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1.
Bull Environ Contam Toxicol ; 105(4): 639-644, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32955595

RESUMO

Arsenic (As) and cadmium (Cd) are common soil pollutants whose opposing geochemical behaviors must be taken into account in the development of cost-effective, environmentally friendly remediation strategies. In this study, a pot experiment with lettuce and a field experiment with wheat were performed to examine the impacts of zeolite, biochar, MnO2, zero-valent iron (ZVI) individually and in binary combinations thereof on As-Cd pollution. The results of the pot experiment showed that biochar, MnO2 and ZVI had good passivation effects on As and Cd when provided individually, but the effects of a combination of 0.2% ZVI/0.5% biochar or 0.2% MnO2/0.5% ZVI were even better. These amendments were further investigated in a field experiment, which confirmed the positive effect of 0.2% MnO2/0.5% ZVI. Therefore, ZVI/biochar and MnO2/ZVI mixtures may offer effective solutions to the remediation of farmland soil contaminated with both As and Cd.


Assuntos
Arsênico/química , Cádmio/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/química , Arsênico/análise , Cádmio/análise , Carvão Vegetal , Poluição Ambiental , Fazendas , Ferro , Alface , Compostos de Manganês , Óxidos , Solo , Poluentes do Solo/análise , Triticum
2.
Bull Environ Contam Toxicol ; 105(2): 283-290, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32734360

RESUMO

The current study investigated the efficiency of sepiolite (SE), sodium humate (HS), microbial fertilizer (JF) and SE combined with JF/HS in a ratio of 2:1 (w/w) (JF-2SE and HS-2SE) on Cd, Pb and As bioavailability in field trials with rice (Oryza sativa L.). The results showed that all the amendments remarkably decreased (p < 0.05) the contents of available Cd and available Pb in soil. Only JF-2SE treatment reduced available As concentration in soil. All the amendments were found to effectively reduce (p < 0.05) the contents of As in brown rice. Both JF-2SE and HS-2SE co-applications reduced the concentrations of Cd in brown rice to 0.108 and 0.135 mg kg-1, and that of Pb reduced to 0.2 and 0.175 mg kg-1, which met the national standard limit of China. Thus, the co-application of JF/HS-2SE can be a promising remediation strategy in Cd, Pb and As co-contaminated paddy soil.


Assuntos
Cádmio/química , Recuperação e Remediação Ambiental/métodos , Chumbo/química , Poluentes do Solo/química , Disponibilidade Biológica , Cádmio/análise , China , Poluição Ambiental , Fertilizantes , Chumbo/análise , Silicatos de Magnésio , Oryza , Solo/química , Poluentes do Solo/análise
3.
Chemosphere ; 260: 127533, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32679374

RESUMO

In recent decades, nanoscale zero valent iron (nZVI) has been found to be a promising approach for heavy metal remediation. This study is the first report highlighting the role of nZVI to ameliorate Cadmium (Cd) stress in rice along with its effects in expressions of transporter genes, agronomic parameters and grain nutrient status. Initially, 3 concentration of Cd (10, 50, 250 µM) and nZVI (50, 100, 200 mg L-1) were selected. PCA analysis based on growth parameters, photosynthetic pigment contents and lipid peroxidation rate confirmed that 100 mg L-1 nZVI was most suitable for remediation of 10 µM Cd. It was evident that, nZVI can alleviate Cd-induced toxic effects by enhancing antioxidant defense mechanisms and other physiological processes in plants. nZVI treated rice seedlings also showed upregulation of phytochelatins which aided in Cd chelation within vacuoles. Study of root morphology with scanning electron microscopy and ROS imaging with confocal microscopy confirmed that nZVI could alleviate oxidative stress due to Cd uptake. In nZVI treated rice seedlings, gene expressions of iron (Fe) transporters (like, IRT1,IRT2,YSL2,YSL15) which are responsible for both Fe and Cd uptake were significantly down-regulated whereas, OsVIT1 and OsCAX4 genes were over expressed which lead to sequestration of Cd in vacuoles. Cd localization assay with leadmium proved that Cd translocation was reduced with nZVI treatment. To further validate our findings a pot experiment was carried out where it was found that nZVI could immobilize Cd in soil prevented accumulation of Cd in rice grains in addition to improving yield.


