Distribution Pattern Of Heavy Metals Research Articles

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.

Physicochemical characteristics and heavy metal levels in soil samples obtained from selected anthropogenic sites in Abeokuta, Nigeria

This study assessed the effect of heavy metals introduced into the soils through human activities which can bio-accumulate in plants and passed to man via the food chain that can pose health risk. Topsoil samples were collected from selected anthropogenic and control sites (dumpsites, mechanical workshops, abattoirs, fuel filling stations and hospital incinerators) in Abeokuta, Nigeria at the depths 0-5cm, 5-10cm and 10-15cm. Physicochemical parameters such as pH, moisture content, bulk density, organic matter, organic carbon, particle size distribution and Mn, Zn, Pb, and Cd were analyzed in soils using standard methods. Soil pH values ranged from 5.17 - 8.28, moisture content ranged from 3.50 - 28.55 %, bulk density ranged from 0.78 - 2.29 gcm-3, organic matter ranged from 0.09 - 16.01 %, organic carbon ranged from 0.02 % - 8.48 %. Mean concentrations of heavy metals (mgkg-1) ranged from 182.69 ± 61.95 - 697.06 ± 85.62; 122.69 ± 30.04 - 632.94 ± 508.79; 19.38 ± 6.72 - 158.50 ± 71.41; 0.25 ± 0.00 - 1.63 ± 1.38 for Mn, Zn, Pb and Cd respectively. Distribution pattern of heavy metals in petrol stations, abattoirs, mechanic workshops and hospital incinerator sites were Mn > Zn > Pb > Cd, while for dumpsites Zn > Mn > Pb > Cd. Pollution index indicated that soil qualities varied between slightly contaminated to severely polluted status. This showed that the heavy metal contamination of the soils does not call for any alarm; proactive measures must be taken to minimize accumulation of these metals.Keywords: Heavy metals, dumpsites, pollution, physicochemical parameters, abattoirs and soils

Distributions and sources of heavy metals in sediments of the Bohai Sea, China: a review.

This paper summarizes the recent research results from studies concerning heavy metals in the Bohai Sea in recent decades. The temporal and spatial variations and potential sources of the heavy metals in the surface sediments were analyzed. Based on these obtained data, the average concentrations in surface sediments collected in recent years (summarized 3171 samples) were 0.31, 87.0, 25.7, 25.8, 0.11, 16.9, 52.2, and 27.7μg/g for Cd, Zn, Cu, Pb, Hg, As, Cr, and Ni, respectively. In the samples collected in the 1980s, the concentrations were 22.6, 21.3, 69.13, 0.26, and 57.5μg/g (summarized 218 samples) for Cu, Pb, Zn, Cd, and Cr. The concentrations of Cu, Pb, Zn, and Cd increased slightly. Generally, higher concentrations were measured in the Bohai Bay and central Bohai Sea. The distribution patterns of heavy metals were significantly different between samples collected after the year of 2000 and those in the 1980s. In the 1980s and recent years, higher concentrations of Zn, Cd, and Pb were measured in the samples collected from Bohai Bay and Liaodong Bay, respectively. This indicated that the sources of heavy metals in Bohai Sea were changed significantly during the past decades.

Geochemical fractionation and pollution assessment of Zn, Cu, and Fe in surface sediments from Shadegan Wildlife Refuge, southwest of Iran.

This research focuses on the fractionation and distribution patterns of heavy metals (Zn, Cu, and Fe) in surficial sediments collected from Shadegan Wildlife Refuge, the biggest wetland in southern part of Iran, to provide an overall classification for the sources of metals in the study area using a sequential extraction method. For this purpose, a four-step sequential extraction technique was applied to define the partitioning of the metals into different geochemical phases of the sediment. The results illustrated that the average total level of Zn, Cu, and Fe in surface sediments were 55.20±16.04, 22.86±5.68, and 25,979.01±6917.91μg/g dw, respectively. On the average, the chemical partitioning of all metals in most stations was in the order of residual >oxidizable-organic>acid-reducible>exchangeable. In the same way, the results of calculated geochemical indices revealed that Cu, Zn, and Fe concentrations are mainly influenced by lithogenic origins. Compared with consensus-based SQGs, Cu was likely to result in occasionally harmful biological effects on the biota.

