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1.
J Agric Food Chem ; 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32614578

RESUMO

The increased use of the emerging per- and polyfluoroalkyl substances (PFASs) has led to extensive concerns around the world. Effective detection methods to trace their pollution characteristics and environmental behaviors in complex soil-crop systems are urgently needed. In this study, a reliable and matrix effect-free method was developed for simultaneous determination of fourteen legacy and emerging PFASs, including perfluorooctanoic acid, perfluorooctane sulfonate, six hydrogenous PFASs, three chlorinated PFASs, and three hexafluoropropylene oxide (HFPO) homologues in six crop (the edible parts) and five soil matrices, using ultrasonic combining solid-phase extraction and UPLC-MS/MS. The varieties of extractants and cleanup cartridges, the dosage of ammonia hydroxide, and matrix effect (ME) were studied to obtain an optimal pretreatment procedure. The developed method had high sensitivity and accuracy with satisfactory method detection limits (MDLs, 2.40-83.03 pg/g dry weight) and recoveries (72%-117%) of all target analytes in matrices at five concentrations, i.e. 0.1, 1, 10, 100, and 1000 ng/g. In addition, the ME of this method (0.82-1.15) was negligible for all PFASs even considering 11 different matrices. The successful application of the matrix effect-free method to simultaneously determine the legacy and emerging PFASs in crop and soil samples has demonstrated its excellent practicability for monitoring emerging PFASs in soil-crop systems.

2.
Sheng Wu Gong Cheng Xue Bao ; 36(3): 416-425, 2020 Mar 25.
Artigo em Chinês | MEDLINE | ID: mdl-32237536

RESUMO

Phytoremediation is one of the important methods for restoring heavy-metal contaminated soils. Using high-biomass economic plants to restore heavy-metal contaminated soils can have both ecological and economic benefits, with great application prospects. Based on the analysis of current situation and existing problems of phytoremediation, we propose the advantages of high-biomass economic plants in contaminated soil remediation, and summarize the recent advances and mechanisms involved in absorbing heavy metals in high-biomass economic plants. Furthermore, the possible methods for improving the remediation efficiency of high-biomass economic plants are also discussed, to provide insights for improving the economic benefits of phytoremediation and promoting its widespread application in the future.


Assuntos
Metais Pesados , Poluentes do Solo , Biodegradação Ambiental , Biomassa , Metais Pesados/metabolismo , Pesquisa/tendências , Solo
3.
Sheng Wu Gong Cheng Xue Bao ; 36(3): 436-449, 2020 Mar 25.
Artigo em Chinês | MEDLINE | ID: mdl-32237538

RESUMO

Phytomining technology cultivates hyperaccumulator plants on heavy metal contaminated soils, followed by biomass harvesting and incineration to recover valuable metals, offering an opportunity for resource recycling and soil remediation. Large areas of ultramafic soils, naturally rich in nickel (Ni), are present in numerous places around the world. As an environmentally friendly and cost-effective soil remediation technology, phytomining has a broad application prospect in such areas and thus has attracted great attention from global researchers. The key processes of phytomining include: (1) high-selectivity response of hyperaccumulator plants to Ni the underlying mechanisms involved in the rhizosphere; (2) underlying mechanisms of high-efficiency uptake and translocation of Ni in hyperaccumulators; and (3) resource recycling of high-added value Ni products from the Ni-rich bio-ore of hyperaccumulators. In recent 30 years, phytomining practices have successfully carried out in United States, Albania and Malaysia. However, the research and application of this technology in China are still in the fledging stage. This paper reviews the key processes and research progress of phytomining, and points out the bottleneck, to provide theoretical basis and technical guidance for phytomining.


