Trace Metals In Sediments Research Articles

Contamination and ecological risk assessment of trace metals in surface sediments from coastal areas (El Jadida, Safi and Essaouira) along the Atlantic coast of Morocco

Concentrations of four trace metals (Cd, Cr, Cu and Zn) in surface sediments were quantified seasonally to evaluate the metal contamination and to determine the possible environmental risks at three coastal areas in northwest Morocco (El Jadida, Safi and Essaouira). Sampling was conducted quarterly at six intertidal stations with two stations per area (north to south: El Jadida: S1 vs. S2; Safi: S3 vs. S4 and Essaouira: S5 vs. S6). The trace metal concentrations were generally found to be greater in wet seasons for all sampling stations, and their mean values were arranged in the following decreasing order: Zn (28.35–136.10 μg g−1 dry weight) > Cr (6.50–130.90 μg g−1) > Cu (5.00–83.40 μg g−1) > Cd (0.02–5.95 μg g−1). As expected, the highest metal concentrations were recorded at stations exposed to the polluting point-source discharges from important industrial phosphate plants near El Jadida (S2-Jorf Lasfar) and Safi (S4-Jorf Lihoudi), which greatly exceeded the geochemical background values (Cd: 0.3 μg g−1 dry weight, Cr: 90 μg g−1, Cu: 45 μg g−1 and Zn: 95 μg g−1). All of the four trace metals were significantly correlated with each other, implying the same source of contamination and a similar pollution history. This was mainly derived from industrial waste generated by these huge phosphate industry plants. Meanwhile, results from hierarchical cluster analysis confirmed the findings from the correlations. This ecotoxicological evidence was primarily associated with untreated industrial discharge. The contamination Factor, degree of Contamination, and modified Degree of Contamination indices confirmed that these two stations were the metal contamination hotspots, and the most affected in this region, especially for Cd. Moreover, Pollution Load Index and Geo-accumulation Index reflected a spatial distribution of pollution following the decreasing sequence S4 > S2 > S1 > S6 > S3 > S5. Based on the Potential Ecological Risk Index, Cd concentrations indicated a moderate to very high potential ecological risk at all sampling stations, except at one pristine station S5 (Bhibeh). The spatial distribution of Mean-Effect Range Median-Quotient (M-ERM-Q) showed a negligible ecological risk at Cap Beddouza (S3) and Bhibeh. The mean values of Toxic Units (Σ TU) were found in the following decreasing order Cd > Cu > Cr > Zn, with a major contribution to the Σ TU coming from Cd (35.42%) and Cu (24.99%). Comparison of the current results with those found in other areas around the world revealed that the metal levels obtained here are in general low, except for Cd, which appeared to be in higher concentrations. Concentrations of Cd, Cr and Cu in sediments at S2 and S4 exceeded either the Threshold Effect Level of the Canadian sediment quality guidelines and Effect Range Low of the US National Oceanic and Atmospheric Administration, which demonstrated that these trace elements posed environmental risks while Zn appeared to present no environmental threat at all of the studied areas.

Distribution and contamination assessment of trace metals in surface sediments of the South China Sea, Vietnam

The distribution and enrichment of trace metals in sediments of the South China Sea along the entire coast of Vietnam were described. The concentrations of Cr, Ni, Zn, and Pb in the sediments showed a significant positive correlation with fine-sized fractions and TOC. In contrast, the concentration of As was not positively correlated with particle size and other metals. The relatively positive correlations of Cd with Fe, Al, Ti, Sc, TOC, P, Cr, Ni, Zn, and Pb indicated that it comes from different sources. Ecotoxicological indexes of all elements showed low values, except for Cd in the southwestern part of the South China Sea area, which is likely related to the influx of suspended matter from the Mekong River.

