Three-stage Sequential Extraction Research Articles

Chemical availability of fallout radionuclides in cryoconite

Atmospheric deposition on glaciers is a major source of legacy fallout radionuclides (FRNs) accumulating in cryoconite, a dark granular material with surface properties that efficiently bind FRN contaminants (specifically 137Cs; 210Pb; 241Am). Cryoconite-bound FRNs in glaciers can be released when they interact with and are transported by glacial meltwater, resulting in the discharge of amassed particulate contaminants into aquatic and terrestrial environments downstream. The environmental consequences of FRN release from the cryosphere are poorly understood, including impacts of cryoconite-sourced FRNs for alpine food chains. Consequently, there is limited understanding of potential health risks to humans and animals associated with the consumption of radiologically-contaminated meltwater. To assess the chemical availability of cryoconite-adsorbed FRNs we used a three-stage sequential chemical extraction method, applied to cryoconite samples from glaciers in Sweden and Iceland, with original FRN activity concentrations up to 3300 Bq kg−1 for 137Cs, 10,950 Bq kg−1 for unsupported 210Pb (210Pbun) and 24.1 Bq kg−1 for 241Am, and orders of magnitude above regional backgrounds. Our results demonstrate that FRNs attached to cryoconite are solubilized to different degrees, resulting in a stage-wise release of 210Pbun involving significant stepwise solubilization, while 137Cs and 241Am tend to be retained more in the particulate phase. This work provides an insight into the vulnerability of pristine glacial environments to the mobilization of FRN-contaminated particles released during glacier melting, and their potential impact on glacial-dependent ecology.

Chemical Speciation of Trace Elements in Soil Fertilized with Biomass Combustion Ash and Their Accumulation in Winter Oilseed Rape Plants

The impact of fertilization of fly ashes from biomass combustion (BAs) on the changes in the chemical speciation of trace elements (Zn, Cu, Cr, Ni, Pb, Cd) in Gleyic Chernozem soil was analyzed in field-experiment conditions, under cultivation of winter oilseed rape plants. The three-year field experiment was carried out in southeastern Poland (50°3′ N, 22°47′ E). The three-stage sequential extraction procedure developed by the Measurements and Testing Program (BCR) was used for the fractionation of trace elements in BAs and soil. The risk assessment code (RAC) coefficient was used to assess potential soil contamination with trace elements from Bas. The total content of Zn, Cu, Cr, Ni, Pb, and Cd in BAs used in the experiment was 470, 311, 29, 78, 38, and 3.7 mg kg−1, respectively. The present study showed that the application of BAs significantly increased the total concentration of Zn and Cu in the surface layer of the Gleyic Chernozem soil, and did not significantly increase the concentration of Cr, Ni, Pb, and Cd. Generally, using BAs does not significantly change the chemical speciation of trace elements in soil. Regardless of the applied fertilization, residual fraction (F4) was the most abundant, whereas the exchangeable/extractable (F1) fraction and reducible (F2) fraction were present in the smallest amounts. Due to the low share of exchangeable/extractable fraction (F1), the BAs used in the experiment were characterized by a low RAC coefficient; hence, their use as a soil fertilizer is relatively safe for the environment. The BAs fertilization did not cause significant changes in the content of trace elements in the different parts of the winter oilseed rape plants. Due to the relatively high content of trace elements in fly ashes from biomass combustion, an analysis of the content of individual trace element fractions should be carried out to assess their actual impact on the environment. This can help indicate further actions that should be taken to limit their negative environmental impact.

