Distribution Patterns Of Metals Research Articles

Determination of the Sediment Contamination Level in Dangli Waters of Langkawi UNESCO Global Geopark, Kedah, Malaysia

Dangli Waters ecosystem is located at the north of Langkawi UNESCO Global Geopark. Apparently, this area is currently experiencing a significant deterioration of marine habitat. Therefore, 14 stations were set up in this study area to investigate the sediment for metal contents discharged into Dangli Waters using the ecological risk assessment. The sediment samples were collected during four seasons, namely South West Monsoon, First Inter Monsoon, North East Monsoon and Second Inter Monsoon. The spatial distribution pattern of heavy metals in sediment was properly determined as well as the seasonal variation of the contamination. From the results obtained, the average concentration of each heavy metal distributed in the surface sediment of Dangli Waters can be written in decreasing order as Fe>Cr>As>Co>Cd. From the observation, heavy metal concentrations of As was recorded the most higher profiles near to the cement plant production area. Meanwhile, for the pattern of seasonal changes, FIM season was defined as the season with higher concentrations of all metals in the surface sediment compared to other seasons. This is due to highly rainfall distribution and water runoff during this period, leading an increase of sediment deposition into the Dangli Waters. According to the contamination factor (Cf) for each metal, it was shown that some heavy metals such as As were at a risky level with the Cf value was higher than 6 (Cf >6). However, the degree of contamination (Cd) for each station was classified as moderate (7 ≤ Cd < 14), except for ST2 which showed a low degree of contamination.

Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) elemental mapping and its applications in ore geology

With the development of two-dimensional trace element mapping by laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS), it is now possible to reveal in much greater detail any compositional interior textures of the pyrites, thus permitting the investigation of the history of pyrite crystals and providing new insight into the genesis and evolution of mineralisation. Exploiting the advantages of high spatial resolution, low detection limits, and capability of full quantification, LA-ICP-MS elemental mapping is being widely applied to imaging sulphides from various types of deposits. In this study, we applied the LA-ICP-MS elemental mapping technique on pyrites from different types of deposits from China and Canada, for the purpose of monitoring the changes of physio-chemical condition, defining ore genesis, and revealing the distribution patterns of precious metals. The interior compositional textures of pyrites show that the mineralization system of the Bayinwula roll-front U deposit in Inner Mongolia was open and continuously affected by the re-charge of oxidized groundwater, along with a periodic change of pH and Eh that affected the activities of sulphate bacteria and the associated U mineralization. The trace element maps of pyrites from the Zhenzigou Pb-Zn deposit in Liaoning Province indicate that several episodes of fluids were involved and responsible for the mineralisation, namely, an early stage of syn-sedimentary origin and a late hydrothermal mineralisation related to the Yanshanian magmatic activity. The trace element distribution patterns of pyrites from the Palaeoproterozoic placer Au deposit in Canada showed that the subeuhedral-euhedral pyrite, which is a dominant type of pyrite in the conglomerates, is detrital origin and later modified by hydrothermal (or metamorphic) fluids, and Au is mostly associated with the detrital pyrite grains/cores, and disseminated in the porosity on the surface.

The historical trend in trace metal enrichment in core sediments from Cochin Estuary, Southwest coast of India

The sedimentary record of trace metals in Cochin Estuary (Southwest coast of India) during the past few decades have evaluated by analyzing core sediment and examined their ecological risk. The collected cores were examined for the depositional trends, metal enrichment, and distribution of organic carbon. Sedimentation rate was determined using the 210Po/210Pb isotope method. Chronological study reveals that Core I has aged between 1940’s to the present and Core II has been formed since 1880’s. For Core I, the average sedimentation rate obtained is 1.27 ± 0.52 cm/year, and for the Core II, it is 1.19 ± 0.23 cm/year. Both the core samples have shown similar down core distribution pattern of metals and are in the order of Zn > Cu > Pb > Cd. Metal concentration of the core samples displays an increasing trend from the bottom layer to successive upper layers. A notable variation was observed on both the core sample from 30 cm depth to the surface. The results of this study assume that the metal contamination issue of the lake system has been mounting after the industrialization of 1940's. The increase in elemental concentration after 1990's demonstrates the progressive increment and recent addition of metallic contaminants. Present study suggests regional specific preindustrial background concentration of Zn, Pb, Cu, and Cd, which can be utilized for monitoring sediment quality of the estuarine systems in India.