Ecological risk assessment of trace metals in sediment from the Old Brahmaputra River in Bangladesh

ABSTRACT The assessment of trace metal contamination in river sediments is crucial for suggesting effective strategies to protect aquatic ecosystem health. In this study, six toxic trace metals (As, Cd, Cr, Hg, Ni and Pb) in the surface sediments from the Old Brahmaputra River in Bangladesh were examined to evaluate the potential ecological risks. Sediment samples were collected in September 2018 and analysed by an atomic absorption spectrometer. Mean concentrations (mg/kg dw) of trace metals were in the order of Ni (43.49) > Cr (30.25) > Pb (14.29) > As (3.74) > Hg (0.16) > Cd (0.03). Spatially the sedimentary metals did not vary significantly. Source analyses revealed anthropogenic origin for most of the metals. The contamination factor, enrichment factor and geoaccumulation index (I geo) revealed a low degree of contamination for all cases except Hg, which showed a moderate degree of contamination. According to the sediment quality guidelines and sediment screening values, only Cr, Hg and Ni were high enough to cause detrimental effects in aquatic organisms. The potential ecological risk factor (Er i ) and potential ecological risk also revealed low to moderate ecological risk. Comprehensively, the river was in the uncontaminated to moderately contaminated level with low ecological risk.

Geochemical Baseline and Contamination Level Assessment of Antimony (Sb) in Sediment around Agbaou Gold Mine, Côte d’Ivoire

Agbaou is one of the most recent gold mine exploitation sites in Côte d’Ivoire. Little studies are discussed on the geochemical baseline concentration of trace metals in the wetland sediments around Agbaou gold mine. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of antimony (Sb). The geochemical baseline concentration of Sb (GBCSb) was estimated using linear regression method. In this study, total Sb concentration was analysed in sediment (10 sediment samples) collected around Agbaou gold mine site. The average Sb concentration was 5.63 ± 2.50 µg.g-1 ranging from 2.50 to 11.3 µg.g-1. The spatial distribution of Sb showed a tendency to accumulate near gold mine site. Moreover, the GBCSb (5.72 µg.g-1) was slightly higher than the average concentration found in sediments. GBC of Sb was used to calculate the anthropogenic contribution rate (R) which exhibited a positive value (R > 0) for all samples, indicating that the sediments were influenced by gold mining activities. Due to lack of local baseline value in the study area, the GBCSb obtained could be used as reference value for Sb contamination level assessment in the sediments.

Trace metals in surface sediments from the Laptev and East Siberian Seas: Levels, enrichment, contamination assessment, and sources

Trace metals in Laptev and East Siberian Sea sediments were analyzed to examine the element distribution pattern and to assess sediment contamination using contamination indices. The maximum Cr, Zn, Ni, Cu, and As concentrations occurred in the deeper parts of the East Siberian and Laptev Seas and the estuarine shelves of the Lena and Yana Rivers, and a high Cd content was observed in the sediment of the eastern part of the East Siberian Sea. The increased Cd concentration could be a result of the large number of phytoplankton supplied by the highly productive waters of the Bering Sea and the sorption capacity of Cd precipitation on Fe and Mn oxyhydroxides in seawater. The mean enrichment factors and geoaccumulation index values for Cr, Ni, Cu, Zn, Pb, and Cd showed no contamination by these metals at any sampling locations; however, slight As enrichment was found, possibly originating from natural sources.

Monitoring and risk assessment of heavy metals surficial sediments using the 5-step sequential extraction process

