Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 14 de 14
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Huan Jing Ke Xue ; 40(6): 2939-2947, 2019 Jun 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854689

RESUMO

In order to study the effect of nanosilver on soil nitrification microorganisms and nitrogen transformation, soil culture experiments were carried out. Yellow brown soil and paddy soil were first spiked with different doses of nanosilver (10, 50, 100 mg·kg-1) and silver ions (1, 5, 10 mg·kg-1). Then, the number of nitrifying bacteria, activity of soil invertase, amoA gene abundance, NH4+-N content, NO3--N content, and soil potential ammonia oxidation rate were determined. The results showed that the number of nitrite bacteria and nitrate bacteria decreased significantly when the soils were treated with nanosilver and silver ions. Soil invertases were inhibited, and the effect on urease was greater than that on catalase. The amoA gene abundances of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) decreased, and the effect on the gene abundance of AOB was greater than that of AOA. When (NH4)2SO4 was added to the soil, nanosilver and silver ion pollutants caused NH4+-N to accumulate, and the contents of NO3--N were reduced, the rate of ammonia oxidation decreased, and the transformation of ammonium nitrogen to nitrate nitrogen was inhibited. This research suggests that nanosilver and silver ions can have toxic effects on soil nitrification microorganisms and ammonium nitrogen conversion, and the degree of influence was found to be related to the soil physical and chemical properties.

2.
Environ Sci Technol ; 53(7): 3802-3810, 2019 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-30861341

RESUMO

The increasing use of silver-containing nanoparticles (NPs) in commercial products has led to NP accumulation in the environment and potentially in food webs. Identifying the uptake pathways of different chemical species of NPs, such as Ag2S-NP and metallic AgNPs, into plants is important to understanding their entry into food chains. In this study, soybean Glycine max L. was hydroponically exposed to Ag2S-NPs via their roots (10-50 mg L-1) and stable-isotope-enriched 109AgNPs via their leaves [7.9 µg (g fresh weight)-1]. Less than 29% of Ag in treated leaves (in direct contact with 109AgNP) was accumulated from root uptake of Ag2S-NPs, whereas almost all of the Ag in soybean roots and untreated leaves sourced from Ag2S-NPs. Therefore, Ag2S-NPs are phytoavailable and translocate upward. During trophic transfer the Ag isotope signature was preserved, indicating that accumulated Ag in snails most likely originated from Ag2S-NPs. On average, 78% of the Ag in the untreated leaves was assimilated by snails, reinforcing the considerable trophic availability of Ag2S-NPs via root uptake. By highlighting the importance of root uptake of Ag2S-NPs in plant uptake and trophic transfer to herbivores, our study advances current understanding of the biogeochemical fate of Ag-containing NPs in the terrestrial environment.


Assuntos
Nanopartículas Metálicas , Prata , Cadeia Alimentar , Isótopos , Soja
3.
Huan Jing Ke Xue ; 37(4): 1330-6, 2016 Apr 15.
Artigo em Chinês | MEDLINE | ID: mdl-27548953

RESUMO

Mercury is harmful to the environment, which has gradually become one of the research hotspots. Sediments, as a main repository of pollutants, have an important impact on water quality and the internal organisms, which deserves our research. In this paper, we focused on Hefei landscape water sediment and tried to investigate the status of inorganic mercury and methylmercury pollutions in the sediment. To study the conversion process from inorganic mercury to methylmercury and their enrichment levels and mechanism, we established the ecological chain of "sediment-water-grass-fish" through analog microcosm examination. The results were as follows: from ten water and sediment samples in Hefei landscape water sediment, we found that the contents of inorganic mercury and methylmercury ranged 11.74-13.12 µg · kg⁻¹ and 0.37-2.23 µg · kg⁻¹, respectively. The microcosm examination showed that: with increasing culture time, inorganic mercury in sediments gradually decreased. There was a phenomenon that the content of methylmercury increased at first and then decreased to reach the balance later. Both the inorganic mercury and methylmercury in water change showed an increasing trend. The enrichment contents of inorganic mercury in Egeria densa Planch, and golden mandarin fish (Siniperca scherzeri Steindachner) were low while their enrichment of methylmercury could he great. In addition, we found that both the bioaccumulation ability and the enrichment coefficient of methylmercury in the body of golden mandarin fish were the maximum during the same period.