Identification of anthropogenic contributions to heavy metals in wetland soils of the Karuola Glacier in the Qinghai-Tibetan Plateau

Deciphering apportionments of natural and anthropogenic sources to metal concentrations are essential for better understanding impacts of human activities on metal element distribution in remote alpine wetlands. In the present work, we investigated heavy metal distribution patterns and identified the substantial contributions from anthropogenic sources on heavy metal concentrations in wetland soils of the Karuola Glacier in Tibet using a geochemical model and lead isotopes. Mean iron (Fe), aluminum (Al), and scandium (Sc) concentrations were similar to their background values and manganese (Mn) was lower than that. Concentrations of copper (Cu), cadmium (Cd), lead (Pb), zinc (Zn), and chromium (Cr) were much higher than their background values. Cd was the main contaminant because more than 87.7% of Cd was anthropogenic. Al, Pb, and Sc showed significant positive correlations between each other, Cr and Mn concentrations were significantly and negatively correlated with Fe concentrations. No significant correlations were observed among Fe, Pb, Cu, Cd, and Zn. Three components were extracted by factor analysis. Al, Fe, Sc, Cr, and Mn were related primarily to the parent material, Pb in soils was from both endogenous and exogenous sources, and Cd, Zn, and Cu were considerably or mostly from anthropogenic sources. Endogenous sources represented about 59.85%–81%, 69.3%, 12.3%, and 58.1% for total Pb, Cu, Cd, and Zn in soils. Metal accumulation fluxes have been increasing over the past 200 years. Lead isotopic features showed that most anthropogenic Pb was attributed to Pb-Zn ore smelting and coal consumption.

Distribution patterns of trace metals in soils of Gbonganorileowu Area, southwestern Nigeria

One hundred and eighty six (186) in situ soil samples of the B - horizon were collected around Gbongan- Orileowu area of Osun State, Southwestern Nigeria for a reconnaissance geochemical soil survey. The objective was to determine the distribution pattern of some trace metals in the area with a view to discovering anyindication of metallic mineralization and possible correlation with the underlying bedrock. The samples were air-dried and sieved to obtain the minus 230 micron fractions which were split into two portions for hot aqua regia acid digestion and pH determinations. The solutions obtained from the digestion were analyzed for Ag, As, Au, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, and Zn using Atomic Absorption Spectrometric methods. The resulting data were used in preparing distribution maps of the elements in the study area, employing the location point symbol method. Simple statistical treatment was also carried out on the data to determine the mean and standard deviation for each element. With these, the spatial distributions of the trace elements in the area were discussed. The pH of the soils range from 4.70 to 7.59 and this reflects the geochemical distribution patterns of trace metals in the area. The spatial distribution maps of the elements showed similarity in the distributions of Co, Cr, Fe, Ni, Mn and Pb. This suggests close associations between these elements none of which showed any significant anomaly. The association might be due to the scavenging actions of Fe-Mn oxides on the other elements. Ag, Au and Sn on one hand and Zn on the other hand showed significant anomalies, which were thought to be due to mineralization and anthropogenic activities respectively. As, Co, Cu, Fe, Ni and Pb probably occur as sulphides within reported underlying ultramafic rocks or Au bearing quartz veins or both. It is probable that Au and Ag occur as disseminations within the ultramafic rocks, aside from their occurrence in the veins, while Sn is most probably from the pegmatites. The very high Zn in the area is probably due to contamination.Keywords: Significant anomalies, Ultramafic, Anthropogenic, Mineralization

Monitoring and assessment of sediment contamination with toxic heavy metals: case study of industrial effluent dispersion in Alaro River, Nigeria

The influx of effluents from industrial area into the Alaro River in Ibadan has made the investigation of the sediment quality of the river an important environmental issue for discussion. The objective of this study was to determine the concentrations of toxic heavy metals in surface sediment of the river in order to evaluate the impact of the effluent and spatial distribution of the metals downstream. pH, total organic carbon and grain-sized particles of the sediment samples were determined according to standard methods of analysis, while heavy metal concentrations were determined by AAS. Linear least square regression (LLSR) model was employed to describe the distribution pattern of heavy metals along the river network. Hierarchical cluster analysis was applied to locate the heavy metals contamination source and interpret the association between the metal concentrations upstream and downstream, which were found to be significantly different (p = 0.05) The concentrations of Ni, Zn, Cr, Co, Cu, Cd and Pb in downstream sediments were 7.74 ± 0.97, 19.5 ± 4.6, 5.78 ± 0.47, 9.6 ± 1.6. 7.36 ± 0.61, 0.47 ± 0.03 and 7.76 ± 0.80 mg/kg, respectively. The enrichment factor (EF > 1.5) and pollution load index (PLI > 1.0.) showed that the sediment was contaminated with these heavy metals. The toxicity estimation carried out suggested that the sediment was slightly toxic. Metal distribution as shown by LLSR was such that the concentration decreased with distance downstream with R2 ranging from 0.8810 to 0.9990. The LLSR models obtained are useful to predict the metal concentrations based on the known distance of the river.