Laboratory and field magnetic evaluation of the heavy metal contamination on Shilaoren Beach, China

This study uses magnetic measurements to evaluate the heavy metal contamination of the surface sediments on Shilaoren Beach. The values of the laboratory magnetic measurements have a positive relationship with the concentrations of Fe, Mn, Cr, Ni, As and Pb. The field magnetic parameter provides an effective and rapid method for evaluating the distribution and dispersal of heavy metal. Sediments with higher heavy metal contents generally accumulate near higher and lower tide lines on the beach, reflecting the control of waves and tides. The sewage and stormwater outlets are the primary sources of the heavy metal contamination. Variations in seasonal waves and winds affect the sediment transport and the heavy metal distribution patterns. Based on the Australian ISQG-Low sediment quality criteria, Fe, Mn and Cr generally exhibit intermediate accumulation levels, whereas Pb and Zn exhibit higher accumulation levels because of the socioeconomic status of the area surrounding the beach.

Heavy Metal Contamination in the Surface Layer of Bottom Sediments in a Flow-Through Lake: A Case Study of Lake Symsar in Northern Poland

River-lake systems most often behave as hydrographic units, which undergo complex interactions, especially in the contact zone. One such interaction pertains to the role of a river in the dispersal of trace elements carried into and out of a lake. In this study, we aimed to assess the impact of rivers on the accumulation of heavy metals in bottom sediments of natural lakes comprised in postglacial river-lake systems. The results showed that a river flowing through a lake is a key factor responsible for the input of the majority of available fraction of heavy metals (Zn, Mn, Cd and Ni) into the water body and for their accumulation along the flow of river water in the lake. The origin of other accumulated elements were the linear and point sources in catchments. In turn, the Pb content was associated with the location of roads in the direct catchment, while the sediment structure (especially size of fraction and density) could have affected the accumulation of Cr and Zn, which indicated correlations between these metals and fine fraction. Our results suggest that lakes act as filters and contribute to the self-purification of water that flows through them. As a result, the content of most metals in lake sediments showed a decrease by approx. 75% between the upstream (inflow) and downstream (outflow) sections. The increased content of two metals only, such as chromium and cadmium (higher by 2.0 and 2.5 times, respectively, after passing through the lake), was due to the correlation of the metals with fine sand. Both the content and distribution pattern of heavy metals in lake sediments are indicative of the natural response of aquatic ecosystems to environmental stressors, such as pollutant import with river water or climate change. The complex elements creating the water ecosystem of each lake can counteract stress by temporarily removing pollutants such as toxic metals form circulation and depositing them mostly around the delta.

Atmospheric Heavy Metals Biomonitoring Using a Local Pinus eldarica Tree

Background: Trees are one of the most commonly used bio-indicators and have been widely applied for heavy metals (HMs) monitoring in the ambient air because of their simple and efficient sampling and examination. Objectives: The main objective of this study was to evaluate local pine trees for their potential as a bio-indicator of HMs in urban areas. Besides, the distribution pattern of HMs in the study area, meteorological and land use factors affecting this pattern, and HMs source identification were investigated. Methods: Forty-eight sampling locations were selected in the Yazd city, capital of Yazd province in Iran, and concentrations of five HMs- iron (Fe), copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd)- were measured in the leaves of the most abundantly local pine trees, Pinus eldarica, using the atomic absorption spectroscopy method. The obtained data were analyzed for source identification using Spearman’s rank correlation coefficient and principal component analysis (PCA). The ordinary Kriging method was used to obtain a spatial map of HMs distribution in the study area. Results: Iron had the highest concentration (345.0053 mg/kg) in leaves when compared with other HMs. The concentration of Zn, Cu, Pb and Cd were 26.1384, 5.5905, 2.9963 and 0.7383 mg/kg, respectively. Spatial mapping indicated that industrial districts and areas with heavy traffic had the highest HMs pollution. Wind direction was recognized to be the most important factor in HMs transportation. Anthropogenic sources were known as the main responsible factor for HMs emission. Conclusions: Pine trees can be used as a worthy bio-indicator for HMs pollution monitoring in the ambient air in areas with extensive vegetation of pine trees.

Spatial distribution of soil magnetic susceptibility and correlation with heavy metal pollution in Kaifeng City, China

