Vertical Distribution Of Heavy Metals Research Articles

Analysis of the spatial distribution of heavy metals in an area of farmland in Sichuan province, China

To accurately visualize the spatial distribution of heavy metal pollution and provide information that assists in remediating farmland soil, this study employed GIS technology and collected 0–20 cm-depth surface soil and shallow groundwater samples from farmland in Jianxin Village, Xiba Town, Wutongqiao City, Sichuan Province, China. The soil samples were decomposed using a high-temperature closed digestion method, and the contents of Cr, Cd, Pb, As, Cu and Zn were determined using ICP-MS. A geographic semi-variogram analysis was then conducted to delineate spatial variations in the heavy metal concentrations within the soil, and a spatial distribution map of heavy metals in the soil was drawn using ArcGIS10.2 software based on a GIS Kriging interpolation spatial structure analysis. The results showed that all heavy metal element concentrations exceeded the soil background values of Sichuan Province; the exceeded rates of Cr, Cd, and Zn were 100%. All Cd samples exceeded the soil baseline value, and the pollution accumulation of Cr, Cd, and Zn was determined as being serious. Through a comparison of cross-validation methods, a theoretical optimal semi-variogram model of six heavy metal elements was obtained. Indexes C0/(C0 + C) of Cd, Pb, As, Cu, and Zn were in the range of 48–75%, which showed that their contents related to structural factors, such as the soil parent material and topography, and also to non-structural factors such as human activities. The index C0/(C0 + C) of Cr was more than 75%, which indicates that its content is mainly related to non-structural factors and human activities. The spatial correlation followed the order of Cu > Cd > Pb > Zn > As > Cr. The vertical distribution of heavy metals was greatly affected by the soil physical properties: the Cu and Pb contents of sandy soil decreased at first and then increased with depth; the Cr, Zn, and As contents first increased and then decreased with depth; and the Cd contents decreased with depth. In clay soil, there was little change in the Cu content with depth; the Cd, Zn, Pb, and As contents first decreased and then increased with depth, and the Cr content increased first and then decreased with depth. These results show that visualizing the spatial distribution of heavy metal contamination using GIS technology is significant for providing information that can be used to remediate farmland soil.

Heavy metal pollution in urban river sediment of different urban functional areas and its influence on microbial community structure.

In this study, the Songgang River (SR) was selected as a typical contaminated urban river in a highly urbanized city (Shenzhen) that is extensively polluted by heavy metals (HMs). Five representative sampling sites were selected from different urban functional areas along the SR, and the spatial and vertical distributions of HMs and the related environmental risk were investigated. In addition, the distribution variability, composition, and abundance of microbial communities, as well as the correlation between the abundance of the operational taxonomic units (OTUs) and the HM contents were analyzed. The spatial distribution of HMs in the sediment revealed wide variation among the different urban functional areas. Industrial and residential areas had higher HM contents, following the order of Cu>Zn>Ni>Cr>Pb. In addition, the vertical characterization (5-300cm) of HM content showed a decreasing trend with depth, with a distinct layer around 120-180cm that might have been caused by anthropogenic activity. An ecological risk assessment indicated that Cu, Ni, and Cr pose high potential risks in these industrial and residential areas (at the depth of 5-180cm). Furthermore, microbial community analysis indicated that some HM-tolerant bacteria (e.g., Gallionella, Acidovorax, Arenimonas, Curvibacter, and Sideroxydans) were dominant in the 5-120cm layer, corresponding to high HM contents. A canonical correspondence analysis and co-occurrence network further confirmed that there was a strong correlation among the urban functional areas, HM contents, and the abundance of microorganisms in the urban river sediment. The results of this study have the potential to provide a bio-augmentation strategy for the in-situ bioremediation of sediment contaminated by HMs.