Distribution and enrichment of trace metals in surface marine sediments collected by the manned submersible Jiaolong in the Yap Trench, northwest Pacific Ocean

In this study, we carried out grain size and heavy metal analyses and also assessed heavy metal enrichment and ecological risk indices in ten sediment samples collected by the manned submersible Jiaolong at different segments of the Yap Trench. The results showed that the sediments in the Yap Trench were mainly slumping deposits composed of sandy silt. Heavy metals in the sediments showed different spatial distribution patterns from north to south direction of the trench. The distribution pattern of these heavy metals also differed in the eastern and western flanks of the trench. From the results of the enrichment factors, only arsenic, chromium, and manganese showed a slight enrichment. However, all elements were affected by natural factors. Further, most elements showed a low ecological risk, and only arsenic showed a moderate risk at two stations. Finally, the potential ecological risk of the whole study area was at a low level.

Analysis of metal content and vertical stratification of epiphytic mosses along a Karst Mountain highway.

Road-based transport emissions are a major source of atmospheric metal pollution. However, there have been few studies on emissions from road traffic in mountainous areas. In this study, epiphytic mosses from trees at different elevations of a highway, a typical road with extraordinary elevation change in a mountainous area of karst in Guizhou, China, were analyzed for metal content as well as the spatial distribution pattern of metals. Mosses were sampled from three sections of highway at different elevations, from 1292-1357, 1394-1441, to 1481-1548m. Principal component analysis and heat-map clustering were used to identify the principal factors affecting metal deposition. The results show that the metals of mosses from different elevations were divided into four factors. Group 1 which included Ni, Fe, Mg, Ba, and Al was attributed to a dominantly geogenic source. Group 2 included Zn, Cu, Mn, and Cr, from vehicle-related materials including tires and brakes. Group 3, Cd, can be attributed to high Cd background levels from local origins and traffic emissions, particularly tire wear. Group 4, Pb, is associated with brake wear and historical deposition. The epiphytic moss widely distributed in the study area, Ectropothecium aneitense Broth. & Watts, was used to analyze the spatial distribution pattern of the metals. Metal content gradually decreased with increase in elevation. Levels of Ni, Fe, Mn, Ba, and Cd were all significantly correlated with elevation (p < 0.05), simultaneously affected by terrain and vertically stratified. We highlighted the vertical distribution characteristics of metal in epiphytic mosses in this study, which could improve moss application for ecological monitoring due to road-based transport emissions with elevation changes.

Distribution Pattern of Heavy Metals in Roadside Topsoils around the Rasht-Qazvin Freeway

Distribution Pattern of Heavy Metals in Roadside Topsoils around the Rasht-Qazvin Freeway

Metal concentrations in the beach sediments of Bahia Solano and Nuquí along the Pacific coast of Chocó, Colombia: A baseline study

Thirty sediment samples from four different beaches along Bahia Solano and Nuquí (Department of Chocó) of eastern Colombia, with tourism and gold mining activities, were analysed to estimate the concentrations of fourteen different acid leachable metals. Metal distribution patterns showed elevated concentrations of Co, Cr, Cu, Pb and Zn compared with the upper continental crust values. Calculation of geochemical indices confirmed that the enrichment is due to periodic gold mining activities (severe to extremely severe enrichment of Cu, Zn, V, Co, Cr and Pb) along with natural (geological) contributions (minor and moderate enrichment of Ca, Mg, Fe, Ti, Mn and Li). Potential ecological risk index revealed that Pb posed the highest risk. Our results together with a global comparison suggest that the observed metal enrichments are mainly caused by mining and to a lesser extent by tourism in this region, thus instigating continuous monitoring of metal concentrations in this region.

