Fractionation Of Trace Metals Research Articles

Relationship between iron and trace metal fractionation in soils

Iron compounds significantly affect the behaviour of trace elements in soils. Sequential chemical extractions are widely used to estimate not only the solid phase speciation of chemical elements but to study their mobilisation conditions. In this paper, we present results about the effect of iron fractionation on that of trace metals (Co, Cr, Cu, Ni, Pb and Zn) in representative soils for Hungary. Our aim was to study the effect of pedogenic processes and soil parent material on trace metal association with soil iron phases. Two major soil groups, such as Luvisols and non-Luvisols could be established based on trace metal content, distribution and fractionation in the studied soils. Such differences were found to be primarily due to the differences in the pedogenic processes in the studied soils, whereas soil parent material has not affected these characteristics significantly. We found that Fe phases affect trace metal fractionation and mobilisation as their host in form of both inherited and pedogenic phases. However, pedogenic processes, primarily iron and organic matter accumulation in our case, generally overwrite the effect of inherited iron phases on trace metal accumulation, distribution and fractionation. Among the studied metals, fractionation of Co and Cr were found to be much more affected by that of Fe, followed by Cu, Zn and Ni, whereas Pb could be associated with iron phases only subordinately.

Trace metal fractionation in water and sediments of an urban river stretch

In this study, the fractionation and ecotoxic potential of Cr, Ni, Cu and Pb in water and sediments of the river Yamuna (Delhi stretch) is presented. The river water is used for various purposes such as irrigation, industrial, domestic and drinking. The investigations suggest that the availability of metals in water follows the sequence Ni>Cr>Pb>Cu whereas a different pattern (Pb>Cu>Ni>Cr) is observed in sediments. Statistically significant spatial variations are indicated by two-way ANOVA in different geochemical forms of the metals and physicochemical parameters of water and sediments of the river Yamuna. Principal component analysis (PCA) suggests a similar source for all four metals probably from the sewage from municipal drains. PCA also indicates some independent sources of Cu and Pb. The hot spots were identified using hierarchical cluster analysis considering bioavailable forms of the metals in water and sediments as objects and the sampling sites as variables. Risk assessment code analysis indicates that metals generally pose medium to high risk at different sites. However, at a few locations either Ni or Pb cross the level of very high ecological risk.

Trace metal speciation at the sediment–water interface of Vidy Bay: influence of contrasting sediment characteristics

Trace metal analysis and speciation were performed at the sediment–water interface of Vidy Bay (Lake Geneva, Switzerland). This bay is impacted by hazardous compounds released via the sewage effluent of a major wastewater treatment plant (WWTP). Sediment cores and overlying water were sampled simultaneously at 12 sites characterized by contrasting sediment surface characteristics (color, methanogenic activity, bacterial mat) using corers deployed from a MIR submarine or research boat. The concentrations of trace metals in particulate form in the sediment and dissolved in the interstitial water, as well as the particulate, colloidal and dynamic fractions of trace metals in the overlying water were determined by combining an in situ and laboratory multi-method analytical approach. The results indicate differences in trace metal speciation in the sediment and overlying water at the 12 investigated sites. The observed differences were found to be more correlated to bacterial community, abundance, type and activity than to distance from the WWTP sewage outlet.

Bacterially Induced Weathering of Ultramafic Rock and Its Implications for Phytoextraction