Impact of Continuous Fertilization on Heavy Metals Content in Soil and Food Grains under 25 Years of Long-Term Fertilizer Experiment

ABSTRACT In the present investigation, an attempt was made to determine the direct effects of fertilizers on various soil properties like acidification, organic matter content, the content of essential and toxic trace metals in soils and food grains under long term (>25 years) fertilizer experiment. Soil and plant samples were collected from Bengaluru center of All India Coordinated Research Project on Long-Term Fertilizer Experimental site in the sub-regions AESR 8.1 of India, with the treatments e.g. control, 100% N, 100% NP, 100% NPK, 150% NPK, 100% NPK + Lime, 100% NPK+ farmyard manure (FYM) at 0 to 60 cm depth with an interval of 15 cm. Laboratory analysis was conducted to know the vertical distribution of heavy metals and micronutrient cations in soil and plant produce by following the standard method. The DTPA soil Zn remained unchanged with the higher rates of N application, i.e. 100% N. There was very little effect of N, NP, and NPK application on the buildup of DTPA-able Zn, Fe, Mn, and Cu content in both the soils. However, the application of NPK + FYM showed a buildup in comparison to control for Fe 10 mg kg−1, Mn 18 mg kg−1, Zn 1.23 mg kg−1, and Cu 0.84 mg kg−1 in soil. Continuous fertilizer application contributed a meager amount accumulation of Cd, Pb, Ni, Co, and Cr in the soil under the finger millet – maize cropping sequence. The estimation of heavy metals in food grains, supposed to come from fertilizers, lime materials applied in soil was also of our concern. All the cited heavy metals were present in the maize and finger-millet grains. Risk assessment to human health (Hazard Quotient, HQ) for the intake of heavy metals through consumption of contaminated food grains was computed and observed that the values of ‘HQ’ for all the crops were far less than unity (<1) and safe for the consumers.

CHEMICAL FRACTIONS OF HEAVY METALS IN SEDIMENTS OF LAKES ON SAMOYLOV ISLAND, THE LENA DELTA

The article focuses on studying the total content and chemical fractions of heavy metals (Fe, Mn, Co, Cr, Cu, Ni, Pb, V, Zn) in sediments of two lakes on Samoylov Island in the Lena delta. The lakes differ in genesis and hydrological conditions. Geochemical data for the study area were summarized. We used the sequential extraction procedure to research the roles of different sediment components in the accumulation of microelements. ICP AES was the method for all the chemical analyses. The results reveal a quite homogeneous vertical distribution of heavy metals in cores from the two lakes over the entire period of their existence (ca. 3 Ka according to radiocarbon dating). The average concentrations of the heavy metals were comparable to their content in sediments from other lakes, as well in the island soils. Analysis of the chemical fractions of the heavy metals showed that the elements were mainly stored in stable forms (bound to the crystal lattice of minerals). However, humic matter plays a significant role in binding the cations of all the metals to stable complex compounds. Cu, Pb and Zn had the most organophilic properties in the two lakes. It was noted that a significant proportion of Ni, Cr, Zn and Cu was bonded with Fe and Mn oxides. Cr, Cu, Zn and Mn were found in potentially bioavailable forms. The most mobile elements were Mn and Zn. There is a high risk of secondary water pollution with these metals.

A comprehensive survey on the horizontal and vertical distribution of heavy metals and microorganisms in soils of a Pb/Zn smelter

Smelter emissions have brought serious heavy metal contamination. Comprehensive surveys of spatial heavy metal and microorganism distribution in soils of smelters aera are still limited. In this study, the horizontal and vertical profiles of heavy metals as well as microorganisms of 80 samples from 5 soil layers of 16 sites in a Pb/Zn smelter were studied. Pollution index indicated the pollution level as Cd > Zn > Pb > As > Cu > Mn > Co > Cr > V, and the severe pollutants were Cd, Zn, Pb, As and Cu. The hazard quotient and hazard index indicated that the topsoil might pose high chronic risk to children mainly due to high content of Pb, As and Cd. The whole smelter was heavily polluted even to the depth of 100 cm as revealed by Nemerow pollution indices. Depth-related microbiota analysis indicated high richness of indigenous microorganisms and significant differences in vertical microbial structure. Proteobacteria was the dominant phylum in all depth layers, followed by Firmicutes, Actinobacteria, Bacteroidetes and Acidobacteria as major phyla. pH and heavy metals Zn, Cu, As, Mn and Cd significantly influenced the microbiota composition. Metagenomic functional prediction suggested antioxidant response, metal exportation and biotransformation play roles in bio-resistance to and bioremoval of heavy metals.