Assuntos
Monitoramento Ambiental , Mercúrio/análise , Compostos de Metilmercúrio/análise , Poluentes Químicos da Água/análise , Animais , Peixes , Sedimentos Geológicos/química , Masculino , Poaceae/química , Água/química
4.
Water Sci Technol ; 73(12): 2913-20, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27332836

RESUMO

The effects of solid-state NaOH pretreatment on the efficiency of methane production from semi-dry anaerobic digestion of rose (Rosa rugosa) stalk were investigated at various NaOH loadings (0, 1, 2, and 4% (w/w)). Methane production, process stability and energy balance were analyzed. Results showed that solid-state NaOH pretreatment significantly improved biogas and methane yields of 30-day anaerobic digestion, with increases from 143.7 mL/g volatile solids (VS) added to 157.1 mL/g VS -192.1 mL/g VS added and from 81.8 mL/g VS added to 88.8 mL/g VS-117.7 mL/g VS added, respectively. Solid-state NaOH pretreatment resulted in anaerobic digestion with higher VS reduction and lower technical digestion time. The 4% NaOH-treated group had the highest methane yield of 117.7 mL/g VS added, which was 144% higher compared to the no NaOH-treated group, and the highest net energy recovery. Higher rate of lignocellulose breakage and higher process stability of anaerobic digestion facilitated methane production in the NaOH-pretreated groups.


Assuntos
Biocombustíveis/análise , Metano/biossíntese , Rosa/química , Hidróxido de Sódio/química , Anaerobiose , Caules de Planta/química
5.
Huan Jing Ke Xue ; 36(6): 2252-8, 2015 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-26387333

RESUMO

The effects of the biological dissolution and reduction of goethite on mercury methylation by Shewanella oneidensis MR-1 were studied under laboratory conditions. The results showed that S. oneidensis MR-1 could dissolve goethite, and subsequently dissolved Fe3+ which was reduced to Fe2+. S. oneidensis MR-1 was also a kind of mercury methylation bacterial, which had a potential to transform inorganic mercury to methylmercury. The biological dissolution and reduction of goethite declined with the increasing initial dosage of goethite. The dissimilatory reduction of goethite could promote mercury methylation to a certain extent. Weakly acidic condition was more beneficial to mercury methylation than neutral, alkaline or highly acidic conditions. Low humic acid concentration


Assuntos
Compostos de Ferro/química , Mercúrio/química , Minerais/química , Shewanella/química , Concentração de Íons de Hidrogênio , Ferro/química , Metilação , Compostos de Metilmercúrio/química
6.
Huan Jing Ke Xue ; 36(9): 3533-42, 2015 Sep.
Artigo em Chinês | MEDLINE | ID: mdl-26717720

RESUMO

Fe(III) dissimilatory reduction by microbes is an important process of producing energy in the oxidation of organic compounds under anaerobic condition with Fe(III) as the terminal electron acceptor and Fe(II) as the reduction product. This process is of great significance in element biogeochemical cycle. Iron respiration has been described as one of the most ancient forms of microbial metabolism on the earth, which is bound up with material cycle in water, soil and sediments. Dissimilatory iron reduction plays important roles in heavy metal form transformation and the remediation of heavy metal and radionuclide contaminated soils. In this paper, we summarized the research progress of iron reduction in the natural environment, and discussed the influence and the mechanism of dissimilatory iron reduction on the speciation and bioavailability of heavy metals in soil. The effects of dissimilatory iron reduction on the speciation of heavy metals may be attributed to oxidation and reduction, methytation and immobilization of heavy metals in relation to their bioavailability in soils. The mechanisms of Fe(III) dissimilatory reduction on heavy metal form transformation contain biological and chemical interactions, but the mode of interaction remains to be further investigated.


Assuntos
Ferro/química , Metais Pesados/análise , Solo/química , Disponibilidade Biológica , Poluição Ambiental , Compostos Férricos , Microbiologia do Solo , Água
7.
Huan Jing Ke Xue ; 34(11): 4466-72, 2013 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-24455961

RESUMO

The biological dissolution and methylation of solid HgS by Shewanella oneidensis MR-1 and influenced factors under laboratory conditions were studied. Results showed that S. oneidensis MR-1 could grow well at the low concentration of Na2S, but its growth was inhibited at the high concentration of Na2S, which mainly happened in the prolonged lag phase. Iron reducing bacteria S. oneidensis MR-1 could access the solid mercuric sulfide, and rapidly promote the biological dissolution and methylation of HgS. In the appropriate range of sulfide to S. oneidensis MR-1, the biological solubility of HgS was enhanced with the increasing concentration of Na2S, but the methylation just promoted at the low Na2S concentration, and it would be inhibited when the concentration is high. In addition, weakly acidic environment was more beneficial to biological dissolution and methylation of HgS than acidic, neutral or alkaline conditions by S. oneidensis MR-1.