The bioavailability of metals in soil is often cited as a limiting factor of phytoextraction (or phytomining). Bacterial metabolites, such as organic acids, siderophores, or biosurfactants, have been shown to mobilize metals, and their use to improve metal extraction has been proposed. In this study, the weathering capacities of, and Ni mobilization by, bacterial strains were evaluated. Minimal medium containing ground ultramafic rock was inoculated with either of two Arthrobacter strains: LA44 (indole acetic acid [IAA] producer) or SBA82 (siderophore producer, PO4 solubilizer, and IAA producer). Trace elements and organic compounds were determined in aliquots taken at different time intervals after inoculation. Trace metal fractionation was carried out on the remaining rock at the end of the experiment. The results suggest that the strains act upon different mineral phases. LA44 is a more efficient Ni mobilizer, apparently solubilizing Ni associated with Mn oxides, and this appeared to be related to oxalate production. SBA82 also leads to release of Ni and Mn, albeit to a much lower extent. In this case, the concurrent mobilization of Fe and Si indicates preferential weathering of Fe oxides and serpentine minerals, possibly related to the siderophore production capacity of the strain. The same bacterial strains were tested in a soil-plant system: the Ni hyperaccumulator Alyssum serpyllifolium subsp. malacitanum was grown in ultramafic soil in a rhizobox system and inoculated with each bacterial strain. At harvest, biomass production and shoot Ni concentrations were higher in plants from inoculated pots than from noninoculated pots. Ni yield was significantly enhanced in plants inoculated with LA44. These results suggest that Ni-mobilizing inoculants could be useful for improving Ni uptake by hyperaccumulator plants.

Trace metal fractionation as a mean to improve on the management of contaminated sediments from runoff water in infiltration basins

The management of stormwater sediment is a key issue for local authorities due to the pollution load and significant tonnages. In view of reuse, for example for civil engineering, the environmental evaluation of these highly aggregated sediments requires the study of the fractionation and mobility of trace metals. The distribution of trace metals (Cd, Cr, Cu, Ni, Pb, Zn) and their level of lability in three French stormwater sediments was determined using sequential and kinetic extractions (EDTA reagent) associated with mineralogical analysis and scanning electron microscopy observations. Using microanalysis, new data were acquired on the evolution of aggregate state during extractions, and on its significant role in the retention of trace metals. Trace metals were, in particular, observed to be very stable in small aggregates (10–50 μm). Comparison of the two extraction methods revealed that EDTA extraction was not convenient for evaluating the stable fraction of Cr, Ni and Zn. Moreover, the results were relevant for basins presenting similar sources of trace metals, whatever the physicochemical conditions in basins. The results suggest that the management of stormwater sediments could be improved by a better knowledge of metal mobility, as chemical extractions could highlight the localization of the mobile fraction of trace metals. Treatment could be therefore avoided, or specific treatment could be applied to a reduced volume of sediments.

Geochemical and stable isotopic variability within two rivers rising under the same mountain, but belonging to two distant watersheds

Complementary geochemical and stable isotope investigations of the Gorski Kotar karst aquifer system in western Croatia were obtained for the first time, to answer the question whether both studied rivers drain the same aquifer system or not. The two main rivers, the Kupa and the Rječina, rise under the same mountain range, but belong to two different watersheds (Black Sea and Adriatic Sea). The karst aquifer of Gorski Kotar is a potentially important source of drinking water for two neighboring countries, Croatia and Slovenia (Central and South Europe), and is strongly influenced by both Mediterranean and continental weather conditions. It is a part of the Dinaric karst, which is “locus typicus” for karst worldwide and one of the most typical karst areas in the world.To answer the main question of our research, baseline data were thoroughly collected comprising stable isotopes, concentration of dissolved and total trace metals in water, and multi-elemental analyses of river sediments, together with other physical-chemical parameters (pH, dissolved oxygen, electric conductivity and temperature). Total dissolved solid (TDS) was not measured but estimated as (EC) 0.67. Such multi-technique approach was applied for the first time in the Dinaric karst systems.Multi-elemental analysis of fine sediment fraction (<63μm) of eight samples was performed by ICP-MS. Elemental composition of sediments is quite different in the two studied river valleys, which indicates different origin of their waters. Also, concentrations of selected metals were compared with existing sediment quality criteria and anthropogenic influence is evaluated and discussed.Analytical results of major ions determined in three springs (Kupa spring, Rječina spring, Zvir spring in the City of Rijeka) were used to construct a Piper diagram, which showed that they are of a Ca–Na–HCO3–Cl type. The highest concentration of Mg is present in the Kupa spring, while the highest concentrations of Na and Cl are present in the Zvir spring. Groundwaters are underlain by limestone, less by dolomite and are under a maritime influence. There is a big difference with the main groundwater types reported in North Africa, i.e. in the south Mediterranean Sea, where two main groundwater types are Na–Cl and Ca–SO4–Cl.Concentrations of total and dissolved fractions of trace metals in surface water samples were determined by voltammetry and compared to the European Water Framework Directive values. Concentrations of total Pb and Zn are significantly higher in the water of the Kupa spring than the Rječina spring, suggesting that the karst water bodies of the two springs are not of the same origin.In addition, stable isotope composition (deuterium and oxygen-18) was determined in the spring waters sampled during low and high water conditions. Due to the significant difference in oxygen isotope-ratios it was concluded that the karst reservoir for the Kupa and Rječina springs is not identical.The results obtained from the combination of physical–chemical, geochemical (water and sediment) and isotope multi-technique analyses pointed out that even though the springs of the Kupa and Rječina rivers originate from the same mountain range, they do not drain the same karst aquifer.