Distribution and source of heavy metals in the sediments of the coastal East China sea: Geochemical controls and typhoon impact

The present study conducted a comprehensive study on the distribution and source of heavy metals (Cu, Zn, Ni, Pb, Cd) in the sediments of the coastal East China Sea (ECS), one of the most developed regions in China with very active land-sea interactions, using 119 surface sediment samples and a 2-m sediment core collected after super Typhoon Chan-hom in 2015. Heavy metals in the surface sediments exhibited metal-dependent and regional distribution patterns, showing higher levels in the southern inner shelf (SIS) than the Yangtze River estuary (YRE), and generally being evaluated as unpolluted to moderately polluted in the coastal ECS (except few sites adjacent to Xiangshan Harbor were strongly polluted by Cd). Based on the organic carbon isotope compositions (δ13C) data as well as the strong correlations between heavy metals and natural major elemental contents (Al2O3, Fe2O3, and SiO2), we suggest natural weathering detritus as the major source of heavy metals in the YRE region and the spatial distributions were highly controlled by sediment grain size and organic matter. In contrast, the spatial distributions of heavy metals in the SIS region were less correlated with sediment properties, due to more complex sources and stronger hydrodynamic impacts. The vertical distribution of heavy metals in the sediment core indicated significant enrichments since 1950s, but showed unusual gradually decreasing trends in top layer (30 cm–0.5 cm), attributing to the strong disturbance of super Typhoon Chan-hom on sediment transportation and metal partitioning. Besides, we also observed that heavy metal levels in shallow water regions of Zhejiang coast were reduced due to the passage of typhoon. Such strong impacts of super Typhoon Chan-hom on heavy metal distributions in the ECS indicates that the impacts of extreme hydrodynamic events should raise more concern when assessing the distribution and potential risks of contaminants in coastal regions.

The spatial and vertical distribution of heavy metal contamination in sediments of the Three Gorges Reservoir determined by anti-seasonal flow regulation

The contamination of heavy metals in sediments of the Three Gorges Reservoir (TGR) is increasingly concerned as a major issue for water quality since the full impoundment. In this study, the sediment profiles in the riparian and submerged areas from Fuling to Zigui in the middle-low TGR mainstream were collected to investigate the stratified distribution of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and assess their contamination and potential eco-risk. The results showed that the concentrations of these metals in the riparian sediments did not present a marked spatial trend except the concentrations of Cd that increased towards the dam. However, the metal concentrations (except Cd) in the submerged sediments were generally higher near the dam. The concentrations of heavy metals in the riparian sediments did not show marked vertical variation, while in the submerged sediments they fluctuated dramatically with depth, indicating the metal accumulation processes in last few years. Sediment grain sizes as an indicator of hydrodynamic regimes dominated the vertical distribution of heavy metals over organic matters and Fe/Mn oxide/hydroxides. The sediments from both riparian and submerged areas of the TGR were contaminated by anthropogenic metals of Cd, Cu and Pb that were mainly from the ore mining, fossil fuel combustion, agricultural pollution and atmospheric deposition. Cadmium was a major metal pollutant in the sediments with a high contamination and potential eco-risk level. The results of this study indicate that the sorting of sediments with the anti-seasonal flow regulation determines the spatial and temporal distribution of heavy metal contamination in the sediments, and the impoundment stages of the TGR in history regulate the accumulation processes of the metals.