The characterization of heavy metal pollution is urgently needed in modern environmental studies. However, traditional geochemical methods for detecting soil heavy metals are rather time-consuming and expensive. In recent years, non-destructive and rapid magnetic techniques seem promising in monitoring soil pollution but it is questionable how this relates to heavy metal concentrations. Therefore, in order to understand the correlation of heavy metal pollution with environmental magnetism, magnetic susceptibility (χLF) and the concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn were measured in the topsoil (0–15cm) collected from Kaifeng City, China. In this study, the spatial distribution of heavy metals and χLF, as well as the correlation between pollution load index (PLI) and χLF were carried out. Results show that the contamination factor (CF) values of different heavy metals follow the order: Cd (10.48)>Zn (2.28)>Pb (1.68)>Cu (1.51)>Ni (0.81)>Cr (0.80)>As (0.65). The average pollution load index (PLI) of the metals is 2.53, representing a moderate pollution level as a whole of the city soil. In general, similar spatial distribution patterns of heavy metals and χLF were found in this research, which decrease progressively from the southeast/east to the northwest/west in the study area. High concentrations of heavy metals and high levels of χLF appears around the southeast, the north of the older city (within the ancient city wall), and along the Longxi–Haizhou Railway. Moreover, contents of As, Cd, Cr, Cu, Ni, Pb and Zn in soils and PLI are significantly positively correlated with their χLF. The results further attest that the measurement of χLF is a simple, rapid and quantitative method for the assessment of heavy metal contamination of soils. When χLF≤71×10−8m3kg−1, the soil is considered to be non-polluted; 71×10−8<χLF≤162×10−8m3kg−1 represents slightly polluted soils; 162×10−8<χLF≤253×10−8m3kg−1 moderate pollution, and χLF≥253×10−8m3kg−1 corresponds to heavily polluted soils. However, the standard is exclusively valid for the study area and cannot be simply “transferred” to other polluted areas.

The spatial distribution pattern of heavy metals and risk assessment of moso bamboo forest soil around lead–zinc mine in Southeastern China

Southeast China serves as a vast habitat of moso bamboo situated adjacent to the mining area. Heavy metal contamination of the soils poses a great threat to bamboo plantations in the region. The present study aimed at determination of the heavy metals concentration in mined soils and bamboo shoot, the spatial distribution pattern of heavy metals in soils and the spatial correlations between heavy metal pollution in soils and bamboo shoots, and risk assessment of metals in soil. The soil samples (97) were collected from the study area to assess the status of metal pollution in soils adjacent to bamboo plantations around the mining area of southeast China. The median soil Cd, Cr, Cu, Mn, Pb and Zn concentrations were 0.50mgkg−1, 58.31mgkg−1, 27.89mgkg−1, 405.89mgkg−1, 286.32mgkg−1, 209.53mgkg−1, respectively. Correlation analysis suggested that soil metal species except Cr mostly exceeded the threshold values and accumulated as a result of mining activities. In addition, the mean heavy metals concentrations in moso bamboo rhizome were very low from the study area; the metals could be based on their prevalence as: Zn>Mn>Cu>Pb>Cr>Cd. The spatial statistics and autocorrelation analysis showed that most of the soil heavy metals represented a geographically increasing concentric trend (from the surrounding area to mining center). A low correlation existed between metals concentrations of soil and bamboo shoots. Pb concentrations in bamboo shoots exceeded the standard limits and supposed to have spatial correlation with its concentration in soil. The metal distributions in soil were held responsible for their bioaccumulation in edible portions of vegetables. The risk assessment confirmed that about 60.82% of the study area suffered from metal contamination. The pollution evaluation map provides a reference for the food security and the classification management of bamboo forest.

Distribution and contamination pattern of heavy metals from surface sediments in the southern part of Caspian Sea, Iran

This study concentrates on the speciation and distribution patterns of some heavy metals (Pb, Ni, Cd, Zn, and Cu) in surface sediments in the southern part of the Caspian Sea, the biggest lake in the world, to obtain an overall classification for the origins of metals in the area using a sequential extraction technique. At all sampling stations, Pb, Ni, Zn, and Cu were mostly (>50%) accumulated in the resistant fraction, which indicated that there were no significant anthropogenic inputs of Pb, Ni, Zn, and Cu into the surface sediments of the south Caspian Sea. Guilan province on the west coast of Caspian Sea accumulated higher percentages of non-resistant fractions of Pb and Zn, while Mazandaran and Golestan provinces in the middle and western parts of the Caspian Sea, in the Iranian zone, accumulated higher percentages of non-resistant fractions of Ni and Cu. The present study revealed that the coastal area of the south Caspian Sea is still not seriously contaminated. Cadmium in Guilan and Golestan provinces were dominated by non-resistant fractions (55–69%), which indicated more anthropogenic inputs of Cd on the south coast of the Caspian Sea in comparison with other metals.