ABSTRACT Behaviour of heavy metals in the environment is widely acknowledged to be assessed by different physicochemical forms of presence rather than their overall concentration. In this study, Tessier 5-step sequential extraction technique was used to measure the trace metal (Mn, Cu, Zn, Fe, Pb, Co, Cd) fractions in surficial sediments in different seasons, in turn, analyse the risk posed by different fractions to the aquatic ecosystem. The findings reveal that residual fraction (F5) is in highest proportion (~44%) among the trace metals analysed. However, the proportion of carbonate and exchangeable fractions was comparatively higher (~24%), posing amajor risk to the aquatic ecosystem. Particle size v/s metal fraction scatter-plots showed that in the case of Cu, Fe and Mn, there is some form of both anthropogenic and natural pollution during the studied period, whereas, in rest of the metals, pollution is due to natural sources. Principal component analysis (PCA) led to the generation of 2 principal components (PCs), which accounted for approximately 80% of the total variance. PC1 and PC2 accounted for 45% and 35% of the total variance, respectively, which helped identify the pollution source as anthropogenic. Then, risk assessment code (RAC) revealed, Zn (41%), Mn (35%), Cu (35%), and Pb (27%) posed ahigher threat in drier months. In contrast, Co (40%) and Cd (48%) pose a higher threat with monsoon onset, showing variation of mobility of different metals in different seasons. Fe is the least mobile among the metals analysed, posing very little to the aquatic environment. Then, comparison with sediment quality guidelines (SQGs) reveals, although their potential hazard is high, they never surpass the SQGs. Thus, trace metal sediment contamination does not pose any risk to the river’s aquatic environment in the present study but calls for stringent measures employment in river pollution abatement.

Seasonal variation and mobility of trace metals in the beach sediments of NW Borneo

Miri city has a dynamic coastal environment, mainly influenced by intensive sedimentation from the Baram River and excessive trace metal loading by the Miri River, which are significant environmental concerns. As the mobility, bioavailability, and toxicity of the trace metals in the sediments are largely controlled by their particulate speciation, the modified BCR sequential extraction protocol was applied to determine the particulate speciation of trace metals in the coastal sediments of Miri, to unravel the seasonal geochemical processes responsible for known observations, and to identify possible sources of these trace metals. The granulometric analysis results showed that littoral currents aided by the monsoonal winds have influenced the grain size distribution of the sediments, enabling us to divide the study area into north-east and south-west segments where the geochemical composition are distinct. The Cu (>84%) and Zn (82%) concentrations are predominantly associated with the exchangeable fraction, which is readily bioavailable. Pb and Cd are dominant in non-residual fractions and other metals viz., Fe, Mn, Co, Ni, and Cr are dominant in the residual fraction. Using Pearson's correlation and factor analysis, the major mechanisms controlling the chemistry of the sediments are identified as association of Cu and Zn with fine fraction sediments, sulphide oxidation in the SW segment of the study area, atmospheric fallout of Pb and Cd in the river basins, precipitation of dissolved Fe and Mn supplied from the rivers and remobilization of Mn from the coastal sediments. Based on various pollution indices, it is inferred that the coastal sediments of NW Borneo are contaminated with Cu and Zn, and are largely bioavailable, which can be a threat to the local aquatic organisms, coral reefs, and coastal mangroves.

Assessment of Metal Pollution in the Sediments of Ras Al-Ardh and Yacht Club Marinas, Kuwait

This study aims to investigate the fate and behavior of five trace metals (Fe, Ni, Pb, Cu and V) in the surface sediments of two selected marinas, namely Ras Al-Ardh and Yacht Club, along the coastal area of Kuwait. Leached and total concentrations of Fe, Ni, Pb, Cu and V were measured along with the total organic carbon (TOC) and sediment grain size. The bioavailability of the trace metals was also determined using simple extraction techniques. The contamination factor (CF), enrichment factor (EF) and pollution load index (PLI) were used for assessing sediment quality at the marinas. The results indicated that TOC was related to the mean grain size, where higher TOC concentrations were associated with finer grain fractions. Trace metal distribution patterns were similar to the TOC in the sediments. The value of PLI showed that the Ras Al-Ardh marina had higher metal enrichment than that of the Yacht Club marina. The results of CF and EF indicated that the sediments within both marinas are "slightly polluted" to "moderately polluted". The sediments were less contaminated with Cu relative to Pb and Ni. The PLI class of metals at the Yacht Club indicated that the marina can be classified as "non-polluted" to "moderately polluted", while the Ras Al-Ardh marina can be classified as "moderately polluted" to "polluted". The study revealed that sediment grain size, TOC, and trace metal concentrations varied spatially within each marina depending on the type of development and the probable source of metals. Sediment quality has changed tremendously due to the expansion of tourism, progress in industrial activities and increase in recreational requirements near the coastal areas.

