Fractions Of Zn Research Articles

Mitigation of arsenic and zinc toxicity in municipal sewage sludge through co-pyrolysis with zero-valent iron: A promising approach for toxicity reduction of sewage sludge

Abstract The co-pyrolysis (at 300°C and 600°C) of municipal sewage sludge (SS) with zero-valent iron (Fe0: 1.5% and 3%) was investigated to reduce the toxicity of arsenic (As) and zinc (Zn) in SS. The BCR sequential extraction method, desorption kinetic analysis, and material characterization techniques (Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, X-ray diffraction) were used to evaluate the effects of the treatments on Zn and As behavior. The results showed that co-pyrolysis significantly reduced the acid-soluble fraction (18–43% for Zn; 83–95% for As) and mobility factor (45–85% for Zn; 86–96% for As) of Zn and As compared to untreated SS. Desorption experiments indicated a significant reduction in Zn and As release in treated samples, particularly in the co-pyrolysis sample at 600°C and Fe0 3% (67% for Zn; 88% for As) in comparison with untreated SS. Co-pyrolysis of Fe0 and SS led to the formation of new functional groups (Si–O, aromatic), a more porous surface morphology, and highly stable chemical crystals (ferric arsenate, zinc arsenide), which played a crucial role in Zn and As stabilization. The findings of this study suggest that co-pyrolysis is a promising approach for mitigating As and Zn toxicity in SS. However, additional field testing with plant-based systems is necessary for confirmation.

Lead and zinc chemical fraction alterations in multi-metal contaminated soil with pomelo peel biochar and biochar/apatite incubation

The issue of heavy metal soil contamination is widespread, and the negative effects of heavy metals on the ecosystem depend on their chemical speciation in contaminated soil. Pomelo peel-derived biochar produced at 300 °C (PPB300) and 500 °C (PPB500) and its combination with apatite ore (AP) was applied to immobilize lead (Pb) and zinc (Zn) in agricultural multi-metal polluted soil. Soil amendments including biochar (PPB300 and PPB500) at concentrations of 3%, 5%, and 10%, as well as a mixture of biochar and apatite (AP) at 3:3% and 5:5% weight ratios, were introduced into the soil matrix. The chemical forms of Pb and Zn in incubated soil samples and control soil (CS) were studied utilizing the Tessier’s sequential extraction procedure. The chemical partitioning of heavy metals was carried out using Tessier’s extraction protocol, yielding fractions representing exchangeable (F1), carbonate (F2), Fe/Mn oxide (F3), organic matter (F4), and residual (F5) forms. Quantification of Pb and Zn concentrations was accomplished via inductively coupled plasma mass spectrometry (ICP-MS). Observations revealed notable elevations in pH, organic carbon (OC), and electrical conductivity (EC) levels within the treated soil relative to the control soil (p < 0.05). After incubating PPB300, PPB500, and AP for 30 days, there was a reduction in the exchangeable fraction of Pb and Zn by approximately 64% and 58% respectively. This reduction was achieved by transforming heavy metals from mobile fractions to immobile fractions using five primary mechanisms: chemical and physical adsorption, electrostatic attraction, the formation of complexes via interactions with active groups, cation exchange processes, and precipitation events mediated by phosphate, carbonate ions, or hydroxyl ions within an alkaline environment. Therefore, pomelo peel-derived biochar and the blend of biochar/apatite show promise as materials for mitigating heavy metal pollution in soil.

Soil Contamination and Biomarkers in Ucides cordatus in Mangroves from Baía de Todos os Santos, Bahia, Brazil