Assuntos
Cádmio/química , Poluentes do Solo/química , Antioxidantes/metabolismo , Transporte Biológico , Cádmio/análise , Grão Comestível/química , Ferro/análise , Metais Pesados/análise , Oryza/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Fitoquelatinas/metabolismo , Plântula/efeitos dos fármacos , Solo , Poluentes do Solo/análise
4.
Chemosphere ; 260: 127652, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688325

RESUMO

Cadmium (Cd) contamination in soil negatively impacts crop productivity, grain quality, and human health. Wheat seeds, with different concentrations of intrinsic zinc (Zn): low Zn (35 mg kg-1), medium (42 mg kg-1), and high Zn (49 mg kg-1), were planted in artificially contaminated soil (10 mg Cd kg-1 soil). Zinc (5 g kg-1) and biochar (20 g kg-1 soil) were applied alone or in combination at sowing. Cadmium contamination reduced wheat growth, productivity, and grain Zn concentration, relative to the respective no-Cd treatments, with greater reductions in plants with low intrinsic Zn. Among the soil amendments, Zn and/or biochar improved wheat productivity and grain Zn and reduced grain Cd concentration in plants grown from seed with varying intrinsic Zn levels. Plants from high intrinsic Zn seeds performed better under Cd stress with the application of soil amendments than seeds with low or medium intrinsic Zn levels. The combined application of Zn and biochar had the highest increases in grain yield (9.51%) and grain Zn concentration (12.2%), relative to the control (no Cd, no Zn, and no biochar). This treatment also decreased the Cd concentrations in straw (7.1%) and grain (95.6%). The sole application of Zn or biochar improved wheat productivity and grain Zn concentration and deceased grain Cd concentration under Cd stress, but more improvements resulted from the combined application of Zn and biochar. Plants grown from seed with high Zn were better able to tolerate Cd stress than the plants raised from seeds with medium and low Zn levels.


Assuntos
Cádmio/toxicidade , Poluentes do Solo/toxicidade , Triticum/fisiologia , Zinco/análise , Pão , Cádmio/química , Carvão Vegetal , Grão Comestível/química , Poluição Ambiental , Humanos , Sementes/química , Solo , Poluentes do Solo/análise , Poluentes do Solo/química , Triticum/crescimento & desenvolvimento
5.
Bull Environ Contam Toxicol ; 105(1): 146-154, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32488396

RESUMO

Biochar was for the first time produced from Suaeda glauca. The immobilization of Pb and Cd by this biochar and pig manure biochar was examined in two types of soils by diethylene triamine pentaacetic acid (DTPA) extraction. Addition of biochars decreased DTPA extractable Pb and Cd in Fluvo-aquic soil with reduction rates being 11.3%-48.4% and 0.74%-64.9% compared with the control treatment. The pig manure biochar favored the immobilization of Pb and S. glauca biochar favored the immobilization of Cd. Biochars can effectively immobilize heavy metals in Fluvo-aquic soil. However, the addition of biochars increased extractable Pb and Cd in red soil, with pig manure biochars showing greater rates. This is ascribed to that the competition effects of ions released from biochar enhanced the moving of heavy metals from iron and manganese oxides bound form to organic matter bound form, and hence enhanced the mobility and bioavailability of heavy metals.