Anthropogenically-induced ecological risks in Lake Erikli, NW Turkey

This study examined the vertical distribution of heavy metals in the core sediments of Lake Erikli, Turkey and their potential ecological risks. Two core samples 48 and 34 cm in length were taken with a Kajak gravity core sampler. The samples were divided into 2 cm sub-samples in the laboratory and analyzed using ICP-MS. The enrichment factor (EF), potential ecological risk factor (PERI) and pollution load index (PLI) were calculated to evaluate the environmental quality of the sediment. According to the results, Cu, Pb, Zn, Ni, and Cr come from natural sources in both cores and there is no anthropogenic contribution to the distribution of these elements, while some anthropogenic effects were detected for As, Cd and Hg. According to the calculated risk index (CRI) for each metal, the potential risk of Cu, Pb, Zn, Ni, As and Cr is low. Two metals posing a threat to the ecosystem were identified; Cd and Hg. PLI values significantly increased from the bottom of the slice to the surface in accordance with the EF and PERI values. Continuation of the pumping of domestic waste into Lake Erikli will accelerate the process of deterioration.

Vertical distribution of heavy metals in seawater column during IBA construction in land reclamation – Re-exploration of a large-scale field trial experiment

Data from large-scale field trial experiments simulating the application of incineration bottom ash (IBA) for land reclamation were re-explored, to understand the spot-specific leaching characteristics and re-adsorption of heavy metals associated with various reclamation scenarios. Data showed that IBA leaching changed significantly as a function of seawater depth rather than time. The application of a chute had a minor effect on the total metal leached amounts; however, it would magnify the gradient of leaching concentrations across depths. Metal re-adsorption occurred within half an hour after IBA dumping, which however was significantly alleviated when a chute was applied. It may be ascribed to various degrees of contact with seawater of IBA, seawater movements and particle resuspension. Batch leaching tests from the laboratory under different L/S ratios were conducted as the references to “effective” leaching behaviors in the large-scale experiments, suggesting that the batch leaching test with the liquid to solid ratio = 10 provide a closer estimation of IBA leaching concentrations during land reclamation. As the current study took account of major field factors during land reclamation, including seawater depth (m), IBA loading (ton), IBA dropping method, particle dispersive area (m2), and settling time (min), these findings are valuable for the risk assessment of IBA utilization in land reclamation.

Availability and vertical distribution of Cu, Cd, Ca, and P in soil as influenced by lime and apatite with different dosages: a 7-year field study.

It is well known that alkaline amendments could effectively decrease the bioavailability of heavy metals in soils. However, the vertical distribution of heavy metals and the nutrients enriching in amendments are little concerned during long-term field remediation. Thus, the objective of the present study was to investigate the vertical distribution and availability of Cu, Cd, Ca, and P after a 7-year field experiment. In this study, a single application of lime and apatite was conducted with the rates of 1.71-6.84 and 6.84-19.8tons/ha, respectively. Soil pH and immobilization efficiency of Cu and Cd were both increased with increasing dosages of lime and apatite (0-50cm). Applications of lime and apatite decreased the mobility of Cu and Cd although soil Cu and Cd in the surface soil were increased due to the input by atmospheric dry and wet deposition. Moreover, concentrations of Cu and Cd in lime- and apatite-amended soils (0-13cm) were higher than those in the control group. However, applications of lime and apatite decreased the downward eluviations of heavy metals in soils (13-50cm). For soil nutrients, the Ca concentrations at 0-13 and 13-30cm were both enhanced with increasing amendment dosages, while only soil P concentration at 0-13cm was increased in apatite-treated soils and majority of them presented in stable-P. In addition, resin-P was increased with increasing dosages of the apatite, which suggested that high eutrophication risk was induced by excessive P loss. Thus, more attention should be paid to the nutrients (phosphorus) and pollutants enriching in the amendments during in-situ remediation of heavy metal-contaminated soils.

