Modified BCR Sequential Extraction Research Articles

Ecological risk and chemical speciation of heavy metals in surface sediments of the Pearl River Estuary for comprehensive assessment

The Pearl River Estuary, a vital ecological and economic zone in Southern China, has been heavily impacted by industrial discharges, leading to significant heavy metal contamination. To address the ecological implications of different chemical forms of heavy metals, this study systematically evaluated the total concentrations and chemical speciation of Cu, Zn, Cd, and Pb in surface sediments (0–2 cm) collected from 17 sites. Chemical speciation was determined using a modified BCR sequential extraction procedure, and pollution and ecological risks were assessed via the geo-accumulation index (Igeo), potential ecological risk index (RI), and risk assessment code (RAC). The results showed that all four metals exceeded background values, with Cd presenting the highest enrichment (39 times) and contributing 97% of the ecological risk. Speciation analysis revealed that Cd predominantly exists in bioavailable forms, posing severe ecological threats. This study highlights the urgent need for targeted remediation strategies to mitigate Cd contamination and its ecological impact on the estuary.

Evaluation of Total Concentrations and Extractable Fractionations of Cd, Co and Ni in Soils from Dumpsites across Rivers State, Nigeria

The mobility of trace metals in soils strongly depends on the forms in which the metals are bound to major soil components. This study aims to determine the total concentrations and extractable fractionations of Cd, Co and Ni in soil samples collected from dumpsites across Rivers State, Nigeria. Solar Thermo Elemental Atomic Absorption Spectrometer model (SG 71906) was used after mixed acid digestion (HCl: HNO3 in a ratio of 3:1 v/v) and modified BCR sequential extraction procedure. The concentration levels of Cd, Co and Ni in all the samples varied, with mean values of 13.48 11.85, 25.29 17.62 and 20.52 15.66 mg/kg, respectively. Using the Community Bureau of Reference (BCR) sequential extraction procedure, the elements recoveries were within the acceptable range varying between 92.10% and 98.33% for Co and Cd, respectively. Data from the BCR extraction procedure revealed that the majority of Cd fraction was associated with residual fraction, Co fraction bound to the exchangeable fraction, while Ni was found to be associated with oxidisable fraction. These results suggest that the trace elements in the soil were highly mobile and bioavailable for plant uptake. Results from the findings particularly correlation analysis is indicative of the fact that some of the contaminants may have anthropogenic and natural origin. Hence, these contaminants could pose significant threat to human health and the environment.

First Comprehensive Analysis of Potential Ecological Risk and Factors Influencing Heavy Metals Binding in Sewage Sludge from WWTPs Using the Ultrasonic Disintegration Process

In this study, the occurrence, fractionation, and potential ecological risk associated with seven heavy metals (HMs), i.e., Cd, Cr, Cu, Ni, Pb, Zn and Hg in sewage sludge (SS) were investigated. The main aim of the study was to conduct the first comprehensive analysis of the potential ecological risk of HMs in SS collected from two municipal wastewater treatment plants (WWTPs) using ultrasonic disintegration (UD) of thickened excess sludge aimed at improving the effects of anaerobic digestion (AD). In order to assess the level of potential ecological risk, two groups of indices related to the total content of HMs and their chemical forms were used. For this purpose, a modified BCR sequential extraction was conducted. The obtained results revealed that according to the values of total indices, the highest potential ecological risk was posed by Cd, Cu and Zn (and to a lesser extent by Ni and Cr), while in relation to speciation indices by Ni, Zn, Cd (and in some cases by Cr). In general, the highest risk was indicated at the beginning (primary and excess SS) and the two final stages of sludge processing (digested and dewatered SS). This means that the level of ecological risk may strongly depend on the processes used in WWTPs and especially on AD, dehydration and the activated sludge process, as well as on the characteristics of raw wastewater. The results of the statistical analysis and balance sheets revealed that the key factors which may influence the way that HMs bind in SS are: pH, TOC, OM and Eh. The obtained results showed that UD does not cause any significant changes in the total HMs concentrations in SS, and their release into supernatant in the mobile forms. This proves that UD is a safe and environmentally friendly method of sewage sludge pretreatment.

