Fractionation Of Metals In Sediments Research Articles

Spatial and Temporal Variations and Risk Assessment of Heavy Metal Fractions in Sediments of the Pearl River Estuary, Southern China.

Sequential extraction was used to study the mobility and ecological risk of chemical fractions of six heavy metals in sediments collected from the Pearl River Delta (PRE) in China. Results revealed that residual fractions (F4) were the dominant forms for Cr and Ni in surface sediments, indicating that they were primarily stable in nature and had low bioavailability and ecotoxicity. Cd had a high environmental risk owing to its higher availability in acid-soluble fraction (F1), whereas Pb occurred predominantly in the reducible fraction (F2) in surface sediments. The profile variations of bioavailable fractions were generally consistent with socioeconomic development in the Pearl River Delta (PRD). A decreasing trend after 2006 suggested a reduction in heavy metal bioavailable fractions owing to the removal of heavy polluting industries and the effective control of sewage discharge. The risk assessment code suggested that the high mobility of Cd posed an extremely high risk and a threat to the aquatic environment.

Spatio-Temporal Variations and Risk Assessment of Heavy Metal Fractions in Sediments of the Pearl River Estuary, Southern China

Spatio-Temporal Variations and Risk Assessment of Heavy Metal Fractions in Sediments of the Pearl River Estuary, Southern China

Effect of Water Level and Salinity on Metal Fractionation in Sediments of the Yellow River Delta

In estuarine wetland ecosystems, the heavy metal content and especially the metal fractionation are influenced by water and salinity conditions. We collected sediments from the intertidal zone of the Yellow River Delta, where the water and salinity conditions changed frequently. The incubation experiments at different water and salinity levels were carried out in the laboratory to investigate the migration of Cr, Cu, Zn, Cd and Pb in the intertidal sediments. The results showed that the proportions of the residual fractions of Cr, Cu, Zn and Pb in the intertidal sediments were high, and the exchangeable Cd fraction was the highest. The Cr and Pb fractionations were significantly associated with the water level conditions. Different water level conditions were significantly related to the contents of the oxidizable fractions of Cr, Zn, and Cd. Except for the oxidizable Cu fraction, all Cu fractions were significantly correlated with the water conditions. Increasing salinity enhanced the migration risk of Cd and Pb. High salinity reduced the migration risk of Cr, Cd and Cu. The results of this study demonstrated that tidal floods increased the migration risk of Cd and Pb, and high salinity reduced the migration of Cr, Cd and Cu.

Waste management: impact on metal accumulation and speciation in Aba River channel, Nigeria

ABSTRACT The impact of indiscriminate disposal of waste materials on the quality of Aba River was examined in this research. Levels of Cd, Pb, Cu, Ni, Fe, Zn, Cr, and Mn were determined in water and sediments from Aba River. Modified BCR sequential extraction procedure was employed for the fractionation of metals in sediments. Levels of toxic metals in water (Cd, Pb, Ni, and Cr) were higher than their recommended limits for potable water. However, mean levels of all the metals except Fe were within their safe limits in sediment. Levels of all the metals in sediments were also higher than in water significantly at p < 0.05. Results showed that Cd, Pb, Ni, and Cr existed mostly in the non-residual fractions while essential elements (Cu, Fe, Zn, and Mn) existed mainly in the residual fraction. Consequently, toxic metals were more mobile and bio-available than the essential ones in Aba River. Cd, Pb, and Ni were metals with serious potential health risk to those exposed to the River. Principal component analysis revealed natural and anthropogenic factors as being responsible for the accumulation of metals in the studied Aba River.

