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1.
Environ Sci Technol ; 56(13): 9446-9452, 2022 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-35733356

RESUMO

Tooeleite [FeIII6(AsIIIO3)4SO4(OH)4.4H2O] is an important As(III) host phase in diverse mining-impacted environments. Tooeleite has also received attention as a target phase for immobilizing As(III) in environmental and engineered settings. However, little is known regarding tooeleite's environmental stability, with no previous research examining the possible role of Fe(II) in inducing tooeleite transformation (as occurs for Fe(III) oxide minerals). We investigated shifts in solid-phase Fe and As speciation and associated As mobilization into the aqueous phase during exposure of tooeleite to aqueous Fe(II) under anoxic conditions at pH 4 to 8. Our results demonstrate that environmentally relevant concentrations of aqueous Fe(II) (i.e., 1 to 10 mM) induce significant mobilization of As(III) from tooeleite under near-neutral pH conditions, with greater As(III) mobilization occurring at higher pH. Extended X-ray absorption fine structure spectroscopy at both the As and Fe K-edge reveals that the observed As(III) mobilization was coupled with partial Fe(II)-induced transformation of tooeleite to As(III)-bearing ferrihydrite at pH 6 to 8. These results provide new insights into the environmental stability of tooeleite and demonstrate a novel pathway for As(III) mobilization in tooeleite-bearing systems.


Assuntos
Arsênio , Compostos Férricos , Arsênio/química , Compostos Férricos/química , Compostos Ferrosos/química , Ferro/química , Minerais/química , Oxirredução
2.
Environ Res ; 204(Pt A): 111924, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34487695

RESUMO

This study assessed the ability of phosphorus (P) fertilizer to remediate the rhizosphere of three wild plant species (Banksia seminuda, a tree; Chloris truncata, a grass; and Hakea prostrata, a shrub) growing in a soil contaminated with total (aliphatic) petroleum hydrocarbon (TPH). Plant growth, photosynthesis (via chlorophyll fluorescence), soil microbial activity, alkane hydroxylase AlkB (aliphatic hydrocarbon-degrading) gene abundance, and TPH removal were evaluated 120 days after planting. Overall, although TPH served as an additional carbon source for soil microorganisms, the presence of TPH in soil resulted in decreased plant growth and photosynthesis. However, growth, photosynthesis, microbial activities, and AlkB gene abundance were enhanced by the application of P fertilizer, thereby increasing TPH removal rates, although the extent and optimum P dosage varied among the plant species. The highest TPH removal (64.66%) was observed in soil planted with the Poaceae species, C. truncata, and amended with 100 mg P kg-1 soil, while H. prostrata showed higher TPH removal compared to the plant belonging to the same Proteaceae family, B. seminuda. The presence of plants resulted in higher AlkB gene abundance and TPH removal relative to the unplanted control. The removal of TPH was associated directly with AlkB gene abundance (R2 > 0.9, p < 0.001), which was affected by plant identity and P levels. The results indicated that an integrated approach involving wild plant species and optimum P amendment, which was determined through experimentation using different plant species, was an efficient way to remediate soil contaminated with TPH.


Assuntos
Petróleo , Poluentes do Solo , Biodegradação Ambiental , Citocromo P-450 CYP4A/genética , Hidrocarbonetos , Fósforo , Rizosfera , Solo , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
3.
Environ Sci Technol ; 55(3): 1779-1789, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33449633

