Distribution Of Heavy Metal Contamination Research Articles

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.

Geochronological and spatial distribution of heavy metal contamination in sediment from Lake Naivasha, Kenya

Sediment cores hold large information on the history of human interactions with lakes and surrounding environments. Hence, this study investigated the geochronological and heavy metals characterist...

Spatial variation of heavy metal contamination in the riparian sediments after two-year flow regulation in the Three Gorges Reservoir, China

Regular impoundment of the Three Gorges Reservoir (TGR) with intensified human activities in the watershed imparts a significant effect on the environmental changes in the riparian zone. In this study, six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the riparian sediments of the entire TGR mainstream were investigated in 2014 and 2016 to identify their contamination and risk characteristics and decipher the main factors for the variation of the metal contamination. The results showed that the concentrations of the heavy metals in the sediments did not vary significantly between 2014 and 2016, and their contamination degrees decreased in the order of Cd> > Cu ≈ Zn > Pb > Cr ≈ Ni in 2014 and Cd> > Zn > Cu ≈ Pb > Cr ≈ Ni in 2016. The potential eco-risk of Cd was extremely high in the two years, while the eco-risk of other metals was very low. The sediments showed a moderate to high contamination level, a high potential eco-risk but a low toxic risk to aquatic biota in the two years. Spatially, the contamination and risk levels of heavy metals were relatively higher in the downstream TGR region in 2014 except for the sites close to the urban areas but in the upper-middle TGR region in 2016. Increasing anthropogenic influence contributed to the high contamination and risk levels of Cd, Cu, Pb and Zn in the upper-middle region in 2016. The results indicated that the Cd contamination in the riparian sediments of the TGR was still a vital environmental issue, and the decreased sediment inputs from the upstream major tributaries, the periodic and anti-seasonal flow regulation, local geomorphological characteristics and anthropogenic activities determined the contamination distribution of heavy metals in the riparian sediments.

Spatial Variation and Assessment of Heavy Metal and Radioactive Risk in Farmland around a Retired Uranium Mine

In recent years, heavy metal contamination in the environment has been attracted worldwide attention due to their toxicity, persistence,extensive sources and non-biodegradable properties. We herein investigate variation trend and risk of heavy metal and radiation distribution in the former mine stope, former mineral ore stockyard, and mine road with surface soils of a retired uranium mine in the mid-south of China. The mean concentrations (mg/kg) of Pb,Cd,Cu,Zn,As,Hg,Cr,Mn,Ni,U, and 232Th were analyzed according to the corresponding background values in Hunan, China. The Geo-accumulation index (Igeo) were used for the assessment of pollution level of heavy metals and the radioactive elements of U and 232Th. Then, Pollution load index (PLI) and GIS techniquewere integrated to assess spatial distribution of heavy metal contamination and radioactive contamination. Results confirmed that three areas in the retired uranium mine was a primary source of pollution, which showed anthropogenic origin mainly from agricultural runoff, hydrometallurgy from chemical industries, radioactive tailings, and electroplating industriesfinally drained into Zishui River and Xiangjiang River. Based on the actual situation, some suggestions were put forward for the treatment of the retired uranium mine in conclusion.

Measuring Spatial Distribution Characteristics of Heavy Metal Contaminations in a Network-Constrained Environment: A Case Study in River Network of Daye, China

Measuring the spatial distribution of heavy metal contaminants is the basis of pollution evaluation and risk control. Considering the cost of soil sampling and analysis, spatial interpolation methods have been widely applied to estimate the heavy metal concentrations at unsampled locations. However, traditional spatial interpolation methods assume the sample sites can be located stochastically on a plane and the spatial association between sample locations is analyzed using Euclidean distances, which may lead to biased conclusions in some circumstances. This study aims to analyze the spatial distribution characteristics of copper and lead contamination in river sediments of Daye using network spatial analysis methods. The results demonstrate that network inverse distance weighted interpolation methods are more accurate than planar interpolation methods. Furthermore, the method named local indicators of network-constrained clusters based on local Moran’ I statistic (ILINCS) is applied to explore the local spatial patterns of copper and lead pollution in river sediments, which is helpful for identifying the contaminated areas and assessing heavy metal pollution of Daye.

Spatial distribution of heavy metal contamination in soils near a primitive e-waste recycling site.