Mobility and potential risk of sediment-associated heavy metal fractions under continuous drought-rewetting cycles

Ecological decline in the water level fluctuating (WLF) zone of the Three Gorges Reservoir (TGR) has been well established over the past decades. However, the effect of heavy metal fractions present in the sediment and their potential ecological risk under the anti-seasonal hydrological regime are still unclear. The Pengxi River is a tributary of the Yangtze River and it has a typical annual water level fluctuation ranging from 145 to 175m above sea level. The current study examined heavy metal fractions in sediments containing Cr, Cd, Cu, Pb and Mn collected along the WLF zone using the Tessier sequential extraction scheme. The total organic carbon (TC), total nitrogen (TN), carbon/nitrogen ratio (C/N), pH, particle size composition and content of nitrate (NO3−-N), and ammonium (NH4+-N) differed dramatically among the sampled altitudes and depths and was significantly correlated with the flooding time of the WLF zone. At lower altitudes of the WLF zone, the amounts of the exchangeable (EXC), carbonate-bound (CA) and total heavy metal contents of the surface sediment were much higher compared to those of higher altitudes of the WLF zone. The risk assessment code (RAC) for Cd and Mn showed an opposite trend to that of Cr, Cu, and Pb and mainly depended on the organic matter-bound fraction (OM). The modified RAC (mRAC) indicated a very high potential adverse effect for the whole WLF zone, although the risk value was much lower at the lower altitudes and upper depths of the WLF zone. Our results showed that the positive response of the loosely bound fractions (LOS) of heavy metals to the drought-rewetting (DRW) process minimizes the risk of heavy metals in the WLF zone sediment.

Contamination, Fractionation and Biological Risk Related to Metals in Surface Sediments from the Largest Deep Freshwater Lake in China.

The toxicity and mobility of metals in the environment are driven by their specific chemical forms and binding states. However, heavy metal fractionation in sediments from plateau deep lakes in China is rare. This study analyzed surface sediments collected from Fuxian Lake, the largest deep freshwater lake in China; parameters examined included total metal concentrations, chemical partitioning, and biological risk assessment. The average total concentrations (mg/kg) were 7.9 for Cd, 97.6 for Pb, 102.8 for Cr, 60.8 for Ni, 73.6 for Cu, and 112.9 for Zn; these levels were significantly higher than their corresponding background values. Cd was preferentially associated with the acid-soluble fraction; significant portions of the Pb, Cr, Ni, Cu, and Zn were mainly associated with the residual fractions. Overall, surface sediments of Fuxian Lake were associated with a 21% incidence of toxicity based on the mean effects range-median quotient. Cd was mainly at high or very high risk levels, and Cu and Zn were mainly at medium or high risk levels based on the risk assessment code (RAC).

Microplastics and potentially toxic elements in coastal sediments of Iran's main oil terminal (Khark Island)

Marine pollutants are becoming a growing concern due to their ecological consequences. This study investigates the potential risk posed by microplastics and toxic elements in coastal sediments of Khark Island, the main oil export hub of Iran. Principal component biplots exhibited a significant positive correlation between microplastic quantities (ranging in shape and color) and concentration of heavy metals with industrial activity. Source identification of the heavy metals indicated both natural and anthropogenic origin. Quality and risk assessment of the sediments revealed low to moderate pollution of Zn, Mo, Pb, Cu, Cd and As in some stations. Results of metal fractionation in sediments demonstrated that Cd, Mn, Zn, As and Pb are capable of posing a serious ecological risk due to potential bioavailability. Microplastics, mostly fragments and fibers, were detected in all sediment samples (ranging from 59 to 217 items/200 g dry sediment). A relatively good significant linear relationship exists between microplastic quantities and potentially toxic element/polycyclic aromatic hydrocarbon concentrations in coastal sediments. The results of this study confirmed the key role of microplastics as a “potential contaminant vector” for other types of pollutants.

Effects of algal bloom formation, outbreak, and extinction on heavy metal fractionation in the surficial sediments of Chaohu Lake.