Assuntos
Cádmio/química , Chumbo/química , Poluentes do Solo/química , Animais , Disponibilidade Biológica , Carvão Vegetal/química , Chenopodiaceae , Compostos de Manganês , Esterco , Metais Pesados/análise , Óxidos , Solo , Poluentes do Solo/análise , Suínos
6.
Bull Environ Contam Toxicol ; 105(2): 277-282, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32556688

RESUMO

A bulky waste, oyster shell (OS), was calcinated at 400-800°C to produce Ca-rich products (OS400-OS800) to reduce the human health risk of soil cadmium (Cd) and arsenic (As). Thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET method were used to characterize OS and its calcined products. OS and OS400-OS700 removed little Cd and As from water, whereas OS800 removed 1508 mg Cd or 514 mg As per kg of OS800 from solutions of 1032 mg Cd/L or 257 mg As/L via adsorption and precipitation. Adding OS800 at a 2% dose to a Cd- and As-contaminated soil lowered its exchangeable Cd from 60% to 27%, and reduced Cd content in the edible part of vegetable Bok Choy from 2.80 to 0.048 mg/kg and As from 1.73 to 0.47 mg/kg. Converting OS to soil amendment has the dual benefits to soil remediation and sustainable oyster aquaculture.


Assuntos
Exoesqueleto , Cádmio/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/química , Adsorção , Agricultura , Animais , Arsênico/análise , Cádmio/análise , Carbonato de Cálcio , Humanos , Ostreidae , Solo , Poluentes do Solo/análise , Verduras
7.
Food Chem ; 330: 127212, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32526650

RESUMO

In this work, a facile solid phase extraction (SPE) method was developed for the analysis of trace Pb2+ and Cd2+ by using chitosan/thiol modified metal-organic frameworks (CS/MOF-SH) composite as adsorbent followed by graphite furnace atomic absorption spectrometer (GF-AAS) detection. The potential influencing factors, such as solution pH, adsorbent dosage, and extraction time, were fully estimated. Under the optimized extraction conditions, the detection limits of Pb2+ and Cd2+ were 0.033 µg L-1 and 0.008 µg L-1, respectively. Compared to other studies, CS/MOF-SH not only possessed superior adsorption performance, but also had the advantages of ease of handling and recyclability. Encouragingly, the developed method was of high accuracy and could monitor trace Pb2+ and Cd2+ in various certified reference materials (rice, wheat and tea) with complicated matrices, demonstrating its practical potential for regular monitoring of trace heavy metal ions in real food samples.


Assuntos
Cádmio/análise , Quitosana/química , Chumbo/análise , Estruturas Metalorgânicas/química , Compostos de Sulfidrila/química , Cádmio/química , Cátions Bivalentes , Análise de Alimentos , Chumbo/química , Oryza/química , Extração em Fase Sólida/métodos , Chá/química , Triticum/química
8.
Chemosphere ; 259: 127441, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32593826

RESUMO

In this study, a porous reduced graphene oxide (PRGO) carbon nanomaterial was successfully obtained by activation of natural graphite with KOH at high temperature and was applied as an auxiliary electrode in soil electrokinetic remediation to investigate the promoting effect on Cd migration. We found that PRGO contained a large amount of oxygen-containing groups (hydroxyl and carboxyl groups) and exhibited high Cd2+ adsorption efficiency at pH values above 4, achieving a maximum adsorption capacity of 434.78 mg/g for Cd. In addition, PRGO could selectively adsorb Cd, Pb, Cu, and Zn but not K, Na, or Mg from soil solution. The electrokinetic remediation experiment showed that the PRGO auxiliary electrode promoted the migration of Cd and effectively controlled the increase in soil pH near the cathode, possibly due to ion exchange between the surface functional groups on the auxiliary electrode and Cd2+. In addition, the location of the PRGO auxiliary electrode strongly influenced the migration of Cd. For instance, the soil Cd concentration of treatment H-5 was 57.86% lower than that of H-0 at a distance of 5-10 cm from the electrode; however, the soil Cd concentration measured at 0-5 cm for treatment H-5 was 34.84% higher than that of treatment H-0. Our study demonstrated that PRGO could be applied as an auxiliary electrode to promote Cd migration during electrokinetic remediation of Cd-contaminated soil.