Extraction of bioactive compounds from Leptocarpha rivularis stems by three-stage sequential supercritical extraction in fixed bed extractor using CO2 and ethanol-modified CO2

Sequential supercritical extraction experiments were carried out in three stages each using CO2 and ethanol-modified-CO2, to improve the extraction yield of bioactive compounds from L. rivularis stems. Four experiments were carried out, each in three stages, combining different levels of temperature (40 or 60 °C) and pressure (20–50 MPa). The increase in pressure and use of a cosolvent increased the total yield of extract and target compounds compared to one-stage extraction. The highest extraction yields of extract (6.29 g/kg d.s.), terpenes (699.9 mg/kg d.s.), flavonoids (741.9 mg/kg d.s.), and alkaloids (6.22 mg/kg d.s.) were obtained in Experiment 4. Sequential extraction of compounds was superior to one-stage extraction using CO2, but inferior when using ethanol-modified CO2. Both sequential and one-stage cumulative extraction curves were modeled, and the effective diffusivity coefficients ranged between 1.51 and 63.3 × 10–13 m2/s, being highest in Stage 3 where the extraction yield was greatest.

Three-stage sequential supercritical extraction in fixed bed extractor to obtain bioactive compounds from Leptocarpha rivularis leaves

This work studied sequential supercritical extraction to obtain extracts from L. rivularis leaves. Extraction assays were carried out in three stages at 40 or 70 °C, with stage 1: 20 MPa with CO2, stage 2: 40 MPa with CO2, and stage 3: 40 MPa with ethanol-modified CO2 (5% wt.). The total extraction yield was higher at 70 °C (41.77 g/kg d.s.) than at 40 °C (32.57 g/kg d.s.). The total content of terpenes and flavonoids and the ability of the extracts to inhibit the α-amylase and α-glucosidase enzymes were measured. At 40 °C the stage 1 extract had a greater inhibition effect on α-glucosidase and the stage 2 extract a greater inhibition effect on α-amylase. Sequential supercritical extraction was properly modeled using a diffusion model based on Fick's second law, and an effective diffusion coefficient was determined for each stage. Sequential supercritical extraction can be a method to increase the extraction of bioactive compounds.

Volatilisation of selenium from coals by heating at different temperature: application of sequential extraction scheme on ash

ABSTRACT An important issue to the earth’s atmosphere is the volatilisation of elements such as selenium, from the burning of coal at different temperatures. In the current work, the volatilisation of selenium (Se) during combustion of coal samples at different control temperature range in an electrically controlled furnace was carried out. The coal samples were obtained from various coal fields of Sindh, Pakistan. The duplicate coal samples were combusted in controlled furnace by applying three temperature rounds (200°C, 400°C and 900°C). The ash formed following each temperature round was examined to know the volatilisation contents of Se after burning of coal samples at different temperature. The fractionation of Se in coal ash gained after combustion at 900°C was subjected to three-stage sequential extraction scheme (SES). The obtained data indicated that the total contents of Se in coal samples of block II of Thar coal field (TCF), and Site I and Site II of Lakhra coal field (LCF) were observed in the range of 7.72–14.3, 9.02–16.3 and 8.92–14.2 mg/kg, respectively. It was observed that after the burning of coal samples at 900°C, about 75–81.8% of the total Se was volatised out into atmosphere.

Effect of high-moisture extrusion and addition of transglutaminase on major peanut allergens content extracted by three step sequential method

The effect of high-moisture extrusion (HME) with or without transglutaminase (TGase) on peanut allergen levels and their extractability was studied. A three-stage sequential protein extraction significantly improved the protein recovery in processed samples (extrudate meat analogue); from 5.56 to 18.75 mg/100 mg without TGase, and from 4.59 to 20.82 mg/100 mg with 0.3% TGase. The total major allergen content was reduced by 91% (Ara h 1), 61% (Ara h 2), 60% (Ara h 6), and 55% (Ara h 3). Western-blot analysis of soluble extracts reflected the presence of Ara h 1 and Ara h 2 in significantly lower, indicating a potential reduction in IgE binding. During different processing zones, the most significant reduction in allergenic proteins was in the melting zone. The significant alteration in secondary and tertiary structures as a result of crosslinking shearing and degradation of proteins is likely to lead to allergen reduction.