The total concentrations of 12 heavy metals in surface soils (SS, 0-20 cm), middle soils (MS, 30-50 cm) and deep soils (DS, 60-80 cm) from an acid-leaching area, a deserted paddy field and a deserted area of Guiyu were measured. The results showed that the acid-leaching area was heavily contaminated with heavy metals, especially in SS. The mean concentrations of Ni, Cu, Zn, Cd, Sn, Sb and Pb in SS from the acid-leaching area were 278.4, 684.1, 572.8, 1.36, 3,472, 1,706 and 222.8 mg/kg, respectively. Heavy metal pollution in the deserted paddy field was mainly concentrated in SS and MS. The average values of Sb in SS and MS from the deserted paddy field were 16.3 and 20.2 mg/kg, respectively. However, heavy metal contamination of the deserted area was principally found in the DS. Extremely high concentrations of heavy metals were also observed at some special research sites, further confirming that the level of heavy metal pollution was very serious. The geoaccumulation index (Igeo) values revealed that the acid-leaching area was severely polluted with heavy metals in the order of Sb > Sn > Cu > Cd > Ni > Zn > Pb, while deserted paddy field was contaminated predominately by metals in the order of Sb > Sn > Cu. It was obvious that the concentrations of some uncommon contaminants, such as Sb and Sn, were higher than principal contaminants, such as Ni, Cu, Zn and Pb, suggesting that particular attention should be directed to Sn and Sb contamination in the future research of heavy metals in soils from e-waste-processing areas. Correlation analysis suggested that Li and Be in soils from the acid-leaching area and its surrounding environment might have originated from other industrial activities and from batteries, whereas Ni, Cu, Zn, Cd, Pb, Sn and Sb contamination was most likely caused by uncontrolled electronic waste (e-waste) processing. These results indicate the significant need for optimisation of e-waste-dismantling technologies and remediation of polluted soil environment.

Distribution of Heavy-Metal Contamination in Regulated River-Channel Deposits: a Magnetic Susceptibility and Grain-Size Approach; River Morava, Czech Republic

Anthropogenic contamination by heavy metals in fluvial systems is mostly bound to fine- grained clay minerals and organic substances, which accumulate by vertical accretion in sediment traps along river courses (oxbow lakes, dams and flood- plains). These environmental settings are considered as good archives of historical changes in contamina- tion. Much less attention, however, is paid to deposits of river channels, which act as sourcing transport paths for these archives and/or build archives of their own. In order to provide a better insight into the spatio- temporal distribution of pollutants in channel deposits, we investigated contamination levels of Cu, Pb and Zn in a series of sediment cores along the River Morava, a left-hand tributary of the Danube River, Czech Republic. In particular, the relationships between metal concentrations, sediment lithology (facies), grain size, magnetic susceptibility and min- eralogy and chemistry of fly-ash particles were inves- tigated. Element chemistry and lithology of channel deposits were compared with those of the nearby floodplain deposits in the same catchment. Four river-channel facies were defined, ranging from sandy gravels to clayey silts, and confronted with the flood- plain sediments. Al/Si ratios were found to be useful proxies of grain size, and Al was utilized as an excellent normalizing element for heavy metals, which filters out much of the grain size effects on contamination. The floodplain deposits are significantly less contaminated than their river-channel counterparts. Heavy-metal contamination of river bed sediments (expressed as enrichment factors, EFs) is not simply bound to fine-grained particles, and much of the contamination was found in coarse-grained, sandy facies. Elevated EFs of Zn, Cu and Pb in several sediment layers, which show high magnetic suscep- tibility (MS), high values of MS normalized to Fe and a high proportion of magnetic fly-ash spherules and their chemistry suggest that significant part of the heavy-metal contamination can be carried by magnetic fly-ash spherules. A part of this contamina- tion is bound to coarse-grained fluvial facies, indi- cating that the magnetic spherules can be transported as bed load sediments. Magnetic pollution and heavy-metal pollution can therefore coincide in river bed deposits. It is suggested that most of this con- tamination can be related to local point sources of pollutants (fly-ash deposit spills).

Assessment of heavy metal contamination and its ecological risk in the surface sediments along the coast of Korea

Ra, K., Kim, E.-S., Kim, K.-T., Kim, J.-K., Lee, J.-M., and Choi, J.-Y., 2013. Assessment of heavy metal contamination and its ecological risk in the surface sediments along the coast of Korea.We studied the spatial distribution of heavy metal contamination and its ecological risk assessment in sediments from the Korean coast. Surface sediments collected from 12 coastal zones of Korea (total 200 sediment samples) along the west, south and east coast of Korea have been analyzed for heavy metals including Cr, Co, Ni, Cu, Zn, As, Cd, Pb and Hg using ICP-MS. Mean concentrations were 58.3 mg/kg for Cr, 10.2 mg/kg for Co, 24.3 mg/kg for Ni, 36.5 mg/kg for Cu, 122 mg/kg for Zn, 9.1 mg/kg for As, 0.25 mg/kg for Cd, 35.0 mg/kg for Pb and 0.046 mg/kg for Hg, respectively. Sediments sampled from heavily industrialized areas such as Shihwa, Masan, Gwangyang and Ulsan were highly contaminated with Cu, Zn, Cd and Hg. Significantly positive correlation among metals were observed (p<0.01). This suggests that sources of metal contamination were mainly attributed to anthropogenic inputs from surrounding environment, especially national industrial complexes that consist of iron, steel, machinery, electronics and petrochemical. The results of metal assessment indices indicated that the Korean coast sediments were moderately contaminated with Cu, Zn, As, Cd, Pb and Hg. The mean of metal enrichment levels decreased following the order of Cu>Hg>Cd>Zn>As>Pb>Co>Cr>Ni. Based on the comparison with sediment quality guidelines (SQGs), Cu, As and Zn levels at more than 40% of sediment samples exceeding TEL values are likely to result in potential adverse effects on sediment-dwelling organisms.