Assuntos
Compostos de Mercúrio/química , Shewanella/metabolismo , Sulfetos/química , Concentração de Íons de Hidrogênio
8.
Huan Jing Ke Xue ; 33(8): 2875-81, 2012 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-23213918

RESUMO

Competitive adsorption kinetics of aqueous Pb2+ and Cu2+ on Nano-HAP surfaces were investigated by performing the adsorption kinetic experiments and comparing the change of zeta potentials and XRD-map before and after metal adsorption. The results showed that the adsorption quantity of Pb2+ on Nano-HAP was higher than that of Cu2+ in the single system. However, the competitive adsorption of Pb2+ and Cu2+ occurred in the co-existence system of Pb2+ and Cu2+. The adsorption quantity of Cu2+ on Nano-HAP increased, while that of Pb2+ decreased. The X-ray diffraction (XRD) and adsorption quantities of Ca2+ surface analysis indicated that dissolution-precipitation is the primary immobilization mechanism for Pb2+, while surface complexation and electrostatic adsorption account for Cu2+ sequestration. The adsorption quantities of Pb2+ and Cu2+ on Nano-HAP had marked linear relationship with Ca2+ release from Nano-HAP (R2 0.861-0.954). The adsorption kinetics were fitted with the equations of first-order, second-order, parabola, Elovich, double constant equation and LJ function, respectively, in which the second-order and power function kinetics equation fitted the results best. According to above results, the adsorption kinetics of Pb2+ and Cu2+ on Nano-HAP is a complex adsorption processes with both chemical reaction and physical adsorption.


Assuntos
Cobre/isolamento & purificação , Durapatita/química , Chumbo/isolamento & purificação , Nanopartículas/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Cinética , Propriedades de Superfície
9.
Huan Jing Ke Xue ; 33(9): 3247-52, 2012 Sep.
Artigo em Chinês | MEDLINE | ID: mdl-23243888

RESUMO

Mercury methylation by Geobacter sulfurreducens and the effects of environmental factors were studied under laboratory conditions. The results showed that G. sulfurreducens could grow well in the presence of low concentrations of mercuric chloride, but its growth was inhibited to a certain extent, mainly expressed in the prolonged lag phase. G. sulfurreducens could transform inorganic mercury into methylmercury, and this process was affected by many environmental factors. The efficiency of mercury methylation reached 38% under anaerobic conditions with 1 mg x L(-1) HgCl2 and 0.9% salinity at 35 degrees C, pH 6.0. Increasing the initial HgCl2 concentration or salinity in an appropriate manner improved mercury methylation, but the concentration of methylmercury reduced when the concentrations of HgCl2 and salinity were too high. The efficiency of mercury methylation increased with the increasing temperature in range of 4-35 degrees C. Weakly acidic environment was more beneficial to mercury methylation than acidic, neutral or alkaline conditions. In addition, the efficiency of mercury methylation was also affected by humic acid and cysteine. Humic acid inhibited mercury methyaltion, whereas cysteine could improve the efficiency of mercury methylation. This study provided a direct evidence for mercury methylation mediated by iron-reducing bacteria in the natural aquatic ecosystem.


Assuntos
Geobacter/metabolismo , Mercúrio/química , Compostos de Metilmercúrio/metabolismo , Biodegradação Ambiental , Poluentes Ambientais/química , Poluentes Ambientais/isolamento & purificação , Geobacter/classificação , Cloreto de Mercúrio/química , Cloreto de Mercúrio/isolamento & purificação , Mercúrio/isolamento & purificação , Mercúrio/metabolismo , Compostos de Metilmercúrio/química
10.
Huan Jing Ke Xue ; 32(8): 2284-91, 2011 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-22619951

RESUMO

Quartz sand was selected as collector and saturated packed column was constructed to explore the effects of environmental factors (humic acid, pH and ionic strengths of the bulk solution) on the transport and fate of hydroxyapatite nanoparticles (Nano-HAP) through measuring zeta potentials and representative c(i)/c(0) of Nano-HAP. It was suggested that zeta potentials of Nano-HAP colloids became more negative with increasing humic acid concentration and the change in solution composition from 0 to 10 mg/L humic acid yielded an increase in the zeta potentials of Nano-HAP colloids from -15 mV to -55 mV and a sharp decrease in a (attachment efficiency) from 1.0 to 0.012, meanwhile, the increase in bulk solution pH yielded a slight decrease in a which enhancing its transportation in saturated packed column. However, zeta potentials of Nano-HAP colloids became less negative as the ionic strength of bulk solution increased due to the compression of diffuse double layer and yielded an increase in a which greatly impeded its mobility during the pore-water solution, meanwhile, divalent cations have significantly stronger influence on the transport of Nano-HAP than monovalent cations of the bulk solution. The increase in the concentration of monovalent cation (Na+) from 1 to 100 mmol/L yielded an increase in a from 0.030 to 0.13, and divalent cations (Ca2+) from 0.2 to 10 mmol/L yielded a greatly increase in alpha from 0.030 to 1.0. It is important to note that the results could considerably contribute to gain insights in the transport and fate of Nano-HAP in natured and engineered porous media.


