg kg⁻¹), Pb (3060 mg kg⁻¹) and Zn (2112 mg kg⁻¹), and in previous agricultural areas for Ag and Hg, indicating significant contributions from industrial activities and prior agricultural activities.     

Magnetic enhancement of urban roadside soils as a proxy of degree of pollution by traffic-related activities

Detailed magnetic and geochemical measurements were performed on urban roadside soils collected from Lishui city, China, to establish a possible link between the enhanced concentration of traffic-related magnetic particles and heavy metals. Relatively higher magnetic susceptibility (mean: 124.1 × 10⁻⁸ m³ kg⁻¹) and concentrations of metals (Cd, Cu, Pb and Zn) were observed for roadside soils. Concentration-dependent magnetic parameters (χ and SIRM) are highly significantly positively correlated to the concentration of metals (Ca, Cr, Ni, Cu, Zn, Cd, Pb, Fe, and V), but not significantly correlated with As, Mn, Co, Mg, and K. The principal component analysis showed that χ and SIRM significantly correspond to elements Ca, Cd, Cu, Pb, and Zn. The χ and SIRM also have significant linear correlation with integrated pollution index, indicating that χ and SIRM can be used as effective proxy indicators for the pollution of heavy metals. Magnetite in the pseudo-single-domain/multidomain (PSD/MD) grain size was identified as the dominant magnetic carrier by temperature-dependent measurements of saturation magnetization (Ms–T curve), XRD and hysteresis loops. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis of the magnetic particles revealed the presence of large traffic-related angular-subangular, blocky, and spherical iron oxide particles. These iron oxide particles are typical for particles produced by traffic-related anthropogenic activities. It is concluded that vehicle emissions may be the major source of elevated heavy metals and magnetic particles in roadside soils. The results proved the applicability of magnetic method in detecting roadside pollution derived from vehicle emissions.     

Deciphering factors controlling trace element distribution in the soils of Karaduvar industrial-agricultural area (Mersin,SE Turkey)

In this study, 30 topsoil samples were collected from Karaduvar area (Mersin, SE Turkey) where at present various industrial and agricultural activities are occurring. Using a five-step ultrasound-assisted sequential extraction (UASE) procedure, trace elements in soil samples were partitioned into the following: (1) soluble-exchangeable; (2) bound to carbonates; (3) bound to Fe- and Mn-oxides; (4) bound to organic matter and sulfide compounds, and (5) residual fraction. Concentrations of 11 trace elements in the extracts were determined using ICP-MS. Total concentrations ranged between (in mg kg⁻¹) 3.35 and 7.26 for As; 1.18 and 3.96 for Cd; 10.76 and 20.26 for Co; 37.99 and 63.48 for Cr; 18.55 and 243.1 for Cu; 338.7 and 565.6 for Mn; 4.42 and 6.44 for Mo; 148 and 279.3 for Ni; 10.12 and 73.71 for Pb; 17.93 and 36.55 for V, and 25.46 and 331.7 for Zn. Factor analysis was applied to dataset in order to discriminate between natural and anthropogenic pollution sources and factors controlling the spatial distribution of trace elements in the area. Results suggest that distributions of Co, Cr, Mn, and Ni are mainly controlled by lithological factors, whereas, distributions of Cu, Pb, and Zn can be attributed to agricultural activities such as pesticide/herbicide use and fertilizer application, as well as irrigation with petroleum hydrocarbon-contaminated groundwater. Highest concentrations of Cd and Mo are generally observed around the diesel-fired thermal power plant and ATAŞ refinery. Highest concentrations of As and V are generally observed at the NW sector of the area; however, no definitive source can be designated for both of these elements.     

Mobilization of Ag,heavy metals and Eu from the waste deposit of the Las Herrerias mine (Almería,SE Spain)

We studied the mobility of silver, heavy metals and europium in waste from the Las Herrerías mine in Almería (SE Spain). The most abundant primary mineral phases in the mine wastes are hematite, hydrohematite, barite, quartz, muscovite, anorthite, calcite and phillipsite. The minor phase consisted of primary minerals including ankerite, cinnabar, digenite, magnesite, stannite, siderite and jamesonite, and secondary minerals such as glauberite, szomolnokite, thenardite and uklonscovite. The soils show high concentrations of Ag (mean 21.6 mg kg^–1), Ba (mean 2.5%), Fe (mean 114,000 mg kg^–1), Sb (mean 342.5 mg kg^–1), Pb (mean 1,229.8 mg kg^–1), Zn (mean 493 mg kg^–1), Mn (mean 4,321.1 mg kg^–1), Cd (mean 1.2 mg kg^–1) and Eu (mean 4.0 mg kg^–1). The column experiments showed mobilization of Ag, Al, Ba, Cu, Cd, Eu, Fe, Mn, Ni, Sb, Pb and Zn, and the inverse modelling showed that the dissolution of hematite, hausmannite, pyrolusite and anglesite can largely account for the mobilization of Fe, Mn and Pb in the leaching experiment. The mobility of silver may be caused by the presence of kongsbergite and chlorargyrite in the waste, while the mobility of Eu seems to be determined by Eu(OH)₃, which controls the solubility of Eu in the pH–Eh conditions of the experiments. The mineralogy, pH, Eh and geochemical composition of the mine wastes may explain the possible mobilization of heavy metals and metalloids. However, the absence of contaminants in the groundwater may be caused by the carbonate-rich environment of “host-rocks” that limits their mobility.