RESUMO

The influence of soil properties on PFOS sorption are not fully understood, particularly for variable charge soils. PFOS batch sorption isotherms were conducted for 114 temperate and tropical soils from Australia and Fiji, that were well-characterized for their soil properties, including total organic carbon (TOC), anion exchange capacity, and surface charge. In most soils, PFOS sorption isotherms were nonlinear. PFOS sorption distribution coefficients (Kd) ranged from 5 to 229 mL/g (median: 28 mL/g), with 63% of the Fijian soils and 35% of the Australian soils showing Kd values that exceeded the observed median Kd. Multiple linear regression showed that TOC, amorphous aluminum and iron oxides contents, anion exchange capacity, pH, and silt content, jointly explained about 53% of the variance in PFOS Kd in soils. Variable charge soils with net positive surface charges, and moderate to elevated TOC content, generally displayed enhanced PFOS sorption than in temperate or tropical soils with TOC as the only sorbent phase, especially at acidic pH ranges. For the first time, two artificial neural networks were developed to predict the measured PFOS Kd (R2 = 0.80) in the soils. Overall, both TOC and surface charge characteristics of soils are important for describing PFOS sorption.


Assuntos
Poluentes do Solo , Solo , Adsorção , Austrália , Redes Neurais de Computação , Poluentes do Solo/análise
4.
Environ Sci Technol ; 55(13): 8877-8887, 2021 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-34152751

RESUMO

Microplastics (MPs) exposed to the natural environment provide an ideal surface for biofilm formation, which potentially acts as a reactive phase facilitating the sorption of hazardous contaminants. Until now, changes in the contaminant sorption capacity of MPs due to biofilm formation have not been quantified. This is the first study that compared the capacity of naturally aged, biofilm-covered microplastic fibers (BMFs) to adsorb perfluorooctane sulfonate (PFOS) and lead (Pb) at environmentally relevant concentrations. Changes in the surface properties and morphology of aged microplastic fibers (MF) were studied by surface area analysis, infrared spectroscopy, and scanning electron microscopy. Results revealed that aged MFs exhibited higher surface areas because of biomass accumulation compared to virgin samples and followed the order polypropylene>polyethylene>nylon>polyester. The concentrations of adsorbed Pb and PFOS were 4-25% and 20-85% higher in aged MFs and varied among the polymer types. The increased contaminant adsorption was linked with the altered surface area and the hydrophobic/hydrophilic characteristics of the samples. Overall, the present study demonstrates that biofilms play a decisive role in contaminant-plastic interactions and significantly enhance the vector potential of MFs for toxic environmental contaminants. We anticipate that knowledge generated from this study will help refine the planetary risk assessment of MPs.


Assuntos
Plásticos , Poluentes Químicos da Água , Adsorção , Biofilmes , Microplásticos , Poluentes Químicos da Água/análise
5.
Ecotoxicol Environ Saf ; 223: 112611, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34385057

RESUMO

Understanding the transport behaviour of arsenic (As) from soils to humans is critical when undertaking human health risk assessment and contamination control. This research examined As bioaccessibility in different As fractions and particle size fractions of As-enriched mine soils using different extractions. Bioaccessibility of As ranged from 0.24% to 32% for Solubility Bioaccessibility Research Consortium (SBRC) and Physiologically Based Extraction Test (PBET) methods, with extractable As (using 0.43 M HNO3) being 1.3-24.9%. The highest As bioaccessibility (19-32%) was consistently observed in the fine particle size fraction (< 53 µm) of all three extractions. Sequential extractions revealed that As fractions were mostly associated with crystalline (30-73%) and amorphous (9-59%) Fe/Al oxyhydroxides. The bioaccessibility of As in the gastric phase of SBRC and PBET methods highlighted a positive correlation (R2 = 0.83-0.88, p < 0.01) with exchangeable, surface and amorphous- bound As fractions, while the intestinal phase showed a strong positive correlation (R2 = 0.85-0.89, p < 0.01) with exchangeable and surface bound fractions. The study revealed that As bioaccessibility in soils can potentially be determined using the 0.43 M HNO3 extraction procedure. Health risk assessment confirmed that there was a strong increase in chronic daily intake, hazard quotient and cancer risk, with a reduction in particle size.