Effects of Biochars Derived from Sewage Sludge and Olive Tree Prunings on Cu Fractionation and Mobility in Vineyard Soils over Time

Copper-contained products that are widely employed yearly in viticulture for vine disease management, lead to Cu accumulation in topsoil creating an increased risk for land workers and for leaching and/or uptake of Cu by plants, especially in acidic soils where Cu mobility is higher. In this study, the impact of two biochar types on Cu distribution and redistribution in fractions was evaluated in four acidic vineyard soils in relation to incubation time. The two biochars were derived from sewage sludge (SG) and olive tree prunings (OL). Soils (control) and biochar-amended soils with application rate of 20 % (w/w) were spiked with CuCl2 (160 mg kg−1) and incubated in the laboratory at ambient temperature 22 ± 5 °C. After 1, 3, 7, 15, 36, and 90 days of incubation, modified BCR sequential extraction procedure was used to determine Cu distribution in the four soil chemical phases and to examine potential Cu redistribution between these fractions both in soils and in amended soils with biochars. Results show that biochar amendment affects Cu distribution in different soil fractions. In SG treatment, from the 1st and up to 36th incubation day, both exchangeable and reducible Cu fractions decreased, while oxidizable Cu increased, in relation to control soils. At 90th incubation day, a redistribution of Cu was observed, mainly from the oxidizable to the residual fraction. In OL treatment, during the first 36 incubation days exchangeable and oxidizable Cu slightly increased, while reducible Cu decreased. At the 90th incubation day the higher percentage of Cu was extracted from the residual fraction, but exchangeable Cu was present in remarkable quantities in the three of the four studies soils. SG application in the studied soils highly restricted the availability of added Cu promoting Cu-stable forms thus reducing the environmental risk while OL did not substantially reduce Cu available fraction over the experimental incubation period. Fourier transformation infrared analysis (FTIR) provided convincing explanations for the different behavior of the two biochar types.

Estimating remobilization of potentially toxic elements in soil and road dust of an industrialized urban environment.

The mobility of potentially toxic elements (PTEs) is of paramount concern in urban settings, particularly those affected by industrial activities. Here, contaminated soils and road dusts of the medium-size, industrialized city of Volos, Central Greece, were subjected to single-step extractions (0.43M HNO3 and 0.5M HCl) and the modified BCR sequential extraction procedure. This approach will allow for a better understanding of the geochemical phase partitioning of PTEs and associated risks in urban environmental matrices. Based on single extraction procedures, Pb and Zn exhibited the highest remobilization potential. Of the non-residual phases, the reducible was the most important for Pb, and the oxidizable for Cu and Zn in both media. On the other hand, mobility of Ni, Cr, and Fe was low, as inferred by their dominance into the residual fraction. Interestingly, we found a significant increase of the residual fraction in the road dust samples compared to soils. Carbonate content and organic matter controlled the extractabilities of PTEs in the soil samples. By contrast, for the road dust, magnetic susceptibility exerted the main control on the geochemical partitioning of PTEs. We suggest that anthropogenic particles emitted by heavy industries reside in the residual fraction of the SEP, raising concerns about the assessment of this fraction in terms of origin of PTEs and potential environmental risks. Conclusively, the application of sequential extraction procedures should be complemented with source identification of PTEs with the aim to better estimate the remobilization of PHEs in soil and road dust influenced by industrial emissions.

Fractionation, Mobility and Environmental Risk of Trace Metals in the Sediments from N’zi River, Côte d’Ivoire

Despite increasing human activities, such as agriculture, little information is available on the status of trace metals contamination in rivers in developing countries including Côte d’Ivoire (West Africa). The aim of this study was study chemical fractions of Cu, Pb, Zn, and Ni, to identify mobility, sources and to evaluate ecological risks of traces metal in sediment of N’zi River using modified BCR sequential extraction procedure. The results showed that all metal were dominated by residual fractions. Labile fractions of Pb accounted for 0.0 – 68% of total contents indicating significant anthropogenic sources for Pb, while for Cu, Ni and Zn results suggesting natural sources. The potential mobility of the metals manifested following order: Ni > Zn > Cu > Pb. Risk assessment code indicated low to medium risk for Pb and low risk for other metals in the sediments.
 Cluster analysis (CA) and Matrix correlation were used to detect the relationship between the studied sampling sites and to see if some of the parameters interrelated with each trace metal concentration in exchangeable fraction. Results indicated high anthropogenic contamination at stations near to urban and agricultural areas.

Heavy-Metal Speciation Distribution and Adsorption Characteristics of Cr (VI) in the Soil within Sewage Irrigation Areas.

