Tessier Sequential Extraction Procedure Research Articles

Environmental hazard assessment of metals in marine sediments of Sabah and Sarawak, Malaysia

The fractionation of 10 metals (As, Co, Cr, Cu, Mn, Ni, Pb, Se, V, and Zn) within labile fractions in shallow marine sediments collected from the coasts of Sabah and Sarawak, Malaysia, was evaluated. Spatial distribution revealed that coastal sediments from Sabah were approximately 10% higher in metal content than sediments from Sarawak. Risk assessment code, enrichment factor, and pollution accumulation index calculations were used to investigate the environmental hazards of elements. For the risk assessment code, the modified Tessier sequential extraction procedure was applied. The risk assessment code values showed that metal V recorded the lowest environment risk (~ 10%) while As, Co, Cr, Cu, Mn, and Zn exhibited medium risk (Risk assessment code range of 11%–30%). The element Ni displayed no risk (0.67%) to the environment, whereas Se and Pb recorded the highest risk with values of 47% and 52%, respectively. For the enrichment factor calculation, the continental crust data presented by Taylor (Taylor, Geochim Cosmochim Acta 28:1273–1285, 1964) were used as background, with metal Al used as a reference element. Results illustrated that most of the metals show enrichment (enrichment factor > 1). However, Se was considered extremely severe to the environment (enrichment factor > 50). While the pollution accumulation index calculation demonstrated that all metals under study can be considered as non-contaminant elements except for Ni, V, and Co. These findings indicated that marine sediments in Sabah are more polluted with metal contaminants than the sediments in Sarawak, despite both states having numerous active oil- and gas-related production facilities.

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.

Stabilization of arsenic and antimony Co-contaminated soil with an iron-based stabilizer: Assessment of strength, leaching and hydraulic properties and immobilization mechanisms

Soils with relatively high concentrations of arsenic (As) and antimony (Sb) in mining areas would impose significant risks to human health and ecosystem. A new stabilizer PFSC composed of polymerized ferric sulfate (PFS) and calcium hydroxide (Ca(OH)2) is proposed to stabilize the soil with co-existed As and Sb sampled at an abandoned arsenic factory site. The effects of stabilizer dosage on the properties of the stabilized soil including leached concentrations of As and Sb, unconfined compressive strength (UCS), and hydraulic conductivity (kw) were investigated. The mechanisms of As and Sb immobilization in the soils were interpreted by Tessier's sequential extraction procedure (SEP), scanning electron microscope (SEM), and X-ray diffraction (XRD) results. The results showed increasing PFSC dosage was effective for reducing leached concentrations of As and Sb. When the PFSC dosage increased from 2% to 10%, the UCS and kw increased from 84 to 206 kPa and decreased from 6.48 × 10−8 to 6.33 × 10−9 m s−1, respectively. Tessier's SEP results showed that the leachable As and Sb fractions decreased from 12% to 5.6% and 7.5% to 3.8%, while the Fe–Mn oxides bound fractions increased from 22.3% to 29.4% and 13.2% to 19.5%. The SEM images and XRD patterns of untreated and PFSC stabilized contaminated soils indicated that hematite and calcite (CaCO3) were the main products of PFSC stabilization processes. Adsorption on ferrihydrite, entrapment in hematite lattices, and co-precipitate with calcite might were the main mechanisms of As and Sb immobilization.

Using modified Tessier sequential extraction to specify potentially toxic metals at a former sewage farm

The main objectives of this study were to evaluate the Cu, Zn, Pb, Cr and Ni mobility using modified Tessier sequential extraction procedure and to study the functional group changes affected by each extraction step using FTIR analysis in the soil of a former sewage farm sedimentation basin. Tessier extraction revealed element dependent fractionation of studied metals: Pb was mostly discovered in the residual fraction (77%) followed by Cr (53%), Cu (8%), and Zn (5%), while Ni was not extracted in this fraction. The organic matter-bound was the dominant species of Cu (77%). Zn and Ni exhibited the highest affinity for Fe/Mn oxides fraction (55% and 39%, respectively). The average recovery rate was 62–111%, whereas the lowest rate was obtained for Ni (62%) and the highest for Cu/Pb (110–111%). Results indicated elevated concentrations of studied elements, with the following order of mobility factor: Ni > Zn > Cu > PbCr. The preliminary interpretation of the sequential extraction FTIR spectral response revealed that DRIFT is applicable to interpret the sequential metal extraction and revealed three most profound changes correlated to the carbonate, Fe/Mn oxides, and OM fraction.