The aim of the present study was to analyze the response to exposure to pollutants (trace elements and organic pollutants) using biomarkers (micronucleated cells and glutathione S-transferase and catalase activity) in uçá crab Ucides cordatus. The study was carried out at four sites: Cacha Prego (CP) and Ponta Grossa (PG), areas with low anthropic activity; and Ilha de Maré (IM) and Pitinga (PT), areas affected by industrial activity. At each site, soil and crab samples were collected to analyze the contents of potentially toxic elements (total concentration and chemical partitioning of trace elements), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Both total concentrations and geochemical fractions of Cu, Zn, and Ni in soils were significantly higher in IM. Likewise, higher reactive Pb contents were observed in mangroves both in IM and in PG. Values above quality limits were observed for organic pollutants (PAHs) in soils from CP and PT, while PCB contents were below the maximum permissible levels. Metals in crabs also showed spatial variations, with higher Cu concentrations in all tissues in IM and PT and higher Ni concentrations in hepatopancreas in PT during the dry season. PAH values in crabs did not show spatial variations; however, crustaceans with contents above maximum limits in their muscle tissue were found in CP. Crabs from the Baia de Todos Santos showed different responses in biomarker expression, with higher enzymatic activity and greater numbers of micronucleated cells in crabs from IM, suggesting oxidative stress and genotoxicity in this mangrove forest.

Cadmium, zinc, and copper leaching rates determined in large monolith lysimeters

Soil mass balances are used to assess the risk of trace metals that are inadvertently applied with fertilizers into agroecosystems. The accuracy of such balances is limited by leaching rates, as they are difficult to measure. Here, we used monolith lysimeters to precisely determine Cd, Cu, and Zn leaching rates in 2021 and 2022. The large lysimeters (n = 12, 1 m diameter, 1.35 m depth) included one soil type (cambisol, weakly acidic) and distinct cropping systems with three experimental replicates. Stable isotope tracers were applied to determine the direct transfer of these trace metals from the soil surface into the seepage water. The annual leaching rates ranged from 0.04 to 0.30 for Cd, 2.65 to 11.7 for Cu, and 7.27 to 39.0 g (ha a)−1 for Zn. These leaching rates were up to four times higher in the year with several heavy rain periods compared to the dry year. Monthly resolved data revealed that distinct climatic conditions in combination with crop development have a strong impact on trace metal leaching rates. In contrast, fertilization strategy (e.g., conventional vs. organic) had a minor effect on leaching rates. Trace metal leaching rates were up to 10 times smaller than fertilizer inputs and had therefore a minor impact on soil mass balances. This was further confirmed with isotope source tracing that showed that only small fractions of Cd, Cu, and Zn were directly transferred from the soil surface to the leached seepage water within two years (< 0.07 %). A comparison with models that predict Cd leaching rates in the EU suggests that the models overestimate the Cd soil output with seepage water. Hence, monolith lysimeters can help to refine leaching models and thereby also soil mass balances that are used to assess the risk of trace metals inputs with fertilizers.

Application of thermally treated sludge residues on an e-waste contaminated soil: effects on PTE bioavailability, soil physicochemical and biological properties, and L. perenne growth.

In the context of sustainable development, potentially toxic element (PTE) contamination of soil and large-scale disposal of sludge are two major environmental issues that need to be addressed urgently. It is of great significance to develop efficient and green technologies to solve these problems simultaneously. This study investigated the effects of a 5% addition of thermally treated sludge residues (fermentation and pyrolysis residues) in synergy with L. perenne on soil organic matter, mineral nutrients, PTE speciation, and PTE uptake and transport by L. perenne in an e-waste-contaminated soil through pot experiments. The results showed that the thermally treated sludge residues significantly increased soil electrical conductivity, cation exchange capacity, organic matter, available phosphorus, and exchangeable potassium contents. New PTE-containing crystalline phases were detected, and dissolved humic substances were found. Sludge fermentation residue significantly increased dissolved organic matter content, whereas sludge pyrolysis residue showed no significant effect. The combination of thermally treated sludge residues and L. perenne increased the residual fractions of Cu, Zn, Pb, and Cd. The thermally treated sludge residues promoted L. perenne growth, increasing fresh weight, plant height, and phosphorus and potassium uptake. The uptake of Cu, Zn, Pb, and Cd by L. perenne was significantly reduced. This approach has the potential for applications in the ecological restoration of e-waste-contaminated soils.