Trace metal fractionation in the Pichavaram mangrove–estuarine sediments in southeast India after the tsunami of 2004

The geochemistry of coastal sediments of southern India was altered after the tsunami in 2004. A five-step sequential extraction procedure was applied to assess the effects of tsunami on mobility and redistribution of selected elements (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn). Ten surface sediments and three cores were analyzed for different metal fractions (exchangeable, carbonate, reduced, oxidized, and residual). Total metal concentrations increased in mangrove sediments after the tsunami, but their spatial distribution did not show significant variation (except Mn). The sediments were mixed by the tsunami, and there was lack of variation in metal concentrations in different fractions with depth (except Pb and Mn). High concentrations of Pb and Zn occurred in the oxide fractions, whereas Cu, Cr, Cd, and Ni were high in the organic and sulfide-rich fractions. Metals in the residual fraction (lattice bound) had the highest concentration suggesting their non-availability and limited biological uptake in the system. Most of the metals (except Mn) do not constitute a risk based on the different geochemical indices.

Comparison of the extraction efficiencies of different leaching agents for reliable assessment of bio-accessible trace metal fractions in airborne particulate matter

In present study, an in-vitro physiologically based extraction test has been applied for extraction of bio-accessible trace metal fractions in airborne particulate matter (APM) samples collected from different urban sites in Austria and Pakistan using the leaching agents H2O, sodium chloride, ammonium acetate, ammonium citrate, synthetic gastric juice and artificial lung fluids. Obtained extracts were then measured using an ETV-ICP-OES procedure which allowed highly sensitive measurement of dissolved analytes even in the presence of leaching agents. Derived results indicated that the investigated leaching agents extract different amounts of trace metals. In general, leaching agents with organic nature yielded comparatively greater extractable and thus bio-accessible trace metal fractions to that of simple solvents like H2O or aqueous NaCl solution. With water, only 26.3±4.0% of Cd was found to be bio-accessible whereas 88.4±24.8 of Cd was obtained as bio-accessible fraction with the use of synthetic gastric juice. The concentrations of bio-accessible metal fractions varied from 0.4 ng m−3 (Cd) to 714 ng m−3 (Zn) and 0.3 ng m−3 (Cd) to 190 ng m−3 (Zn) for PM10 samples collected from Karachi (Pakistan) and Graz (Austria) respectively.

Fractionation of trace metals in a contaminated freshwater stream using membrane filtration, ultrafiltration, DGT and transplanted aquatic moss