Characterization of metals in indoor dusts from electronic workshops, cybercafés and offices in southern Nigeria: Implications for on-site human exposure

The levels of Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn, Zn, Al and Fe were evaluated in indoor dusts from electronic workshops, cybercafés and offices in southern Nigeria. The study was aimed at providing information on the distribution patterns, and the associated risks that may arise from exposure of humans to these metals in indoor dusts from the three work environments. The dust samples were digested with aqua-regia and analyzed for the metal concentrations by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The metal concentrations (mg kg−1) in the indoor dusts from these work environments ranged from 0.2 to 20.5 Cd, 0.6–4810 Pb, 8.65–2210 Cr, 1.85–209 Ni, 6.75–2820 Cu, 0.25–19.6 Co, 22.7–597 Mn, 6.65–140 Ba, 43.3–7310 Zn, 1040–16,800 Al and 969–78,300 Fe. The metal distribution patterns in these dust samples followed the order: electronic workshops > cybercafés > offices. The concentrations of Cd, Pb and Cu in significant proportions of the dust samples from the electronic workshops and cybercafés surpassed their respective permissible limits in soils. The health risk assessment suggests considerable non-cancer risks arising from childhood contact with Pb in dust from the electronic workshops while no considerable non-cancer risk is associated with the adult and child exposure to dust from the cybercafés and offices. The results indicated that Cr and Pb are the main elements responsible for the non-carcinogenic risk arising from childhood exposure to electronic workshop dusts. The carcinogenic risk due to exposure of humans to metals in these dust samples were within the range regarded as safe by the USEPA.

Distribution pattern of some heavy metals in the dust particulates of Funtua Textile Limited, Katsina, Nigeria

The sequential extraction of Cd, Cr, Cu, Ni, and Pb in industrial dust particulates collected in ten different sections/Departments of Funtua textile limited and the control site from Dikke village was carried out in order to ascertain the percentage of bioavailable fractions. Analyses of metals in the extracts were done using Flame Atomic Absorption Spectrometry (FAAS). The sequential extractions showed that significant amount of Cu25.87(O 1 ) to 92.73% (E 1 ) was associated with non-residual and 0.09 (E 1 ) to 56.94% (O 2 ) organic bound fractions; similarly, Cd was also associated with the non- residual fractions across the sites with values 42.22(W 2 ) to 97.78% (E 2 ). Cr and Ni exhibited the highest percentage of 73.46(W 1 ) to 100.00 % (W 2 ) and 23.64 (E 2 ) to 77.26 % (S 1 ), respectively. Pb in the particulate dust samples was significantly associated with the non-residual fraction and carbonate bound fraction with range of 21.71(D)–61.68(S2) % across the sites. This study revealed contamination of the particulates dust especially with Cu, Cr and Pb; this implies health risks to human, living or carrying out daily activities along the corridors of this industry. Keywords: Flame Atomic Absorption Spectrometry, Funtua textile, Heavy metals, Particulates dust, Sequential extraction

Heavy metal concentrations in sediments and in mussels from Argentinean coastal environments, South America

Among environmental contaminants, heavy metals are currently considered to be some of the most toxic ones present worldwide due to their harmful effects on organisms and ability to bioaccumulate in aquatic systems. In this work, the concentration of heavy metals (Cd, Cu, Pb, Zn, Ni and Cr) in Brachidontes rodriguezii and in the fine sediments of several coastal sites at the southwest of Buenos Aires Province, Argentina is analyzed. The Bahia Blanca Estuary and Pehuen-Co beach are located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing commercial species. An assessment, which involved analyzing distribution pattern of trace metals, comparative studies with sediment and ecological quality guidelines; and a sequential and integrated index analyses approach (containing Metal Pollution Index, Biosediment Accumulation Factor, Geo-accumulation Index (Igeo), Pollution Load Index and the mean Probable Effect Level quotients), was followed to estimate enrichment and risks of heavy metals in the sediments and in the mussels from these study areas. The results showed higher concentrations of some heavy metals (e.g., Cd, Cr and Ni) in mussels collected at Pehuen-Co, while no spatial differences in sediments were observed. According to the international environmental regulations, mean values of trace metals in mussels allowed to place both sites between “unpolluted and moderately polluted” and between the “low and medium category” of pollution. Furthermore, the mean concentrations found were within the detected ranges in other coastal sites worldwide.