Assessment of Heavy Metals Contamination in Agricultural Soil of Southwestern Nile Delta, Egypt

ABSTRACTThe spatial and vertical distributions of heavy metals were quantitatively determined for organic-rich agricultural soils in the Southwestern Nile Delta. This study aims to undertake an assessment of heavy metals contamination in the soils of Quessna district using the inductively coupled plasma-optical emission spectroscopy, remote sensing, and geographic information system techniques. In this study, 24 soil samples were collected at 12 sites representing the main suburbs in the Quessna district. The concentrations of the studied metals decreased in the order of Zn > Cr > Pb > Cu > Ni > Co. The contamination degree and ecological risk assessment for metals in soil samples were evaluated using the enrichment factor, geoaccumulation index, improved Nemerow's pollution index, Pollution load index, and potential ecological risk index. The spatial and vertical distribution of heavy metals concentrations were affected by soil properties such as clay and organic matter content and scavenger metals (Fe and Mn). The intensive urbanization, industrial activity, and agricultural practices are thought to be the main anthropogenic sources of heavy metals contamination. Further studies especially human health risk assessment are recommended to investigate possible risks for humans from heavy metals in this area.

Ecological risk evaluation of sediment core samples, Lake Tortum (Erzurum, NE Turkey) using environmental indices

This study aimed to determine the vertical distribution of heavy metals in a 72 cm-long core sample from Lake Tortum in order to shed light on the implications of potential ecological risks. Analysis was based on the use of environmental indices such as the Integrated Pollution Load Index (PLI) and Potential Ecological Risk Index (PER). Results reveal that, except for Pb, Mn and Hg, the lowest concentrations of heavy metals occur at a core depth of between 2 cm and 20 cm for Cu, Zn, Ni, Fe, As, Cd, Cr and Al. The highest concentration was found at sampling intervals of 36 cm and 50 cm, with the exception of Pb, Mn, Hg and Ni. The PLI values from bottom to top are less than 1 while the level with the nearest value to the background value lies at a depth between 24 cm and 26 cm. The PER index results suggest a low ecological risk level for Cu, Pb, Zn, Ni, Mn, Fe, As, Cr, and Al; however, Cd and Hg constitute an ecological threat to the lake ecosystem.

SPATIAL DISTRIBUTION OF THE CONTENT OF HEAVY METALS IN THE BELAYA RIVER ECOSYSTEM

This paper presents the results of the research on the content and spatial distribution of heavy metals in the system of “water – bottom sediments” of the Belaya River. Quantitative data were obtained and the authors performed comparative analysis of the pollution of various abiotic environments of the river ecosystem. The pattern of vertical distribution of heavy metals in bottom sediments is shown to be linked to the level of pollution and conditions of the river flowage. Concentration of dissolved and suspended forms of the studied elements (the content of Fe, Mn, Cu, Pb, Zn, the oxidation-reduction potential, рН, turbidity and water temperature) in water samples from different gauge stations of the Belaya River is characterized by heterogeneity. There is a clear tendency for the increase of the content of Fe, Mn, Zn, and Cu down the river flow with the maximum concentrations in the foothill zone of the Republic. The studied heavy metals have prevalence of the suspended form of migration. Concentration of heavy metals in bottom sediments is considerably uneven in their distribution in different sites of the Belaya River. Bottom sediments are noticeably polluted with Zn and Pb at the village of Ministochnik, the aul of Bzhedugkhabl, and at the river mouth. In the lower watercourse of the Belaya River, contamination of bottom sediments with Cu prevails. In the gauge stations with low content of heavy metals, their vertical distribution is quite homogenous. In less polluted parts of the river, flowage plays an important role in vertical distribution of heavy metals. For example, with weak flowage (the part of the river from the village of Ministochnik to the aul of Bzhedugkhabl), the highest concentrations are in the surface layers of 0-10 cm in comparison to the layer of 10‒30 cm. With strong flowage (Dakhovskaya stanitsa), the lowest content of heavy metals is in the upper layer of 0‒10 cm, and the highest is in the layer of 10‒30 cm.