Heavy metals in nearshore sediments of Kalpakkam, southeast coast of India

Kalpakkam, a tiny fishing hamlet dotting the east coast, halfway between Chennai and Pondicherry has become prominent due to the Madras Atomic Power Station. The present study aims at assessing the spatial and temporal distribution pattern of heavy metals (Cd, Pb, Zn, Cu, Ni, Cr, and Fe) from 12 stations along the inner shelf of Bay of Bengal, India, during pre-monsoon (PRM), monsoon, and post-monsoon (POM) seasons. The order of occurrence of the metals in sediments of Kalpakkam is Cr > Zn > Ni > Cu > Pb > Cd (excluding Fe since unit is in %) and exhibits a unique seasonal pattern with the highest values (average) during POM except for Cd which shows highest (average) concentration during PRM. In order to determine the sample association according to their geochemical composition and their granulometric characteristics, a correlation matrix was generated and sediment pollution indices viz., sediment enrichment factor and geoaccumulation index were computed. The results confirm anthropogenic input of Cd to nearshore sediments of Kalpakkam. Sources of Cd can be attributed to dredging activities at Edaiyur, direct dumping and sewage sludge from anthropogenic activities, which reach the study area through the Buckingham Canal opening at the backwaters—Sadras and Edaiyur, and extreme use of antifouling paints by fishing trawlers.

Potential ecological risk assessment of heavy metal contamination in sediment and water body around Dhaka export processing zone, Bangladesh

Sediments and surface water contamination by the industrial effluents containing heavy metals is the most detrimental environmental impact. Therefore, the present work attempts to determine the status of eight heavy metal distribution in sediments and water samples, and their ecological risks’ assessment in the studied area. The distribution pattern of heavy metals in the water and sediment follows the sequences: Zn > Cu > Pb > Cr > Mn > Ni > As > Cd and Mn > Zn > Cr > Pb > Cu > Ni > As > Cd, respectively. Gross water pollution is observed at different sampling points of Dhalai Beel and Bangshi River. The comparison of sedimentary mean metal concentrations with several environmental contamination monitoring parameters, viz, threshold effect level (TEL), probable effect level (PEL), and severe effect lever (SEL) indicates that the metal levels are less than PEL except Cr. Moreover, the level of contamination degree (C d) and modified degree of contamination (mC d) indicates ‘low’ and ‘nil to low’ degree of contamination, respectively. Pollution load indices (PLI) of the studied area are lower than unity, indicates no pollution. Furthermore, a toxic-response factor is applied to assess the potential ecological risk of these heavy metals into the water body. The results of this study exhibit a low potential ecological risk of heavy metals. The Pearson’s correlation and cluster analysis are also performed to assess the heavy metal interactions in water and sediment samples.

DISTRIBUTION PATTERN OF HEAVY METALS IN THE SURFACE SEDIMENTS AND ENVIRONMENT QUALITY EVALUATION FOR THE YANGTZE RIVER DELTAIC ECONOMIC ZONE

This paper,based on the 1871 of geochemical data of surface sediments and other geological data,deals with the contents and distribution pattern of heavy metals in the Yangtze River Delta Economic Zone.The results show that,in the surface sediments of the study area,the average contents of As,Cd,Cr,Cu,Hg,Pb,Zn are 8.12×10-6,101.53×10-9,74.79×10-6,19.33×10-6,34.87×10-9,22.31× 10-6,and 67.13×10-6respectively.The higher values of heavy metal elements appear in the area from the Xiangshan to the Yueqing Bay,while the lower values occur along the Jiangsu coast.The comprehensive index method was adopted for environmental quality assessment.It is revealed that the heavily polluted area is located along the channel of the Yangtze River,while slightly polluted area is near the Yangtze River Estuary and the area off Ningbo and Wenzhou.The area along the Jiangsu coat is rather clean.

DISTRIBUTION PATTERN OF HEAVY METALS IN THE SURFACE SEDIMENTS OF THE AREA OF CIRCUM-BOHAI BAY AND ECOLOGICAL ENVIRONMENT ASSESSMENT

The distribution pattern of heavy metals in the surface sediments around the Circum-Bohai Bay and its influencing factors were studied in the paper.The Nemerow comprehensive index method is adopted for ecological assessment.Results show that the Liaodong Bay is the most seriously polluted area from among the three studied areas.Cd and Hg are highly beyond the standard.Spatially,high values occur in the west of the northern Liaodong Bay and the Xiaoling River estuary off the Huludao.Cu,Pb and Zn show similar distribution pattern due to similar provenance and granularity.The assessment of ecological risk indicates that the area near Huludao is the most vulnerable area in heavy metal pollution.