The effects of algal bloom (AB) on the physicochemical and biochemical properties of water and sediment in lakes have been widely studied. However, limited attention has been directed toward the effects of the processes of AB formation, outbreak, and extinction on heavy metal fractionation in sediment. In this study, water and sediment samples were collected from the AB and free algal bloom (FAB) regions of Chaohu Lake from May to September in 2012. The chemical fractionation of seven heavy metals (Cd, Cr, Cu, Mn, Ni, Fe, and Pb) in sediment was determined by using a modified three-step sequential procedure. Evident processes of AB formation, outbreak, and extinction were observed in the AB region, but not in the FAB region. The TN and TP concentrations in water and sediment in the AB region were significantly higher than those in the FAB region. The water DO concentration was higher in the AB region than that in the FAB region before the early stage of the AB outbreak, but an opposite trend was observed in the stages that followed. Metal fractionation in sediment showed that except for Mn and Cu, the majority of metals were in the residual fraction regardless of the AB process. The AB process slightly altered the concentrations of metal fractions, except for reducible Fe and oxidizable Cu. The result showed that AB formation, outbreak, and extinction slightly affected heavy metal fractionation in sediment though water properties were significantly different among AB processes.

Heavy metal fractionation in sediments from the Jarama River (central Spain)

Concentrations of certain heavy metals are analyzed in sediments from the Jarama River, in the autonomous region of Madrid (Spain) as well as their variation along the river course. In addition, the distribution of heavy metals among the solid phases present in the samples is studied in accordance with the sequential extraction procedure of the European Union described in the Standard Material and Testing (SMT the second in the middle course of the river; and the third group, containing the most contaminated sediments, were samples from the lower course of the river.

Metal pollution in a contaminated bay: Relationship between metal geochemical fractionation in sediments and accumulation in a polychaete

Jinzhou Bay in Northern China has been seriously contaminated with metals due to the impacts of smelting activities. In this study, we investigated the relationship between metal accumulation in a deposit-feeding polychaete Neanthes japonica and metal concentration and geochemical fractionation (Cd, Cu, Pb, Zn and Ni) in sediments of Jinzhou Bay. Compared with the historical data, metals in the more mobile geochemical fraction (exchangeable and carbonate fractions) were gradually partitioned into the more stable fraction (Fe–Mn oxides) over time. Metal concentration and geochemical fractionation in sediment significantly affected metal bioavailability and accumulation in polychaetes, except for Ni. Metal accumulation in polychaetes was significantly influenced by Fe or Mn content, and to a lesser degree by organic matter. Prediction of metal bioaccumulation in polychaetes was greatly improved by normalizing metal concentrations to Mn content in sediment. The geochemical fractionation of metals in sediments including the exchangeable, organic matter and Fe–Mn oxides were important in controlling the sediment metal bioavailability to polychaetes.

Fractionation of heavy metals and assessment of contamination of the sediments of Lake Titicaca

Chemical weathering is one of the major geochemical processes that control the mobilization of heavy metals. The present study provides the first report on heavy metal fractionation in sediments (8-156 m) of Lake Titicaca (3,820 m a.s.l.), which is shared by the Republic of Peru and the Plurinational State of Bolivia. Both contents of total Cu, Fe, Ni, Co, Mn, Cd, Pb, and Zn and also the fractionation of these heavy metals associated with four different fractions have been determined following the BCR scheme. The principal component analysis suggests that Co, Ni, and Cd can be attributed to natural sources related to the mineralized geological formations. Moreover, the sources of Cu, Fe, and Mn are effluents and wastes generated from mining activities, while Pb and Zn also suggest that their common source is associated to mining activities. According to the Risk Assessment Code, there is a moderate to high risk related to Zn, Pb, Cd, Mn, Co, and Ni mobilization and/or remobilization from the bottom sediment to the water column. Furthermore, the Geoaccumulation Index and the Enrichment Factor reveal that Zn, Pb, and Cd are enriched in the sediments. The results suggest that the effluents from various traditional mining waste sites in both countries are the main source of heavy metal contamination in the sediments of Lake Titicaca.