Assessment of micronutrients fractionations and mobility in soils of eastern Uttar Pradesh

In the present investigation, an attempt has been made to assess the various chemical forms and mobility factor (MF) for zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) in different soils of eastern Uttar Pradesh. For this purpose, surface soil (0-15 cm) samples from two different locations were collected under Entisol, Inceptisol, Vertisol and Alfisol during 2019-20 and analysis was done in the laboratory of Department of Soil Science and Agricultural Chemistry, BHU, Varanasi. The modified Tessier sequential extraction procedure was used to determine the chemical pools of Zn, Cu, Fe and Mn in each soil. Results indicated that total metal content follows the order of Fe>Mn>Zn>Cu across the soil orders, whereas mobility factor of micronutrients arranged as: Mn>Cu>Zn>Fe. The highest exchangeable (F1), carbonate bound (F2), Fe-Mn oxides bound (F3), organically bound (F4) and residual (F5) fraction were recorded in Inceptisol, Vertisol, Alfisol, Inceptisol and Alfisol, respectively for micronutrients, i.e. Zn, Cu, Fe and Mn. The mean percentage value of various micronutrients fractions were in the order of F5>F3>F4>F2>F1, except Mn, whose chemical forms follows the order of F3>F5>F4>F2>F1. The Zn and Cu were highly mobile in Vertisol while Fe and Mn in Entisol.

Chemical fractionations and mobility of heavy metals in soils of eastern Uttar Pradesh

In the current investigation, an attempt has been made to assess the various chemical forms and mobility factor (MF) for lead (Pb), cadmium (Cd), chromium (Cr) and nickel (Ni) in four soils of eastern Uttar Pradesh. For this purpose, two different surface soil samples were collected from each of Entisol, Inceptisol, Vertisol and Alfisol soil orders during 2019–20. The modified Tessier sequential extraction procedure was applied to determine the chemical pools of Pb, Cd, Cr and Ni in each soil. Results indicated that total metal content follows the order of Pb>Cr>Ni>Cd across the orders, whereas mobility factor of micronutrients could be arranged as: Cd>Pb>Ni>Cr. The bioavailable metal fraction of all micronutrients, i.e. exchangeable pool (F1) was maximum in Inceptisol. The highest carbonate bound (F2), Fe–Mn oxides bound (F3), organically bound (F4) and residual (F5) fraction were recorded in Vertisol, Alfisol, Inceptisol and Alfisol, respectively for all heavy metals. The mean percentage value of Pb and Ni fractions were in the order of F5>F3>F4>F2>F1, whereas Cd whose chemical fractions follows the order of F2>F3>F4>F5>F1. The Pb was highly mobile in Vertisol, Ni in Inceptisol, while Cd and Cr in Entisol. Therefore, availability and mobility of heavy metals in the soil environment depends mainly on their association with various chemical fractions of the soil which relies on the mineralogical origin of the metals.

Early warning on risk development in compound lead and cadmium contaminated sites

Based on the transformation among metal fractions defined by the Tessier sequential extraction procedure and integrated risk information assessed by delayed geochemical hazard (DGH) methodology, including development paths and their burst probabilities, trigger conditions, and the contribution of each metal to risk development, an approach was proposed to provide an early warning on risk development in metal compound-contaminated sites and tested in a lead and cadmium-contaminated site. Risk assessment indicated that the site was at a high to extremely high ecological risk. DGH analysis revealed that the transformation from the fraction bound to carbonate and organic matter to the exchangeable fraction was dominant in the development of either single or combined lead and cadmium risk, which was triggered by soil acidification and the continuous decline of soil organic matter; risk development might have occurred in 6.52–80.4% of the case site with burst probabilities of 6.52–80.4%, 8.70–39.1% and 8.70–80.4% for lead risk, cadmium risk and combined lead-cadmium risk, respectively; with the dominant role of lead, the two metals overall accelerated the development of their compound risk by changing each other’s DGH paths. The proposed DGH-based approach is promising for early warning on risk development in compound contaminated sites.