Impact of disposal of dredged material on sediment quality in the Kaohsiung Ocean Dredged Material Disposal Site, Taiwan

Kaohsiung Ocean Dredged Material Disposal Site (KODMDS) that located in the southwest offshore of Taiwan, has been annually disposed about 500,000 ton dredged sediments of Kaohsiung Harbor from 2003 to 2012. Five sediment cores collected from KODMDS and three from nearby reference sites were analyzed to evaluate their sedimentation rates, vertical profiles of heavy metal, and heavy metal pollution indices to assess the impact of dumping harbor dredged sediments into the ocean on the sediment quality in KODMDS. The sedimentation rate of 0.24 cm/y was estimated by the 210Pb method, which means that the effected depth of the top layer of a core of D1 was affected in the period of dumping dredging sediments. The vertical distribution of heavy metals in the sediment cores from KODMDS showed the concentrations of most heavy metals were slightly elevated in the top layers of the sediment cores, which may be affected by the dumping of harbor dredged sediments. According to the analyzed results of the heavy metal pollution indices, the level of heavy metal pollution, the potential eco-toxicity and the potential ecological risk of the sediments in KODMDS exhibited only a slight increase, which indicated that the increase in concentration of heavy metals may potentially pose the insignificant impact on benthos inhabiting the disposal site.

Исследование выщелачивания вкрапленных медно-никелевых руд при их взаимодействии с шахтными водами

Исследование выщелачивания вкрапленных медно-никелевых руд при их взаимодействии с шахтными водами

Ecological risk and contamination history of heavy metals in the Andong tidal flat, Hangzhou Bay, China

ABSTRACTIn this study, we collected two sediment cores (C1 and C2) from the Andong tidal flat, Hangzhou Bay, and studied the temporal variations of heavy metals in the cores. Vertical distributions of heavy metals were almost unchanged in both the cores before 2000. After 2000, however, the heavy metal concentrations increased dramatically, suggesting that the sediments have been affected by enhanced human pollution in the recent decade. In the core C1, the sediments were severely polluted by Pb, moderately to considerably polluted by Cr and Zn, and low to moderately polluted by other heavy metals. The core C2 was relatively unpolluted before 2000 and low to moderately polluted after 2000. Multi-statistical analyses indicated that the core C1 was additionally contaminated by local human activities such as wastewater discharge and the Hangzhou Bay Bridge. The heavy metals in the core C2, however, were largely contributed by the Yangtze River and controlled by sedimentation process. The calculated sedimentary flux (4–8 g m−2 a−1) of heavy metals generally increased with time. It was closely related to the wastewater discharge in adjacent areas. This study reconstructed the local heavy metal pollution history and provides important information for environmental protection and policy making.

Horizontal and Vertical Distribution of Heavy Metals in Farm Produce and Livestock around Lead-Contaminated Goldmine in Dareta and Abare, Zamfara State, Northern Nigeria.

Background. Hitherto studies in response to the June 2010 lead poisoning, Zamfara State, Nigeria, have focused on clinical interventions without information on livestock and other metals. Objective. This study has investigated the distribution of heavy metals in farm produce and livestock around lead-contaminated goldmine in Dareta and Abare, Zamfara State, Nigeria. Methods. Vegetables, soil, water, blood, and different meat samples were harvested from goat, sheep, cattle, and chicken from Dareta, Abare, and Gusau communities. The samples were digested with 10 mL of a mix of nitric and perchloric acids; the mixture was then heated to dryness. Lead, cadmium, zinc, chromium, copper, magnesium, and nickel were analysed using flame Atomic Absorption Spectrophotometer. The daily intake, bioaccumulation factor, and target hazard quotient (THQ) were calculated. Results. Chicken bone-muscles from Dareta had the highest concentrations of lead, zinc, and nickel (28.2750, 16.1650, and 4.2700 mg/kg, resp.), while chicken brain had the highest levels of cadmium, magnesium (0.3800 and 67.5400 mg/kg), and chromium (6.1650 mg/kg, kidney tissue inclusive). Conclusion. In addition to lead, cadmium may also be of concern in the contaminated mining communities of Zamfara State, Nigeria, given the high levels of cadmium in meat and vegetables samples from these areas.