Distribution, sources and ecological risks of metals in surficial sediments of the Forcados River and its Estuary, Niger Delta, Nigeria

The concentrations of eleven metals (Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn, Zn, Fe and Al) were measured in surficial sediments of the Forcados River and its estuary situated in the Niger Delta, Nigeria. The aim of the study was to provide information on the influence of seasonal changes on the distribution patterns and sources of these metals and the ecological risks associated with exposure to metals in the river sediment system. Samples from nine locations were collected monthly for a period of 6 months covering both the wet and dry seasons. The sediment samples were digested with aqua regia, and the metal concentrations in the digests were quantified by means of inductively coupled plasma-atomic emission spectrometry (ICP-AES). The concentration ranges of metals in the sediments were: Cd 0.78–2.16, Pb 11.5–72.0, Cr 21.9–49.6, Ni 4.75–11.7, Cu 4.48–13.7, Co 5.03–11.7, Ba 2.04–3.34, Mn 153–545, Zn 11.7–35.1, Fe 9350–18,400 and Al 9560–25,000 mg kg−1. The results showed significant spatial and seasonal variations (p < 0.05) in the metal distribution patterns. The ecological risk indices indicate that low ecological risks are associated with exposure to these metals but with significant impact from Cd. The enrichment factors, and geoaccumulation and contamination/pollution indices, suggested that Cd is the main metal contaminant in the riverbed. Principal component analysis found that the sources of metals in the sediments include natural inputs, vehicular emissions and discharges from oil industries, waste dumps and riparian farmlands.

Geochemical Assessment and Spatial Analysis of Heavy Metals in the Surface Sediments in the Eastern Beibu Gulf: A Reflection on the Industrial Development of the South China Coast.

The Beibu Gulf (also named the Gulf of Tonkin), located in the northwest of the South China Sea, is representative of a bay suffering from turbulence and contamination associated with rapid industrialization and urbanization. In this study, we aim to provide the novel baseline levels of heavy metals for the research area. Concentrations of five heavy metals (i.e., Cu, Pb, Zn, Cd and Cr) were determined in surface sediments from 35 sites in the eastern Beibu Gulf. The heavy metal content varied from 6.72 to 25.95 mg/kg for Cu, 16.99 to 57.98 mg/kg for Pb, 73.15 to 112.25 mg/kg for Zn, 0.03 to 0.12 mg/kg for Cd, and 20.69 to 56.47 mg/kg for Cr, respectively. With respect to the Chinese sediment quality criteria, sediments in the eastern Beibu Gulf have not been significantly affected by coastal metal pollutions. The results deduced from the geoaccumulation index (Igeo) showed that the study area has been slightly polluted by Pb, which might be caused by non-point sources. Relatively high concentrations of Cu, Pb and Cd were found around the coastal areas of Guangxi province, the Leizhou Peninsula and the northwest coast of Hainan Island, whereas the highest concentrations of Zn and Cr were found on the northwest coast of Hainan Island. Spatial distribution patterns of the heavy metals showed that bioavailable fractions of Pb were higher than in the residual fractions, while Cu and Cd concentrations in exchangeable and carbonate fractions were relatively higher than those in the bioavailable fractions. Hierarchical clustering analysis suggested that the sampling stations could be separated into three groups with different geographical distributions. Accompanying their similar spatial distribution in the study area, significant correlation coefficients among Cu, Cd and Pb were also found, indicating that these three metals might have had similar sources. Overall, the results indicated that the distribution of these heavy metals in the surface sediments collected from the Beibu Gulf was complex.

Heavy metals in coastal sediments of South Caspian Sea: natural or anthropogenic source?

This paper focuses on heavy metal distribution patterns in sediments of central Guilan (CG) and east Mazandaran (EM) in the south Caspian Sea coasts, north of Iran. Sediment sub-samples were retrieved from core and surficial samples in different environments of marine and coastal lagoons as well as coastal outcrops. Inductively Coupled Plasma Mass Spectrometry and Atomic Emission Spectrometry (ICP-MS and ICP-AES) analysis were used to determine the metal chemistry. Concentration of the selected heavy metals exhibited variations through sediment samples which are partially related to grain size and organic matter content. Geoaccumulation index and statistical procedures have been implemented for analyzing the absolute metal values. Result of the geoaccumulation index demonstrated that the metal distribution reflects the influence of geological background of the watershed area. Some elements including Pb, Ni, Cu, Sr and Ba showed elevated concentration in the CG that could be attributed to development of industrial activities. A comparison of the metal concentration in the marine sediments and the Late Holocene outcrops revealed that the level of the metals concentration at the sea generally corresponds to natural background. The northern part of Iranian multi-lithological catchments basin is the main source for the sediments that drained by the rivers to the South Caspian Sea basin

Spatial Distribution of Heavy Metals in the Surface Sediments of the Southern Coast of Pacitan, Indonesia