Diffusive Gradients in Thin-films as passive sampling tool for the measurement of labile species in fractionation analysis of metals (Fe, Mn, Cu, Zn and Pb) in beer

Fractionation analysis of Fe, Mn, Cu, Zn and Pb in beer is of high interest since their labile forms affect its stability and have implications for toxicity. In this study, we used the Diffusive Gradient in Thin-film (DGT) technique for the first time as a tool for passive sampling of labile species of Fe, Mn, Cu, Zn and Pb from beer. The validity of methodologies for total, total-dissolved and DGT-labile concentrations of Fe, Cu, Mn, Zn and Pb in beer was checked and then were applied to measure metals concentrations in two beer sorts: filtered and unfiltered (craft) beer. Commercial beer spiked with target analytes was used to check the linear accumulation of metals by DGT for 72 h DGT deployment period. The obtained determination coefficients were in the range of 0.986–0.998. The total concentrations of metals in beers determined by GFAAS were in the range of 60.4–957 µg/L (Fe), 58.0–206 µg/L (Mn), 45.6–314 µg/L (Cu), 70.0–313 µg/L (Zn) and 0.75–4.22 µg/L (Pb). Of these, the DGT-labile fractions of Fe, Cu, Mn, Zn and Pb were 5.0 – 7.8 µg/L Fe, 4.5 – 15.0 µg/L Cu, 23.1 – 37.0 µg/L Mn, 17.7 – 41.5 µg/L Zn and 0.15 – 0.35 µg/L Pb. This study provides a simple and reliable methodology for the fractionation of metals in beer.

Effect of Sintering Time and Cl Doping Concentrations on Structural, Optical, and Luminescence Properties of ZnO Nanoparticles

Zinc oxide (ZnO) nanoparticles were synthesized hydrothermally using zinc acetate dihydrate and sodium thiosulfate pentahydrate precursors. The synthesized powders were sintered in air at 600 °C for different durations with a Cl-doping concentration of 25 mg/g. The optimal sintering time was found to be 5 h, resulting in the successful formation of the ZnO phase with small particle sizes of around 90 nm, nominal atomic fractions of Zn and O (~50%, ~50%), and increased luminescence intensity. The ideal concentration of Cl was discovered to be 25 mg/g of ZnO, which resulted in the highest luminescence intensity. The ZnO luminescence characteristics were observed in emission bands peaking at approximately 503 nm attributed to the transition from oxygen vacancies. A considerable improvement in the emission intensity was observed with increased Cl doping concentration, up to eight orders of magnitude, compared to pristine ZnO nanoparticles. However, the luminescence intensity decreased in samples with higher concentrations of Cl doping due to concentration quenching. These preliminary outcomes suggest that Cl-doped ZnO nanoparticles could be used for radiation detector development for radon monitoring and other related applications.

Insights on hazardous metal bioaccessibility, and groundwater impacted by Zn residues from a legacy mine and risk evaluation of adjacent soils.

This study explored the legacy impact of Zinc plant residues (ZPRs) in Kabwe, Zambia, on the environment and human health, particularly in light of the town's reputation for Pb pollution. ZPRs solid samples and groundwater within and around ZPRs zone were collected from the legacy mine, along with soils in a 10km radius from the mine site. Bioaccessible fractions of Pb and Zn were elucidated by Japanese leaching test (JLT) and simple bioaccessibility extraction test (SBET). Cationic speciation of Pb and Zn from inhalable and ingestible ZPRs particles was investigated via sequential extraction. Groundwater in the ZPRs area showed higher Zn levels (1490mg/L) compared to Pb (1.7mg/L). Elevated Zn concentration were facilitated by the presence of soluble Zn sulfates while Pb was constrained due to its precipitation as anglesite. Groundwater sampled outside the ZPRs area was within the Zambia regulatory limits (< 0.5mg/L for Pb and < 1mg/L for Zn). Inhalation exposure to < 30µm dust particles from ZPRs and soils near the mine indicated negligible risk, with < 3% of bioaccessible Pb in artificial lysosomal fluid. Meanwhile, oral intake of ZPRs particles < 250µm revealed elevated bioaccessible fractions (36% for Pb and 70% for Zn). ZPRs cationic speciation of ingestible particles < 30µm, 30-75µm, 75-150µm and 150-250µm indicated that the bioaccessible Pb predominantly emanated from labile Pb fractions under gastric conditions with pH < 1. This was due to the dissolution of Pb associated with the exchangeable phase, carbonates and iron/manganese oxides; however, only exchangeable/carbonate Pb was bioaccessible at pH < 2. Hazard quotients indicated increased risks of Pb intoxication through the ingestion of ZPRs and soils near the legacy mine, with higher risks observed in children, emphasizing the need to remediate legacy mine wastes to reduce health risks and protect groundwater through monitoring in mining-affected regions.