Assuntos
Biodegradação Ambiental , Níquel , Poluentes do Solo , China , Níquel/metabolismo , Solo , Poluentes do Solo/metabolismo
4.
J Hazard Mater ; 393: 122410, 2020 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-32120221

RESUMO

Pyrolysis technology is advised to dispose nonmetallic particles of waste printed circuit boards to produce oils and gases. During pyrolysis, brominated flame retardants in nonmetallic particles are converted into small-molecular Br-containing substances. They disperse into oil and gas so as to cause secondary pollution. Then, CaCO3 is suggested to be employed to capture the small-molecular Br-containing substances. However, too much CaCO3 will produce over solid wastes. Less CaCO3 might not capture the total Br-containing substances. How to ration the mass of adsorbent for capturing pollutant has not been detailed investigated. This paper found HBr was the main Br-containing substances during high temperature pyrolysis of nonmetallic particles. The capture process of HBr was detailed investigated by the method of computational chemistry. At the condition of 973 K and 100 Pa, HBr was captured by chemical reaction and physical absorption of CaCO3. Unit cell of CaCO3 reacted with two HBr to form CaBr2, and the generated unit cell of CaBr2 can adsorb 0.011 HBr. 0.0106 g CaCO3 can absorb all HBr produced by high temperature vacuum pyrolysis of 1 g nonmetallic particles. This paper contributes a novel approach to accurately ration the mass of adsorbents employed for capturing pollutants.

5.
J Hazard Mater ; 393: 122390, 2020 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-32114130

RESUMO

Iron oxide nanoparticles (IONPs), commonly occurring in soils, aquifers and subsurface sediments, may serve as important electron shuttles for the biotransformation of coexisting toxic metals. Here, we explored the impact of different IONPs (low-crystallinity goethite and ferrihydrite, high-crystallinity magnetite and hematite) on the reduction of Cu(II) by Geobacter sulfurreducens and the associated electron shuttle mechanisms. All four IONPs tested can function as electron shuttles to enhance long distance electron transfer from bacteria to Cu(II). Upon IONPs addition, the rate of Cu(II) reduction increased from 14.9 to 65.0-83.8 % in solution after 7 days of incubation. Formation of both Cu(I) and Cu(0) on the iron oxide nanoparticles was revealed by the X-ray absorption near-edge spectroscopy. The IONPs can be utilized as conduits by bacteria to directly transfer electrons and they can also reversibly accept and donate electrons as batteries through a charging-discharging cycle to transfer electron. The latter mechanism (geo-battery) played an important role in all four types of IONPs while the former one (geo-conductor) can only be found in the magnetite and hematite treatments due to the higher crystallinity. Our results shed new light on the biogeochemically mediated electron flux in microbe-IONPs-metal networks under anaerobic iron-reduction conditions.

6.
Chemosphere ; 249: 126447, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32208216

RESUMO

Novel alternatives of perfluorooctane sulfonate (PFOS), chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are increasingly being detected in the aquatic and terrestrial environment. Previous studies mainly focused on aquatic biota; however, the knowledge about the ecotoxicological risk they pose to terrestrial plants was still lacking. In this study, the accumulation of two Cl-PFAES (6:2 and 8:2 Cl-PFAES) and PFOS in wheat seedlings at environmentally relevant levels (50 and 100 µg L-1) was investigated. Concentrations of Cl-PFAESs in the roots were an order of magnitude higher than those in shoots, indicating that they were primarily accumulated in the roots. The values of root and shoot bioconcentration factor was comparable between 6:2 Cl-PFAES and PFOS. However, these indexes of 8:2 Cl-PFAES were 42-91% higher and 70-76% lower than PFOS, respectively. As a result, 6:2 Cl-PFAES had a similar accumulation pattern as PFOS, whereas 8:2 Cl-PFAES was predominantly restricted to the roots, which might be attributed to their hydrophobicity and carbon chain length. In addition, at 250 mg L-1 of Cl-PFAESs, plant biomass and pigment content were 24-30% and 0.4-18%, respectively, which were lower than those of PFOS. As compared with PFOS, Cl-PFAESs induced higher levels of root membrane permeability, reactive oxygen species and malondialdehyde content, as well as reduced the activities of antioxidant enzymes and glutathione content. These suggested the occurrence of a severer oxidative damage and the breakdown of the antioxidant defence system in wheat cells. Therefore, we conclude that Cl-PFAESs might pose a higher potential threat to the environment than PFOS.