While sewage irrigation relieves water shortages in Northern China, its excessive application triggers a series of environmental problems, such as heavy-metal pollution. Soil profile and river sediment profile samples from the sewage irrigation area (SIA) were collected by selecting the farmlands in which sewage irrigation activity has been reported since the 1960s, around Huiji River (HJR) and Huafei River (HFR) in Kaifeng, Henan Province, China, as research areas. In this study, the total amount of heavy metals (Cr, Cd, Pb, Mn, Zn, and Ni) and the heavy-metal speciation analysis using the modified BCR sequential extraction method were used to evaluate the impacts of wastewater on agricultural soils and the potential risk. Furthermore, the least contaminated Cr (VI) was selected for the study of adsorption characteristics to determine the environmental capacity of soils for heavy metals when the composition of wastewater changes under long-term effluent irrigation conditions. The results show that: (1) the concentrations of heavy metals in soil continuously decreased with depth, while the opposite was observed in sediment, reflecting the continuous improvement in water quality over the historical period; (2) In the topsoil, the mean concentrations (mg·kg−1) in rank order are as follows: Mn (588.68) > Zn (284.21) > Pb (99.76) > Cr (76.84) > Ni (34.71) > Cd (3.25), where Cd exceeded the control value by 3.15 times around HFR, and sediment samples also showed higher heavy metal concentrations in HFR than in HJR; (3) Speciation distribution and risk assessment code (RAC) indicate that Mn and Cd were at medium risk and that Cd warrants attention due to its being a non-essential toxic element in humans; (4) The adsorption rates of soil in various layers in different profiles within SIAs for Cr (VI) gradually increased with the increasing initial content of Cr (VI). Among the three isothermal adsorption models, the fit result obtained by the Langmuir equation was superior to those obtained by the Freundlich equation and the linear equation.

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.

Geochemical fractions of trace metals in surface and core sections of aggregates in agricultural soils

Agrochemicals containing trace metals such as pesticides and fertilizer are intensively used in apple production systems in many countries. There is a risk of accumulation of trace metals, particularly in the sensitive root rhizosphere area. In this study, the trace metal concentrations of soils were determined in macroaggregates at the “mm scale” sampled from apple orchards. Soil samples were taken from five different locations at 0–20 cm soil depths in an apple orchard. Pseudo-total trace metal (Cd, Cr, Cu, Ni, Pb, and Zn) concentrations of soil samples separated from the surface and core sections of the soil aggregate were determined by digestion with Aqua regia. The modified BCR sequential extraction method was used to determine four operationally defined geochemical trace metal fractions in soil samples. The pseudo-total concentrations of Cd and Cu were significantly higher, and Zn was lower at the surface than in the core sections (paired-t test, p < 0.05) of soil aggregates. The concentrations of all trace metals in the acid-soluble fraction and reducible fractions were significantly higher at the surface of soil aggregates than those in the core section. The same was true for the sum of trace metal concentrations in the extracts of the three fractions considered potentially mobilizable, except for Cr. Our results demonstrated that Cd and Cu originated probably from agrochemicals accumulating significantly on aggregate surfaces, where they were in close contact with plant roots. The generally higher extractability of all trace metals on the surface of aggregates can be attributed to the preferential accumulation of newly-added trace metals in comparatively weakly bound chemical forms.

Sequential extraction studies on the river Tisa sediments for the assessment of the metal pollution

The sequential extraction procedure was applied for partitioning of metals in river sediments collected along the course of the river Tisa (Serbia). Eight elements (Sb, Sn, As, Cd, Cu, Hg, Pb and Zn) from twenty-one sampling site were analyzed using the modified BCR sequential extraction procedure in combination with ICP-OES. The results of sequential extraction, statistical analyses and calculation of EF and lithogenic and anthro?pogenic ratio of metals are similar. In the river Tisa sediments Sn, Cd, Hg, Pb and Zn are of anthropogenic origin, while As, Cu and Sb are of lithogenic and anthropogenic origin. The sediments from the river Tisa show high risk for Cd, medium risk for Hg and Zn, low risk for Sn, As, Cu and Pb, whereas Sb does not show the risk for the aquatic environment.

Rice busk biochar treatment to cobalt-polluted fluvo-aquic soil: speciation and enzyme activities.