Assuntos
Arsênio , Poluentes do Solo , Arsênio/análise , Austrália , Disponibilidade Biológica , Humanos , New South Wales , Medição de Risco , Solo , Poluentes do Solo/análise
6.
J Environ Manage ; 239: 73-83, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30889520

RESUMO

This study aimed to investigate the potential of energy crops for biomethane production by examining the influence of abattoir and municipal wastewater irrigation on biomass production and the Biochemical Methane Potential (BMP). The experiments covered seven energy crops including sugar beet, alfalfa, maize, giant reed, napier grass, sunflower and canola. The biomass was harvested at three months of planting and BMP of each energy crops was assessed using anaerobic digestion. Giant reed yielded the highest biomass (22.3 t ha-1) from A800 treatment compared to the other species. The best performance for BMP (793.56 Nml CH4 g VS-1) was recorded for maize biomass irrigated with abattoir wastewater which is equivalent to gross energy yield 1041 GJ ha-1 yr-1 or electricity yield 284.8 MW h ha-1 yr-1. The digestate samples collected after anaerobic digestion of biomass from plants were analysed for their nutrient value. Nutrient content of digestates varied between energy crops, waste water sources and irrigation levels. The highest nitrate content was measured for giant reed (A800) and phosphate and sulphate contents for sugar beet leaf (A800). The results indicated that wastewater sources can be used to grow energy crops, thereby producing biomethane for energy and digestate for plant nutrition through anaerobic digestion process.


Assuntos
Fertilizantes , Águas Residuárias , Anaerobiose , Biocombustíveis , Biomassa , Metano
7.
Ecotoxicol Environ Saf ; 148: 738-746, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29179146

RESUMO

Arsenic (As) and copper (Cu) are co-contaminants in the environment but little is known about their ecological impact as mixtures in soil. In this study, we investigated the combined As-Cu interactions on toxicity and uptake as binary mixtures in 5 contrasting soils. The study included solubility, contaminant uptake and toxicity in cucumber (Cucumis sativus L.) as a model plant species. Soils were spiked individually and as a mixtures at 10 different As levels (2, 4, 8 up to 1024mgkg-1). Copper was added with As at two effective concentration levels (EC10Cu and EC50Cu). Arsenic uptake was significantly reduced in the presence of Cu and a higher effect was demonstrated with increasing pore-water pH. Copper accumulation was not significantly influenced by As. An additive response on plant growth was predominant overall when expressed from pore-water parameters with root mean square errors of 12.6 and 13.2 for EC10Cu and EC50Cu treatments, respectively.


Assuntos
Arsênio/toxicidade , Cobre/toxicidade , Cucumis sativus/efeitos dos fármacos , Poluentes do Solo/toxicidade , Solo/química , Arsênio/metabolismo , Disponibilidade Biológica , Cobre/metabolismo , Cucumis sativus/crescimento & desenvolvimento , Cucumis sativus/metabolismo , Sinergismo Farmacológico , Poluentes do Solo/metabolismo , Solubilidade , Água/química
8.
Environ Sci Technol ; 50(23): 13062-13069, 2016 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-27797507

RESUMO

Phytotoxicity of inorganic contaminants is influenced by the presence of competing ions at the site of uptake. In this study, interaction of soil pore-water constituents with arsenate toxicity was investigated in cucumber (Cucumis sativa L) using 10 contrasting soils. Arsenate phytotoxicity was shown to be related to soluble carbonate and phosphate. The data indicated that dissolved phosphate and carbonate had an antagonistic impact on arsenate toxicity to cucumber. To predict arsenate phytotoxicity in soils with a diverse range of soil solution properties, both carbonate and phosphate were required. The relationship between arsenic and pore-water toxicity parameters was established initially using multiple regression. In addition, based on the relationship with carbonate and phosphate we successively applied a terrestrial biotic ligand-like model (BLM) including carbonate and phosphate. Estimated effective concentrations from the BLM-like parametrization were strongly correlated to measured arsenate values in pore-water (R2 = 0.76, P < 0.001). The data indicates that an ion interaction model similar to the BLM for arsenate is possible, potentially improving current risk assessments at arsenic and co-contaminated soils.