Conventional, microwave, and ultrasound sequential extractions for the fractionation of metals in sediments within the Petrochemical Industry, Serbia

In this paper, the main objective was fractionation of Cd, Cu, Ni, Pb, Zn, Ca, Fe, and K in certificate material and sediment samples gathered from and around the Petrochemical Industry using the conventional, microwave and ultrasonic sequential extraction. Microwave oven and ultrasound bath were used as an energy source for achieving faster extraction. Additional heating and boiling of samples were avoided by using lower power and shorter time for microwave and ultrasound extraction. Precision and accuracy of procedure were evaluated by using certificate material (BCR701). Acceptable accuracy of metals (87.0-111.3 %) was achieved for all three-step sequential of conventional extraction protocol. An accuracy of the fourth step has been verified with two certificate materials: BCR143R and 146R. The range of total extracted metal concentrations from sediments was similar for all three extraction techniques. A significant high percentage of Cd, Cu, and Zn were obtained after extraction of the exchangeable and acid soluble sediment fraction. Principal component analysis of values obtained after determination of risk assessment code using conventional and ultrasound sequential extraction show similarity of these values. Accuracy, recovery, and risk assessment code values imply that ultrasound sequential extraction is a more suitable, accelerated sequential extraction procedure (30 min per extraction step) than microwave extraction in applied conditions.

Metal fractionation in sediments as a tool for assessing the availability of trace metals: The case of Apipucos Reservoir

The worldwide concern about trace metal pollution has been increasing in recent years due to the increase in anthropogenic trace metal inputs to the various ecosystems. The quantification of the chemical species of metals in sediments is essential for estimating the bioavailability of the metals in the environment. The objective of this study was to characterize the present level of metal pollution in the Apipucos Reservoir, Brazil, and determine its degree of toxicity to plants and animals. For this purpose, sediment cores were collected and its metal content (Zn, Pb, Cd, Co, Mn, Fe, Cu) was analyzed by atomic absorption spectrometry after sequential extraction. The results showed that there is more Fe and Mn than other metals (Fe>Mn>Pb>Zn>Cu). Besides, the concentrations of Fe and Mn are very high in the exchangeable and available phases, which are mobile and available fractions in sediments. The results also indicate that Fe, Mn and Cu could be mobilized under oxidizing conditions. Lead was found mainly in the reducible phase whereas Zn was found on available and reducible phases. Cobalt and Cadmium, although included in the set of metals analyzed, were not found in the sampled sediments. Sediment dating showed that the first sedimentary layers are about 30 years old.

Bioavailability of Metals in Contaminated Sediments

Bioavailability controls the transfer of metals from sediments to ecological receptors and humans. It can rarely be predicted from total metal concentrations because it is affected by metal geochemistry in sediments as well as the biochemistry, physiology, and behavior of benthic organisms. There is no single approach for including bioavailability in risk assessments because of variability in site specific conditions and the difficulty of validating methods. Acid-volatile sulfide and simultaneously extracted metals are useful in predicting bioavailability in anoxic sediments containing sulfides that react to form insoluble metal complexes. This method can be improved by adjusting for organic carbon and other ligands that also bind free metals. Site-specific desorption Kd values calculated by sequential extraction methods can be useful in predicting bioavailable metal fractions in oxic and anoxic sediments. A modified desorption distribution coefficient (Kdg) can be calculated by extraction with the digestive gut fluids of sediment feeding organisms to account for the effects of ingestion on metal release from sediments. Recently developed in situ measurement technologies can accumulate dissolved metals in a controlled fashion that may correspond with bioavailable metal fractions in sediment. Successful evaluation of bioavailability requires the selection of methods suitable for the organisms and sediment environments under consideration. A weight-of-evidence approach that incorporates multiple lines of evidence can help address uncertainties and increase the likelihood of incorporating bioavailability into remedial decisions.

Geochemical distribution and fractionation of heavy metals in sediments of a freshwater reservoir of India