A promising amendment for the immobilization of heavy metal(loid)s in agricultural soil, northwest China

In situ remediation techniques are currently limited for agricultural soil contaminated by heavy metal(loid)s, particularly for alkaline soil. In this study, we applied the amendments (Chinese loess, attapulgites, and composted sludge) to a contaminated alkaline agricultural soil to compare their effectiveness in immobilizing heavy metal(loid)s. Soil was collected from the uppermost 20 cm of a heavily contaminated cornfield in Baiyin, China. The amendments were added to the soil at the ratios of 1%, 5%, 10%, and 15%. Controls without amendment were also included. The effectiveness of amendments was evaluated using single extractions and Tessier sequential extraction procedure. The extractants in the single-step extraction were H2O, calcium chloride (CaCl2), diethylenetriaminepentaacetic acid (DTPA), and hydrochloric acid (HCl). Seed germination was performed with the soil after immobilization for 180 days. Chinese loess effectively reduced the toxicity of heavy metal(loid)s and improve seed germination rates compared with attapulgites (ATPs) and composted sludge. Composted sludge effectively transformed heavy metal(loid)s, particularly Cu, from the carbonate fraction into the organic matter or the residual fraction. The concentrations of heavy metal(loid)s extracted with DTPA were positively correlated with the summation of the exchangeable and carbonate fractions (P < 0.05). A high seed germination rate could be obtained when the four amendments were added at the ratios between 5 and 10%. Chinese loess was effective and safe to immobilize heavy metal(loid)s in contaminated alkaline agricultural soil. DTPA performed the best in predicting the availabilities of As, Cd, Pb, Cu, and Zn in the soil.

RETRACTED: Removal of cadmium from mining soil using organic acid and ultrasonic waves

Ultrasonic techniques are applied to treat polluted soils because they are efficient, expeditious, inexpensive, and environmentally safe. In this study, the ultrasonic-assisted organic acid removal of cadmium from mining soil was investigated using the following setup: 0.1 mol/L citric and oxalic acid, a 1:20 solid-liquid ratio, and 30 min of ultrasonic-assisted time. A cadmium removal rate of 69.10% was obtained when using organic acids, while it was only 61.82% for removal by oscillation extraction. This implies that the ultrasonic-assisted removal method has beneficial effects on the removal of cadmium via organic acid. Speciation analysis of cadmium in mining soils before and after organic acid removal was performed using the Tessier sequential extraction procedure. The results showed that exchangeable species and those bound to manganese, iron and carbonates were lower after ultrasonic-assisted organic acid removal. This indicates that organic acids can remove most of the removable cadmium from soil in mining areas fast and efficiently.

Tessier sequential extraction on 17 elements from three marine sediment certified reference materials (HISS-1, MESS-4, and PACS-3).

The four-step Tessier sequential extraction procedure is a well-known approach used for environmental and geochemical studies in soil and sediments. However, a lack of reference materials limits its use making implementation and quality control cumbersome. This study applied Tessier sequential extraction to three globally used marine sediment certified reference materials (CRMs) including HISS-1, MESS-4, and PACS-3 with varying levels of contamination. The study analyzed the distribution of 17 elements throughout the extraction phases. Overall, the percent recovery (sum of steps vs total metal concentration) of all analyzed elements in Tessier extraction was 92%+40% in HISS-1, 101%+12% in MESS-4, and 102%+10% in PACS-3. The observed uncertainty of the individual elemental concentrations averaged at 13%, which compares favorably with the 16% target uncertainty derived from the Horwitz equation. The reference data set produced here using the Tessier sequential extraction procedure will serve as a quality control and method development tool for laboratories. Graphical abstract.

Combined effects of arbuscular mycorrhizae fungus and composted pig manure on the growth of ryegrass and uptake of Cd and Zn in the soil from an e-waste recycling site.