Geochemical behavior and remobilization potential of trace elements in surface sediments from the baixada santista industrial area, Southeastern Brazilian coast

A three-stage sequential extraction procedure optimized by the European Community Bureau of Reference (BCR) was applied to assess the geochemical behavior and environmental mobility of As, Cr, Cu, Ni, Pb and Zn in surface sediments from two ecosystems under different anthropogenic influences, the Estuarine Complex of Santos and Sao Vicente (ECSSV) upper estuary (high anthropogenic influence) and the Bertioga channel (low anthropogenic influence), both of which are located on the coast of Sao Paulo, Brazil. In general, the difference between the regions varied considerably for almost all these elements, and the values for the Bertioga channel were always lower than those found in the upper estuary. Among all the elements, Zn showed the greatest mobility, being present mainly in the acid-soluble fraction. Arsenic and Pb were associated with the reducible fraction, and Cu and Ni in the oxidizable fraction. Meanwhile, Cr was mainly found in the residual fraction. Although previous studies, regarding total concentrations suggest the probable enrichment of Cu, Pb and Zn in the surface sediments of the ECSSV, according to our results and the Risk Assessment Code (RAC) analysis, only Zn presented a high risk of bioavailability, and the modified Risk Assessment Code (mRAC) only showed six samples in the inner estuary with a medium risk of mobilization. Therefore, this study can serve as a management tool and optimize the monitoring efforts of chemical pollution in the region.

Physicochemical and environmental properties of arsenic sulfide sludge from copper and lead−zinc smelter

Abstract Physicochemical properties of arsenic sulfide sludge (ASS) from copper smelter (ASS-I) and lead−zinc smelter (ASS-II) were examined by XRD, Raman spectroscopy, SEM−EDS, TG−DTA, XPS and chemical phase analysis method. The toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), three-stage sequential extraction procedure (BCR) and batch leaching experiments (BLE) were used to investigate the environmental stability. The ASSs from different smelters had obviously different physicochemical and environmental properties. The phase composition and micrograph analysis indicate that ASS-I mainly consists of super refined flocculent particles including amorphous arsenic sulfide adhered with amorphous sulfur and that ASS-II mainly consists of amorphous arsenic sulfide. The valence state of arsenic in both sludges is trivalent, but the valence composition of sulfur is quite different. The ASSs have thermal instability properties. The results of TCLP and CSLT indicate that the concentrations of As and Pd in the leaching solution exceed the standard limits. More than 5% and 90% of arsenic are in the form of acid soluble and oxidizable fractions, respectively, which explains the high arsenic leaching toxicity and environmental activity of ASS. This research provides comprehensive information for the disposal of ASS from copper and lead−zinc smelter.

Bioleaching of dewatered electroplating sludge for the extraction of base metals using an adapted microbial consortium: Process optimization and kinetics

The main objective of this study was to optimize bioleaching process parameters for high co-extraction of base metals (Cu, Ni, Zn, and Cr) from hazardous electroplating sludge using an adapted microbial consortium and to explore the relevant bioleaching mechanisms. Microbial cultivation and sludge bioleaching were separated. The effect of the relevant process parameters (i.e., bulk pH, pulp density, and Fe2+ concentration) on the extraction of four selected metals through bioleaching by an adapted microbial consortium was investigated in a 1 L stirred tank reactor. Results indicated that maximum metal solubilization (>95.6% for each of Cu, Zn, and Ni, and 90.3% of Cr) was achieved at a bulk pH of 2.0, Fe2+ of 9.0 g/L, and pulp density of 15% (w/v). Bioleaching kinetics of the selected metals was described by a modified shrinking core model. This indicated that the interfacial transfer and diffusion across the solid film layer was the rate controlling step and controlled the dissolution kinetics. Data from bioleaching and chemical leaching systems showed that bioleaching had some advantages over simple chemical leaching. The mechanisms of improved Cu, Ni, Zn, and Cr extraction by bioleaching were demonstrated. Bioleaching improved metal release, especially from the residual fraction, as indicated by Community Bureau of Reference (BCR) three-stage sequential extraction analysis. Most of the Cu, Ni, and Zn extraction was attributed to H+ attack, as these metals were primarily distributed in the water/acid soluble and exchangeable fractions, along with Fe and Mn oxyhydroxides (>72.3%). For the extraction of Cr, besides H+, microorganisms and Fe3+ were also responsible. They improved Cr extraction, especially from the residual fraction. These findings indicate that bioleaching with an adapted microbial consortium appears promising for recycling and reutilizing valuable heavy metals from hazardous electroplating waste.