Assuntos
Cádmio/química , Recuperação e Remediação Ambiental , Grafite/química , Adsorção , Cádmio/análise , Eletrodos , Poluição Ambiental , Concentração de Íons de Hidrogênio , Porosidade , Solo/química , Poluentes do Solo/análise
9.
Chemosphere ; 255: 126995, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32416394

RESUMO

In this paper, we present the preparation of MoS2-modified magnetic biochar (MoS2@MBC) as a novel adsorbent by a simple hydrothermal method. MoS2@MBC contains abundant S-containing functional groups that facilitate efficient Cd(II) removal from aqueous systems. We employed various characterization techniques to explore the morphology, surface area, and chemical composition of MoS2@MBC; these included Brunauer-Emmett-Teller analysis scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction,. The results indicated the successful decoration of the surface of MoS2@MBC with iron and MoS2, and a higher surface area of MoS2@MBC than that of unmodified biochar. Moreover, adsorption properties including thermodynamics and kinetics were investigated along with the effects of pH, humic acid, and ionic strength on the Cd(II) adsorption onto MoS2@MBC. The O-, C-, S-, and Fe-containing functional groups on the surface of MoS2@MBC led to an electrostatic attraction of Cd(II) and strong Cd-S complexation. The Langmuir and pseudo second-order models fitted best for the batch adsorption experiments results. The adsorption capacity of MoS2@MBC (139 mg g-1 on the basis of the Langmuir model) was 7.81 times higher than that of pristine biochar. The adsorption process was found to be pH-dependent. The experimental results indicated that MoS2@MBC is an effective adsorbent for removing Cd(II) from water solutions. Further, the adsorption process involved the complexation of Cd(II) with oxygen-based functional groups, ion exchange, electrostatic attraction, Cd(II)-π interactions, metal-sulfur complexation, and inner-surface complexation. This work provides new insights into the Cd(II) ions removal from water via adsorption. It also demonstrates that MoS2@MBC is an efficient and economic adsorbent to treat Cd(II)-contaminated water.


Assuntos
Adsorção , Cádmio/isolamento & purificação , Carvão Vegetal/química , Dissulfetos/química , Molibdênio/química , Purificação da Água/métodos , Cádmio/química , Cinética , Concentração Osmolar , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
10.
Chemosphere ; 250: 126268, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234619

RESUMO

The effectiveness of rice waste biochars on heavy metal and metalloid abatement and detoxification was investigated using comprehensive studies based on As and Cd immobilization, bioaccumulation in tubifex, and microbial community changes in contaminated sediment. The remediation effects of biochars produced at different pyrolytic temperatures (400-700 °C) were evaluated. Bioaccumulation of heavy metal and metalloid in the tubifex tissue and change of indigenous microbial community under treatment of different biochars were assessed. Biochars produced at 700 °C exhibited greater effect on decreasing the concentrations of As and Cd in aqueous phase, and TCLP extractable and bioavailable metal(loid) in solid phase of sediment. The concentration of As and Cd in water phase decreased by 26%-89% and 22%-71% under the treatment of straw biochar, and decreased by 13%-92% and 5%-64% under the treatment of rice husk biochar, respectively. As and Cd contents in the tubifex tissue were positively correlated with their concentrations in aqueous phase. High-temperature biochars significantly reduced metal(loid) bioaccumulation in tubifex. The richness and biodiversity of microbial community were both greater in all biochars remediated sediment compared to non-treated sediment. These results indicated that rice waste biochars could effectively inhibit the bio-availability and toxicity of heavy metal and metalloid in sediment, and the higher-temperature biochar exhibited better performance.


Assuntos
Arsênico/química , Cádmio/química , Carvão Vegetal/química , Recuperação e Remediação Ambiental , Disponibilidade Biológica , Inativação Metabólica , Metais Pesados , Oryza , Pirólise , Temperatura , Água
11.
Ecotoxicol Environ Saf ; 196: 110545, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32276162