Little attention has been paid to the combined effects of arbuscular mycorrhizae (AM) fungus and composted manure on heavy metal bioavailability and its uptake by plants grown in heavy metal-contaminated soils from electronic-waste (e-waste) recycling sites. A greenhouse pot experiment was conducted to investigate the effects of AM fungus, composted pig manure (CM) and AM fungus + CM (ACM) on the growth of ryegrass and uptake of Cd and Zn in the soil collected from an e-waste recycling site. The calcium chloride (CaCl2) and Tessier sequential extraction procedure were adopted to evaluate the bioavailability and chemical speciation of Cd and Zn in the soil. Results showed that the application of CM and ACM significantly increased the pH but decreased the CaCl2-extractable Cd and Zn concentrations in the rhizosphere and bulk soils. ACM treatment significantly shifted Cd from exchangeable fraction to other more stable fractions, and transformed the exchangeable Zn fraction to the carbonate-bound and reducible iron and manganese-bound fractions. Furthermore, the application of ACM can enhance the growth of plant shoots, and decrease the uptake of Cd and Zn in the ryegrass plants. This work suggests that AM fungus in combination with CM amendment may be a potential method for not only remediation of soil Cd and Zn pollution, but also reduction of Cd and Zn uptake by ryegrass grown in the soil from e-waste recycling sites.

Magnetite nanoparticles for the remediation of soils co-contaminated with As and PAHs

Commercial magnetite nanoparticles (NPs) were used to immobilize As and organic pollutants, mainly PAHs, in a polluted soil. The composition, structure and morphology of the NPs were examined by means of electron microscopy, X-ray analysis, infrared spectroscopy, dynamic light scattering, thermogravimetric analysis, and magnetic property determination. To evaluate the immobilization of As and organic pollutants, soil subsamples were treated with the magnetite NPs at different doses (0.2%, 1%, 2% and 5%). The availability of As was then examined by the TCLP test and the Tessier sequential extraction procedure, whereas TPH and PAHs were measured by GC–MS. Notable results for As immobilization were achieved at a dose of 1% NPs (42.5% decrease in As, TCLP test), although the best result was obtained at the highest dose of 5% (92.3% decrease in As, TCLP test) without significant variations in As speciation. Regarding organic pollutants, a decrease in TPH and PAHs content was detected even at the lowest dose of NPs tested (49% and 89% respectively). The treatments had no negative effects on soil parameters such as soil pH and electrical conductivity. In turn, the increase in Fe availability after application of NPs was insignificant whereas soil phytotoxicity assessed by germination test was reduced. In conclusion, the use of magnetite NPs opens up new nanoremediation options to treat soils affected by both organic and metal(loid) pollution.

Zero valent iron and goethite nanoparticles as new promising remediation techniques for As-polluted soils

The capacity of two iron-based nanomaterials, namely goethite nanospheres (nGoethite) and zero valent iron nanoparticles (nZVI), to immobilize As in a polluted soil was evaluated and compared. The composition and morphology of the products were studied by energy dispersive X-ray analysis and transmission electron microscopy, while zeta potential and average sizes were determined by dynamic light scattering. To assess As immobilization, soil subsamples were treated with nGoethite or nZVI at a range of Fe doses (0.5%, 2%, 5% and 10%) and then studied by the TCLP test and the Tessier sequential extraction procedure. The influence of both nanoparticles on As speciation was determined, as was impact on soil pH, electrical conductivity, Fe availability and phytotoxicity (watercress germination). For nZVI, notable results were achieved at a dose of 2% (89.5% decrease in As, TCLP test), and no negative effects on soil parameters were detected. Indeed, even soil phytotoxicity was reduced and only at the highest dose was a slight increase in As3+ detected. In contrast, excellent results were obtained for nGoethite at the lowest dose (0.2%) (82.5% decrease in As, TCLP test); however, soil phytotoxicity was increased at higher doses, probably due to a marked enhancement of electrical conductivity. For both types of nanoparticle, slight increases in Fe availability were observed. Thus, our results show that both nZVI and nGoethite have the capacity to effectively immobilize As in this brownfield. The use of lower doses of nGoethite emerges as a promising soil remediation strategy for soils affected by As pollution.

English

The purpose of this study was to determine the concentration of heavy metals (Cr, Cd and Pb) in vegetables and the soil contaminating levels as a result of irrigation using Flame Atomic Absorption Spectrophotometer (FAAS). The wet digestion and sequential fractionation extraction procedures were employed to solubilize the metals from the collected samples. The results obtained from this study showed overall concentration of heavy metals Cr, Cd and Pb respectively, in the range of (2.90-3.77), (2.20-3.68) and (4.60-5.50) (mg/Kg) in the edible parts of sampled vegetables. Whereas, concentrations (mg/Kg) of the metals in the soil samples were found to be in the ranges of 22.37-66.30, 27.93-45.33 and 18.82-64.87 for Cr, Cd and Pb, respectively. The modified Tessier sequential extraction procedure was used to fractionate the above three metals from the soil samples into five fractions. In this study the heavy metals were predominantly concentrated in residual fraction (F5); since lead was mainly associated with the organic matter bounded fraction (F4) (34.33-43.45%), it was found to be more bioavailable and mobile than the other investigated heavy metals. The concentrations of heavy metals (Cr, Cd and Pb) in the soil and vegetable samples were above the recommended limit of both WHO and FAO. But Pb for the soil samples was smaller than WHO and FAO recommended limit. Based on facts obtained from this study we suggests concerned official body (ies) to take the necessary precaution measures for cleaning the polluted area. Key words: Heavy metals, sequential fractionation, eastern industry zone.