Assuntos
Fluorcarbonetos/toxicidade , Poluentes do Solo/toxicidade , Triticum/fisiologia , Alcanossulfonatos , Ácidos Alcanossulfônicos , Éter , Éteres , Fluorcarbonetos/metabolismo , Malondialdeído , Plântula , Poluentes do Solo/metabolismo
7.
J Environ Manage ; 263: 110323, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32174515

RESUMO

Metal tailings are potential sources of strong environmental pollution. In situ remediation involves the installation of a plant cover to stabilize materials and pollutants. Whether metal(loid)s are effectively immobilized in remediated tailing ponds submitted to heavy rainfall remains uncertain. In this study, tailing materials were collected from bare tailings (control), grass-planted (G) and grass-shrub planted (GS) areas on a former Pb/Zn mine site. Batch column experiments were performed with three rainfall intensities of 0.36, 0.48, and 0.50 mL min-1 for 18 d in the lab. The pH, Eh, Cd, Pb, Zn and As concentration in leachate were recorded. Selected leached tailing materials were finally characterized. Results showed that leachates from control were strongly acidic (pH 3.11-4.65), and that Cd, Pb, Zn and As were quickly released at high rate (e.g., 945 mg L-1 Zn). During the experiment up to 4% Cd present in the material was released and almost 1% Zn. With material collected from the G area, leachates were even more acidic (2.16-2.84) with a rainfall intensity of 0.50 mL min-1 and exhibited a high redox potential (588-639 mV). However, concentrations of metals in leachates were much lower than that in the control, except for Zn (e.g., 433 mg L-1), and they tended to decrease with time. Cumulative leaching rate was still relatively high (e.g., 0.68% Cd; 0.75% Zn) during the first eight days (stage I). However, with the GS treatment, leachate pH gradually raised from acid to alkaline values (3.9-8.2) during stage I, then remained high until the end of the experiment (stage II). Also, amounts of elements released during the 18 d were low in general. The releasing ratios of Cd (R2 > 0.95), Pb (R2 > 0.95), As (R2 > 0.87), and Zn (R2 > 0.90) fitted well with a two-constant model. In conclusion, under subtropical climate with heavy rainfall, phytostabilization is effective but immobilization of metals is higher with a combination of grass and shrub than with only grass to reduce leaching of As and Zn.

8.
Environ Pollut ; 262: 114234, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32126438

RESUMO

The widespread use of rare earth elements (REEs) in numerous sectors have resulted in their release into the environment. Existing knowledge about the effects of REEs were acquired mainly based on toxicity tests with aquatic organisms and a fixed exposure time, Here, the dynamic accumulation and toxicity of REEs (La, Ce, and Gd) in soil organism Enchytraeus crypticus were determined and modeled by a first-order one-compartment model and a time-toxicity logistic model, respectively. Generally, the accumulation and toxicity of REEs were both exposure level- and time-dependent. The overall uptake rate constants were 2.97, 2.48, and 2.38 L kg-1d-1 for La, Ce, and Gd, respectively. The corresponding elimination rate constants were 0.99, 0.78, and 0.56 d-1, respectively. The worms exhibited faster uptake and elimination ability for light REEs (La and Ce) than for heavy REEs (Gd). For all three REEs, the LC50 values based on exposure concentrations decreased with time and reached ultimate values after approximately 10 d exposure. The estimated ultimate LC50 values (LC50∞) were 279, 334, and 358 mg L-1 for Ce, Gd, and La, respectively. When expressed as body concentration, the LC50inter value was almost constant with time, demonstrating that internal body concentration could be a better indicator of dynamic toxicity of REEs than external dose. This study highlights that specific REE and exposure time should be taken into account in accurately assessing risk of REEs.