Assuntos
Arseniatos , Solo , Arsênio , Carbonatos , Fosfatos , Poluentes do Solo , Água
9.
Ecotoxicology ; 25(3): 481-90, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26738879

RESUMO

The free ion activity and "biotic ligand" models predict that the free metal ion and other pore-water parameters describe terrestrial phytotoxicity. In this study, pore-water chemistry and measured Cu(2+) was used to describe phytotoxicity of cucumber (Cucumis sativa L) in 10 contrasting soils at different soil Cu loadings. Both soil solution Cu (Cu(pw)) and Cu(2+) successfully described the response variable for all ten soils with R(2) values of 0.73 and 0.66, respectively. Separation of soils as acid and alkaline and fitting separately showed that there was a strongly significant fit for both log Cu(2+) and log Cu(pw) in acidic soils (R(2) = 0.92 and 0.86, respectively) but weakly significant fit for alkaline soils. The pCu EC50 and EC10 values in all acidic soils for cucumber were 5.83 (6.03-5.63) and 7.53 (8.27-7.00), respectively. In our dataset alkaline soils need to be treated individually. In addition, pCu could be predicted based on pH and total concentration alone. Despite only 12 weeks 'ageing' there was quantitative agreement between pCu model from this study and predicted pCu from Sauvé et al. This agreement from studies performed independently indicates that, at least in the case of Cu(2+), the difference in an ageing period of ≥10 years appears minimal.


Assuntos
Cobre/toxicidade , Modelos Químicos , Plantas/efeitos dos fármacos , Poluentes do Solo/toxicidade , Testes de Toxicidade/métodos
10.
Ecotoxicology ; 25(8): 1563-1574, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27619689

RESUMO

Cadmium accumulates in plant tissues at low soil loadings and is a concern for human health. Yet at higher levels it is also of concern for ecological receptors. We determined Cd partitioning constants for 41 soils to examine the role of soil properties controlling Cd partitioning and plant uptake. From a series of sorption and dose response studies, transfer functions were developed for predicting Cd uptake in Cucumis sativa L. (cucumber). The parameter log Kf was predicted with soil pHca, logCEC and log OC. Transfer of soil pore-water Cd2+ to shoots was described with a power function (R 2 = 0.73). The dataset was validated with 13 long-term contaminated soils (plus 2 control soils) ranging in Cd concentration from 0.2 to 300 mg kg-1. The series of equations predicting Cdshoot from pore-water Cd2+ were able to predict the measured data in the independent dataset (root mean square error = 2.2). The good relationship indicated that Cd uptake to cucumber shoots could be predicted with Cdpore and Cd2+ without other pore-water parameters such as pH or Ca2+. The approach may be adapted to a range of plant species.


Assuntos
Cádmio/metabolismo , Monitoramento Ambiental/métodos , Plantas/metabolismo , Poluentes do Solo/metabolismo , Solo/química
11.
Ecotoxicol Environ Saf ; 122: 252-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26283289

RESUMO

Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC.


Assuntos
Cucumis sativus/efeitos dos fármacos , Modelos Teóricos , Poluentes do Solo/toxicidade , Solo/química , Água/química , Zinco/toxicidade , Cucumis sativus/crescimento & desenvolvimento , Poluentes do Solo/análise , Zinco/análise
12.
Environ Technol ; : 1-13, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38748546

RESUMO

Australia's metalliferous abandoned mine sites (MAMSs), pose tangible threats to the environment and human health. To address these concerns, our study utilised state-of-the-art handheld XRF technology to conduct a real-time assessment of the Mole River arsenic mine site. The data revealed notably elevated levels of arsenic and manganese, with the southeast corner of the site identified as a contaminant hotspot. We used a tiered risk assessment approach to compare the detected contaminant concentrations to the Australian health investigation levels (tier 1). This led us to a broader examination of erosion vulnerabilities and the potential migration of contaminants (tier 2). Further, a hydrological assessment (tier 3) identified significant erosion in southern regions, indicating the potential for contaminants to be transported off-site through surface water runoff to Sam's Creek and Mole River. The proximity of a reservoir to these runoff pathways brought forth additional challenges, especially during heavy rainfall events. Subsequent laboratory analysis of water samples reinforced our findings, as they confirmed heightened arsenic concentrations in Mole River downstream, accentuating the potential risks to ecosystems and human health. By integrating the XRF contour map and erosion assessment with the RUSLE model, valuable insights are gained into critical hotspots with high contamination and erosion potential. By directing rehabilitation efforts towards critical hotspots, resources can be allocated more efficiently and cost-effectively.