This study was conducted to analyze the spatial distribution of heavy metals from four different coastal areas in southern Pacitan, Indonesia: Pantai Watu Karung (WK), Pantai Teleng Ria (TL), Pantai Pancer (TP) dan Pantai Soge (SG). Data collected in this study included: temperature, salinity, DO, pH, sediment, organic matter and heavy metals in the sediments (Pb, Hg and Cd). The results showed different distribution patterns of heavy metals. Heavy metal concentrations, especially Pb and Hg, were found to be higher in Pantai Soge, while the concentration of Cd was higher in Pantai Pancer. An ANOVA test showed the distributions of Pb and Cd were significantly different (p &lt; 0.01) between sampling sites. Variability of the physicochemical parameters influenced the variabilities of heavy metal concentrations among sampling sites. Overall, heavy metal concentrations in the study areas are rather low; however, attention is still needed due to heavy activities in the coastal areas of southern Pacitan that can contribute to heavy metal pollution.

Heavy Metals Distribution in the Artisanal Gold Mining Area in Wonogiri

Artisanal and small gold mining activity in Wonogiri Regency has long been done with problems on environmental quality. This study was aimed to analyze the levels and spatial distribution of heavy metals in the mining area. Survey of mining and amalgamation sites, sampling the soil and tailings had been conducted. There were 66 samples of soil and tailing were collected, analysis of heavy Fe, Mn, Pb, Hg, As and Co, using X-ray fluorescence (XRF). Normal distribution test of data was conducted using the Kolmogorov-Smirnov and Shapiro Wilk. The spatial distribution of heavy metals was described using Krigging method. Contents of most heavy metals in the area studied were high, except for Co. According to the distribution pattern of heavy metals indicated that the contamination caused by the mining.

Distribution, contamination and accumulation of heavy metals in water, sediments, and freshwater shellfish from Liuyang River, Southern China.

Heavy metal distributions in water, sediments, and freshwater shellfish collected from Liuyang River in China have been investigated. The concentrations of heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were determined by ICP-MS. The distribution pattern of heavy metals in sediments was different from that in water. Large coefficients of variation of heavy metal concentrations were observed in water due to the susceptibility to discharge fluctuation and seasonal variation. Multivariate statistical analysis such as Pearson's correlation analysis, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were employed to identify the possible sources of heavy metals in sediments. These heavy metals were categorized into three distinct groups, one was derived from natural existence and two were associated with anthropogenic activities. Five shellfish species including three species of gastropod mollusks (Parafossarulus eximius, Semisulcospira cancellata, and Pomacea canaliculata) and two species of bivalve mollusks (Corbicula fluminea and Anodonta woodiana) were collected and investigated. The distribution pattern of heavy metals in shellfish species was visualized by the nonmetric multidimensional scaling (NMDS) plot. The metal pollution index (MPI) values for the shellfish species were in the descending order of C. fluminea > A. woodiana > S. cancellata > P. eximius > P. canaliculata.

Assessment of spatial distribution pattern of heavy metals surrounding a lead and zinc production plant in Zanjan Province, Iran

The present study aimed at characterizing the spatial distributions and investigating the contents of six heavy metals (Co, Ni, Cu, Zn, Cd and Pb) in top soils, surrounding the National Iranian Lead and Zinc Company (NILZ) in Bonab Industrial Estate (Zanjan-Iran) by Geostatistical analyst and Moran's I autocorrelation index. The soil samples (126) were collected from the area with a radius of 5km of the NILZ Company. The average amount of Co, Ni, Cu, Zn, Cd and Pb metals were 4.16mgkg−1, 26.38mgkg−1, 18.31mgkg−1, 684.11mgkg−1, 5.79mgkg−1, and 119.59mgkg−1, respectively. Principal Components Analysis (PCA) classified the investigated heavy metals in two groups. These groups were Factor I (Pb and Cu) and Factor II (Co, Ni, Zn and Cd) that confirm exist the anthropogenic source of the pollutants. Moran's I autocorrelation index was cleared that the high–high spatial clusters of topsoils contaminated with heavy metal were located in the center of study area, near NILZ Company. It was deduced that the company activities have a big impact on distribution of heavy metal in study area. Geostatistical analysis revealed that the high values of all studied heavy metals were located near the NILZ Company. According to comparison the prepared and land use maps, it was cleared that pesticides and chemical fertilizers, geochemistry and anthropogenic sources are the main factors in spatial variation of heavy metals.