Enhancing properties of Al-Zn-Mg-Cu alloy through microalloying and heat treatment

This paper aims to understand the influence of microalloying constituents (Ti, Zr, Sr and Sc), and three heat treatment conditions i.e., T6, retrogression and reaging (RRA) and high temperature aging (HTA) on mechanical and thermal characteristics of modified Al-Zn-Mg-Cu-X alloy using microstructural analyses consist of precipitation characteristics, phase fraction and phase morphology. Addition of 0.25 wt % Sc significantly refines the grain structure, reducing the grain size from 62 μm to 34 μm and increasing Al3Zr, Al3(Zr, Ti), and Al3(Sc, Zr) precipitate fraction. After T6 aging, the alloy exhibits primary precipitates of fine η and T phases, accompanied by secondary intermetallics as well as S phases. RRA treatment led to a slightly larger fraction of coarse Zn and Cu-rich phases, while HTA results in larger η, T, and S phases due to high-temperature aging. The addition of Sc reduces the cooling rate by raising the transition temperature to 532 °C with an enthalpy of 22.1 J/g. T6 treatment shows dissolution of most η phases within the matrix, although RRA and HTA exhibit higher enthalpy due to a greater fraction of η phases. The tensile strength of Al-Zn-Mg-Cu-X alloy follows the following sequence: T6 > RRA > HTA > as-cast condition, regardless of micro-alloy additions. Under T6 conditions, Sc added alloy achieves 30 % higher strength, i.e., 575 MPa, than base alloy due to fine dispersoids. RRA treatment enhances elongation without compromising mechanical properties, resulting in a shift from transgranular brittle fracture to intergranular-dominated mix-mode fracture, with the presence of secondary cracking.

The interplay between crystallinity and the levels of Zn and carbonate in synthetic microcalcifications directs thyroid cell malignancy.

One of the key challenges in diagnosing thyroid cancer lies in the substantial percentage of indeterminate diagnoses of thyroid nodules that have undergone ultrasound-guided fine-needle aspiration (FNA) biopsy for cytological evaluation. This delays the definitive diagnosis and treatment plans. We recently demonstrated that hydroxyapatite microcalcifications (MCs) aspirated from thyroid nodules may aid nodule diagnosis based on their composition. In particular, Zn-enriched MCs have emerged as potential cancer biomarkers. However, a pertinent question remains: is the elevated Zn content within MCs a consequence of cancer, or do the Zn-enriched MCs encourage tumorigenesis? To address this, we treated the human thyroid cancer cell line MDA-T32 with synthetic MC analogs comprising hydroxyapatite crystals with varied pathologically relevant Zn fractions and assessed the cellular response. The MC analogs exhibited an irregular surface morphology similar to FNA MCs observed in cancerous thyroid nodules. These MC analogs displayed an inverse relationship between Zn fraction and crystallinity, as shown by X-ray diffractometry. The zeta potential of the non-Zn-bearing hydroxyapatite crystals was negative, which decreased once Zn was incorporated into the crystal. The MC analogs were not cytotoxic. The cellular response to exposure to these crystals was evaluated in terms of cell migration, proliferation, the tendency of the cells to form multicellular spheroids, and the expression of cancer markers. Our findings suggest that, if thyroid MCs play a role in promoting cancerous behavior in vivo, it is likely a result of the interplay of crystallinity with Zn and carbonate fractions in MCs.

Evaluation of Total Concentrations and Bioaccessible Fractions of Essential and Toxic Elements in Amaranth, Quinoa and Chia by MIP OES

The total concentrations and the bioaccessible fractions of Al, B, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Ni, V and Zn were evaluated in 10 samples of pseudocereals, being 3 of amaranth, 3 of quinoa and 4 of chia. The samples were decomposed in a digester block with a reflux system under conditions optimized and the analyses were performed by microwave-induced plasma optical emission spectrometry. In all grains investigated, the highest total concentrations were found for the macroelements K, Mg and Ca, as well as the microelements Fe, Mn, and Zn. When the bioaccessible fraction was evaluated, negative correlations were observed between the content of total phenolic compounds and the bioaccessibility for most elements, in all samples. Among the elements considered essential in our diet, K (99%) and Cu (59%) presented the highest percentages of bioaccessible fraction. Among those elements considered potentially toxic, Ba did not exceed 15% bioaccessible fraction and Al presented concentrations lower than the limit of detection in all samples.