Metal(loid) speciation in a river subjected to industrial anthropopressure: chemometric and environmental studies

High-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was applied to the speciation of arsenic [As(III), As(V), and AsB (arsenobetaine)], MMA (monomethylarsonic acid), DMA (dimethylarsinic acid), antimony [Sb(III) and Sb(V)], and chromium [Cr(III) and Cr(VI)] in water and bottom sediment samples collected from the urban Bytomka River (Poland). The main objective of the study was the research of As, Cr and Sb species in the Bytomka River, as well as the simplified three-stage sequential chemical extraction of bottom sediments according to the Institute for Reference Materials and Measurements (BCR). The contents of V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Ag, Cd, Te, Ba, Tl, Pb, Fe, Ga, and U in the water and bottom sediments were tested using the ICP-MS technique. The risk assessment code (RAC) indicated a medium risk for As and a high risk for Sb to the environment. Sequential chemical extraction of bottom sediments showed that As and Cr were strongly demobilized. Sb was mainly bound with the ion-exchange fraction and posed a serious threat to the environment. Chemometric analysis with the (dis)similarity analysis and principal component analysis (PCA) allowed for visualization of the variability and correlations of the analyzed elements.

Environmental assessment concerning trace metals and ecological risks at Guanabara Bay, RJ, Brazil.

Three-stage sequential extraction BCR was applied to surface sediments from the west part of Guanabara Bay to assess the mobility of Zn, Cu, Pb, Ni, Cr, and Mn. Results were satisfactory for the analysis of certificate standard material (BCR 701), with recoveries between 71 (Cu) and 123% (Cr). Evaluation of organic matter composition classified the area as eutrophic (CHO:PRT > 1), with aged organic detritus at some stations. Zn exhibited by far the greatest bioavailability, with 43.49% of its concentrations associated with the exchangeable fraction. Cu and Cr showed stronger affinity for organic matter, with 51.18 and 48.73% of their concentrations, respectively, bounded to the oxidizable fraction. Pb presented higher concentrations in the reducible fraction (45.41%). The strongest lithogenic contribution was shown by Ni (31.91%) and Mn (35.44%). PCA clearly showed the determinant role of organic matter and fine sediments in the distribution of metals in the study area and also a common source for these elements, with the exception of Cu. Risk Assessment Code (RAC) established Zn as the most concerning element in the study area. The decreasing mobility order, based on the sum of the three extractable fractions of BCR, was Pb > Cu > Cr > Zn > Ni > Mn. The comparison of the results with sediments quality guidelines (SQG) proved fractionation to be mandatory in the evaluation of effective ecological risk concerning trace elements in sediments.

Fractionation of Heavy Metals in Fly Ash from Wood Biomass Using the BCR Sequential Extraction Procedure.

The aim of this study was to extract the wood biomass fly ash fractions by a three-stage sequential extraction method for acetic acid and ion exchangeable (BCR 1), hydroxylamine hydrochloride reduction (BCR 2), and hydrogen peroxide oxidation (BCR 3) fractions in order to access the leaching behavior of this residue. The fly ash was collected as a by-product from the processing of mixed wood biomass in Udbina combustion facility, Croatia. Concentrations of several elements (As, Cd, Cr, Cu, Ni, Pb and Zn) in all extracts were determined by inductively coupled plasma atomic emission spectrometry. The acidic exchangeable form of the metals was used to evaluate the potential ecological risk of biomass fly ash. According to calculated potential ecological risk index, it is confirmed that mobility of Ni and As has major environmental impact. However the results of potential ecological risk show that biomass fly ash had a low risk.