13.
Environ Sci Technol ; 47(9): 4670-6, 2013 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-23484806

RESUMO

Barium (Ba) is a nonessential element to terrestrial organisms and is known to be toxic at elevated concentrations. In this study, the bioavailability and toxicity of Ba in barite (BaSO4) contaminated soils was studied using standard test organisms (Lactuca sativa L. "Great Lakes", Eisenia fetida). Contamination resulted from barite mining activities. Barium concentrations in contaminated soils determined by X-ray fluorescence were in the range 0.13-29.2%. Barite contaminated soils were shown to negatively impact both E. fetida and L. sativa relative to control soil. For E. fetida, pore-water concentrations and acid extractable Ba were linearly related to % body weight loss. In L. sativa, pore-water Ba and exchangeable Ba were both strongly related to shoot Ba and shoot biomass production. A negative linear relationship was observed between shoot Ba content and shoot weight (P < 0.0004, R(2) = 0.39), indicating that Ba accumulation is likely to have induced phytotoxicity. Plant weights were correlated to % weight loss in earthworm (r = -0.568, P = 0.028). Barium concentrations in pore-water were lower than predicted from barite solubility estimates but strongly related to exchangeable Ba, indicating an influence of ion exchange on Ba solubility and toxicity to E. fetida and L. sativa.


Assuntos
Sulfato de Bário/toxicidade , Bário/farmacocinética , Invertebrados/metabolismo , Plantas/metabolismo , Poluentes do Solo/toxicidade , Animais , Sulfato de Bário/farmacocinética , Disponibilidade Biológica , Humanos , Oligoquetos , Poluentes do Solo/farmacocinética
14.
J Hazard Mater ; 455: 131575, 2023 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-37172380

RESUMO

Contaminant containment measures are often necessary to prevent or minimize offsite movement of contaminated materials for disposal or other purposes when they can be buried or left in place due to extensive subsurface contamination. These measures can include physical, chemical, and biological technologies such as impermeable and permeable barriers, stabilization and solidification, and phytostabilization. Contaminant containment is advantageous because it can stop contaminant plumes from migrating further and allow for pollutant reduction at sites where the source is inaccessible or cannot be removed. Moreover, unlike other options, contaminant containment measures do not require the excavation of contaminated substrates. However, contaminant containment measures require regular inspections to monitor for contaminant mobilization and migration. This review critically evaluates the sources of persistent contaminants, the different approaches to contaminant remediation, and the various physical-chemical-biological processes of contaminant containment. Additionally, the review provides case studies of contaminant containment operations under real or simulated field conditions. In summary, contaminant containment measures are essential for preventing further contamination and reducing risks to public health and the environment. While periodic monitoring is necessary, the benefits of contaminant containment make it a valuable remediation option when other methods are not feasible.