The Chemical Nature of Mercury and Copper Sulfides and Its Implication for Bioavailability Assessments in Sediments

Sulfur chemistry plays an important role in regulating the bioavailability of heavy metals (HMs) because HM sulfides are extremely insoluble in sediments. However, quantifying HM sulfides in sediments has been difficult because they are considered acid-extractable (AE). Previous studies also found that Hg and Cu behaved differently from other HMs in sediments. This study investigated the chemical nature of Hg and Cu sulfides and the causes of Hg and Cu anomalies in sediments. The results indicated that Hg and Cu sulfides are not mono-sulfides (HS− or S=) but bi-sulfides (S2=), which are non-acid-extractable (NAE) under nitrogen. These results explain the Hg and Cu anomalies compared to other HMs and facilitate a procedure to quantify Hg and Cu sulfides in sediments. We analyzed the AE and NAE fractions of Hg, Cu, and Zn under nitrogen in the sediments of Apalachicola Bay, North Florida. Zn was included for comparison because Zn sulfide is mono-sulfide. The NAE Hg and Cu were, on average, 97.9 ± 2.7% and 84.6%, respectively, of the total, much higher than that of Zn (24.3% of the total) in the sediments, as expected. The NAE fractions of Hg and Cu were sulfides and thus could be excluded from the bioavailability assessments.

Oxidation potential of PM2.5 in a mechanical processing plant and its association with metal composition

Oxidative potential (OP) of particles is an emerging indicator of health that reflects their ability to induce oxidative stress and cause adverse health effects. It offers us a useful tool to evaluate the health effects of particles released by different industrial processes. We measured the OPv (volume normalized OP characterizes overall oxidative burden) and OPm (mass normalized OP characterizes intrinsic toxicity) of PM2.5 from a casting workshop, a machining workshop, a meeting room of a machining processing plant, and outdoors using dithiothreitol (DTT) assay. The observed variations were substantial and varied greatly, underscoring the diverse toxicological profiles of particulates from distinct sources. Overall, PM2.5 mass concentration and OPv were highest in the casting workshop (PM2.5: 669.26 ± 402.62 μg/m3, OPv: 69.55 ± 128.35 nmol/(min·m3)), followed by the machining workshop (PM2.5 = 85.51 ± 41.89 μg/m3, OPv = :5.38 ± 2.68 nmol/(min·m3)), outdoor (PM2.5: 30.77 ± 13.34 μg/m3, OPv: 1.83 ± 0.92 nmol/(min·m3)), and meeting room (PM2.5: 26.97 ± 12.03 μg/m3, OPv: 1.86 ± 1 nmol/(min·m3)). However, localized variances influenced by PM's intrinsic toxicity (OPm) reordered these rankings. For example, PM2.5 mass concentration at the spheroidizing/pouring zone in the casting workshop was the highest, but the OPv was not due to the low intrinsic toxicity of the particles. Spearman's correlation analysis implied that the OPv was significantly correlated with the concentration of transition metals Mn (ρ = 0.47, P < 0.01), Fe (ρ = 0.503, P < 0.01), and Zn (ρ = 0.507, P < 0.01) in addition to PM2.5 mass concentration (ρ = 0.879, P<0.01), and the OPm was significantly correlated with the mass fraction of Zn (ρ = 0.34, P < 0.05) and Al (ρ = 0.333, P < 0.05). Besides, environmental factors (wind speed, temperature relative humidity, CO2) did not contribute to the oxidation potential. Higher oxidation potential (OPv) means higher health risks, our findings underscore the imperative to consider both PM mass concentration and intrinsic toxicity for future air pollution control efforts.

