Speciation Of Pb Research Articles

Speciation and risk assessment of Zn, Pb, and Cd in bottom sediments of two small upland dam reservoirs, Poland

Sediments of two small dam reservoirs in Poland, Zalew Zemborzycki (ZZ) and Brody Iłżeckie (BI), were studied. Sediments from both reservoirs were sampled at 17 sites in the transects perpendicular to the shoreline, at the river inflow and the frontal dam and analysed using the BCR procedure for speciation of zinc (Zn), lead (Pb) and cadmium (Cd). The risk assessment code (RAC) and the individual contamination factor (ICF) were determined. In BI, the sediments were removed from the considerable part of the reservoir, creating an opportunity to study the effect of dredging on the speciation of trace metals. Trace metals partitioning was differentiated according to the transect/site and in the case of BI sediments also on the transect location in the dredged or undredged part of the reservoir. Considering ZZ sediments, the order of fractions for Zn, Pb and Cd according to a decreasing overall mean percentage contribution to total metal content was the same: F4 (residual) >F3 (oxidisable) >F2 (reducible) >F1 (acid soluble). In sediments of ZZ at most sites, the RAC for Zn, Pb and Cd revealed low or medium risk and ICF low or moderate contamination. For BI sediments, the order of fractions for Pb was similar while for Zn and Cd quite the opposite compared to the sediments of ZZ and it was: Pb–F4>F3>F1>F2, Zn–F1>F3>F2>F4, Cd–F1>F2>F3>F4. For BI sediments, RAC values for Zn, on average, indicated high and very high ecological risk; for Pb low and moderate risk and for Cd – high risk in the initial part and dredged part and according to the average value in the reservoir, while a medium risk in undredged part sediments. The ICF index showed high contamination with Cd for all BI sediments. The sequential analysis showed that Pb is poorly mobile as in sediments of both reservoirs residual fractions accounted, on average, for about 60% of the total content.

Contamination Assessment and Chemical Speciation of Lead in Soils and Sediments: A Case Study in Aguascalientes, México

Lead (Pb) contamination was evaluated in 24 contaminated soils and sediments samples, representative of areas affected by mining, agricultural, commercial and residential activity, during the rainy and dry season. Pseudo-total concentration in soils (15.7–527.2 mg kg−1) and sediments (16.3–4273.3 mg kg−1) was determined and protocols were developed to analyze its chemical form, potential mobility and bioavailability. Five geochemical phases (exchangeable fraction, carbonate fraction, Fe/Mn oxide fraction, organic fraction and residual fraction) were obtained for the determination of Pb speciation and mobility using a modified Tessier sequential extraction procedure. The predominant fraction was the Fe/Mn oxide bound (both for soils and for sediments). However, their calculated mobility factors were 26% and 28%, respectively, representing significant risk to the environment. Geo accumulation values ranged from −0.7 to 4.4 (“Unpolluted”–“Highly to extremely polluted”) for soils and from −0.6 to 7.4 (“Unpolluted”–“Extremely polluted”) for sediments, suggesting the influence of human activity on the environment, mainly at sites located in the vicinity of the mine. Enrichment Factor values ranged from 2.1 to 87.8 for soils and from 2.5 to 698.7 for sediments (“Moderated enrichment”–“Extremely high enrichment”); values above 1.5 suggesting anthropogenic origin, thus representing a risk for biological organisms present in freshwater. In summary, these environmental indicators demonstrated than even in sites with low Pb concentration, contamination was observed, thus highlighting the need for continued monitoring due to the potential for significant public health risks.