RESUMO

The relationship between the chemical forms of Cu2+ and Cd2+ adsorbed on the roots of different wheat cultivars and their phytotoxic effects on the plants were investigated. The wheat varieties Dunmaiwang (DMW), Tekang 6 (TK6), Zhongmai895 (ZM895), and Chaojixiaomai (AK68) were used. The zeta potentials of wheat roots, measured by the streaming potential method, were used to characterize root charge properties. Results indicated that the changes in zeta potential at pH 4.01-6.61 were 14.7, 15.53, 13.01, and 12.06 mV for ZM895, AK68, DMW, and TK6, respectively. The negative charge and functional groups on ZM895 and AK68 roots were greater than on DMW and TK6 roots, which led to more exchangeable and complexed Cu2+ and Cd2+ on ZM895 and AK68 roots and increased Cu2+ and Cd2+ toxicity compared to DMW and TK6. Coexisting cations, such as Ca2+, Mg2+, K+, and NH4+, alleviated Cu2+ and Cd2+ toxicity to wheat roots through competition for adsorption sites on the roots, which decreased exchangeable and complexed Cu2+ and Cd2+ on wheat roots. The Ca2+ and Mg2+ were most effective in alleviating heavy metal toxicity and they decreased exchangeable Cu2+ on AK68 roots by 39.14% and 47.82%, and exchangeable Cd2+ by 8.51% and 28.23%, respectively.


Assuntos
Cádmio/toxicidade , Cobre/toxicidade , Poluentes do Solo/toxicidade , Triticum/efeitos dos fármacos , Adsorção , Cádmio/química , Cádmio/farmacocinética , Cátions , Cobre/química , Cobre/farmacocinética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Raízes de Plantas/fisiologia , Poluentes do Solo/química , Poluentes do Solo/farmacocinética , Triticum/metabolismo , Triticum/fisiologia
12.
Ecotoxicol Environ Saf ; 197: 110572, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32283410

RESUMO

The abuse of tetracycline arises the risk of antibiotic resistance genes and has been paid much attention. To understand the potential bioavailability of tetracycline (TC) in soil environments, this study explored the behaviors of TC adsorbing to six types of soils sampled from different regions of China. Moreover, the solution pH and existence of Cd2+ effect on TC sorption to soils were investigated to understand the influential factors affecting TC sorption. The results showed that the soil properties and sorption capacity of TC varied significantly with different soils. The sorption capacity of TC to soils might be largely affected by cation exchange capacity (CEC) and soil organic carbon (SOC), while the sorption rate, interaction strength and equilibrium sorption binding might be affected by soil pH, pHPZC, soil inorganic carbon (SIC) and H content. The result of solution pH effect suggested that the predominant sorption mechanism for acid soils might be hydrophobic interactions between soils and H2TC0, and the cation exchange was possibly proposed as the primary mechanism for TC sorption to alkaline soils. Furthermore, the presence of Cd2+ might increase TC sorption to acid soil, while reduce TC sorption to alkaline soil. It is expected that this study may provide important information for predicting the potential fate of TC (or similar antibiotics) in different soils, and thus helping to assess the bioavailability of TC in soils.


Assuntos
Cádmio/análise , Carbono/análise , Poluentes do Solo/química , Solo/química , Tetraciclina/química , Adsorção , Antibacterianos/análise , Antibacterianos/química , Cádmio/química , Cátions/análise , Cátions/química , China , Concentração de Íons de Hidrogênio , Poluentes do Solo/análise , Tetraciclina/análise
13.
Ecotoxicol Environ Saf ; 196: 110539, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32247959