Prevalence of antibiotic and metal resistance genes in phytoremediated cadmium and zinc contaminated soil assisted by chitosan and Trichoderma harzianum

Heavy metal in soil have been shown to be toxic with high concentrations and acts as selective pressure on both bacterial metal and antibiotic resistance determinants, posing a serious risk to public health. In cadmium (Cd) and zinc (Zn) contaminated soil, chitosan (Chi) and Trichoderma harzianum (Tri) were applied alone and in combination to assist phytoremediation by Amaranthus hypochondriacus L. Prevalence of antibiotic and metal resistance genes (ARGs and MRGs) in the soil was also evaluated using metagenomic approach. Results indicated that the phytoremediation of Cd and Zn contaminated soil was promoted by Chi, and Tri further reinforced this effect, along with the increased availability of Cd and Zn in soil. Meanwhile, combination of Chi and Tri enhanced the prevalence of ARGs (e.g., multidrug and β-lactam resistance genes) and maintained a high level of MRGs (e.g., chromium, copper) in soil. Soil available Zn and Cd fractions were the main factors contributing to ARGs profile by co-selection, while boosted bacterial hosts (e.g., Mitsuaria, Solirubrobacter, Ramlibacter) contributed to prevalence of most MRGs (e.g., Cd). These findings indicate the potential risk of ARGs and MRGs propagation in phytoremediation of metal contaminated soils assisted by organic and biological agents.

Source apportionment and source-specific risk assessment of bioavailable metals in river sediments of an anthropogenically influenced watershed in China

Integrated source analysis and risk assessment of metals facilitate the development of targeted risk management strategies. However, previous studies usually addressed total concentration rather than bioavailability, and consequently overestimated metal risk, especially natural source-related risk. In this study, a source-specific risk assessment was conducted by integrating the source analysis of bioavailable metals in surface sediments. Moreover, risk assessment was performed using two bioavailability-based indices: the total availability risk index (TARI) and a modified index of mean probable effect concentration quotients (mPEC-Q). A representative river watershed in eastern China was selected as the study area. Findings revealed that the total concentrations of Pb, Cu, Zn, Cr, and Ni in the sediments were 1.4–2.2 times higher than the local soil background values. Using a modified community bureau of reference (BCR) sequential extraction procedure, the dominant fraction for Pb, Cu, Zn, and Cr in the studied area was found to be the residual fraction, constituting 53.63–62.44% of the total concentrations. This suggested that a significant portion of the metals potentially originated from natural sources. Nevertheless, the concentration enrichment ratio (CER) indicated that anthropogenic sources contributed significantly, accounting for 67.84–87.68% of bioavailable metals. The positive matrix factorization (PMF) model further identified three different sources of bioavailable metals, with a descending concentration contribution sequence of industrial sources (37.61%), mixed traffic and natural sources (33.17%), and agricultural sources (29.22%). Both the TARI and mPEC-Q index values indicated that the bioavailable metals generally posed a moderate risk, and Ni was the priority pollutant. Industrial sources contributed the most to the total risk, although the contribution from TARI-based assessment (37.27%) was lower than that from the mPEC-Q assessment (46.43%). This study provides an example of the consideration of metal bioavailability in the context of source-specific risk assessments to develop more reasonable management strategies.

AG1®, a Novel Synbiotic, Demonstrates Superior Mineral Bioaccessibility and Bioavailability Compared to a Tablet Multivitamin and Mineral Supplement Using an In Vitro Model of the Upper Gastrointestinal Tract

While traditional multivitamin and mineral (MVM) supplements generally come in tablet form, new powder forms of MVM supplements are available with theoretically higher bioavailability relative to tablet MVM supplements. The purpose of this study was to assess the bioaccessibility and bioavailability of minerals (magnesium (Mg), zinc (Zn), calcium (Ca), and potassium (K)) in a tablet MVM supplement compared to a novel powder Foundational Nutrition supplement (AG1®), containing minerals, vitamins, phytochemicals, and pre-/probiotics, in the upper gastrointestinal tract. The tablet MVM supplement was specifically formulated for this study, with matched mineral contents and identical chemical structures. The adapted Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) model was used to assess the bioaccessibility and bioavailability of soluble minerals using a simulated upper gastrointestinal tract and dialysis membrane to mimic human digestion and absorption. The bioaccessibility was assessed at the end of the stomach and duodenum. The bioaccessibility and bioavailability were assessed at 1, 2, and 3 h following dialysis. The preliminary soluble mineral analysis of the tablet (crushed to a powder) and AG1 powder demonstrated significantly higher (p &lt; 0.05) soluble fractions of Zn and Ca, but lower Mg in the AG1 powder vs. the tablet. The total soluble mineral percentages at the stomach and duodenum end were all significantly higher for the AG1 powder vs. the tablet (p &lt; 0.05). Mg, Ca, and Zn were more (p &lt; 0.05) bioaccessible and bioavailable in the powder compared to the tablet during the small intestine simulation. The bioaccessible fraction of K was higher (p &lt; 0.05) only at 3 h for the tablet vs. the powder. These preclinical data demonstrate that the AG1 powder has superior dissolution and disintegration characteristics compared to the tablet, leading to increased bioaccessibility and bioavailability in vitro.