Four metal speciation and fractionation techniques – DGT (diffusive gradients in thin films), 1-kDa ultrafiltration, 0.22-µm membrane filtration and aquatic moss – were simultaneously applied to a small, contaminated freshwater stream in northern Sweden to investigate differences and similarities between the methods regarding trace metal speciation and their dependence on geochemical water properties. The investigated metals comprise Al, Cd, Co, Cu, Fe, Mn, Ni, and Zn. The normal DGT devices with Chelex cation exchanger were used. Shoots from the aquatic moss Fontinalis antipyretica L ex Hedw. were collected in a non-polluted brook and transplanted to the sampling site for exposure. It was evident that 0.22-µm membrane filtration, 1-kDa ultrafiltration and DGT generally measured different metal fractions where &lt;1-kDa ultrafiltered concentrations were lower than DGT labile concentrations which in turn were lower than &lt;0.22-µm concentrations. The differences between DGT and &lt;1-kDa concentrations indicate the occurrence of labile colloids discriminated by ultrafiltration. Strong correlations between DGT and &lt;1 kDa concentrations were found for Al, Cu, Cd, Co and Zn. Despite a rigorous sample cleaning, retention of particulate matter on the moss samples was revealed by a significant correlation between metal concentrations in moss and particulate Fe. Generally, elevated trace metal concentrations were found in moss exposed at the sampling site compared to reference moss from the non-polluted brook. No significant correlations were found between DGT-labile concentrations and moss concentrations. Supplementary material: DGT – labile concentrations of Al, Cd, Co, Cu, Fe, Mn, Ni and Zn from deployments in Gråbergsbäcken Stream is available online at http://www.geolsoc.org.uk/SUP18566 . A hard copy can be obtained from the Society Library.

Distribution of PAH residues in humic and mineral fractions of sediments from stormwater infiltration basins

The management of sediments from stormwater infiltration basins is nowadays a key issue for local authorities to ensure long-term performance. Speciation of pollutants is particularly required in view of reuse of these materials. If fractionation of trace metals in sediments is relatively well described, polycyclic aromatic hydrocarbons (PAHs) speciation was only studied using particle size distribution. Therefore, this study aims at the characterization of the PAHs-bearing fractions in sediments. Three sediments with various physicochemical properties were sampled in the west and north of France to characterize the distribution of PAHs among organic and inorganic components. Respective organic and inorganic matrixes were obtained by alkaline extraction and methyl isobutyl ketone (MIBK) fractionation procedure. The nature of the solid fractions was assessed through microanalyses: infrared spectroscopy (Fourier transform infrared spectroscopy), X-ray diffraction (XRD), and scanning electron microscopy with X-ray spectroscopy. Bulk sediments and extracted fractions were analyzed for organic matter parameters: elemental analysis (C, N, and H), total organic matter, total organic carbon, hydrocarbons (C10–C40), and PAHs. The characterization of bulk sediments highlighted that they were mainly composed of single particles, originating from the geological background, and aggregates (10 to 300 μm) composed of minerals and large organic matter content. The C/N ratio and PAH ratios were shown to be helpful for the determination of the natural or anthropogenic origin of organic matter or to evaluate additional contribution of industrial activities. The fractionation results underlined the role of the aggregates on the distribution of PAHs. Humin fraction and bound-humic acids were mainly composed of aggregates (10 to 150 μm) and accounted for 60 to 70 % of sample mass. The PAHs are mainly sequestrated in these fractions. Only up to 1 % of PAHs are adsorbed on the mineral fraction. Both alkaline extraction and MIBK procedure demonstrated that PAH residues were readily sequestrated in humin and bound-humic acids fractions and that fulvic acids, humic acids, and mineral fractions contained poor concentrations of PAHs. Microanalyses underlined the high level of aggregation of particles in sediments and their mixed inorganic and organic nature. In case of stormwater sediments, the location of PAHs in highly organic aggregates is consistent with their sources, being both oil products and debris from vehicles and road.

Concentration and fractionation of trace metals in surface sediments of intertidal Bohai Bay, China

Surface sediments from intertidal Bohai Bay were sampled for the geochemical and environmental assessment of six trace metals (Cd, Cr, Cu, Ni, Pb and Zn). Results indicate that sediment grain size plays an important role in controlling the distribution and fractionation of them. Metal concentrations in clayey silt sediments are all clearly higher than in sand and silty sand ones. Cd and Pb in clayey silt sediments are more mobile than in sand and silty sand ones. Two sediment quality guidelines and two geochemical normalization methods (index of geoaccumulation and enrichment factor) were used to judge the potential risk and accumulation of metals. According to the mean probable effects level quotient, the combination of studied metals may have a 21% probability of being toxic. The sediments with high fraction of clay and silt have been contaminated by trace metals to various degrees, among which Cr contributes the most to contamination.