Sediments of a polluted reservoir were evaluated for total contents of Cd, Cr, Cu, Ni, Pb and Zn along with their different geochemical forms (exchangeable, carbonate, Fe–Mn, organic matter and residual). Mineralogy of the sediments and physico-chemical parameters i.e. pH, OC and percentage of sand, silt and clay were also evaluated to see the dependency of heavy metals concentration on these parameters. The total concentration of heavy metals in the sediments varied according to sites and seasons. Except for station H1 which had moderately higher concentration of Cu (45.5 mg kg-1), concentrations of all other metals at all the sites under study were below the standard shale value. Maximum proportions of all metals were associated with the carbonate and residual fractions. The Risk Assessment Code showed a low risk for Cr, Ni and Zn, and a medium risk for Cu at station H3 and H4. On the basis of freshwater sediment quality guidelines, there is a strong possibility of Cr and Cu toxicity for aquatic biota of the reservoir. The data were further processed using Pearson’s correlation and factor analysis to obtain more accurate information about the behaviour of these metals. A positive relationship among the metals confirmed the anthropogenic sources of pollution in the reservoir. Significant positive relationships of heavy metals with the texture of the sediment were also obtained.

Mining-related contamination of surface water and sediments of the Kafue River drainage system in the Copperbelt district, Zambia: An example of a high neutralization capacity system

Contamination of the Kafue River network in the Copperbelt, northern Zambia, was investigated using sampling and analyses of solid phases and water, speciation modeling, and multivariate statistics. Total metal contents in stream sediments show that the Kafue River and especially its tributaries downstream from the main contamination sources are highly enriched with respect to Cu and exceed the Canadian limit for freshwater sediments. Results of sequential analyses of stream sediments revealed that the amounts of Cu, Co and Mn bound to extractable/carbonate, reducible (poorly crystalline Fe- and Mn oxides and hydroxides) and oxidizable (organic matter and sulfides) fractions are higher than in the residual ( Aqua Regia) fraction. Compared to Cu, Co and Mn, Fe is bound predominantly to the residual fraction. Values of pH in the Kafue River and its tributaries are alkaline in the contaminated area and concentrations of sulfate gradually increase downstream. Water balance based on sulfate indicates that inflow from the most contaminated tributaries is less than 5% of total discharge in the Kafue River. There is a significant input of Cu and Co from multiple contamination sources close to the town of Chingola, located on the Mushishima tributary, but both metals are mostly bound to suspended particles, which settle in the Kafue River. Additional contaminant sources such as the Uchi mine tailings and Nkana smelter are located in the industrial area around Kitwe, but metals released from these sources are mostly found in suspension and are attenuated efficiently. Low Fe/Cu ratios in suspension and mineralogical composition of stream sediments downstream of contaminant sources around Chingola indicate that native copper, Cu-sulfides, and Cu carbonates are present in stream sediments in addition to Cu bound to Fe(III) oxide and hydroxides. The Nkana smelter fingerprint in stream sediments is recognized by the presence of slag glass and a Cu-Fe-S intermediate solid solution (ISS). Speciation modeling suggests a possibility of precipitation of some Cu phases in the most contaminated tributaries such as the Mushishima. In the early dry period (mid-May) dissolved and suspended Cu and Co concentrations are lower than in the advanced dry period (late June). When the scale of mining and related activities in the Copperbelt is taken into account, the environmental impact of mining and related activities on the Kafue River is relatively limited due to a high neutralizing capacity of the mining wastes which control the rapid precipitation of iron oxides and hydroxides as well as adsorption and/or co-precipitation of copper, and cobalt. The high metal content in stream sediments, however, may pose a potential environmental risk during accidental acid spikes, when significant fractions of metals in sediments can be re-mobilized.

Study of heavy metal concentration and partitioning in the Estrela River: implications for the pollution in Guanabara Bay - SE Brazil

In this study, the geochemical analysis of ten sediment samples collected along the fluvial system of the Estrela River, which flows into the northern portion of Guanabara Bay, shows the presence of anthropogenic impacts in this area. Concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni obtained were slightly higher, when compared with values found in natural environments. The particle size and organic matter content in most of the analyzed stations showed features not conducive to the accumulation of pollutants due to the low organic matter content and the strong presence of sand fraction. There was also the fractionation of heavy metals in sediments and it was found the prominence of residual and reducible phase, besides the significant occurrence of organic fractions in some analyzed stations. These factors, thus, highlight the potential risks of contamination, where the metals associated with the organic phase can become bioavailable in processes of dissolution, provided by physico-chemical changes that can occur in this aquatic environment.