Potential toxic trace element (PTE) contamination in Baoji urban soil (NW China): spatial distribution, mobility behavior, and health risk.

Rapid urbanization and industrialization may cause increased exposure levels to potential toxic trace elements (PTEs) and associated health risks for population living in cities. The main objectives of this study are to investigate systematically the occurrence, source, fate, and risk of PTE contamination from industrial influence in Baoji urban soil. Seven PTE levels (Pb, Zn, Cu, Cr, V, Sb, and As) were surveyed in 50 composite samples from Baoji urban soil by wavelength dispersive X-ray fluorescence spectrometry. Results reveal that the long-term industrial activities have increased PTEs Pb (409.20mg/kg mean value), Cu (107.19mg/kg mean value), Zn (374.47mg/kg mean value), and Sb (26.00mg/kg mean value) to enrich in urban soil at the different extents. The same results concur with the significant similarity of spatial distribution patterns of Pb, Zn, Cu, and Sb (slightly similar distribution) interpolated by GIS, implying a considerable Pb, Zn, Cu, and Sb contamination pool in urban soil disturbance from local metallic industrial activities. Whereas As in study area mainly controls parent material leaching and therefore has natural sources. Cr and V with the heterogeneous spatial distributions are possibly inclined to coal combustion sources. Those conclusions are also confirmed by the results of multivariate analysis. The chemical forms of PTEs fractionated by BCR three-stage sequential extraction procedure show that Pb and Cu are highly associated to the reducible phase (62.55 and 36.41%, respectively). However, Zn is highly associated to the oxidizable phase (33.68%), and a significant concentration is associated to acid and water extractable fractionation of 15.93% for Zn and 34.40% for Pb. In contrast, As, Cr, V, and Sb are mainly bound to the residual phase (>65% for all elements) with low concentrations retained to water extractable fractionation. The health risk assessed by a new classification Modified Integrate Risk Assessment Code (MI-RAC) reveals that the Pb poses the extremely high risk for human health than others. The results of PTE leaching in organic acids (artificial chelating agent and LMMOAs) indicate that low pH and more carboxyl groups of organic acid can quickly increase the PTEs release from soil and induce more mobility. By comparison, DTPA and EDTA are the effective extractant for Pb and Sb. The leaching kinetics of most PTEs are best described with the Elovich equation model and which involve the ligand exchange (LE) and ligand-enhanced dissolution (LED) two major process. It is a conclusion that long-term metallic industrial activities would accelerate the PTE accumulations in Baoji urban soil and enhance their mobility in a local scale. The considerable mobility and extremely high risk of Pb in Baoji ecoenvironment should be paid more attentions, and the phytoremediation with organic acid leaching assistant could be used to reduce total metal content of multiPTE contaminants in Baoji soils. The research will give the scientific knowledge for controlling the pollution of PTEs in urban soil and can be used as guidance to control the soil pollution in similar cities worldwide.