9.
Artigo em Inglês | MEDLINE | ID: mdl-32143354

RESUMO

In-situ remediation of heavy-metal-contaminated soil in farmland using phytostabilization combined with soil amendments is a low-cost and effective technology for soil pollution remediation. In this study, coconut shell biochar (CB, 0.1% and 0.5%), organic fertilizer (OF, 3.0%), and Fe-Si-Ca material (IS, 3.0%) were used to enhance the phytostabilization effect of ramie (Boehmeria nivea L.) on Cd and Pb in highly polluted soils collected at Dabaoshan (DB) and Yangshuo (YS) mine sites. Results showed that simultaneous application of CB, OF, and IS amendments (0.1% CB + 3.0% OF + 3.0% IS and 0.5% CB + 3.0% OF + 3.0% IS, DB-T5 and DB-T6) could significantly increase soil pH, reduce the concentrations of CaCl2-extractable Cd and Pb, and increase the contents of Ca, P, S, and Si in DB soil. Under these two treatments, the growth of ramie was significantly improved, its photosynthesis was enhanced, and its levels of Cd and Pb were reduced, in comparison with the control (DB-CK). After applying DB-T5 and DB-T6, the concentrations of Cd and Pb in roots were decreased by 97.7-100% and 64.6-77.9%, while in shoots they were decreased by up to 100% and 92.9-100%, respectively. In YS-T4 (0.5% CB + 3.0% OF), the concentrations of Cd and Pb in roots were decreased by 39.5% and 46.0%, and in shoots they were decreased by 44.7% and 88.3%. We posit that phytostabilization using ramie and amendments could reduce the Cd and Pb bioavailability in the soil mainly through rhizosphere immobilization and plant absorption. In summary, this study suggests that the use of tolerant plant ramie and simultaneous application of coconut shell biochar, organic fertilizer, and Fe-Si-Ca materials is an effective stabilization strategy that can reduce Cd and Pb availabilities in soil. Ultimately, this strategy may reduce the exposure risk of crops to heavy metal pollution in farmland.

10.
Sci Total Environ ; 717: 136894, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32084677

RESUMO

Biochar has been widely studied as an amendment for use in remediation of water and soil contaminated with heavy metals such as Pb2+ and Zn2+, but the effects of biochar characteristics, including stability, on the competitive adsorption of Pb2+ and Zn2+ by biochars from various sources are incompletely understood. In this work, biochars from three different feedstocks, including rice straw (RS), chicken manure (CM), and sewage sludge (SS), were prepared at two pyrolysis temperatures, 550 and 350 °C, and tested to investigate the influence of their stabilities and other characteristics on their adsorption of Pb2+ and Zn2+ in both single- and binary-metal systems. RS biochar had the highest carbon and hydrogen contents, greatest number of functional groups (e.g., OH and C=C/C=O), highest pH, most negative surface charge, and highest physical stability, and thus the highest adsorption capacity for Pb2+ and Zn2+. Pyrolysis at the higher temperature resulted in a slight decrease in aromatic functional groups on biochar surfaces but higher adsorption capacities for Pb2+ and Zn2+ due to the decreased biochar particle size and increased specific surface area. FTIR, XRD, and XPS analyses indicated that Pb2+ and Zn2+ were absorbed on the biochars primarily via chemical complexation with aromatic functional groups. Quantum chemistry calculations confirmed that these functional groups (e.g., -OH and-COOH) tended to bind more strongly with Pb2+ than with Zn2+ due to the former's lower binding energies, which also accounted for the notable decrease in adsorption of Zn2+ in the presence of Pb2+. In addition, compared to carboxyl groups, hydroxyl groups had smaller binding energies and stronger metal complexation. These findings provide a theoretical basis for improved understanding of potential applications of biochars in environmental remediation.