Rice busk biochar was mixed with cobalt (Co)-polluted soil to examine the efficacy of biochar for Co immobilization and detoxification in fluvo-aquic soil. The Co speciation (modified BCR sequential extraction), fluorescein diacetate (FDA) hydrolysis and soil enzyme activities were investigated. In soil, the Co ions (acid-soluble fraction) could be uptake by biochar due to the microporous structure on the surface, as well as the oxygen-containing functional groups and conjugated structure in the molecular structure. Therefore, when the biochar concentration was lower than the optimum concentration (~6 g·kg-1), there was transformation of Co from the acid-soluble fraction to the oxidizable fraction, resulting in lower environmental risk. However, if the biochar concentration continued increasing, the distribution coefficient of Co in the acid-soluble fraction increased (P < 0.05). The biochar could also reduce the toxicity of Co, resulting in the negative correlations between soil enzyme activities (FDA hydrolysis, urease and alkaline phosphatases) and Co in the acid-soluble fraction (r = -0.816, -0.928 and -0.908, respectively, P < 0.01). When the biochar concentration ranged from 5.83 to 6.76 g·kg-1, the efficacy for Co immobilization and detoxification reached the maxima. To conclude, in fluvo-aquic soil, rice busk biochar is an effective amendment for immobilizing Co ions and reducing the toxicity of Co. The biochar concentration in soil should range from 5.83 to 6.76 g·kg-1 to reach the optimum efficacy.

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.

Distribution and partitioning of heavy metals in large anthropogenically impacted river, the Pearl River, China

In order to evaluate the distribution and partitioning characteristics of heavy metals in the large anthropogenically impacted Pearl River Basin, the contents of “anthropophile” elements (Cr, Ni, Cu, Zn, Cd and Pb, which are clearly influenced by human activities) were determined, and their partitioning coefficients (Kd) between water and sediments and enrichment factors (EF) were calculated for samples collected at different locations along the Pearl River main stream. The modified BCR sequential extraction procedure (proposed by the European Community Bureau of Reference in 1993), which involves the successive extraction of metals in a decreasing order of reactivity, was applied. Sediment samples from the upper, middle, and lower reaches were included in this study. The results showed that the content of most metals in water and sediment samples gradually increases from upstream to downstream, suggesting a possible input from human activities as shown by their increasing high EF, ranged from 1.4 to 3.9 for Cu, from 1.4 to 6.7 for Zn, from 2.5 to 59.1 for Cd, and from 1.7 to 8.9 for Pb, respectively. The higher partition coefficients (Kd) for Cr, Zn, and Pb (105–106) indicated that they were mainly transported in solid phase, while parts of Ni, Cu, and Cd were transported in dissolved phase as they display relatively lower Kd in the range of 104–105. According to the results of the BCR leaching, the percentage of non-residual fraction of heavy metals in the sediments showed a decreasing order of Cd > Pb > Zn > Cu > Ni > Cr, implying that Cd and Pb were more active and bioavailable compared to the other four metals, and thus would be potentially more harmful to the watershed ecosystem.

Cobalt speciation and phytoavailability in fluvo-aquic soil under treatments of spent mushroom substrate from Pleurotus ostreatus.

Cobalt (Co) is a nutrient for soil microorganisms and crops, as well as a worldwide industrial pollutant. When the level of Co exceeds the acceptable limit, this heavy metal can lead to devastating consequences for soil environments. There is considerable attention and concern about elevated levels of Co contaminating soil and crops. Spent mushroom substrate (SMS) is a potential amendment for the adsorption of pollutants, which has potential for resolving Co-polluted soil that spans the world. To investigate the environmental behavior and risks associated with Co in fluvo-aquic soil under specific treatments of SMS from Pleurotus ostreatus, a lab-scale pot experiment was conducted. SMS and exogenous Co were added to soil, which was retained for approximately 30days. Pakchois (Brassica chinensis L.) were planted in the treated soil for 28days until harvest. The Co speciation in soil (modified BCR sequential extraction) and Co accumulation in pakchoi tissue were studied. When the SMS concentration was within a range of 0 to 9gkg-1 (total amount = 0 to 2.7g), Co in the acid-soluble fraction was transformed to the oxidizable fraction in soil, resulting from the mesh structure on the surface of SMS, as well as the amide and carboxyl in the SMS molecular structure. In this situation, the Co accumulation levels in the pakchois decreased significantly (P < 0.05), indicating the efficacy of SMS for reducing Co phytoavailability. However, when the SMS concentration reached 12gkg-1, the phytoavailability increased again (P < 0.05). When the SMS concentration ranged from 8.86 to 9.51gkg-1, the Co phytoavailability in soil reached a minimum, while the biomass of pakchoi reached a maximum. Conclusively, SMS from Pleurotus ostreatus are effective for reducing the Co phytoavailability, as well as for reducing the chance of Co transferring into a human's body through crops (i.e., food consumption). In order to achieve the optimum efficacy, the SMS concentration in soil should be maintained at a range of 8.86 to 9.51gkg-1.