ASSESSMENT OF BIOAVAILABILITY OF HEAVY METALS AFTER VERMICOMPOSTING IN THE PRESENCE OF ELECTRONIC WASTE

ABSTRACT Heavy metals contained in electronic waste, if discarded improperly, can become bioavailable after vermicomposting, posing a risk to the environment. Small-scale vermicomposting experiments were carried out with printed circuit boards (PCBs) to investigate the migration of heavy metals (Cu, Pb, Zn, Ni, and Sn) to the final compost, as well as the mobility and bioavailability of these metals. High total levels of Pb, Sn and Cu in samples of manure with electronic waste (MEW) and vegetables with electronic waste (VEW) were detected. Based on the initial metal levels in the PCBs and their concentration in the resulting compost, the order of migration of these metals to the MEW and VEW samples was Sn (23.1 %)>Pb (18.4 %)>Ni (4.63 %)>Zn (0.46 %)>Cu (0.14 %) and Sn (24.3 %)>Pb (23.6 %)>Ni (11.33 %)>Zn (1.76 %)>Cu (0.60 %), respectively. Mobility and bioavailability of these metals in the compost were evaluated by three-stage sequential extraction, where F1 was the exchangeable fraction, F2 the organic fraction and F3 the residual fraction. The bioavailability factor (BF) was calculated by the ratio of the sum of fractions F1 and F2 divided by the total sum of the fractions (F1 + F2 + F3). The highest bioavailability factor (BF = 0.92) was found for Pb, the heavy metal considered the greatest environmental concern in this study, indicating the high mobility and the possibility of becoming bioavailable of this metal.

Environmental risk assessment on slag and iron-rich matte produced from reducing-matting smelting of lead-bearing wastes and iron-rich wastes

A new process for utilization of hazardous lead-bearing wastes and iron-rich wastes by reducing-matting smelting has been developed. The slag (SG) and the iron-rich matte (IRM) are the main by-products from reducing-matting smelting of lead-bearing wastes and iron-rich wastes. The environmental risk of heavy metals (Cd, Zn, Pb and As) in the main by-products versus the charging material for reducing-matting smelting (CM) has been systematically assessed using leaching toxicity test, the three-stage sequential extraction procedure of European Community Bureau of Reference (BCR) and Hakanson Potential Ecological Risk Index Method (PERI). The results demonstrate that the ecological risk level of heavy metals for SG and IRM is significantly reduced after the reducing-matting smelting process compared with that for CM.

Spatial and vertical distributions of natural and anthropogenic radionuclides and cesium fractionation in sediments of the Var river and its tributaries (southeast France)

This paper reports results on the natural and anthropogenic radionuclides activity concentrations in sediments of the Var river and its tributaries. Natural (238U, 232Th and 40K) and artificial (137Cs) radionuclides activities were measured using high purity germanium detector. Measured activity concentrations differ widely; they depend on the pertinent environmental situation such as the presence of dams, and sediments type. Other factors controlling the distribution of the studied radioisotopes have been discussed. A sequential extraction method consisting of six operationally-defined fractions has been used for determining the geochemical partitioning of anthropogenic radionuclide 137Cs in a 405–410 cm deep sediments collected in the lower valley of the Var river. This method corresponds to a modification of the three-stage sequential extraction procedure proposed by the Commission of the European Communities Bureau of Reference (BCR, now Standards, Measurements and Testing Program). Two steps with weak reagents, (fraction A: water; fraction B: nitric acid 0.001 M), were added before the first step of BCR (carbonate fraction) in order to better detect anthropogenic components. A total acid digestion of solid residues by microwave assisted was also added. The 6-steps extraction method was tested and validated by certified reference materials. 137Cs was found mostly in the hydrosoluble fraction (20–24 %), oxide and hydroxide fraction (22–25 %) and in the residue (51–58 %), while 133Cs was mostly found in the residual fraction (>97 %).

The Use of a Sequential Extraction Procedure for Heavy Metal Analysis of House Dusts by Atomic Absorption Spectrometry

In general, dust is considered as house or street dust. Indoor dust, as a contamination source, has been studied for many years. In this work, the original Community Bureau of Reference of the European Commission (BCR) three-stage sequential extraction procedure was applied to the fractionation of Cr, Cu, Fe, Mn, Pb, and Zn in 20 house dust samples from five different areas of Sakarya, Turkey. Acetic acid, hydroxylammonium chloride, and hydrogen peroxide plus ammonium acetate were used for the first, second, and third steps of the BCR method, respectively. The extracts were analyzed for the studied heavy metals using flame atomic absorption spectrometry. Validation of the results was performed by using a standard reference material (BCR 701 Sediment) to certify the experimental results obtained and to evaluate the reliability of the method used. The elemental loadings typically increased in magnitude according to the area order: Izmit Caddesi>Ankara Caddesi >Erenler>Karaman>Korucuk. The results were in agreement with values reported in the literature.