Heavy Metal Contamination and Distribution in the Urban Environment of Guangzhou, SE China

Ever-increasing heavy metal accumulation in the urban environment of Guangzhou, the largest light industrial production base and one of the most rapidly developing cities in China, poses a serious threat to environment as well as to human health in the region. As a sink or source, urban deposits are good indicators of the level and extent of heavy metal accumulation in the surface environment. The aim of this preliminary study was to examine the distribution of heavy metal contamination in the urban environment of Guangzhou. It was based on a systematic sampling of road dusts and corresponding gully sediments along major roads running mainly through commercial and residential to industrial districts of the city. In addition to road dusts and gully sediments, ceiling dusts from the Pearl River Tunnel were also collected to characterize anthropogenic emissions dominated by traffic-related activities. In general, the level of Cd, Cu, Pb and Zn contaminations were more severe on the industrialized side of Guangzhou than on the western side where heavy traffic and industrial activities were limited. The primary determinants of the level of heavy metal contamination and the distribution of this contamination in the urban environment of Guangzhou were the site-specific conditions of its urban setting, particularly the types of industries, the nature of the traffic flow, sample residence times and variations in grain size of the particulate contaminants. This study highlights the complexity of the urban system and indicates that in just such a system individual urban components should be interlinked to assess the long-term environmental and health effects of heavy metal contamination. Among the heavy metals tested--Cd, Cu, Pb and Zn--the level of Zn contamination was the most severe and widespread, and thus requires immediate attention.

GIS techniques for mapping and evaluating sources and distribution of heavy metal contaminants

Abstract Spatially dependent phenomena related to heavy metal concentration in a drainage system have been evaluated using GIS methodology, so providing an indication of areas which may contain contaminated land. The geochemical distribution is used to identify the heavy metal sources. The GIS facilitates dispersion modelling defined by a digital elevation model. This can be used to delineate drainage catchments and to examine its interaction with stream sediment geochemistry. The resulting drainage basin-segment images can then be used to identify heavy metal sources. Such modelling of geochemical dispersion of metals within drainage basins allows predictions to be made as to which areas of contamination originate from which point source. The accuracy of such maps depends fundamentally on the accuracy of the dispersion model. This model includes both descriptive and deductive components concerning the influential criteria for describing the distribution of heavy metals. Each criterion is defined using an interactive discussion process that leads to the generation of a set of weighting coefficients. The integration of such criteria is achieved using fuzzy set methodology to produce images ranked according to how well they meet the selected site assessment criteria.

The spatial distribution of heavy metal contaminated sediment across terraced floodplains

Deposits of fine alluvial sediment contaminated by heavy metals derived from mining provide an opportunity to reconstruct the alluvial histories of mineralised catchments. Field data were collected to identify the spatial distribution of heavy metal contamination in surficial floodplain sediments and establish the relationships between terrace height, terrace age and metal concentrations. Floodplain terrace morphology was mapped and terrace heights were measured for three separate study reaches in the upper Sevem Basin, mid-Wales. Concentrations of Pb, Ba and Zn were determined in 97 samples taken from fine overbank units capping these terrace surfaces. Between the three study reaches, element concentrations showed wide ranges (Pb 11–964ppm; Ba 141–1118 ppm; Zn 73–1134 ppm). They also exhibited significant spatial variation across the floodplain at each study reach (e.g. at Llandinam, Pb 36–964ppm, Ba 141–1118 ppm and Zn 173–1134 ppm). Peak metal concentrations at Morfodion (Pb 399 ppm, Ba 474 ppm) and Welsh-pool (Pb 149 ppm, Ba 558 ppm) were found on terrace surfaces 1.5–2.5m and 2.0–3.0 m, above present river level, respectively. Lower concentrations reflect natural background levels of contaminants (higher terraces) and post-mining reworking of spoil heaps and floodplains (lower terraces). In general, the spatial distribution of floodplain contaminants is more significantly correlated with terrace height than with terrace age. Different flooding mechanisms and styles of channel instability in relation to the timing and mode of sedimentation have resulted in different patterns of floodplain contamination. Focused deposition, particularly in palaeochannels, is also an important mechanism for creating strongly contaminated sites within the floodplain environment.