Speciation of Metals in Soils and Water: Risk Assessment

Scarce management of solid wastes, excessive wastewater discharge and irrigation with noxious water are among the main causes of heavy metal contamination in agricultural soils. The soils of upper Litani basin in Lebanon are subjected to these sources, beside soil irrigation by Litani river water, contaminated by wastewater. However, the metal mobility, bioavailability, or potential risk can be elucidated by metal soil and water chemical speciation. This study involved the metal speciation in soils of the upper Litani basin, and computation of pollution indices for risk assessment. A modified BCR sequential extraction technique was implemented to soil samples that operationally extract metals sequentially from fractions termed as acid soluble, reducible, oxidizing, and residual. Beside, soil pH, Eh and TOC, macro-water parameters, and metal water content were measured. The geochemical computer model PHREEQC was used to predict water metal species. Data indicated that Mn, Zn, Cr, and As had their highest average percentage from total metal in the reducible and acid soluble soil fractions, while Cu, Ni, Cd, Hg were in the oxidizing and acid soluble soil fractions. Metal speciation was related to TOC, Eh and water BOD. The average values for the indices indicated: enrichment factor and geo-accumulation of severe enrichment and very strong contamination for Cd and Hg; risk assessment high risk for Cr, Ni, and Cd; and 50% of sites suffered from considerable contamination according to the global contamination factor. The highest percentage of water species were for Mn, Zn, Ni, and Cd, the free metal aqua ion.

Solid-phase distribution and mobility of thallium in mining-metallurgical residues: Environmental hazard implications

Thallium (Tl) and its compounds are non-essential and highly toxic for living organisms, even at low concentrations. In this paper, we analyzed the presence and geochemical distribution of Tl in different mining-metallurgical and sediment samples collected from several mining zones of Mexico. A modified BCR sequential extraction procedure was also applied to the samples to investigate the geochemical behavior and potential environmental risk of Tl according to types of ore deposit and mineral processing method applied. Results revealed the presence of Tl in the majority of the mining-metallurgical samples, with labile concentrations reaching up to values of 184.4 mg kg−1, well above the environmental standards. A comparison of Tl partitioning in different samples showed that Tl was usually found associated with labile fractions instead of entrapped in the environmentally-passive residual fraction. Specifically, high levels of Tl were extracted from the exchangeable/acid-extractable and poorly-crystalline reducible fractions, suggesting its association with both soluble and amorphous Fe-Mn oxyhydroxides, respectively. Besides, Tl was also frequently found associated with the crystalline reducible fraction, presumably bonded to manganese oxides and jarosite-like minerals. Lastly, little amounts of Tl were extracted from the oxidizable fraction. Considering the fractionation of Tl in these mining-metallurgical samples, they may pose a significant environmental hazard. This study provides useful insights into the potential sources of Tl pollution in Mexico and emphasizes the need for further research to determine the extent of its impact and to develop effective remediation protocols to protect the environment from Tl toxicity.

Heavy metal mobility and valuable contents of processed municipal solid waste incineration residues from Southwestern Germany

As conventional end-of-life disposal, municipal solid waste (MSW) incineration residues can be problematic due to potential release of toxic compounds into the environment. Using municipal solid waste incineration residues as urban-mine of valuable metals (e.g. precious metals) could provide a trash-to-treasure possibility. The objectives of the study are to (i) determine the contents of different contaminant metallic elements (Zn, Cu, Ba, Pb, Cr and Ni) in four size fractions of MSW incineration residues and discuss their mobility potential by using the modified BCR sequential extraction method; (ii) investigate the level of valuable critical contents (precious metals, rare earth elements, etc.) in these wastes. We also characterized mineralogy and elemental composition of four different grain size fractions (0–0.5, 0.5–2.0, 2.0–4.0 and 4.0–16.0 mm) of processed municipal solid waste incineration residue (PIR) from the Southwestern region of Germany, using X-ray fluorescence, X-ray powder diffraction and different spectroscopic techniques. Among all studied size fractions, grains smaller than 2 mm contained higher amounts of total extractable heavy metals in most cases. The most important finding of the study is that the total contents of Cu, Au and Pt in the incineration residues reached economically profitable levels (5.1 g/kg, 21.69 mg/kg and 17.45 mg/kg, respectively).