Impact of smelter re-development on spatial and temporal airborne Pb concentrations

Total suspended particulate (TSP) and PM10 filters collected from two ambient air monitoring stations in Port Pirie were analysed to determine the impact of a lead (Pb) smelter redevelopment on air quality parameters including total elemental concentration, Pb isotopic ratio, Pb bioaccessibility and Pb speciation. Filters from 2009 to 2020 were analysed with a focus on samples from 2017 (immediately prior to smelter redevelopment) and 2020 (post-smelter redevelopment). Lead concentration in 2009–2020 TSP was variable ranging up to 6.94 μg m−3 (mean = 0.57 μg m−3), however, no significant decrease in Pb concentration was observed at either Port Pirie West (p = 0.56, n = 34) or Oliver Street (p = 0.32, n = 28) monitoring stations when 2017 and 2020 TSP values were compared. Similarly, no significant difference (p = 0.42) in PM10 Pb concentration was observed in 2017 (mean = 0.80 μg m−3) and 2020 (0.60 μg m−3) Oliver Street filters. Although no change in percentage Pb bioaccessibility was observed when 2017 and 2020 Port Pirie West TSP samples were compared (mean of 88.7% versus 88.0%), Pb bioaccessibility was lower (p < 0.005) in both 2020 TSP (mean of 83.9% versus 62.9%) and PM10 (mean of 70.8% versus 58.3%) Oliver Street filters compared to 2017. While scanning electron microscopy, energy dispersive x-ray spectroscopy identified a number of Pb phases within filters (galena, anglesite, cerussite, conglomerates), differences in Pb speciation between 2017 and 2020 filters could not be identified although it was presumed that this influenced Pb bioaccessibility outcomes at Oliver Street. Data from this study suggests that recent smelter redevelopments have not significantly decreased the concentrations of airborne Pb in Port Pirie although re-entrainment of soil-Pb from historical impact may also be a contributing Pb source.

The impact of gold ore mining on total lead (Pb) concentration in some mining and residential communities in Zamfara State, Nigeria

Illegitimate artisanal gold mining quite often results in elevated lead (Pb) concentrations in mining and residential areas close to ore mining sites, which exposes the communities to varying degrees of health and environmental challenges.Here,mining and residential soils from Abare, Dareta and Bagega, Anka local government,Zamfara state's exposed communities, were examined for total Pb concentration.Three replicates of soil from four different soil fields in mining and residential areas were carefully selected for sampling from the surface layer 0 to 21 cm.All thesoil samples were digested and analysed using flame atomic absorption spectrophotometry (Varian model-AA240FS). The total Pb concentration in the mining areas ranges from 466.01-729.13 mg/kg (Abare), 151.34-168.21 mg/kg (Bagega) and 108.89-258.88 mg/kg (Dareta), while those from the residential areas ranges from 326.28-391.38mg/kg (Abare), 67.74-79.44 mg/kg (Bagega) and 17.58-43.40mg/kg (Dareta).This study revealed that the Pb concentration in all mining areas exceeded the standard ofthe department of petroleum resources of Nigeria's 85 mg/kg threshold (DPR).According to the study, the only residential communities with Pb concentrations above the DPR threshold are those in Abare.Based on the computed degree of contamination indices in those areas using the single pollution index (SPI) and Nemerow composite pollution index (NCPI), the study revealed the residential sites are within the safety limit, whereas the mining sites are slightly contaminated. Nevertheless, more studies are needed to determine the Pb speciation in those areas.

Remediation of Pb-contaminated soil using modified bauxite refinery residue

This study examines amendment of Pb-contaminated soil with modified bauxite refinery residue (MBRR) to decrease soil Pb mobility and bioaccessibility. Amendment experiments were conducted using four soils contaminated with Pb from various sources, including smelting, shooting-range activities and Pb-based paint waste. Lead L3-edge X-ray absorption spectroscopy (XAS) indicated that Pb speciation in these soils was a mixture of Pb sorbed to Fe (hydr)oxide and clay minerals, along with Pb bound to organic matter. Amendment with MBRR decreased water-soluble Pb and/or Toxicity Characteristic Leachate Procedure (TCLP) Pb concentrations. Lead L3-edge XAS and X-ray diffraction (XRD) indicated that Pb retention by MBRR occurred via sorption to Fe- and Al-(hydr)oxides at low Pb loadings, in addition to formation of hydrocerussite (Pb3(CO3)2(OH)2) at high loadings. Soil amendment with MBRR had relatively little effect on gastric-phase Pb bioaccessibility; as quantified via the Solubility/Bioavailability Research Consortium, SBRC, in vitro assay. In contrast, amendment with MBRR caused substantial decreases in relative intestinal-phase Pb bioaccessibility (Rel-SBRC-I) due to increased Pb sorption by MBRR’s Fe- and Al-hydr(oxide) minerals as simulated GI tract conditions shifted from the gastric- to the intestinal-phase. These decreases in Rel-SBRC-I point to the potential efficacy of using amendment with MBRR to decrease soil Pb bioavailability.