RESUMO

Contamination of arable land with trace metals is a global environmental issue which has serious consequences on human health and food security. Present study evaluates the adsorption of cadmium (Cd) and lead (Pb) by using different quantities of composite of sepiolite, organic manure and lime (SOL) at field and laboratory scale (batch experiments). Characterization of SOL by SEM, EDS and FTIR spectroscopy revealed the presence of elemental and functional groups (hydroxyl, C⋯H and -COOH groups) on its surface. The field experiment was performed in a paddy field of gleysol having moderate contamination of Cd and Pb (0.64 mg kg-1 and 53.44 mg kg-1). Here, different rates of SOL (0.25, 0.5, 1, 1.5 and 2% w/w) were applied by growing low and high Cd accumulator rice cultivars. Application of SOL at 2% w/w showed considerable efficiency to increase soil pH (up to 19%) and to reduce available Cd (42-66%) and Pb (22-55%) as compared to the control. Moreover, its application reduced metal contents in roots, shoots and grains of rice by 31%, 36% and 72% (for Cd) and 41%, 81% and 84% (for Pb), respectively in low accumulator cultivar. Further, the batch sorption experiment was performed to evaluate the adsorption capacity of SOL in a wide range of contamination. Obtained sorption data was better fitted to the Langmuir equation. Our results highlight the strong efficiency of composite treatment for an enhanced in-situ metal immobilization under field and lab conditions. Further, applied treatments greatly reduced the metal contents in rice grains. In a nut shell, application of SOL in a contaminated gleysol should be considered for soil remediation and safe food production.


Assuntos
Cádmio/química , Compostos de Cálcio/química , Chumbo/química , Silicatos de Magnésio/química , Esterco , Óxidos/química , Adsorção , Disponibilidade Biológica , Cádmio/farmacocinética , Chumbo/farmacocinética , Oryza/metabolismo , Raízes de Plantas/metabolismo , Poluentes do Solo/química , Poluentes do Solo/farmacocinética
14.
Chemosphere ; 249: 126341, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32213393

RESUMO

Current mechanism studies in plant heavy metal tolerance do not consider the effects of different phenolic acids on the bioavailability of heavy metals and the comparison with antioxidant enzyme system in the hydroxyl radical scavenging capacity. In present study, by a set of pot culture experiments with adding cadmium (Cd) and zinc (Zn) to the sediments, the effects of different phenolic acids on the toxicity of Cd and Zn in Kandelia obovata and the dominant role in scavenging hydroxyl radicals were evaluated. The results showed that 100 mg kg-1 Zn treatment promoted the growth of plant under high concentrations of Cd and Zn stress. Under the stress of Cd and Zn, the phenolic acids were mainly metabolized by phenylpropanoid and flavonoid pathways, supplemented by shikimate and monolignol pathways in K. obovata. Eleven phenolic acids with different abilities of scavenging free radicals were detected in the plant, including pyrogallic acid (Gal), coumaric acid (Cou), protocatechuic acid (Pro), chlorogenic acid (Chl), 4-hydroxy benzoic acid (Hyd), caffeic acid (Caf), vanillic acid (Van), ferulic acid (Fer), benzoic acid (Ben), and salicylic acid (Sal). By adding phenolic acids to the sediments, chlorogenic acid (Chl), pyrogallic acid (Gal), cinnamic acid (Cin), and coumaric acid (Cou) behave as more reactive in changing Cd or Zn into residual fractions than the others, and chlorogenic acid (Chl), pyrogallic acid (Gal), ferulic acid (Fer) and caffeic acid (Caf) have higher ability of scavenging hydroxyl radicals than the others. In summary, K. obovata tends to synthesize phenolic acids with strong scavenging ability of free radicals and changing the bioavailability of Cd and Zn under high concentration of Cd and Zn stress. Phenolic acids played a crucial role in the mitigative effect of heavy metal stress via scavenging free radicals and involving in the process of Cd and Zn uptake and tolerance. The results will provide important theoretical basis and method guidance for mangrove wetland conservation.


Assuntos
Hidroxibenzoatos/química , Metais Pesados/química , Rhizophoraceae/fisiologia , Antioxidantes/metabolismo , Disponibilidade Biológica , Cádmio/química , Cádmio/metabolismo , Ácidos Cafeicos , Ácidos Cumáricos , Metais Pesados/metabolismo , Rhizophoraceae/efeitos dos fármacos , Áreas Alagadas , Zinco/química , Zinco/metabolismo
15.
Chemosphere ; 251: 126355, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32169702