Assuntos
Carvão Vegetal/química , Adsorção , Chumbo , Solo , Zinco
11.
Environ Sci Technol ; 54(5): 3039-3049, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32022549

RESUMO

Due to the increasing need for sustainable energy and environmental quality in urban areas, the combination of aquifer thermal energy storage (ATES) and in situ bioremediation (ISB) has drawn much attention as it can deliver an integrated contribution to fulfill both demands. Yet, little is known about the overall environmental impacts of ATES-ISB. Hence, we applied a life-cycle assessment (LCA) to evaluate the environmental performance of ATES-ISB, which is also compared with the conventional heating and cooling system plus ISB alone (CHC + ISB). Energy supply via electricity is revealed as the primary cause of the environmental impacts, contributing 61.26% impacts of ATES-ISB and 72.91% impacts of CHC + ISB. Specifically, electricity is responsible for over 95% of water use, global warming potential, acidification potential, and respiratory inorganics, whereas the production of the biological medium for bioremediation causes more than 85% of the eco- and human toxicity impacts in both cases. The overall environmental impact of ATES-ISB is two times smaller than that of CHC + ISB. Sensitivity analysis confirms the importance of electricity consumption and electron donor production to the environmental impacts in both energy supply and bioremediation. Thus, future studies and practical applications seeking possible optimization of the environmental performances of ATES-ISB are recommended to focus more on these two essential elements, e.g., electricity and electron donor, and their related parameters. With the comprehensive LCA, insight is obtained for better characterizing the crucial factors as well as the relevant direction for future optimization research of the ATES-ISB system.


Assuntos
Água Subterrânea , Compostos Orgânicos Voláteis , Biodegradação Ambiental , Eletricidade , Temperatura Alta , Humanos
12.
Sci Total Environ ; 715: 137032, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32041005

RESUMO

To understand the recovery of the biological functions of washed soil, we studied changes in the microbial communities of soils washed with 10 or 60 mmol kg-1 ethylenediaminetetraacetic acid (EDTA) for 90 d of incubation. The relative abundance of tolerant or degrading species decreased, while that of microorganisms with chemical autotrophic ability increased as the incubation time increased. The changes in the enzyme activity followed different trends. As an intracellular enzyme, dehydrogenase was initially most severely damaged by the washing process but could recover over time, while the activity of urease increased after washing with EDTA, which may be related to the use of N as a nutrient source by microorganisms. Phosphatase did not significantly change over time. The redundancy discriminant analyses indicated that there were distinct factors driving such changes in the soils washed with different EDTA dosages. For the soil washed with 10 mmol kg-1 EDTA, bacteria with tolerance or degradation capacity of toxic pollutants, such as Nocardioidaceae, played a more important role in the recovery of soil functions; therefore, the EDTA stress indicator was the main driving factor. However, in the soil washed with 60 mmol kg-1 EDTA, chemolithoautotrophic bacteria, such as Nitrososphaeraceae, exerted a greater influence on the recovery of biological functions due to the higher loss of nutrients and EDTA residue; therefore, the main driving factor was the nutrients supply.


Assuntos
Solo , Bactérias , Ácido Edético , Microbiologia do Solo , Poluentes do Solo
13.
Environ Sci Technol ; 54(6): 3487-3498, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32083472