Impact of Pyrolysis Temperature and Application Amount of Sewage Sludge Biochar on the Speciation and Bioavailability of Cd and Pb in Paddy Soil

Impact of Pyrolysis Temperature and Application Amount of Sewage Sludge Biochar on the Speciation and Bioavailability of Cd and Pb in Paddy Soil

Heavy metals concentrations and speciation of Pb and Ni in airborne particulate matter over two residential sites in Greater Cairo - reflection from synchrotron radiation.

Synchrotron radiation-based techniques [X-ray absorption near-edge structure (XANES) and X-ray fluorescence (XRF)] combined with inductively coupled plasma-mass spectrometry (ICP-MS) were used for the assessment of heavy metals concentrations as well as lead (Pb) and nickel (Ni) speciation in airborne particulate matter (PM10) over two residential sites in Greater Cairo. Nineteen 24 h high-volume samples collected at Giza (G) Square and Helwan (H) University (Egypt) were selected for this study. Mean concentrations of heavy metals in PM10 at both sites were found to have the same descending order of Pb > Cu > Ni > Cd > Co > As, of which concentrations of Pb, Cu, Ni and Cd in H samples were higher than those in G samples. For Pb, synchrotron-based XRF results were in good agreement with concentrations obtained by ICP-MS. The XANES spectra of PM10 at the Pb L2-edge and Ni K-edge were compared with those of Pb and Ni in model standard compounds to provide information on the potential oxidation states as well as the chemical forms of those elements. The data show that Pb has similar chemical environments in both series G and H with the predominance of Pb2+ oxidation state. Nickel was found as Ni(OH)2, NiO and Ni metal in the analyzed samples. However, the content of Ni in the background filter shows a very strong interference with that of the collected PM10. Carcinogenic and non-carcinogenic risks resulting from the inhalation of the studied heavy metals were assessed for children and adult residents and were found below the safe limits, at both sites.

Exploring Nanogeochemical Environments: New Insights from Single Particle ICP-TOFMS and AF4-ICPMS.

Nanogeochemistry is an emerging focus area recognizing the role of nanoparticles in Earth systems. Engineered nanotechnology has cultivated advanced analytical techniques that are also applicable to nanogeochemistry. Single particle inductively coupled plasma ICP-time-of-flight-mass spectrometry (ICP-TOF-MS) promises a significant step forward, as time-of-flight mass analyzers enable simultaneous quantification of the entire atomic mass spectrum (∼7–250 m/z+). To demonstrate the utility of this approach, samples were collected and analyzed from a large, boreal river, and its surrounding tributaries. These samples provided us with a diversity of particle compositions and morphologies, while their interconnected nature allowed for an examination of the various nanogeochemical processes present in this system. To further expand on this effort, we combined this high-throughput technique with AF4-ICPMS, focusing on major carriers of trace elements. Using spICP-TOF-MS, Al, Si, and Fe were grouped into classes having all combinations of one or more of these elements. Particle-by-particle ICP-TOF-MS analysis found chemically heterogeneous populations, indicating the predominance of diverse mineralogy or heteroaggregates. The importance of suspended Fe and Mn for the speciation of Pb was observed by single particle ICP-TOF-MS and complemented by AF4-ICPMS analysis of dissolved organic matter and nanoparticulate Fe/Mn. Our study exploits the combination of spICP-TOF-MS and AF4-ICP-MS for studying isotopic and elemental ratios (mineralogy) of individual nanoparticles, which opens the door to further explore the mechanisms of colloid facilitated transport of trace elements.