Occurrence, spatial distribution and ecological risk assessment of trace elements in surface sediments of rivers and coastal areas of the East Coast of Bangladesh, North-East Bay of Bengal

Coastal and estuarine ecosystems provide habitats for many organisms. Recently, the estuaries and coastal areas of the East Coast of Bangladesh have become heavily contaminated due to dumping of untreated wastewater into the rivers from a number of different industries. The current study analyzes potentially toxic elements contamination in surface sediments of the Karnaphuli, Sangu, Bakkhali and Naf Rivers, Kutubdia and Moheshkhali Channel, and St. Martin's Island, and assesses the consequent ecological risks. The pollution load index (PLI), geoaccumulation index (Igeo) and potential ecological risk (PER) indices show that the contaminated sediments have negative effects on the aquatic environments. The PLI values ranged between 0.45 and 1.67, which suggests the severity of trace-element contamination. The mean Igeo values showed the sediments range from uncontaminated to heavily contaminated state. The Enrichment Factor (EF) values suggested that the sediments were contaminated by anthropogenic sources, and PER values demonstrate that sites at Sangu, Naf and St Martin's Island are less contaminated compared to sites at Karnaphuli, Bakkhali, Kutubdia and Moheshkhali. Overall, results showed that Karnaphuli river is the most contaminated and St Martin's Island is the least based on the spatial distribution of PLI, Cd, PER and ∑TUs of trace metals in surface sediments. Comparing with the neighboring countries, the concentrations of Cd and Pb were found to be higher while Cr is lower in the East Coast of Bangladesh than the estuarine and coastal waters of the Bay of Bengal rim countries. The present study reveals that the lack of water quality guidelines in Bangladesh for the coastal, estuarine and marine water escalated the dumping of untreated wastewater. Immediate measures need to be taken to address the ecological risks so that an effective management program can be undertaken. A systematic approach for collecting pollutant data and use of isotopes to trace anthropogenic sources of contamination is recommended for pollutants like toxic metals, pesticides and other contaminants in sediment and aquatic products in the entire coastal waters of the Bay of Bengal.

The impact of trace metals in marine sediments after a tailing dam failure: the Fundão dam case (Brazil)

The impact of trace metals in marine sediments after a tailing dam failure: the Fundão dam case (Brazil)

The Long-Term Effect of Industrial Waste Landfill on Surface Water. An Example from Central Poland

Water resources are influenced by many anthropogenic pollutants, which may migrate into the environment. The Bzura River is one of the rivers strongly impacted by human activity e.g., waste landfills and former industrial plants. The objective of this study was to assess the spatial-temporal variability of trace metals in river water and sediments and to recognize the main sources of pollution. An investigation was carried out on the 120 km section, during two hydrological years. Concentrations of Ni, Pb, Cd, Cu, Zn, Fe, and Mn were determined by atomic absorption spectrometry (AAS). The basic statistics were supported by principal component analysis (PCA) and cluster analysis (CA). Generally, only part of the results exceeded the WHO, USEPA, and Polish threshold values. However, one hotspot burdened by nickel was found. The spatial trend of Ni indicates long-distance migration. The PCA and CA confirmed that the Ni mainly comes from the old industrial waste landfill. Variability of the remaining metals was affected by more mixed sources. None of the metals showed any consistent temporal pattern. The PCA revealed that the anthropogenic factor explained over 50% of the variability in both years; therefore, intensive monitoring of the water river quality is still required.