Organic amendment application affects the release behaviour, bioavailability, and speciation of heavy metals in zinc smelting slag: Insight into dissolved organic matter

Organic amendments are commonly used in assisted phytostabilization of mine wastes by improving their physicochemical and biological properties. These amendments are susceptible to leaching and degradation, resulting in the generation of dissolved organic matter (DOM), which significantly influences the geochemical behaviour of heavy metals (HMs). However, the geochemical behaviour of HMs in metal smelting slag driven by organic amendment-derived DOM remains unclear. In this study, we investigated the impact of cow manure-derived DOM on the release behaviour, bioavailability, and speciation of HMs (Cu, Pb, Zn, and Cd) in zinc smelting slag using a multidisciplinary approach. The results showed that DOM enhanced the weathering of the slag, with a minimal impact on the slag’s mineral phases, except for causing gypsum dissolution. The DOM addition resulted in a slight increase in HM release from the slag during the initial inoculation period, followed by a reduction in HM release during the later period. Furthermore, the DOM addition increased the diversity and relative abundance of the bacterial community. This, in turn, led to a decrease in the dissolved organic carbon (DOC) content and enhanced the transformation of labile DOM compounds into recalcitrant compounds. The variation in HM release during various inoculation periods can be attributed to the bacterial decomposition and transformation of DOM, which further enhanced the transformation of HM fractions. Specifically, during the later period, DOM promoted the conversion of a portion of the reducible and oxidizable fractions of Cu, Pb, and Zn into the acid-soluble and residual fractions. Moreover, it partially transformed the reducible, oxidizable, and residual fractions of Cd into the acid-soluble fraction. Overall, this study provides new insights into the geochemical behaviour of HMs in slag governed by the coupling effect of DOM and the bacterial community. These findings have implications for the use of organic amendments in assisted phytostabilization of metal smelting slag. Environmental implicationMetal smelting slag is hazardous due to its high levels of HMs, and its improper disposal has serious consequences for the ecosystem. Organic amendments are employed in assisted phytostabilization of the slag site by improving its microecological properties. However, the impact of organic amendment-derived DOM on HM migration and transformation in slag remains unclear. This study indicated that the coupling effects of DOM and microbes governed the geochemical behaviour of HMs in slag. These findings provide new insights into how organic amendments impact the geochemical behaviour of HMs in slag, contributing to the development of phytostabilization technology.

Performance of Cu/ZnO/Al2O3 Catalysts Prepared by Sol–Gel Methods on Methanol Steam Reforming

Cu/ZnO/Al2O3 catalysts were prepared for online methanol steam reforming (MSR) using a conventional sol–gel method in this study. The optimal preparation conditions, including the calcination temperature, Cu loading, molar ratio of citric acid to metal ions (CA/M), and pH, were investigated. CZA50 exhibited the highest MSR activity among all catalysts. It was prepared at a calcination temperature of 350 °C; Cu, Zn, and Al molar fractions of 50%, 30%, and 20%; CA/M of 1.5; and without adjusting pH. Furthermore, a modified sol–gel method was proposed to enhance the mechanical strength of Cu/ZnO/Al2O3 catalysts by using γ-Al2O3 powders as catalyst precursors instead of aluminum nitrates. In this modified method, part of Cu2+ and Zn2+ ions were impregnated firstly on γ-Al2O3 powders, and then the remaining metal ions formed sol–gel with citric acid. MCZA-0.25 catalysts prepared by this modified method showed superior catalytic activity at an Al/(Cu+Zn) ratio of 0.25. The methanol conversion rates of CZA50, MCZA-025, and CZA-Commercial were 82.9%, 79.4%, and 74.7% at the temperature of 200 °C and methanol liquid phase space velocity (LHSV) of 1.0/h, respectively. The average crushing strength of CZA50, MCZA-0.25, and CZA-Commercial were measured as 28 N/cm, 37 N/cm, and 32 N/cm, respectively.