Yield Potential, Nutrient Uptake, Metal Fractionation and Effect on Soil Properties under Integrative Use of Varied C:N Ratio Composts, Fly Ash and Inorganic Fertilizer Nitrogen in Rice Grown on Inceptisol

Field experiment was conducted to evaluate the effect of incorporating fly ash and spent mushroom composts of varied C:N ratio with and without fertilizer nitrogen on yield, trace metal content, nitrogen uptake, metal fractions and soil properties. Fertilizer nitrogen, fly ash and white button spent mushroom compost of narrow C:N ratio increased whereas oyster spent mushroom compost of wider C:N ratio decreased the paddy and straw yield. Cd and Ni content in paddy and straw, in the treatment comprising oyster spent mushroom compost did not vary significantly, however addition of fly ash or white button spent mushroom compost enhanced their content in paddy and straw. Zn content of paddy and straw in composts were higher as compared to fertilizer nitrogen, fly ash. Uptake of nitrogen by paddy and straw was higher under integrated nutrient treatments, however oyster spent mushroom compost resulted in initial nitrogen starvation, so reduction in nitrogen uptake. Compost mainly one with wider C: N ratio has shown more influence on adsorption of metals especially Zn. The exchangeable, organic matter bound and residual fractionation percentage were higher for Cd, Zn and Ni respectively in compost, especially one with wider C:N ratio.

Trace Metal Accumulation in Sediments and Benthic Macroinvertebrates before and after Maintenance of a Constructed Wetland

Stormwater best management practices (BMPs) require regular maintenance. The impact on trace metal concentrations in a constructed stormwater wetland BMP on Staten Island, New York, was investigated by analyzing sediment concentrations and tissue residues of the dominant macroinvertebrates (Tubifex tubifex) prior and subsequent to maintenance. Trace metal concentrations were assessed using standard serial extraction (for sediment) and acid digestion (for tissue burdens) techniques, followed by quantitative determination using graphite furnace atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry, respectively. The results suggest that disturbance of sediment during maintenance of the BMP resulted in an increase in the most mobile fraction of trace metals, especially those associated with finer grained sediments (< 63 tm), and as a consequence, measured metal concentrations in macroinvertebrates increased. Regressions of a subset of metal concentrations (copper, lead, and zinc) in sediment and the macroinvertebrate tissue burden samples generally increased as a result of maintenance. A follow-up sampling event 9 months after maintenance demonstrated that the most readily available form of trace metal in the BMP was reduced, which supports (1) long-term sequestration of metals in the BMP and (2) that elevated bioavailability following maintenance was potentially a transient feature of the disturbance. This study suggests that in the long-term, performing sediment removal might help reduce bioavailability of trace metal concentrations in both the BMP and the receiving water to which a BMP discharges. However, alternative practices might need to be implemented to reduce trace metal bioavailability in the short-term.

Effect of Polyelectrolyte Conditioning and Voltages on Fractionation of Macro and Trace Metals due to Sludge Electro-Dewatering

The purpose of this laboratory study was to investigate the simultaneous impacts of the electro-dewatering process on dry solids (DS) content and mobilization of metals in sewage sludge. The results suggested that the use of polyelectrolytes is necessary in mechanical pressure-driven dewatering and also in electro-dewatering. With polyelectrolyte conditioning, the DS content in the final sludge cake could be increased to 39%. Dewatering with slightly cationic polymer was not effective, but medium, strongly and very strongly cationic polymers performed equally. During electro-dewatering, an increase of voltage from 10 to 40 V resulted in a dryer sludge cake. Polyelectrolyte addition reduced the content of exchangeable metal species and increased less mobile, reducible species in the sludge. Furthermore, the more stable or immobile metal fractions were more likely to remain intact in dewatered sludge. Among heavy metals, Cu and Pb were immobile but Cr, Co, Ni, and Zn could more easily be mobilized during electro-dewatering. The application of high voltage had a direct effect on the migration of metal fractions, whereas, the sludge conditioning by a different cationic polymer had an indirect effect on the migration of these metals during electro-dewatering.