RESUMO

Much effort has been devoted to clarifying the comparative toxicity of ZnO nanoparticles (NPs) and Zn ions; however, little is known about their toxicodynamic processes at the metabolic level. Here, we investigated the acute (2d) and chronic (7d) effects to a soil species, Enchytraeus crypticus, of two sublethal doses of ZnO-NPs and ZnCl2 (10 and 30 mg/L Zn) using ultrahigh performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry-based metabolomics. The metabolomics analysis identified 99, 128, 121, and 183 significantly changed metabolites (SCMs) in E. crypticus exposed to ZnO-NPs for 2d, ZnCl2 for 2d, ZnO-NPs for 7d, and ZnCl2 for 7d, respectively, suggesting that ZnCl2 induced stronger metabolic reprogramming than ZnO-NPs, and a longer exposure time caused greater metabolite changes. Among the SCMs, 67 were shared by ZnO-NPs and ZnCl2 after 2d and 84 after 7d. These metabolites were mainly related to oxidative stress and antioxidant defense, membrane disturbance, and energy expenditure. The targeted analysis on physiological and biochemical responses further proved the metabolic observations. Nevertheless, 32 (33%) and 37 (31%) SCMs were found only in ZnO-NP treatments after 2 and 7d, respectively, suggesting that the toxicity of ZnO-NPs cannot be solely attributed to the released Zn ions. Metabolic pathway analysis revealed significant perturbations of galactose metabolism, amino sugar and nucleotide sugar metabolism, and glycerophospholipid metabolism in all test groups. Based on involvement frequency, glucose-1-phosphate, glycerol 3-phosphate, and phosphorylcholine could serve as universal biomarkers for exposure to different Zn forms. Four pathways perturbed by ZnO-NPs were nanospecific upon acute exposure and three upon chronic exposure. Our findings demonstrated that metabolomics is an effective tool for understanding the molecular toxicity mechanism and highlighted that time-series measurements are essential for discovering and comparing modes of action of metal ions and NPs.


Assuntos
Nanopartículas Metálicas , Nanopartículas , Oligoquetos , Óxido de Zinco , Animais , Metabolômica , Solo
14.
Environ Sci Technol ; 54(4): 2287-2294, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31951400

RESUMO

The fern Dicranopteris linearis (Gleicheniaceae) from China is a hyperaccumulator of rare earth element (REE), but little is known about the ecophysiology of REE in this species. This study aimed to clarify tissue-level and organ-level distribution of REEs via synchrotron-based X-ray fluorescence microscopy (XFM). The results show that REEs (La + Ce) are mainly colocalized with Mn in the pinnae and pinnules, with the highest concentrations in necrotic lesions and lower concentrations in veins. In the cross sections of the pinnules, midveins, rachis, and stolons, La + Ce and Mn are enriched in the epidermis, vascular bundles, and pericycle (midvein). In these tissues, Mn is localized mainly in the cortex and mesophyll. We hypothesize that the movement of REEs in the transpiration flow in the veins is initially restricted in the veins by the pericycle between vascular bundle and cortex, while excess REEs are transported by evaporation and cocompartmentalized with Mn in the necrotic lesions and epidermis in an immobile form, possibly a Si-coprecipitate. The results presented here provide insights on how D. linearis regulates high concentrations of REEs in vivo, and this knowledge is useful for developing phytotechnological applications (such as REE agromining) using this fern in REE-contaminated sites in China.


Assuntos
Cério , Gleiquênias , Metais Terras Raras , China , Lantânio
15.
Sci Total Environ ; 714: 136721, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-31978776

RESUMO

Considering the high Zn content of municipal sewage sludge and its competition with Cd during plant uptake due to their similar properties, the presence of Zn in sludge-derived biochar (SDBC) may affect Cd immobilization and uptake by plants. To confirm this, SDBC samples with different Zn contents were prepared and characterized. Their Cd immobilization behavior was studied by conducting batch sorption experiments, and their effects on Cd uptake by lettuce were explored by conducting hydroponic experiments. The results reveal that some Zn contained in the sewage sludge was transformed into ZnO during pyrolysis. The Brunauer-Emmett-Teller (BET) surface area of the SDBC samples containing 2324 mg kg-1 Zn (BC-2324) was 18.3 m2 g-1, which was 132% larger than that of the samples containing 1438 mg kg-1 Zn (BC-1438). The SDBC samples containing 1901 mg kg-1 (BC-1901) exhibited the highest Langmuir sorption capacity of 3476 mg kg-1, which is 115% higher than that of SB-1438. Furthermore, the lettuce remedied with SB-1901 exhibited 44% more biomass; lower peroxidase, catalase, and malondialdehyde activity; and 18.4% less Cd in the leaves of the lettuce than the lettuce remedied with BC-1438, suggesting the potential benefits of using Zn-rich SDBC for soil amendment.