Metal fractionation in sediments of the Sergipe River, northeast, Brazil

The sequential extraction procedure proposed by the European Community Bureau of Reference (BCR) was applied for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in sediments from the Sergipe Estuary, Brazil. The method showed satisfactory recoveries, detection limits and standard deviations for trace metals determinations in sediment samples. Cd was the metal with the greatest percentage in the exchangeable fraction. Pb and Ni were present mainly in the reducible and oxidizable fractions. Cr, Cu and Zn were predominantly associated with the residual fraction. The order of mobility of metals extracted was Pb > Cd > Ni > Cu > Cr > Zn. According to the risk assessment code (RAC), the sediments showed low to medium risk for all metals.

Bioavailability and Concentration of Heavy Metals in the Sediments and Leaves of Grey Mangrove, Avicennia marina (Forsk.) Vierh, in Sirik Azini Creek, Iran

The concentration and bioavailability of Ni, Cu, Cd, Zn, and Pb in the sediments and leaves of grey mangrove, Avicennia marina, were studied throughout Sirik Azini creek (Iran) with a view to determine heavy metals bioavailability, and two methods were used. Results show that Zn and Ni had the highest concentrations in the sediments, while Cd and Cu were found to have the lowest concentrations in the sediments. Compared to the mean concentrations of heavy metals in sedimentary rock (shales), Zn and Cu showed lower concentration, possibly indicating that the origin of these heavy metals is natural. A geo-accumulation index (Igeo) was used to determine the degree of contamination in the sediments. Igeo values for Zn, Cu, Pb, and Ni showed that there is no pollution from these metals in the study area. As heavy metal concentrations in leaves were higher than the bioavailable fraction of metals in sediments, it follows that bioconcentration factors (leaf/bioavailable sediment) for some metals were higher than 1.

BIOACCUMULATION DYNAMICS OF HEAVY METALS IN &lt;sub&gt;Oreochromis nilotycus&lt;/sub&gt;: PREDICTED THROUGH A BIOACCUMULATION MODEL CONSTRUCTED BASED ON BIOTIC LIGAND MODEL (BLM)

In estuarine ecosystem, sediments are not only functioning as heavy metal scavenger, but also as one of potential sources for heavy metals to the ecosystem. Due the capability of aquatic organisms to accumulate heavy metals, there is possibility of heavy metals to exert their toxic effect towards the organisms and other organisms positioned in higher trophic level, such as fish, and further to human beings. To understand the different processes of heavy metal bioaccumulation in a dynamic manner, a bioaccumulation model is required. Since bioaccumulation starts with the uptake of chemical across a biological membrane, the bioaccumulation model was constructed based on Biotic Ligand Model (BLM). The input for the model was determined from laboratory scale simulated estuarine ecosystem of sediment-brackish water (seawater:Aquaâ 1:1) for determining the heavy metal fractions in sediments; simulated Oreochromis nilotycus - brackish water (fish-water) ecosystem for determining the rate constants; simulated fish-water-sediment ecosystem for evaluating the closeness between model-predicted and measured concentration, routes and distribution within specific internal organs. From these bioaccumulation studies, it was confirmed that the internalization of metals into the cells of gills and internal epithelias follows similar mechanisms, and governed mostly by the waterborne or hydrophilic heavy metals. The level of hydrophilic heavy metals are determined by desorption equilibrium coefficients, 1/KD, and influenced by salinity. Physiologically, the essential Cu and Zn body burden in O. nilotycus are tightly homeostasis regulated, shown as decreasing uptake efficiency factor, EW, at higher exposure concentrations, while non essential Cd and Hg were less or not regulated. From the distribution within specific internal organs, it was revealed that carcass was more relevant in describing the bioaccumulation condition than liver. It is clear that every heavy metal has its own bioaccumulation dynamics, depend to the metal studied and environmental conditions, however the obtained parameters are applicable to bioaccumulation of Cd and Hg in natural estuarine ecosystem of Segara Anakan, Central Java. Keywords: heavy metal, estuarine, bioaccumulation, model, dynamics