Assessment of trace metal contamination in the Kol wetland, a Ramsar site, Southwest coast of India

The present study quantified the agrarian quality and assessment of 16 sediment samples in two seasons from the identified three representative zones (North, Center and south) of Kol wetlands in Vembanad system, situated in the west coast of Kerala, India. Estimated the pollution quality indices (Enrichment Factor, Geoaccumulation index and Contamination Factor), sediment quality (Organic matter, texture and nutrients) and their ecological risk . Water Quality parameters (pH, salinity, DO) of the residing habit were also examined. The overall seasonal analyses of sediment trace metal’s mean concentration of these three zones exhibited in the following order: Fe>Zn>Pb>Cr>Mn>Ni>Co>Cu>Cd. The nutrient quality parameters inferred high concentration with spatial disparity. The Enrichment factor of Co, Cr, Zn, Cu and Ni varies from moderate to severe; and the potential ecological index of Cd in the studied Kol sampling sites were likely to result in a dangerous situation in the near future. Water Quality of the surface water noticed a putrefied condition with negligible Dissolved Oxygen (DO) at Tholur (8) in the non monsoon season. While comparing the Sediment Quality Guidelines (SQGs) and the recommended food and Agriculture Organization (FAO) standard values, the Cd, Zn and Cu concentration were exceeded the recommended limit. These scenario alter the ecological and environmental feasibility of the habitat including the sediment dwelling organisms. Multivariate statistics Analysis infers the anthropogenic and domestic source input of Cd, Ni, Mn, Co and Cu in the central basin and the correlation pattern with respect to Pb, Zn, Total Sulfur (TS), NO2-N and NH4+-N indicates an agriculture input. Among these three distinct zones the cluster results shows that the central agriculture sites confronts elevated trace metal concentration.

Combined use of high-resolution dialysis, diffusive gradient in thin films (DGT) technique, and conventional methods to assess trace metals in reservoir sediments.

Recently, reservoirs in southern China are witnessing incidents involving black water, which are harmful to the aquatic ecosystem. This study unravels the cause of the black water events by studying the occurrence and the ecological risks of contaminants (Pb, Cu, Cd, Zn, Ni, TFe, Mn, S, P, and DOC) in sediments of Tianbao reservoir. Due to the significantly high concentration of TFe, Mn, and P in the sediments, the study further used the thin film diffusion gradient (DGT) technology and high-resolution dialysis method to investigate the movement of Fe2+, Mn2+, S2-, and reactive P within the sediments. The ecological risk assessment (threshold effect level and probable effect level) showed that the sediments had a low concentration of Pb, Cu, Cd, Zn, and Ni. High organic matter from the Eucalyptus plantation surrounding the reservoir, as well as the intense thermal stratification of the reservoir, caused the hypolimnion to be hypoxic (DO < 2mg/L). The diffusion fluxes at the water-sediment boundary (WSB) demonstrated a significant movement of Fe2+, Mn2+, and PO43- from the sediments into the overlying water, while the movement of S2- was in both directions due to hypoxia. A high correlation Fe-DOC (r = 0.9), Fe-S (r = 0.8), and Mn-S (r = 0.7) and the redox interaction of Fe2+, Mn2+, S2-, P, and DOC at the hypoxic WSB caused the production of black substances in the hypolimnion contributing to the so-called black water reservoir.

Spatial distribution, contamination assessment and potential ecological risk of some trace metals in the surface sediments of the Gulf of Tunis, North Tunisia

To evaluate the trace metals contamination status in the Gulf of Tunis, forty one sediment samples were analyzed using different approaches. According to certain contamination and ecological risk indices (Contamination Factor, Geoaccumulation index and Ecological risk index), Hg has the highest contamination level while pollution by Ni, Pb, Cd and Cr was absent. The highest concentrations of trace metals were found in sediments collected from the offshore and coastal areas located opposite the main exchange points with the gulf particularly, the Mejerda and Meliane Rivers, the Khalij Channel, Ghar El Melh and El Malah lagoons, Tunis Lake and Sebkhat Ariana. However, further ecological indices (Potential ecological risk index, Toxic unit and Mean effect-range median quotient) and comparison with sediment quality guidelines suggest that in addition to Mercury, Cr, Pb and Ni concentrations are detrimental to biota in both the offshore and areas near to the exchange points with the gulf. Moreover, in these areas the results from sequential extraction and individual contamination factor calculation pointed to the mobility and bioavailability of Cr, Pb and Ni.