Assuntos
Esgotos , Cádmio , Carvão Vegetal , Alface , Solo , Poluentes do Solo , Zinco
16.
Int J Phytoremediation ; 22(5): 451-458, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31564121

RESUMO

Microorganisms are used to alleviate heavy metal stress in plants cultivated in contaminated fields. However, the relevant mechanisms have been rarely explored. The goal of this study was to investigate effects of arbuscular mycorrhizal fungus Funneliformis mosseae and two Cd-resistant bacterial strains (Enterobacter sp. EG16 and Enterobacter ludwigii DJ3) on growth and Cd tolerance of tomato when applied with different inoculation strategies (single or dual) and Cd concentrations (50 and 100 mg kg-1). Better plant growth was observed in mycorrhizal alone or combined treatments. In F. mosseae and EG16 co-inoculation treatment, shoot and root dry weight were 119-154% and 91-173% higher than those of the control, respectively. Higher bacterial and mycorrhizal colonization rate and root Cd concentration were also found in this treatment. However, the decrease of shoot Cd concentration and translocation factor values indicated this treatment was effective in improving Cd tolerance of the host plants. In addition, the increase in soil pH and decline in bioavailable Cd in the rhizosphere might be partly involved in reduction of Cd accumulation in plants. Our results suggest that co-inoculation with suitable microorganisms is important in plant growth and tolerance to Cd in Cd-contaminated soil.


Assuntos
Lycopersicon esculentum , Micorrizas , Poluentes do Solo , Biodegradação Ambiental , Cádmio , Raízes de Plantas
17.
Sci Total Environ ; 704: 135284, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31806318

RESUMO

The efficient removal of toxic hexavalent chromium (Cr(VI)) is crucial for waste water treatment. Herein, we report a new strategy to couple adsorption and in situ photo-reduction of Cr(VI) to Cr (III) using metal-free, N-doped carbon facilely derived from naturally abundant biomass cellulose. Experimental results exhibited the removal rate of Cr(VI) can be significantly enhanced from 43.25 mg/g to 98.25 mg/g after visible light irradiation under acidic conditions. We demonstrated that toxic Cr(VI) ions were firstly adsorbed on N-doped carbon via electrostatic attraction, and then photo-reduced into Cr(III), followed by re-adsorption through chemical complexation. The carbon sp2-hybridized structures and electro-attracting graphic-N groups (N-(C)3) are proposed to be responsible for this photo-reduction effect. This work reveals the efficient removal of heavy metals through the cooperative adsorption and photo-reduction using the materials synthesized from biomass waste.


Assuntos
Cromo/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Cromo/química , Poluentes Químicos da Água/química
18.
Environ Int ; 134: 105340, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31775092

RESUMO

Shrimp processing and consumption generate large amounts of waste shrimp shell (WSS) rich in chitin and protein. Herein, we successfully synthesized WSS-based hydrochar (WSH) adsorbent through deproteinization and deacetylation followed by hydrothermal carbonization (HTC) and acid washing. For comparison, another hydrochar (CCH) adsorbent was synthesized from HTC of commercial chitosan under identical conditions. Specifically, WSH contained rich nitrogen-containing functional groups with a long aliphatic chains structure. Acid etching of calcium carbonate in WSS led to a higher specific surface area of WSH (12.65 m2/g) which was nearly 6 times higher than that of CCH (2.13 m2/g). The lower deacetylation degree of WSH was responsible for higher amide I and amino groups retained therein. Under an optimal initial solution pH of 4.0, WSH could rapidly achieve a superb adsorption capacity of 755.08 mg/g for methyl orange molecule. Moreover, the adsorption process followed a pseudo-second-order kinetics model and was well described by a monolayer adsorption pattern based on the Langmuir isotherm model with correlation coefficients higher than 0.9989. Prominent adsorption performance of WSH for methyl orange was mainly attributed to electrostatic interactions, while steric hindrance effect had a detrimental impact on the adsorption capacity of CCH. Superb adsorption capacity and excellent regeneration performance suggest WSH could be a promising and affordable adsorbent candidate for anionic dye removal.