Vertical Distribution of Heavy Metals and Its Response to Organic Carbon in Red Soil Profile

The vertical distribution patterns, the source and correlation of heavy metals were characterized in the bulk soil and different soil aggregates of arable red soil profile (0-100 cm) in Hunan province. Their response to organic carbons in proflie was explored as well. Principal component analysis (PCA) suggested that elements could be divided into two principal components, the metals of the first group were Zn,Cu,Pb,As,Cd, and the second group metals were Cr, Ni. Priniciple component elements had similar sources. In 0-30 cm, The first group metals decreased with increasing depth, the second group metals increased with increasing depth. The concentrations of typical heavy metals were in the order of Zn >Cr >Cu >Pb >Ni >As >Cd. Cd in each soil layer was severely polluted, Zn was at level of light pollution, while other metals were at clean levels. In terms of different size of soil aggregate, it was found that colloids played an important role in facilitating transport of heavy metals, such as As, Cu, Zn, Cd, Cr, Ni. While Pb was still mainly enriched in clay component (<53 μm). Infrared spectrum analysis showed that the main functional groups of organic carbon were polysaccharide (22.07%-47.13%), aromatic (13.88%-34.37%) and alcohol (21.04%-59.49%). Correlation analysis showed that stable organic carbon such as polysaccharide and aromatic organic carbon could stablize the metals of first group in profiles, which would delay the migration of heavy metals to deeper soil. However, the active alcohol carbon would enhance the migration.

Assessment of Heavy Metal Contamination and Wetland Management in a Newly Created Coastal Natural Reserve, China

ABSTRACT Xie, Z.; Zhang, H.; Zhao, X.; Du, Z.; Xiang, L., and Wang, W., 2016. Assessment of heavy metal contamination and wetland management in a newly created coastal natural reserve, China. The investigation of the content and distribution of heavy metals in coastal soils is useful for improving our understanding of biogeochemical cycles and their potential feedback to global environmental change. The accumulation of heavy metals in the Yellow River Delta (YRD) was investigated using 43 sampling sites to determine the concentrations and vertical distribution of heavy metals. Factor analysis, contamination factors, and the geoaccumulation index were applied to evaluate the contamination condition. The contamination factors and geoaccumulation index clearly indicated that the coastal ecosystems are still in their pristine state with respect to metal pollution. Factor loadings reveal that the first principal component was strongly and positively related to arsenic, chromium, copper, nickel, lead, and zinc,...

Impacts of urbanization on the distribution of heavy metals in soils along the Huangpu River, the drinking water source for Shanghai

We investigated the horizontal and vertical distribution of heavy metals (Hg, Pb, Zn, Cu, Cd, As, Ni, and Cr) in soils in the water source protection zone for Shanghai to study the origins of these metals, their connections with urbanization, and their potential risk posed on the ecosystem. Determination of metal concentrations in 50 topsoil samples and nine soil profiles indicated that Hg, Pb, Zn, and Cu were present in significantly higher concentrations in topsoil than in deep soil layers. The spatial distributions of Hg, Pb, Zn, and Cu and contamination hotspots for these metals in the study area were similar to those near heavy industries and urban built-up areas. Emissions from automobiles resulted in increased soil concentrations of Cu, Pb, and Zn along roadsides, while high concentrations of Hg in the soil resulted from recent atmospheric deposition. Calculation of the potential ecological risk indicated that the integrative risk of these heavy metals in most areas was low, but a few sites surrounding high density of factories showed moderate risks.