Evaluation of the impact of gold mining activities on the waters and sediments of Lom River, Wakaso, Cameroon and the restorative effect of Moringa Oleifera seeds

The impact of gold mining activities on the Lom River in Wakaso (Adamawa Cameroon) and the potential of Moringa Oleifera seeds for the removal of pollutants from wastewater is evaluated on this paper. Water samples were collected for physicochemical (hydrogen potential, electrical conductivity, turbidity and suspended solids) and chemical (major ions and heavy metals) analyses. To evaluate the effect of mining activities on waters and sediments, a combination of multivariate statistical analysis (MSA) and methods to assess the sediment quality was used. The restorative effect of Moringa oleifera seeds was studied with the determination of the maximum removal efficiencies and the maximum adsorption capacities. The results of the physicochemical characterization of waters showed that these waters were slightly acidic to slightly basic (6.12–8.12), weakly conductive (185.8–584.1 μS cm−1), turbid (345–801NTU) and had high content of suspended solids (167–700 mg L−1). The average concentrations of studied heavy metals (Ni, Cd, Fe, Mn, As and Hg) in waters exceeded the limits recommended by the World Health Organization (WHO) standards. Physicochemical characterization of sediments revealed that they were acidic to neutral (5.95–6.80) and organic matter (OM) content ranged from 11.11 to 15.78%. The concentrations of studied trace metals (Ni, Cd, Fe, Hg, Mn and As) in sediments were below the limits recommended by the WHO except for Cd and Hg. The study of the capacity of Moringa oleifera seeds to remove pollutants in waters showed that 54% of the electrical conductivity, 80% of turbidity and 94% of suspended solids were reduced. The maximum removal efficiency of 91.66, 92.30 and 24.48 and the maximum adsorption capacity of 2.4, 2.6 and 16.6 mg g−1were observed for Cd (II), Hg (II) and Fe (II), respectively. Thus, the Moringa oleifera seeds which are locally available natural bio-adsorbent exhibit attractive property to treat wastewater.

Distribution, Risk Assessment, and Sources of Trace Metals in Surface Sediments from the Sea Area of Macao, South China.

Due to rapid economic development in the Pearl River Delta, South China, trace metals pose a significant threat to the coastal ecosystems. In this study, we investigated the spatial distribution, contamination status, ecological risk, and possible sources of trace metals in 150 surface sediment samples from the Macao sea area. The results showed that concentrations of Ag, Pb, Cu, Zn, and Cd were highest in the Inner Harbour, whereas Cr, Co, As, and Ni were mainly accumulated in the downstream area of the Maliuzhou Waterway and the eastern area of Macao International Airport. Sediment grain composition, organic matter, total phosphorus, and hydrological regime were key factors influencing the spatial distribution patterns of trace metals. According to the environmental contamination indices of the enrichment factor, geo-accumulation index, and contamination factor, moderate contamination of trace metals occurs in the study area, while Ag and Pb contribute significantly to the contamination. Based on the potential ecological risk index, trace metals in surface sediments pose a low ecological risk. Correlation analysis and principal component analysis indicated that Cr, Co, Ni, and As were mainly derived from natural sources, whereas Ag, Pb, Cu, Zn, and Cd were mainly associated with anthropogenic sources.

Trace Metals in Sediments from El-Ryah El Twfiky and some of Its Extensions.(Dept.P)

The trace concentrations of a number of elements including: Ti, Cr, Mn, Fe, Co, Zn and Ag have been determined in sediments taken from El-Ryah El Twfiky and some of its extensions through El-Kallobia, El-Dakahlia and Damietta provinces, Egypt, where these water streams are considered the main source for drinking, irrigation and industrial waters, to the three mentioned provinces. The concentration value of the trace elements have been determined and associated with the specific surface area, organic carbon, fraction of particles ( < 100 µ m) and with each other. The levels of metal concentration are compared generally with levels found elsewhere in some river sediments. The high values and trends in metal content of the sediments compared with natural levels may be ascribed to the dumping of metallic waste materials nearby the water course, industrial and domestic effluents discharged into the stream from a number of outfalls within the area, in addition to fertilizers washed down from cultivated land.