Carbothermal treatment of municipal solid waste incineration fly ash: Purification and valuable elements extraction

Thermal separation of heavy metals from municipal solid waste incineration fly ash (MSWI FA) is a promising approach for both fly ash purification and heavy metal recovery. However, its commercial viability is hindered by excessive energy consumption. In this study, we introduce carbothermal reduction for MSWI FA treatment as an innovative strategy to enhance heavy metal volatilization and reduce the required heating temperature. By incorporating carbon (FA/Carbon = 1:0.2), the volatilization fractions of Pb, Cd and Zn reached 96.5 %, 100 %, and 63.9 %, respectively, when subjected to 900 °C for 2 h. Remarkably, these volatilization amount surpassed the volatilization fractions attained when raw fly ash (RFA) was independently calcined at 1000 °C for 2 h: Pb (90.2 %), Cd (92.9 %) and Zn (30.2 %). Conversely, Cu volatilization was impeded by carbon inclusion. Comparable trends were shown in washing fly ash (WFA). Notably, concentrated carbothermal reduction led to substantial concentrations of Pb (2.5–7.1 %) and Zn (4.9–20.7 %), rendering them amenable for recycling through metallurgical routes. Intriguingly, higher carbon content (FA/Carbon = 1:0.3) hindered rather than enhanced heavy metal volatilization from RFA. We found that condensation of NaCl and KCl occurred in carbon pores, causing the formation of molten eutectic which trapped the heavy metals at high temperatures. Therefore, more carbon showed more enhancement of heavy metal volatilization from WFA which was free of NaCl and KCl. Ultimately, two comprehensive pathways for the resourceful utilization of fly ash based on carbon thermal reduction were proposed and compared. This study demonstrates carbothermal reduction as an effective approach for simultaneous purification and metal recovery of MSWI FA, exhibiting promising potential for industrial application.

Different Source Contributions of Bioactive Trace Metals in Sinking Particles in the Northern South China Sea

Time-series samples intercepted via three synchronized moored sediment traps, deployed at 1000 m, 2150 m, and 3200 m in the northern South China Sea (NSCS) during June 2009–May 2010, were analyzed to quantify the bioactive trace metal fluxes in sinking particles and investigate their different source contributions. Iron (Fe) primarily originated from lithogenic sources. Manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) exhibited various degrees of enrichment over their continental crustal ratios. Since the sources of bioactive trace metals in sinking particles can be divided into lithogenic, biogenic, and excess fractions, mass conservation calculations were used to quantify the contribution of each source. The results showed that Fe, Mn, and Co had extremely low biogenic proportions (0.1–3.3%), while Ni, Cu, and Zn had higher proportions (2.7–17.3%), with the biogenic fraction decreasing with the depth. Moreover, excess sources accounted for a significant proportion of Mn (68–75%), Co (34–54%), Ni (60–62%), Cu (59–74%), and Zn (56–65%) in sinking particles at the three sampling depths. The excess fractions of Mn, Co, and Cu in sinking particles can be affected by authigenic particles. This is supported by their similar scavenging-type behavior, as observed via the increase in their fluxes and enrichment patterns with the increasing depth. Furthermore, the excess fractions of Ni, Cu, and Zn may have significant contributions from anthropogenic sources. The variability of Fe in sinking particles was mainly controlled via lithogenic matter. Notably, organic matter and opal were found to be pivotal carriers in the export of excess bioactive trace metals (Mn, Co, Ni, and Cu) via the water column, accompanied with the elevated ballast effect of lithogenic matter with the depth. However, the transportation of excess Zn was more complicated due to the intricate processes involved in Zn dynamics. These findings contribute to our understanding of the sources and transport mechanisms of bioactive trace metals in the marine environment.