Spatial Distribution and Contamination Assessments of Heavy Metals in Sediments of Wenruitang River, Wenzhou, China

Sediments from 29 stations within Wenruitang River basin were sampled to investigate the spatial distribution patterns of heavy metals in sediments and to assess the pollution status of heavy metal elements (Cd, Cr, Cu, Ni, Zn and Pb). Heavy metal concentrations showed significant spatial variation in sediments from different areas. Enrichment factors (EF) indicated that the order of pollution level was as follows: Cd＞Cu＞Zn＞Ni＞Cr＞Pb. The major heavy metal contaminants were derived from human impacts. Correlation analysis suggested that Cu, Zn, Ni, Cd and Pb were significantly related to total organic carbon (TOC); Cu, Ni, Pb, Zn and Cr had a close association with each other; Cd was closely associated with Zn.

The interactive effects of petroleum-hydrocarbon spillage and plant rhizosphere on concentrations and distribution of heavy metals in sediments in the Yellow River Delta, China

In order to understand how petroleum-hydrocarbon spillage and plant rhizosphere interact to affect concentrations and distribution of heavy metals, nine metals were analyzed from four different types of sediments (i.e. petroleum-hydrocarbon spilled rhizosphere, pristine rhizosphere, petroleum-hydrocarbon spilled unvegetated, and pristine unvegetated) in the Yellow River Delta, China. Our results showed that petroleum-hydrocarbon spillage together with rhizosphere effects were responsible for the significantly higher levels of metals in these four types of sediments. Compared to unvegetated sediments, rhizosphere sediments were well grouped into petroleum-hydrocarbon spilled and pristine sites on the basis of the concentrations of heavy metals by the correspondence analysis (CA). Furthermore, analysis of the transfer factors indicated that the capacity of rhizosphere sediments to stabilize heavy metals increased with increasing petroleum-hydrocarbon spillage, which might be due to the changes of sediment profiles by plant rhizosphere. Our results suggested that interactive effects of petroleum-hydrocarbon spillage and plant rhizosphere played an important role in determining concentrations and spatial distribution pattern of heavy metals.

Temporal and spatial distribution patterns of heavy metals in soil at a long-standing sewage farm

Australia's oldest sewage farm in Werribee, Victoria is a significant public asset with more than 110 years of history and it now treats half of Melbourne's municipal sewage. Currently three parallel methods, i.e. lagoon, land filtration and grass filtration were used to treat raw sewage from Melbourne. The land filtration area is soil-pasture-cattle complex system and it operates on 3,633 ha of permanent pastures for livestock grazing. The land filtration area by intermittent irrigation of sewage occurs during the months of high evaporation from October to April. The monitoring study was aimed to find out the temporal and spatial distribution patterns of heavy metals in the soil at land filtration area in the long standing sewage farm. The monitoring results show that the temporal distribution patterns of Cd, Cr, Cu, Ni, Pb and Zn follow the exponential regression equations in soil layer 0-20 cm and the linear equations in soil layer 20-40 cm respectively. The accumulated concentrations of heavy metals in the soils are high enough for the land to be considered contaminated. The exponential trend of heavy metal of soil in land filtration area should be controlled immediately by soil remediation or by change of treatment process of flow configuration.

Copper, zinc and lead impact in SW Iberian shelf sediments: An assessment of recent historical changes in Guadiana river basin

In the present study, lithogenic/biogenic and anthropogenic elements were determined in five sediment cores collected at the SW Iberian Continental Shelf in order to investigate the spatial and temporal heavy metal distribution and to associate them with specific continental influences/events. Elemental concentrations suggest a heavy metal (Cu, Zn and Pb) enrichment at the upper sections of all the cores. This enrichment is larger for cores localised closer to the coastline and probably exposed to a stronger continental influence. The geochemical regional background values for the studied elements are reached at ∼25-30 cm for all the studied cores with one exception (core 8), which showed to be metal-enriched down to ∼80 cm. It is worthnoting that core 8 is located closer to the coastal area, in a different fine sedimentary deposit, in which the deposition rates seem to be considerably higher. Enrichment factors (EF) calculated by using the natural background value determined at the deeper layers show that the EF values vary at the upper sections of cores, between 1.0 and 4.5 and the spatial distribution of the sediment cores show a similar behaviour in the heavy metal distribution patterns along this area of the continental shelf. Cu, Zn and Pb are heavy metals associated with mining exploitation along the Iberian Pyrite Belt, one of the most important mining areas of southwestern Europe, with massive orebodies of these metals. The combination of enrichment factors downcore profiles with sedimentation rate values signifies the beginning of heavy metal pollution in shelf sediments (∼200-250 years ago) and is coincident with the mining exploitation reactivation during the XIX century.