Size fractionation of trace metals in the Edmond hydrothermal plume, Central Indian Ocean

The investigation of the distribution of trace elements between the dissolved, colloidal and particulate phases within a hydrothermal plume is key to understanding plume processes. Particulate and colloidal size fractions of four trace elements (iron, manganese, copper and phosphorus) along with the dissolved size fraction of iron, manganese and copper have been determined in the hydrothermal plume overlying the Edmond vent-site in the Central Indian Ocean. Dissolved iron and manganese are the most heavily enriched metals in hydrothermal fluids emerging from vents and iron plays a significant role in subsequent dissolved-particulate interactions within hydrothermal plumes. Copper and phosphorus are each representative members of discrete groups of tracers (chalcophile elements and oxyanions, respectively) that are known to exhibit distinct patterns of behaviour, relative to iron, within hydrothermal plumes. Here we show that iron is present in all three hydrothermal plume fractions (dissolved, colloidal and particulate), being least abundant in dissolved form. Manganese resides predominantly in the dissolved fraction, copper resides primarily in the particulate phase and phosphorus is abundant in both the colloidal and coarser particulate phases, but not the dissolved fraction. The correlation of phosphorus to iron in the Edmond hydrothermal plume is both (i) constant across the colloidal and coarser particulate phases and (ii) matches well to broader inter-ocean trends reported previously from the Atlantic and Pacific Oceans. These results demonstrate a mechanism whereby plume-height P:Fe ratios are established during the very earliest stages of dissolved Fe(II) oxidation, followed by aggregation into coarser hydrothermal plume particles. This provides a strong argument for the study of P:Fe ratios in hydrothermal sediments as potential paleotracers of deep-water dissolved phosphate distributions and, hence, past deep-ocean circulation patterns.

Fractionation of Trace Metals and Arsenic in Coastal Sediments From Admiralty Bay, Antarctica

Fractionation of Trace Metals and Arsenic in Coastal Sediments From Admiralty Bay, Antarctica

The hookah series part 1: total metal analysis in hookah tobacco (narghile, shisha) – an initial study

In this initial study, the concentrations of eighteen elements (Na, K, Mg, Ca, Al, Fe, V, Cr, Mn, Ni, Cu, Zn, Se, Mo, As, Cd, Sb and Pb) in 12 hookah tobacco formulations (mo'assel) were studied by ICPMS. Eight of these were formulated in the United States, and four were from the Middle East. The analyses were made from two of the hookah compartments; as homogenized material of the hookah samples as received and by separating the received samples into the actual tobacco and a hot water extract that removed as much of the other formulation substances as possible. The extractable portion that represents up to 50% in mass of the total hookah sample is made up of honey/molasses, glycerin, colorants and flavorings, but this study shows the hot water extract to be relatively free of toxic elements. The elemental ranges found for the homogenized hookah mixtures are as follows: V, 0.03–0.16 μg g−1; Cr, 0.15–0.37 μg g−1; Mn 8.82–17.2 μg g−1; Ni, 0.14–0.64 μg g−1; Cu, 0.93–5.67 μg g−1; Zn, 3.51–5.62 μg g−1; As, 0.01–0.04 μg g−1; Se, 0.002–0.014 μg g−1; Mo, 0.05–0.13 μg g−1; Cd, 0.10–0.27 μg g−1 and Pb, <0.001–0.07 μg g−1. Given the very small fraction of trace metals in the extract, most of the metals are contained in the tobacco leaves. It was found that the major variation in the concentrations owe to the geographic production regions; namely the USA and the Middle East. A principal component analysis was performed as an explorative tool, and a good separation was found, when grouping according to preparation by geographic production region. Based on these results the average mass of the more toxic elements (As, Cd, Cr and Pb) present in a hookah smoking portion of about 15 g, is smaller than that contained in a normal cigarette. However, before any true comparisons can be made on the differences between the hookah formulations and actual dryer tobaccos, the temperature at which the smoke is produced, the length of time per smoking session, any possible metal contamination from the apparatus and contamination from the charcoal used to ignite the hookah formulation must be taken into account.