15.
Ecotoxicol Environ Saf ; 85: 23-9, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22995781

RESUMO

Copper (Cu) is a widespread soil contaminant that is known to be highly toxic to soil biota. Limited information is available on the response of wild endemic species to Cu in the literature, which hinders ecological risk assessments and revegetation. In the present study, the phytotoxicity of Cu in nutrient solution was studied in five Australian endemic plant species (Acacia decurrens, Austrodanthonia richardsonii (Wallaby Grass), Bothriochloa macra (Redgrass), Eucalyptus camaldulensis var. camaldulensis (River Red-Gum) and Dichanthium sericeum (Bluegrass) and two vegetable plants species (Lactuca sativa L. 'Great lakes' and Raphanus sativa L.). Vegetable species were grown in a more concentrated nutrient solution. The response of B. macra was also compared between the two nutrient solutions (dilute and concentrated nutrient solution). In the first experiment, D. sericeum and E. camaldulensis were found to be highly sensitive to Cu exposure in nutrient culture. Critical exogenous Cu concentrations (50 percent reduction in roots) for E. camaldulensis, D. sericeum, A. richardsonii, B. macra (dilute), L. sativa, B. macra (concentrated), R. sativa and A. decurrens were, respectively, (µg/L) 16, 35, 83, 88, 97, 105, 128 and 186. Copper tolerance in B. macra was observed to be higher in the more concentrated nutrient solution despite the estimated Cu(2+) concentration being very similar in treatment solutions. Additional short-term rhizo-accumulation studies showed that neither Ca(2+) not K(+) was responsible for reduced uptake at the roots. However, the estimated maximum shoot Cu was reduced from 41 to 24mg/kg in the more concentrated solution.


Assuntos
Acacia/efeitos dos fármacos , Cobre/toxicidade , Produtos Agrícolas/efeitos dos fármacos , Eucalyptus/efeitos dos fármacos , Poaceae/efeitos dos fármacos , Poluentes do Solo/toxicidade , Austrália , Cálcio/metabolismo , Raízes de Plantas/metabolismo , Potássio/metabolismo , Verduras/efeitos dos fármacos
16.
Ecotoxicol Environ Saf ; 78: 344-50, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22226328

RESUMO

Long-term lead (Pb) contaminated soils from two lead-zinc smelters and a shooting range, along with freshly spiked control soil, were studied by means of chemical, biological or a physiological method to examine the effect of ageing on Pb bioavailability. The freshly Pb spiked control soil was subjected to an earthworm toxicity test to observe the avoidance and mortality response of the earthworms. Meanwhile, an extractable fraction of Pb on the spiked soil as a result of ageing was examined and further compared with physiologically based in vitro bioaccessibility extraction tests. Their differences in lethal concentration, LC(50), to the earthworm population from spiked soils varied substantially as a function of soil pH. The strong effect of ageing on toxicity was also reflected in the extractability of Pb which was far greater in acidic soil, labelled AC, compared to the alkaline soil, labelled BC. This demonstrates that the bioavailable fraction causing toxicity to earthworms was achieved at a much lower total Pb content for acidic soils relative to alkaline soils. Moreover, the effect of ageing also exhibits that a marked decline in bioavailable Pb results in lowering toxicity. Significant amounts of weight loss in earthworms during an acute toxicity test in long-term contaminated soils at a relatively low Pb concentration suggested that other metal or combined metal toxicity may also play a significant role. This study demonstrates that the soil characteristics and ageing period greatly influence the bioavailable fraction of Pb which is related to the bioreceptor.


Assuntos
Chumbo/metabolismo , Poluentes do Solo/metabolismo , Animais , Chumbo/análise , Chumbo/toxicidade , Dose Letal Mediana , Natureza , Oligoquetos/efeitos dos fármacos , Solo/química , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
17.
J Hazard Mater ; 437: 129339, 2022 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-35709620

RESUMO

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


Assuntos
Poluentes do Solo , Óxido de Alumínio , Chumbo , Óxidos/química , Solo/química , Poluentes do Solo/metabolismo
18.
Chemosphere ; 296: 134053, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35183586