English

The purpose of this study was to determine the concentration of selected metals (Fe, Zn and Cu) in vegetables and the soil contaminating levels due to irrigation, using Flame Atomic Absorption Spectrophotometer (FAAS). The wet digestion and sequential fractionation extraction procedures were employed to solubilize the metals from the collected samples. The results obtained from this study showed overall concentration of selected metals Fe, Zn and Cu respectively, in the range of (358.17 to 547.17), (45.63 to 62.46) and (10.20 to 15.07) (mg /Kg) in the edible parts of sampled vegetables whereas, concentrations (mg/kg) of the metals in the soil samples were found to be in the ranges of (12051 to 20065), (69.37 to 123.77) and (68.47 to 146.10) for Fe, Zn and Cu, respectively. The modified Tessier sequential extraction procedure was used to fractionate the above three metals from the soil samples into five fractions. In this study the detected metals were predominantly concentrated in residual fraction (F5); zinc was mainly associated with the residual fraction (F5) (87.14 to 96.40%) which is highly stable. The mobility factors of Zn, Fe and Cu were 0.908 to 3.044, 0.216 to 0.443 and 0.314 to 1.968, respectively. The concentrations of Fe and Cu in the soil and vegetable samples were above the recommended limit of both WHO and FAO; also, Zn vegetable samples was above the limit. However, Zn for the soil samples was smaller than WHO and FAO recommended limit. Based on facts obtained from this study, it was suggested that concerned official body (ies) take the necessary precaution measures to clean the polluted area. Key words: Metals, sequential fractionation, soil, vegetables, quantity.

In vitro bioaccessibility of potentially toxic metals (PTMs) in Baoji urban soil (NW China) from different functional areas and its implication for health risk assessment

In order to better understand both the conceptual and operational aspects of bioaccessibility and phytobioavailability of PTMs (Co, Cr, Cu, Li, Mn, Ni, Pb, Zn) in different urban soils, a total of 30 soil samples from agricultural region, entertainment district, education area, traffic area, residential area and industrial area (IA) in Baoji urban city (NW China) were collected and the bioaccessibility and phytobioavailability were measured by multi-in vitro models of PBET, SBET, citric acid leaching and Tessier sequential extraction procedure, respectively. The suitable in vitro measurement of bioaccessibility and phytobioavailability for each PTM was selected and would be reliably applied for health risk assessment. The results indicated that the bioaccessibility and phytobioavailability for each PTM evaluated by in vitro models depended on PTM total concentration and anthropologic activity influence. The health risks associated with bioaccessibility of PTMs exposure showed that the carcinogenic and non-carcinogenic risks in all areas for children and adults were below the threshold or acceptable risk levels except lead exposure on children in IA, indicating there were more health risks to the children in than that in other functional areas. It was worth that the highest observation of Pb in IA would strongly correlate with lead-acid battery industries, which the emissions would influence on the occurrences of Pb distributing in the other functional areas, which were supported from the analysis results of XPS. Therefore, the continuous monitoring and attention to the health risk of inhabitants in different functional areas should be paid.