RESUMO

Iron (Fe) in soil is closely related to cadmium (Cd) uptake by rice plants, and soil pe + pH significantly influences Fe redox behavior. This study aimed to explore the influential mechanisms of varying pe + pH conditions on the transformation of iron oxides in the rhizosphere and the subsequent effect on Cd accumulation in rice plants. A two-month pot experiment was conducted to investigate the effect of soil pe + pH on the fractions of iron oxides and formation of iron plaque (IP), as well as the effect of these changes on Cd uptake by rice plants (Oryza sativa L.). Different irrigation strategies, 70% water holding capacity (DY), continuous flooding (FL), and alternate flooding/drying weekly (AWD), were used to achieve various soil pe + pH levels. The results showed that low pe + pH conditions (under the FL and AWD treatments) were more beneficial to the transformation of crystalline iron oxides into amorphous forms in rhizosphere soil and the precipitation of IP on rice roots. The increase of amorphous iron oxides resulted in the reduction of Cd availability in rhizosphere soil by immobilizing more Cd on Fe oxides. Moreover, Cd adsorbed on rice root surfaces reacted with IP, inhibiting Cd soil-to-root transport. The two mechanisms combinatively functioned at decreasing Cd concentration in rice shoots by 14.1-33.1% at low pe + pH conditions compared to that of the high pe + pH (DY treatment). These results indicate that lowering soil pe + pH effectively reduced Cd accumulation in rice plants, probably through the immobilization of amorphous Fe oxides on Cd and sequestration of iron-plaque on Cd.


Assuntos
Cádmio/química , Ferro/química , Poluentes do Solo/química , Adsorção , Disponibilidade Biológica , Cádmio/análise , Concentração de Íons de Hidrogênio , Oryza/química , Óxidos/farmacologia , Raízes de Plantas/efeitos dos fármacos , Rizosfera , Solo/química , Poluentes do Solo/análise
16.
Nat Commun ; 11(1): 1262, 2020 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-32152269

RESUMO

Binding of biomolecules to crystal surfaces is critical for effective biological applications of crystalline nanomaterials. Here, we present the modulation of exposed crystal facets as a feasible approach to enhance specific nanocrystal-biomolecule associations for improving cellular targeting and nanomaterial uptake. We demonstrate that facet-engineering significantly enhances transferrin binding to cadmium chalcogenide nanocrystals and their subsequent delivery into cancer cells, mediated by transferrin receptors, in a complex biological matrix. Competitive adsorption experiments coupled with theoretical calculations reveal that the (100) facet of cadmoselite and (002) facet of greenockite preferentially bind with transferrin via inner-sphere thiol complexation. Molecular dynamics simulation infers that facet-dependent transferrin binding is also induced by the differential affinity of crystal facets to water molecules in the first solvation shell, which affects access to exposed facets. Overall, this research underlines the promise of facet engineering to improve the efficacy of crystalline nanomaterials in biological applications.


Assuntos
Proteínas de Transporte/química , Sistemas de Liberação de Medicamentos/métodos , Nanopartículas/química , Transferrina/química , Adsorção , Fenômenos Biofísicos , Cádmio/química , Células HeLa , Humanos , Simulação de Dinâmica Molecular , Tamanho da Partícula , Receptores da Transferrina , Propriedades de Superfície , Difração de Raios X
17.
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.


Assuntos
Boehmeria , Cádmio , Recuperação e Remediação Ambiental , Chumbo , Poluentes do Solo , Boehmeria/metabolismo , Cádmio/química , Cálcio/química , China , Recuperação e Remediação Ambiental/métodos , Fazendas , Fertilizantes , Ferro/química , Chumbo/química , Metais Pesados/química , Dióxido de Silício/química , Solo , Poluentes do Solo/química
18.
Artigo em Inglês | MEDLINE | ID: mdl-32131442