Vertical Distributions and Bioavailabilities of Heavy Metals in Soil in An-Tea Plantations in Qimen County, China

Heavy metals mainly enter tea from the soil. In this study, stratified soil samples were collected, at a depth of 0–60 cm, using a soil drill in An-tea plantations. Speciation of As, Cd, Cr, Cu, Ni, Pb, and Zn was determined using the European Community Bureau of Reference sequential extraction method, and the heavy metal concentrations in the extracts were determined by inductively coupled plasma−mass spectrometry. Compared with other soil layers, the mean Cd, Cu, Pb, and Zn concentrations were highest in the 0–20 cm layer, the Ni concentrations were highest in the 20–40 cm layer, and the As and Cr concentrations were highest in the 40–60 cm layer. The mean contributions of the non-residual fractions, including the acid-soluble, reducible, and oxidizable fractions, to the total concentrations were higher than those of the residual fraction for Cr, Cu, and Ni at all depths in soil from a flat area, as well as for Cd and Zn at all depths in soil from a sloping area. The contributions of non-residual fractions to the total As and Pb concentrations were higher than those of the residual fraction in soil from a depth of 0–20 cm from the flat area and soil from a depth of 20–60 cm from the sloping area. The total heavy metal concentrations correlated well with the acid-soluble fraction and reducible fraction concentrations in soil from 0–40 cm.

Ecological and Health Risk Assessments Based on the Total Amount and Speciation of Heavy Metals in Soils Around Mining Areas

Topsoil and supporting crop samples around a mining area were collected in Longyan City, and the total amounts and speciation of Pb, Cd, and As in the samples were determined. The ecological risk and human health risk assessment of soil heavy metals Pb, Cd, and As were carried out using the Hakanson potential ecological risk assessment method, the ecological risk classification method based on the principle of geochemical statistics, and the health risk assessment method in accordance with the characteristics of human exposure parameters in China. The results indicated that the heavy metal elements in the soil in the study area exceeded the environmental quality standards for Pb and Cd, and the heavy metal contents in cereal grains exceeded the food limit value mainly for Pb. The proportion of the four bioavailable forms except the residue state followed the order of Pb>Cd>As. The ecological risk assessment results based on the total amount of heavy metals and bioavailable forms showed that Cd was the most important ecological risk factor. The single potential ecological risk of Cd and the comprehensive ecological risk of Pb, Cd, and As in the soil based on bioavailable forms were significantly reduced compared with that based on the total amount. The proportion of medium and superior samples decreased from 100% and 50.0% to 17.2% and 7.81%, respectively, and the divided risk zone basically contained all the warning points of exceeding the standard of crops. Oral ingestion was the main carcinogenic and non-carcinogenic exposure route of heavy metals. In terms of carcinogenic risk, the risk of human carcinogenic health exposure to Cd and As was within the acceptable range, regardless of whether bioavailability was considered. Among the non-carcinogenic risks, the non-carcinogenic risk of the heavy metal Cd was negligible. When only the total amount of heavy metals was considered, the non-carcinogenic risk index of Pb and As under the three exposure pathways ranged from 0.14 to 8.65 and from 0.04 to 2.85, respectively. After considering the adjustment of bioavailability, the non-carcinogenic risk of As was greatly reduced and could be considered to no longer have non-carcinogenic risk. Although the non-carcinogenic exposure risk index of Pb was reduced by 84.7%, the maximum value still reached 1.69, which would cause non-carcinogenic harm to the population and was the key to soil remediation in mining areas.

Vinegar residue biochar: A possible conditioner for the safe remediation of alkaline Pb-contaminated soil