Migration and Transformation of Vanadium and Nickel in High Sulfur Petroleum Coke during Gasification Processes

The volatilization characteristics and occurrence forms of V and Ni in petroleum coke (petcoke) were investigated during steam (H2O) and carbon dioxide (CO2) gasification on a fixed bed reactor at 800–1100 °C. The Tessier sequential chemical extraction procedure was employed to determine the different forms of V and Ni. The results showed their volatilities were not dependent on the gasification atmosphere, but rather relied mainly on the reaction temperature. The CO2 atmosphere accelerated the conversion of organic-bound nickel to residual form at low temperature and promoted Fe-Mn oxides formation at high temperature. However, the H2O atmosphere was conducive to form vanadium bound to Fe-Mn oxides and promoted the decomposition of residual forms. In addition, the thermodynamic equilibrium calculations showed the volatilization of Ni mainly released Ni3S2 between 800–1100 °C. The H2O atmosphere was favorable to generate the more stable NixSy compound, thereby suppressing the volatilization of Ni, while the presence of CO2 led to an increase in residual V and decrease of Fe-Mn oxides. The V and Ni mainly caused erosion problems under the CO2 atmosphere while the fouling and slagging obviously increased under the H2O atmosphere with impacts gradually weakened with the increase of temperature.

The effect of simulated acid rain on the stabilization of cadmium in contaminated agricultural soils treated with stabilizing agents.

Stabilization technology is one of widely used remediation technologies for cadmium (Cd)-contaminated agricultural soils, but stabilized Cd in soil may be activated again when external conditions such as acid rain occurred. Therefore, it is necessary to study the effect of acid rain on the performance of different stabilizing agents on Cd-polluted agriculture soils. In this study, Cd-contaminated soils were treated with mono-calcium phosphate (MCP), mono-ammonium phosphate (MAP), and artificial zeolite (AZ) respectively and incubated 3months. These treatments were followed by two types of simulated acid rain (sulfuric acid rain and mixed acid rain) with three levels of acidity (pH = 3.0, 4.0, and 5.6). The chemical forms of Cd in the soils were determined by Tessier's sequential extraction procedure, and the leaching toxicities of Cd in the soils were assessed by toxicity characteristic leaching procedure (TCLP). The results show that the three stabilizing agents could decrease the mobility of Cd in soil to some degree with or without simulated acid rain (SAR) treatment. The stabilization performances followed the order of AZ < MAP < MCP. Acid rain soaking promoted the activation of Cd in stabilized soil, and both anion composition and pH of acid rain were two important factors that influenced the stabilization effect of Cd.

Chemical speciation and risk assessment of Cu and Zn in biochars derived from co-pyrolysis of pig manure with rice straw

Pig manure has been utilized as a good feedstock to produce biochar. However, the pig manure-derived biochar from intensive pig cultivation contains high levels of total and bioavailable heavy metals. In this study, the co-pyrolysis of pig manure with other biomass (e.g. rice straw) at 300–700 °C was investigated to solve the above-mentioned topic. The ammonium acetate (CH3COONH4), Tessier sequential extraction procedure and hydrogen peroxide were adopted to evaluate the bioavailability, chemical speciation, and potential risk of Cu and Zn in the biochars. Results showed that the addition of rice straw significantly reduced the concentrations of total, exchangeable and carbonate-associated Cu and Zn in the biochars compared to the single pig manure biochars. Co-pyrolysis of pig manure with rice straw at a mass ratio of 1:3 and at 600 °C could be most effective to reduce the concentrations of CH3COONH4-extractable and potential released Cu and Zn in the biochars. In conclusion, the co-pyrolysis process is a feasible management for the safe disposal of metal-polluted pig manure in an attempt to reduce the bioavailability and potential risk of heavy metals at relatively high pyrolysis temperatures.

Heavy metals immobilization in contaminated soil by grape-pruning-residue biochar

ABSTRACTTo investigate the influence of grape-pruning-residue (GPR) biochar on cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) immobilization in a contaminated soil, a laboratory study was conducted with different rates of GPR biochar (0, 2, 5 and 10% w/w) at 25°C. After 1, 2, 4, and 8 weeks of incubation, the Tessier sequential extraction procedure was performed and metal mobility factor (MF) and metal stability index (IR) were calculated. The exchangeable (EX) and carbonate (CAR) fractions of the metals decreased significantly (p ≤ 0.05) with the biochar addition. The EX metal fractions decreased by 23 to 72%, and the CAR fractions decreased by 51 to 67% in the 10% biochar treatment after 8-week incubation. The MF values of Cd, Pb, Cu and Zn decreased by 47, 62, 70 and 49%, respectively, with addition %10 of the biochar. Biochar addition favored the metal redistribution into more stable fractions and resulted in an increase in IR values. The results demonstrated that the GPR biochar, especially at high application rate (10%), can effectively immobilize the heavy metals, thereby reducing their mobility in contaminated soils.