RESUMO

The present study investigated the adsorption of Cd2+ by nonmagnetic and magnetic biochars (CMB and M-CMB) derived from chicken manure, respectively. The adsorption characteristics were investigated as a function of initial pH, contact time, initial Cd2+ concentration and magnetic separation. Adsorption process of both biochars were better described by Pseudo-second-order kinetic equation and Freundlich isotherm model, which were spontaneous and endothermic in nature. It was found that maximum capacities were 60.69 and 41.07 mg/g obtained at the initial Cd2+ concentration of 180 mg/L for CMB and M-CMB, and the turbidity of adsorption-treated solution was reduced from 244.3 to 11.3 NTU after magnetic separation of 0.5 min. These indicated that M-CMB had lower adsorption capacity of Cd2+ than CMB, though it was successfully separated from the treated solutions. Furthermore, both biochars before and after adsorption were analyzed by SEM-EDS, XRD and FTIR. Adsorption mechanisms mainly included precipitation, ion-exchange, complexation and Cπ-coordination, in which precipitation and ion-exchange dominated the adsorption process by CMB, while in M-CMB, precipitation was always predominant mechanism, followed by ion-exchange. The two other mechanisms of complexation and Cπ-coordination were trivial in both biochars, jointly contributing 7.21% for CMB and 5.05% for M-CMB to total adsorption. The findings deepen our understanding of the mechanisms governing the adsorption process, which are also important for future practical applications in the removal of heavy metals from wastewater by the biochars.


Assuntos
Cádmio , Carvão Vegetal , Esterco , Poluentes Químicos da Água , Adsorção , Animais , Cádmio/química , Galinhas , Fenômenos Magnéticos
19.
Mar Pollut Bull ; 151: 110797, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32056592

RESUMO

This study aimed to investigate if microplastics (MPs) type (polyethylene microspheres (mPE), fishing line fibers, film plastic bags MPs and bottle cap particles) and aging affect MPs capacity to sorb Cd or Cu in estuarine salt marsh medium. Tests were carried out in elutriate solution, a simple medium obtained by mixing rhizosediment (sediment in contact with plants roots) with the respective estuarine water, that can be used to simulate water-sediment exchanges in estuarine salt marsh environments. After 7 days of exposure, metals adsorption was only detected for film MPs. No differences were observed between virgin and aged MPs. Salinity also did not influence metal adsorption to mPE. Present results indicate that in estuarine salt marsh areas some types of MPs might adsorb metals, which could affect metals availability.


Assuntos
Cádmio/química , Cobre/química , Microplásticos/química , Poluentes Químicos da Água , Áreas Alagadas , Adsorção , Plásticos
20.
Artigo em Inglês | MEDLINE | ID: mdl-32109747

RESUMO

Cd(II) is toxic to many species, including humans, because it inactivates a number of enzymes and induces cytopathic effects in the liver, kidney, and skeletal tissues in humans. Metallothionein and glutathione (GSH) play a major role in the protection against Cd(II)-induced toxicity in mammalian cells. In this study, a relatively simple method for detecting trace amounts of Cd(II) chelators was developed by using 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (TPPS). The TPPS-Cd(II) complex was added to the elutions of high-performance liquid chromatography. The Cd(II) chelators separated by column chromatography were mixed with Cd(II)-bound TPPS (TPPS-Cd(II)). Cd(II) from TPPS-Cd(II) was chelated by the eluted Cd(II) chelators, resulting in the formation of free TPPS. The absorbance of TPPS shifted from 434 nm (TPPS-Cd(II)) to 414 nm (TPPS), and this characteristic shift was used to estimate the quantity and affinity of the Cd(II) chelators. This new method was compared with the bathocuproine disulfonate (BCS) method developed in our previous study. Instead of BCS-Cu(I), TPPS-Cd(II) was used as the colorimetric reagent. The experimental setup of the TPPS-based method is more general, and the preparation of the colorimetric solution is also much simpler than the BCS method. To verify the efficacy of this new method, we determined the actual Cd(II)-chelating ability of GSH in horse blood; the obtained concentration was in good agreement with the previously reported value.


Assuntos
Aporfinas/química , Cádmio/química , Quelantes/análise , Quelantes/química , Cromatografia Líquida de Alta Pressão/métodos , Animais , Glutationa , Cavalos , Limite de Detecção , Estresse Oxidativo
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