Assuntos
Durapatita/química , Substâncias Húmicas , Íons/química , Nanopartículas/química , Concentração de Íons de Hidrogênio , Cinética , Movimento (Física) , Concentração Osmolar , Quartzo/química , Dióxido de Silício/química , Poluentes do Solo/química
11.
Huan Jing Ke Xue ; 31(6): 1499-505, 2010 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-20698263

RESUMO

Reductive transformation of 2,4-Dichlorophenoxyacetic acid (2,4-D) by nanoscale Fe3O4 was studied, and the effects of 2,4-D initial concentration, the dosage of nanoscale Fe3O4, pH and temperature on degradation rate of 2,4-D were investigated. The results showed that 48% 2,4-D with initial concentration of 10 mg/L was transformed within 48 h in the presence of 300 mg/L nanoscale Fe3O4. The degradation of 2,4-D was a reductive dechlorination process, and the concentration of chloride ion increased sharply with the degration of the 2,4-D. Disappearance of parent species and formation of reaction intermediates and products were analyzed by LC/MS. The transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP) and phenol. The degradation equations of 2,4-D by nanoscale Fe3O4 conformed to pseudo-first-order kinetics, and the reaction rate constant (K) of 4-CP, 2,4-DCP and phenol were 0.0043 h(-1), 0.0026 h(-1) and 0.0032 h(-1), respectively. The degradation rate increased with an increase in initial concentration of 2,4-D from 0 mg/L to 10 mg/L, and increasing the dosage of nanoscale Fe3O4 from 0 mg/L to 300 mg/L. The pH of reaction solution significantly influenced reductive degradation of 2,4-D, and the optimum pH value was 3.0. Besides, high temperature could improve dechlorination rate of 2,4-D.


Assuntos
Ácido 2,4-Diclorofenoxiacético/isolamento & purificação , Óxido Ferroso-Férrico/química , Nanopartículas Metálicas/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Ácido 2,4-Diclorofenoxiacético/química , Herbicidas/química , Herbicidas/isolamento & purificação , Oxirredução , Poluentes Químicos da Água/química
12.
J Environ Sci (China) ; 16(4): 529-32, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15495949

RESUMO

The electrokinetic removal of chromium and copper from contaminated soils by adding lactic acid in cathode chamber as an enhancing reagent was evaluated. Two sets of duplicate experiments with chromium contaminated kaolinite and with a silty soil sampled from a superfund site in California of USA and polluted by Cr and Cu, were carried out in a constant current mode. Changes of soil water content and soil pH before and after the electrokinetic experiments, and variations of voltage drop and electroosmosis flow during the treatments were examined. The results indicated that Cr, spiked as Cr( VI ) in the kaolinite, was accumulated mainly in the anode chamber, and some of Cr and metal hydroxides precipitated in the soil sections in contact with the cathode, which significantly increased electrical energy consumption. Treatment of the soil collected from the site showed accumulation of large amounts of Cr and Cu in the anode chamber while none was detected in the cathode one. The results suggested that the two metals either complexed with the injected lactic acid at the cathode or existed as negatively charged complex, and electromigrated toward the anode under a voltage gradient.


Assuntos
Cromo/isolamento & purificação , Cobre/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Cromo/química , Cobre/química , Eletroquímica , Eletrodos , Cinética , Ácido Láctico/análise
13.
Pest Manag Sci ; 60(3): 286-90, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15025240

RESUMO

Photolysis of bensulfuron-methyl on soil surface was studied under sunlight and UV light. Seven photoproducts were isolated and characterised by spectroscopic methods. The major processes in the photolysis of bensulfuron-methyl in soil are cleavage of the sulfonylurea bridge, scission of the SO2NH bond and contraction of the sulfuronylurea bridge. The rates of photodegradation of bensulfuron-methyl on different soils followed first-order rate kinetics with half lives of 21.9, 28.4, 36.9, 59.2 and 47.2 h (UV) and 23.1, 27.5, 29.1, 38.9 and 33.8 days (sunlight) for vertisol, alluvial, alfisol, red and laterite soils, respectively. The differences in rates of photodegradation were dependent upon the soil texture and organic matter content.


Assuntos
Resíduos de Praguicidas/metabolismo , Solo/análise , Compostos de Sulfonilureia/metabolismo , Biodegradação Ambiental/efeitos da radiação , Luz , Estrutura Molecular , Resíduos de Praguicidas/química , Compostos de Sulfonilureia/química
14.
J Environ Sci (China) ; 14(4): 439-44, 2002 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-12491715

RESUMO

Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water-soluble and exchangeable(SE), weakly specific adsorbed(WSA), Fe and Mn oxides-bound(OX) and organic-bound(ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic-bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH4Cl, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.


Assuntos
Metais Pesados/química , Poluentes do Solo/análise , Cloreto de Amônio/química , Eletroquímica , Metais Pesados/isolamento & purificação , Propriedades de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...