Chemical Fractionation of Trace Metals in Sewage Water – Irrigated Soils

The bioavailability of trace metals, their biological uptake and ecotoxiccological effect on soil biota can be better understood in terms of their chemical fractionation. The present study examined the mobility and availability of Cd, Cu, Ni, Pb and Zn in sewage water – irrigated soils using sequential extraction technique as a basis for predicting metal uptake by plants. The residual fraction was the most abundant pool for all the five metals examined. A significant amount (2.7 – 70.2%) of all the five metals was also present in the potentially available fraction: - nonresidual fraction. The result further indicated that the contamination of Cd and Ni in these soils was not as severe as Pb, Cu and Zn. Assuming that mobility and bioavailability of these metals are related to their liability and geochemical forms, and that they decrease in the order of extraction sequence. The apparent mobility and potential bioavailability for these five metals in the soils were: - Pb> Zn> Cu> Ni> Cd.

Assessment of background levels of trace metals in water and soil from a remote region of Himalaya

Selected trace metals were estimated by atomic absorption spectrometry in the water and soil samples collected from the remote region of Himalaya. The soil samples were analysed for soluble and acid extractable fraction of trace metals. In water samples, Ca, Na, Mg and K emerged as dominant contributors, whereas, Ca, Na, K, Mg, Fe and Pb were estimated at comparatively higher levels in the water extract of the soil. In case of acid extract of the soil samples, Ca, K, Fe, Mg, Mn and Na were found at elevated concentrations. Based on mean levels of the metals, following decreasing concentration order was observed in water samples: Ca > Na > Mg > K > Pb > Co > Cu > Zn > Mn > Cr > Fe > Cd > Li, however, in the acid extract of the soil, following order was noted: Ca > K > Fe > Mg > Mn > Na > Pb > Zn > Cr > Li > Cu > Co > Cd. The correlation study revealed appreciably diverse mutual relationships of trace metals in the water and soil samples. The multivariate cluster analyses exhibited divergent apportionment of trace metals in water and soil samples. Among the trace metals, Cd, Pb, Li, Zn, Cr, Cu, Mn and Co exhibited extreme to significant anthropogenic enrichment in the soil samples, while the rest of the metals were mostly contributed by the natural processes.

Fractionation of trace metals (Mn, Zn, Cu, Pb) in Red Sea sediments, Gulf of Aden, Yemen

A sequential extraction technique was applied to estimate the chemical association of Mn, Zn, Cu and Pb in five chemical phases (exchangeable, carbonate, Fe–Mn oxides, organic matter and residual) in sediments of the Gulf of Aden, Yemen. The results indicated that a higher level of Mn was associated with the residual fraction (natural sources) than the non-residual fraction (anthropogenic sources). Zn fractionations revealed that it was associated more with Fe–Mn oxides and organic fractions than exchangeable and carbonate fractions. Most of the Cu was present in the residual form (60–72%) except for in the main port area (zone III), where it was associated with the organic phase (77% of the total Cu content, the organic matter content was 5%). Similarly, most Pb was bound in the residual fraction (56–71%) except the main port area where ∼ 62% of the total Pb was bound in non-residual fractions. It was also found that the Pb concentration in the exchangeable fraction was very high compared with other metals. The risk assessment code for the metals showed a low risk for Zn and Cu, but low to medium risk for Mn. Fractionation of Pb showed medium risk at most of the regions except at the eastern area, which revealed a high risk for the aquatic environment.