A better understanding how to modulate alkaline soil-plant systems with lead (Pb) toxicity with by vinegar residue biochar is important for the remediation of Pb-contaminated soil. Leaching column and pot experiments were conducted to investigate the effect of vinegar residue biochar on Pb speciation, soil properties, and plant growth under Pb stress. The results indicate that biochar could effectively decrease the exchangeable and carbonated-bound Pb but increase the Fe–Mn oxide and residue fractions in the soil with Pb at 500 mg kg−1. Biochar did not effectively immobilize Pb in the soil with Pb at 1000 mg kg−1. After leaching, biochar evidently increased the organic carbon and dissolved organic carbon content of the soil, but slightly affected the pH, cation exchange capacity and carbonate content. The biochar addition at 0.5% had no significant effect on soil aggregates, and biochar at 2.0% and 5.0% significantly decreased soil aggregate stability. The dry weight and soluble protein content of pak choi (Brassica chinensis L.) increased with biochar treatment. Lead assimilation by plants was inhibited by the decreased availability of Pb in biochar-treated soils. Soil enzymes activities also significantly increased, then facilitated biochemical reactions in the soil environment. The applied biochar has shown an important role in mitigating Pb toxicity by increasing the soil organic carbon, dissolved organic carbon content, enzyme activities, and plant growth. The low dose biochar (0.5–2.0%) are recommended as references for subsequent experiments, especially in alkaline loam soil.

Chemical and algological composition of the snow cover at the mouth of the Onega river (White Sea basin)

Abstract In the study, the content and speciation of Mn, Pb, Cd, Zn, Cr, Ni, Co, Cu, and Fe in the snow cover at the mouth of the Onega river (White Sea basin) at the end of the winter periods in 2018, 2019 and 2020 were determined. Winter 2019 year was the snowiest, as the maximum values of the snow cover depth and water equivalent were almost two times higher than in all other years. The total content of suspended matter in the snow cover was 0.2–5.5 μg/L. Increased concentrations of suspended solids were identified near highways. Mn, Cr and Ni were present in the snow cover mainly in their dissolved form, while Fe, Pb and Co were mostly contained as solids. The algological composition of the snow cover was also studied.

Plumbojarosite Remediation of Soil Affects Lead Speciation and Elemental Interactions in Soil and in Mice Tissues.

Lead (Pb) contamination of soils is of global concern due to the devastating impacts of Pb exposure in children. Because early-life exposure to Pb has long-lasting health effects, reducing exposure in children is a critical public health goal that has intensified research on the conversion of soil Pb to low bioavailability phases. Recently, plumbojarosite (PLJ) conversion of highly available soil Pb was found to decrease Pb relative bioavailability (RBA <10%). However, there is sparse information concerning interactions between Pb and other elements when contaminated soil, pre- and post-remediation, is ingested and moves through the gastrointestinal tract (GIT). Addressing this may inform drivers of effective chemical remediation strategies. Here, we utilize bulk and micro-focused Pb X-ray absorption spectroscopy to probe elemental interactions and Pb speciation in mouse diet, cecum, and feces samples following ingestion of contaminated soils pre- and post-PLJ treatment. RBA of treated soils was less than 1% with PLJ phases transiting the GIT with little absorption. In contrast, Pb associated with organics was predominantly found in the cecum. These results are consistent with transit of insoluble PLJ to feces following ingestion. The expanded understanding of Pb interactions during GIT transit complements our knowledge of elemental interactions with Pb that occur at higher levels of biological organization.

Immobilization of lead by amendments in a mine-waste impacted soil: Assessing Pb retention with desorption kinetic, sequential extraction and XANES spectroscopy

Chemical stabilization is an in-situ remediation that uses amendments to reduce contaminant availability in polluted soils. Rates of phosphate, lime, biochar, and biosolids were evaluated as affecting Pb speciation and mobility in soil samples of a mining area located in Vazante, state of Minas Gerais, Brazil. Chemical and mineralogical characterization, desorption kinetics, sequential extraction, leaching evaluation in columns and speciation using X-ray absorption near edge structure were performed. Pb adsorbed on bentonite and on anglesite were the predominant species in the unamended soil. The treatments with phosphate and lime transformed part of the Pb species to pyromorphite. Conversely, part of Pb species was transformed to Pb adsorbed on citrate in the soil amended with biochar, while PbCl2 was formed in soil samples amended with biosolids. Phosphate and lime increased the Pb extracted in the residual fraction, thus showing that more recalcitrant species, such as pyromorphite, were formed. Biosolids and biochar treatments decreased the Pb in the residual fraction, and the fraction associated to organic matter increased after the addition of biosolids. Phosphate and lime were effective to immobilize Pb and to decrease Pb desorption kinetics, but the organic amendments increased the desorption kinetics of Pb in all rates applied. The soil amended with phosphate decreased the Pb leached in the experiment with leaching columns.