Trace metal fractions, sources, and risk assessment in sediments from Umurbey Stream (Çanakkale-Turkey).

Trace metal contamination has become a worldwide problem for aquatic systems, as sediments act as a sink for trace metals. This study was conducted to assess geochemical fractions, sources and potential risks of trace metals (Cd, Cr, Cu, Ni, Pb, and Zn) in sediments of Umurbey stream (Çanakkale-Turkey). Sediment samples were taken from seven different locations of Umurbey stream. Aqua regia wet digestion procedure was applied to determine total contents of trace metals and BCR sequential extraction procedure was applied to determine geochemical fractions of trace metals. Trace metal total values were ordered as Zn > Pb > Cr > Cu > Ni > Cd. Just because of topography, geology, and agricultural practices, S4, S5, S6, and S7 sampling points had greater total trace metal concentrations than the other locations. Potential mobility of trace metals in sediment samples was ordered as Cd (62.1%) > Zn (60.8%) > Pb (54.8%) > Cu (46.1%) > Cr (43.0%) > Ni (29.7%). Cd, Zn, Pb, and partially Cu were encountered mostly in mobile phases. Multivariate analyses revealed that pollution in sediment samples was originated from not only anthropogenic but also natural factors. Except for Zn, trace metal concentrations were found to be at tolerable levels of biota. When the contamination factor and risk assessment code results were assessed together, it was observed that Cd, Zn, and partially Pb were weakly adsorbed onto sediments, thus might pose risks on environment in the long run.

Temporal distribution of trace metals pollution load index in the Nile Delta coastal surface sediments

The Mediterranean coastal area of the Nile Delta is socio-economically vital, however, it is under significant environmental stress due to pollution from land-based activities. The study investigates the temporal variations of trace metals to assess the development of the anthropogenic pollution status in the coastal sediments. The average concentrations, the enrichment factor, and the geoaccumulation index revealed that Cr, V, Ni, and Co are pollutants of concern. Trace metals are particularly accumulating in the sediments further offshore and in the middle and eastern sectors of the Nile Delta coast. The temporal patterns of the pollution load index (PLI) along the Nile Delta coastal indicate that pollution hotspots are increasingly exposed to trace metals pollution over time. This is linked to discharges from anthropogenic land-based activities and controlled by sedimentological factors. A conceptual model for the accumulation of trace metals in sediments is proposed based on this study.

Enrichment of Trace Metals (V, Cu, Co, Ni, and Mo) in Arctic Sediments—From Siberian Arctic Shelves to the Basin

AbstractWith 50% of the Arctic Ocean is consisted of continental shelves, extensive shelf‐basin exchange processes exist here and plays a key role in regulating the biogeochemical recycling process of trace metals in the Arctic region. In this study, short sediment cores were collected along three transects from Siberian‐Chukchi shelves to adjacent slope/basin areas. An increasing trend was found for the bulk concentrations of several metals (V, Cu, Co, Ni, and Mo) from shelf to slope/basin cores with increasing water depth. Sequential extraction experiments indicated that the Fe/Mn oxide fractions increased significantly from shelf (9%–21%) to basin cores (24%–76%) for Cu, Co, Ni, and V, while the organic/sulfide phase remained significant (∼40%) for Mo. In addition, the observed dissolved metal concentrations in porewater indicated the remobilization of Fe, Mn, and Mo from shelf sediment, while V was always removed from water to the sediment, both on the shelf or in the slope/basin. Overall, in combination with the statistical analysis, we proposed that metals are transported from shelves to the central Arctic and are scavenged mainly by Mn oxides from the water column, which results in the enrichment of metals in slope/basin sediment. With the climate change, such transport and accumulation mechanism may be intensified over time, slowly leading the Arctic sediment to be a more and more important sink for those metals.