Mobility and ecological risk assessment of trace metals in polluted estuarine sediments using a sequential extraction scheme

The three-stage sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb, and Zn, proposed by the Commission of the European Communities Bureau of Reference, was applied to sediment five samples collected from the Sal estuary, Sergipe State, northeast Brazil, in September 2009. The method showed satisfactory recoveries, detection limits, and standard deviations for determinations of trace metals in the sediments. Cd and Pb were the metals most prevalent in the bioavailable fractions (carbonates, Fe and Mn oxides, organic matter, and sulfides), while Ni, Zn, Cu, and Cr showed higher percentages in the inert fraction. The order of mobility of the metals was Cd (66%) > Pb (65%) > Zn (59%) > Ni (57%) = Cr (57%) > Cu (56%). Possible toxicity related to these metals was examined using the risk assessment code, and by comparing the chemical data with sediment quality guideline ERL-ERM values. Results obtained using the two methods were in agreement, and showed low to medium risk for all metals, indicating that adverse effects on aquatic biota should rarely occur.

Secondary steel mill slags with pulp and paper mill solid residues for soil amendment: mineralogy, relevant physicochemical properties and trace element availability

Inter-industrial utilisation of solid residues for soil amendment was investigated by combining secondary steel mill slags with residuals from a pulp and paper mill. Sample analysis included mineralogical characterisation by X-ray diffraction, relevant physicochemical properties and trace element availability by the original three-stage sequential BCR extraction procedure (CH3COOH, NH2OH·HCl and H2O2 + CH3COONH4) and residual fraction determination by acid digestion (USEPA 3051A). Respectively, the pseudo-total concentrations of trace elements were determined according to USEPA method 3051A. Consequently, the alkalinity of the samples (pH values 12.1–12.2) suggests significant buffering and acid neutralisation capacity with liming effect values (34.9%–35.6%, Ca-equivalents, d.w.) comparable to commercial ground limestone. This was supported by XRD, which only revealed the existence of portlandite [Ca(OH)2] an calcite [CaCO3]. Additionally, the pseudo-total concentrations of trace elements were lower than the respective limit values for EU soil improvers (2006/799/EC). However, Ba and V recovery during sequential extraction (Ba: 40.1–56.0 mg·kg–1, d.w., by CH3COOH; and V: 72.2–96.5 mg·kg–1, d.w., by NH2OH·HCl) indicates potential phytoavailability.

Lead Leachate from Rubies Undergone Heat Treatment Process

Low quality rubies are usually undergone heat treatment to improve their color and clarity. Some chemical additives may have been added during the treatment. Consequently, some toxic elements, particular lead, have been concerned as well as durability of the treated stones. Lead leachates from treated ruby have therefore been investigated; besides, changes of color and clarity have also been observed throughout the experiment. Three-Stage Sequential Extraction Procedure (BCR) was applied for leaching experiment. This process consists of 3 steps including BCR1 (exchangeable step), BCR2 (reduction step) and BCR3 (oxidation step). This procedure has been suggested to represent natural processes that may altered materials including hazardous one. Apart from regular procedure, we also rearrange the step orders. This aims to find out the most effective condition of lead leaching. The results indicate that the most effective step seems to be BCR 3 which is an aggressive reaction compared to the other steps. However, BCR 2 also yields the highest lead concentration after activating initially by BCR I in series I. On the other hand, BCR1 is unable to extract lead from the treated ruby. Moreover, the appearances of rubies in each series have been altered towards the experimental steps and well corresponded to the concentrations of lead in leachate.