Integrated study on subcellular localization and chemical speciation of Pb reveals root strategies for Pb sequestration and detoxification in Salix integra

Integrated study on subcellular localization and chemical speciation of Pb reveals root strategies for Pb sequestration and detoxification in Salix integra

Co-pyrolysis of corn stover with industrial coal ash for in situ efficient remediation of heavy metals in multi-polluted soil

Coal ash incorporated biochar (CA/BC) composite was prepared by co-pyrolysis of agricultural residue and industrial coal ash and applied for remediation of soils polluted by lead (Pb) and cadmium (Cd). The results showed that immobilization efficiency of CA/BC for heavy metals (HMs) was significantly enhanced by 77.1 % (Pb) and 42.7 % (Cd) compared to pristine biochar (BC), and this was mainly due to the increased pH value, surface functionality and surface negative charge. By the introduction of 5 % CA/BC, the polluted soils showed the highest reduction of leaching toxicity by 67.9 % (Pb) and 49.7 % (Cd), respectively. The chemical speciation of Pb and Cd in soils was changed remarkably and the reduced bioavailable Pb and Cd were mainly transformed from acid-soluble fraction into the most stable form of residual fraction. The mechanism study showed that surface precipitation, complexation, cation exchange and cation-π interaction of CA/BC mainly contributed to heavy metals (HMs) immobilization. The pot experiments further confirmed that incorporation of 5 % CA/BC effectively reduced plant Pb and Cd accumulation by 81 % and 62.5 % respectively, and significantly promoted the plant growth of paddy rice by 3.1, 2.2 and 2.0 times in terms of root, stem length and dry mass parameters. The present study offered a cost-effective and green method to prepare soil amendment with great potential for remediation of soils polluted by HMs and realized the value-added utilization of waste agricultural residue and industrial coal ash.

Lead speciation and availability affected by plants in a contaminated soil

Changes in lead (Pb) speciation in the rhizosphere may be plant species-dependent and dictate Pb fate and behavior in the soil-plant system. X-ray absorption near edge structure (XANES) spectroscopy can explain how these changes affect Pb availability in soils and its uptake by plants. We investigated the changes in Pb speciation and availability in the rhizosphere of eucalypt (Eucalyptus urophylla x Eucalyptus grandis), palisade grass (Urochloa brizantha cv. Marandu), and Indian mustard (Brassica juncea L.) using XANES spectroscopy. A greenhouse experiment was performed in a complete randomized design, with three plant species and a no plant control treatment. After three months, rhizosphere and bulk soil samples were collected, Pb speciation was assessed by Pb L3-edge XANES spectroscopy, and Pb concentration was determined in plant tissue. In bulk soil, we found Pb primarily as Pb-Il (Pb sorbed to illite; 48%) and lead monoxide (PbO; 36%). In the rhizosphere, Pb-Ka (Pb sorbed to kaolinite; 33–56%) and (CH₃COO)₂Pb (25–41%) were the main Pb forms, the latter suggesting Pb complexation by low molecular weight organic acids (LMWOAs). Palisade grass rhizospheric soil had a lower abundance of Pb-Ka and a higher abundance of (CH₃COO)₂Pb than eucalypt and mustard, which led to low Pb concentration in plant tissue. LMWOAs exudation followed by Pb2+ complexation is the apparent mechanism used by palisade grass to detoxify the rhizosphere and control Pb uptake. Given its low Pb uptake and potential to complex Pb in organic forms, palisade grass may be a promising species for Pb phytostabilization in contaminated soils.