19.
Chemosphere ; 238: 124630, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31473530

RESUMO

Mercury (Hg) mining activities are an important anthropogenic source of atmospheric Hg. The Xunyang Hg mine located in Shaanxi Province is the largest active Hg producing centre in China. To understand the biogeochemical processes of atmospheric Hg through Hg mining activities, six groups of experimental pots were carefully designed to investigate the effect of Hg mining activities on Hg contamination from atmospheric deposition in the local surface soils. Based on the variations of Hg in the soil from the experimental pots, the deposition flux and loading of Hg in the Xunyang Hg mining district were investigated. The results showed that the average concentration of total gaseous mercury (TGM) as high as 193 ±â€¯122 ng m-3 was observed in the ambient air, which was orders of magnitude higher than that in remote areas. The average deposition flux and annual loading of atmospheric Hg were 72 mg m-2 y-1 and 10 t y-1, respectively. The dominant atmospheric Hg deposition is within a distance range of 6.0-12 km from the Hg retorting facility, accounting for approximately 85% of the total Hg loading. After 14 months of exposure, total mercury (THg) concentrations in the soil from the experimental pots increased 0.35-9.5 times, and the highest concentrations of methylmercury (MeHg) (3.7 ±â€¯2.9 µg kg-1) in soil were observed in February. Concentrations as high as 643 µg kg-1 THg and 13 µg kg-1 MeHg in rice were observed in the second experimental year. Elevated concentrations of both THg and MeHg in rice indicated that the newly deposited atmospheric Hg was bioavailable, readily methylated, and taken up by rice, suggesting that the ongoing Hg mining activities cause serious Hg contamination in the soil-rice ecosystem and posed a threat to local residents in the Xunyang Hg mining area.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Mercúrio/análise , Compostos de Metilmercúrio/análise , Oryza/química , Poluentes do Solo/análise , Atmosfera/química , China , Ecossistema , Mineração , Solo/química
20.
Environ Int ; 135: 105373, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31841802

RESUMO

Bioremediation of sites co-contaminated with organohalides and metal pollutants may have unsatisfactory performance, since metal ions can potentially inhibit organohalide respiration. To understand the detailed impact of metals on organohalide respiration, we tested the effects of four metal ions (i.e., Cu2+, Cd2+, Cr3+ and Pb2+), as well as their mixtures, on reductive dechlorination of perchloroethene (PCE) and polychlorinated biphenyls (PCBs) in three different cultures, including a pure culture of Dehalococcoides mccartyi CG1, a Dehalococcoides-containing microcosm and a Dehalococcoides-Geobacter coculture. Results showed that the inhibitive impact on organohalide respiration depended on both the type and concentration of metal ions. Interestingly, the metal ions might indirectly inhibit organohalide respiration through affecting non-dechlorinating populations in the Dehalococcoides-containing microcosm. Nonetheless, compared to the CG1 pure culture, the Dehalococcoides-containing microcosm had higher tolerance to the individual metal ions. In addition, no synergistic inhibition was observed for reductive dechlorination of PCE and PCBs in cultures amended with metal ion mixtures. These results provide insights into the impact of metal ions on organohalide respiration, which may be helpful for future in situ bioremediation of organohalide-metal co-contaminated sites.

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