Comparison of diffusive gradients in thin-films (DGT) and chemical extraction methods for predicting bioavailability of antimony and arsenic to maize

Antimony (Sb) and arsenic (As) are hazardous metalloids that cause much attention. Assessing the bioavailability is essential for understanding the potential risk and toxicity of Sb and As in soils. In this study, a set of methods were tested to assess the bioavailability of Sb and As to field/potted maize. Twelve soils, 7 maize (Zea mays L.) samples and corresponding root soils were collected from the world's largest active Sb mining area (Xikuangshan, China). The soils contained average 1074 mg/kg Sb and 65 mg/kg As with the pH varied from 4.78–7.70. Eight soil samples with a gradient of Sb and As concentration were selected for pot experiments of maize. Diffusive gradients in thin-films (DGT) and traditional chemical extraction methods, including six single-step extractions (H2O, 0.01 M CaCl2, 1 M NH4NO3, 0.1 M Na2HPO4, 0.05 M EDTA and 0.005 M DTPA) and modified-BCR sequential extraction were used to predict the bioaccumulation of Sb and As by maize. Sb and As measured by DGT, DTPA and modified-BCR correlated better with Sb and As in the shoots and roots of field/potted maize compared to H2O, CaCl2, NH4NO3, Na2HPO4 and EDTA. The correlation coefficients of DGT, DTPA and modified-BCR were at least 0.869 (p < 0.01), 0.866 (p < 0.01) and 0.831 (p < 0.05), respectively. These three techniques are well applicable for simultaneous prediction of Sb and As bioavailability to both field and potted maize in soils.

Relation between different metal pollution criteria in sediments and its contribution on assessing toxicity

Several tools have been developed and applied to evaluate the metal pollution status of sediments and predict their potential ecological risk assessment. To date, a comprehensive relationship between the information given by these sediment tools for predicting metal bioavailability and the effective toxicity observed is lacking. In this work, the possible inter-correlations between the data outcoming from using several qualitative evaluation tools of the sediment contamination (contamination factor, CF, the enrichment factor, EF, or the geoaccumulation index, Igeo), metal speciation on sediments (evaluated by the modified BCR sequential extraction procedure) and free metal concentrations in pore waters were studied. It was also our aim to evaluate if these assessment tools could be used for predicting the pore waters toxicity data as toxicity proxy. Principal component analysis and cluster analysis revealed that two quality indices used (CF and EF) were highly correlatable with the more labile fractions from BCR sediment speciation. However, neither of these parameters did correlate with the toxicity of pore waters measured by the chronic toxicity (72 h) in Pseudokirchneriella subcapitata. In contrast, the toxic effects of the given total metal load in sediments were better evaluated by using an additive metal approach using pore water free metal concentrations.

Speciation of heavy metals Cu, Ni and Zn by modified BCR sequential extraction procedure in sediments from Banten Bay, Banten Province, Indonesia

Banten Bay is categorized as a marine area that is busy with marine tourism activities, settlements and also industries. One potential impact of the condition is the occurrence of pollution from both industrial and domestic sources, erosion and sedimentation in the coastal environment. Samples were collected from 25 representative stations in April 2016. Chemical speciation of three heavy metals (Cu, Ni, and Zn) was studied using a modified sequential extraction procedure proposed by the European Standard, Measurements and Testing (SM&T) program, formerly the Community Bureau of Reference (BCR). The aims of this study are to determine geochemical speciation of 4 bounds of metal: acid-soluble, reducible, oxidizable and residual, and to assess their impacts in the sediments of Banten Bay, Indonesia. The result shows that the percentage of Copper (45.90-83.75%), Nickel (18.28-65.66%), and Zinc (30.45-79.51%) were mostly accumulated in residual fraction of the total concentrations. The Risk Assessment Code (RAC) reveals that about 0-7.07% of Copper and 1.11-24.35 % of Zinc at sites exist in exchangeable fraction and therefore, they are in low risk category. While 7.34-34.90 of Ni at sites exists in exchangeable fraction and therefore, it is in medium risk category to aquatic environment.