RESUMO

Arsenic contamination in abandoned soils is a global concern which warrants an effective method of remediation. In this study, two organic acids and one biodegradable chelating agent were used to treat arsenic (As) contaminated abandoned mine soils. The concentration of As was 19,100 and 75,350 (mg/kg) for Webbs Consols (WC) and Mole River (MR) samples, respectively. X-ray diffraction and scanning electron microscopy confirmed that tooeleite, arsenopyrite, scorodite and quartz were the major minerals in these soils. A major portion of the As was composed of amorphous and crystalline oxides of Fe and Al determined by sequential extraction. Among the three washing reagents (oxalic acid, citric acid and EDDS) oxalic acid showed the best performance for extracting As. Based on the batch experiment, 0.5 M oxalic acid and 3 h of washing was the most efficient treatment to extract As and other trace elements. Extraction of As, Fe, and Pb was 70, 55, and 48% respectively for WC, while 68, 45 and 63% respectively for MR soil. Oxalic acid extracted 75 and 83% of As and Fe, respectively from tooeleite. Leachability and bioaccessibility of As and Fe in the treated soil was reduced due to washing. However, bioaccessibility and leachability of Pb in soil and Fe and As in tooeleite increased in washed samples. Though the leachability and bioaccessibility of As and Fe in soil was reduced in the treated soil, As still exceeded the USEPA criteria (5 mg/L) which is needed to successfully remediate soil by washing. Soil washing and subsequent solidification/stabilization could be an alternative option to remediate extremely contaminated abandoned mine soil.


Assuntos
Arsênio , Poluentes do Solo , Arsênio/análise , Chumbo , Oxalatos , Solo/química , Poluentes do Solo/análise
19.
Environ Pollut ; 305: 119305, 2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35430314

RESUMO

Antimony (Sb) is a toxic metalloid that has been listed as a priority pollutant. The environmental impacts of Sb have recently attracted attention, but its phytotoxicity and biological transformation remain poorly understood. In this study, Sb speciation and transformation in plant roots was quantified by Sb K-edge X-ray absorption spectroscopy. In addition, the phytotoxicity of antimonate (SbV) on six plant species was assessed by measuring plant photosynthesis, growth, and phytochelatin production induced by SbV. Linear combination fitting of the Sb K-edge X-ray absorption near-edge structure (XANES) spectra indicated reduction of SbV was limited to ∼5-33% of Sb. The data confirmed that Sb-polygalacturonic acid was the predominant chemical form in all plant species (up to 95%), indicating Sb was primarily bound to the cell walls of plant roots. Shell fitting of Sb K-edge X-ray absorption fine-structure (EXAFS) spectra confirmed Sb-O and Sb-C were the dominant scattering paths. The fitting indicated that SbV was bound to hydroxyl functional groups of cell walls, via development of a local coordination environment analogous to Sb-polygalacturonic acid. This is the first study to demonstrate the key role of plant cell walls in Sb metabolism.


Assuntos
Antimônio , Fitoquelatinas , Antimônio/química , Raízes de Plantas/metabolismo , Espectroscopia por Absorção de Raios X
20.
Chemosphere ; 286(Pt 2): 131661, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34426135

RESUMO

There is little doubt that 'rock phosphate' reserves are decreasing, with phosphorus (P) peak to be reached in the coming decades. Hence, removal and recovery of phosphorus (P) from alternative nutrient-rich waste streams is critical and of great importance owing to its essential role in agricultural productivity. Adsorption technique is efficient, cost-effective, and sustainable for P recovery from waste streams which otherwise can cause eutrophication in receiving waters. As selective P sorption using rare earth elements (REE) are gaining considerable attention, this review extensively focuses on P recovery by utilising a range of REE-incorporated adsorbents. The review briefly provides existing knowledge of P in various waste streams, and examines the chemistry and behaviour of REE in soil and water in detail. The impact of interfering ions on P removal using REE, adsorbent regeneration for reuse, and life cycle assessment of REE are further explored. While it is clear that REE-sorbents have excellent potential to recover P from wastewaters and to be used as fertilisers, there are gaps to be addressed. Future studies should target recovery and reuse of REE as P fertilisers using real wastewaters. More field trials of synthesized REE-sorbents are highly recommended before practical application.


Assuntos
Metais Terras Raras , Fósforo , Adsorção , Eutrofização , Fertilizantes
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