Plumbojarosite formation in contaminated soil to mitigate childhood exposure to lead, arsenic and antimony

In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils using iron (III) (Fe3+) in conjunction with 0.05 M H2SO4. During method optimization, a range of microwave treatment times, solid to solution ratios, and Fe2(SO4)3/H2SO4 concentrations were assessed using a mining/smelting impacted soil (BHK2, Pb: 3031 mg/kg), followed by treatment of additional Pb contaminated soils (PP, Pb: 1506 mg/kg, G10, Pb: 2454 mg/kg and SoFC-1, Pb: 6340 mg/kg) using the optimized method. Pb bioaccessibility was assessed using USEPA Method 1340, with Pb speciation determined by X-ray Absorption (XAS) spectroscopy. Treatment efficacy was also validated using an in vivo mouse assay, where Pb accumulation in femur, kidney and liver was assessed to confirm in vitro bioaccessibility outcomes. Results showed that Pb bioaccessibility could be reduced by 77.4–97.0% following treatment of soil with Fe2(SO4)3 (0.4–1.0 M), H2SO4 (0.05 M) at 150 °C for 60 min in a closed microwave system. Results of bioavailability assessment demonstrated treatment effect ratio of 0.06–0.07 in femur, 0.06–0.27 in kidney and 0.06–0.11 in liver (bioavailability reduction between 73% and 93%). Formation of plumbojarosite in treated soils was confirmed by XAS analysis.

Effect of biochar amendment on mobility and plant uptake of Zn, Pb and Cd in contaminated soil

This study aimed to assess the effect of rice straw biochar application as a soil amendment on the mobility, availability, speciation and plant uptake of Zn, Pb and Cd in contaminated soil. A pot experiment with maize (Zea mays L.) was conducted using different rates 0, 1, 2, and 5% (w/w) of rice straw biochar. The soil pore water properties; pH, EC, and DOC concentration, the dissolved metal concentrations in soil pore water as well as plant metals uptake were determined at the end of the experiment. The BCR sequential extraction procedure was adopted to determine the effect of biochar on speciation and partitioning of the studied metals.Results showed that the application of biochar is significantly increased the plant shoots biomass by 94.5% with 5% biochar rates compared to untreated soil. Similarly, the soil pore water properties pH, EC, and DOC concentration were also increased with biochar addition compared to untreated soil. The dissolved metal concentrations were decreased in soil pore water with the increasing of biochar rates by 92%, 81.5%, and 90% for Zn, Pb and Cd, respectively at 5% biochar rate. In the same trend, the plant metals uptake reduced significantly with the increasing of biochar dose. Compared to untreated soil, the BCR sequential extraction showed that the biochar addition induced the transformation of the exchangeable metal fractions to oxidizable and residual fractions. These results confirmed the ability of rice straw biochar to immobilize the studied metals and therefore reducing their bioavailability and their uptake by plant.

Mineralogical characterization and speciation of sulfur, zinc and lead in pyrite cinder from Bergvik, Sweden

Roasting of sulfide ores to produce sulfuric acid began on an industrial scale in the middle 1800′s and is still used extensively worldwide. The residual, pyrite cinders, have commonly been disposed in the environment where they pose a potential and serious threat to aquatic life. In this project, two profiles in a pyrite cinder deposit in Bergvik, Sweden, have been sampled and a comprehensive mineralogical characterization have been carried out. The objectives were to investigate the composition and morphology of pyrite cinder grains and the speciation of sulfur, Pb and Zn in the solid phase. Scanning electron microscopy showed pyrite cinder grains with a core of the ore minerals pyrite and sphalerite enclosed in layers of iron oxides/hydroxides (mainly hematite). XANES analysis, supported by X-ray diffraction analysis, SEM-EDS and bulk element analysis, showed that content of the residual sulfur in the cinder is mainly sulfides, 55–80%, predominately sphalerite. The remaining mass of sulfur is assumed to be adsorbed or precipitated as secondary sulfate minerals, predominantly associated with the grain surfaces. Calculated saturation indexes indicated barite, anglesite and perhaps aluminite. EXAFS spectroscopy indicated that about half of the Zn was bound to O and half was bound to S. LCF analysis of EXAFS spectra indicated that the main Zn species were sphalerite (40–50%) and franklinite (10–20%). The remaining Zn was associated with iron oxides/hydroxides and Zn minerals like hydrozincite or possibly zinc oxides. SEM-EDS analysis showed Pb precipitate located on both the surface of the grains and in the interior as inclusions. The analytical interpretation indicated anglesite.