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1.
Chemosphere ; 244: 125411, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32050322

RESUMO

Uranium is a long lived radioactive element which is naturally present in minute concentrations in igneous, sedimentary and metamorphic rocks. These rocks when subjected to weathering results in the formation of soil which also has traces of uranium. Distribution coefficient (Kd) is a crucial parameter in environmental assessment which is used to predict the interaction and transport of uranium in groundwater. The objective of the study is to estimate the Kd of uranium in soils and to develop a relation between this and the soil parameters. Seven rock samples and twenty three soil samples were collected during this study. The Kd of rock samples of different grain sizes where determined and the soil samples were analysed for electrical conductivity, pH, grain size, bulk density, particle density, porosity, calcium carbonate, cation exchange capacity and Kd. The Kd of the soil increases with increase in soil pH up to 6, after which it gradually decreases. Multiple regression analysis was performed to quantify the effect of various soil parameters on soil Kd and equations were statistically significant. Thus, soil Kd in a region could be predicted using limited soil properties with such statistically significant equations.


Assuntos
Água Subterrânea/química , Poluentes Radioativos do Solo/química , Solo/química , Urânio/química , Concentração de Íons de Hidrogênio , Análise de Regressão , Poluentes Radioativos do Solo/análise , Urânio/análise , Poluentes Radioativos da Água/análise , Poluentes Radioativos da Água/química
2.
Sci Total Environ ; 703: 135604, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31771849

RESUMO

Novel iron/carbon composites were successfully prepared via coupling of cellulose with iron oxides (e.g. α-FeOOH, Fe2O3 and Fe(NO3)3·9H2O) at different temperatures under nitrogen atmosphere. Characterization by various techniques implied that chemical interaction between cellulose and Fe3O4/Fe0 existed in the as-prepared iron/carbon composites. The site of interaction between cellulose and iron precursors was illustrated (mainly combined with COO-). The self-reduction of Fe3+ to Fe2+ or even Fe0 and the interaction between carbon and Fe3O4/Fe0 in the calcination process realized the strong magnetism of the composites. Batch experiments and spectroscopic techniques indicated that the maximum adsorption capacity of MHC-7 for U(VI) (105.3 mg/g) was significantly higher than that of MGC-7 (86.0 mg/g) and MFC-7 (79.0 mg/g), indicating that Fe2O3 can be regarded as the remarkable iron resource for the iron/carbon composites. XPS results revealed that the oxygen-containing groups were responsible for the adsorption process of U(VI) on iron/carbon composites, and the adsorption of carbon and reduction of Fe0/Fe3O4 toward U(VI) were synergistic during the reaction process. In addition, the iron/carbon composites exhibited a good recyclability, recoverability and stability for U(VI) adsorption in the regeneration experiments. These findings demonstrated that the iron/carbon composites can be considered as valuable adsorbents in environmental cleanup and the Fe2O3 was a promising iron resource for the preparation of iron/carbon composites.


Assuntos
Celulose/química , Ferro/química , Urânio/química , Poluentes Radioativos da Água/química , Adsorção , Carbono , Recuperação e Remediação Ambiental , Compostos Férricos/química , Nitrogênio
3.
Water Sci Technol ; 80(3): 397-407, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31596251

RESUMO

In this work, the study of copper particles deposition on to carbon felt was presented by pulse electrodeposition method to electrochemically degrade methyl iodide (CH3I, 1 mg L-1) in aqueous solution. In order to solve the problems linked to the heterogeneous potential distribution in the 3-D porous structure, which lead to the so-called 'black core', we successfully used low concentration of copper salt (1 mM) and negative deposition potential (-2.5 V) to obtain Cu-nanoparticles/carbon felt (Cu-nano/CF) electrode, the copper coating improved the specific surface area of carbon felt from ∼0.07 to 0.7 m2 g-1 with high catalytic activity. Results show that 98.1% of CH3I can be removed with the Cu-nano/CF electrode in 120 min.


Assuntos
Cobre , Hidrocarbonetos Iodados/química , Resíduos Radioativos , Poluentes Radioativos da Água/química , Carbono/química , Fibra de Carbono/química , Poluentes Radioativos da Água/análise
4.
Environ Pollut ; 254(Pt B): 113110, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31479808

RESUMO

Abiotic reduction represents an attractive technology to control U(VI) contamination. In this work, an abiotic route of U(VI) reduction with humic acid at mineral surfaces is proposed and reaction mechanisms are addressed by periodic density functional theory calculations. Different influencing factors such as ligand effect, content of CO32- ligands and substituent effect are inspected. The coordination chemistry of uranyl(VI) surface complexes relies strongly on substrates and ligands, and the calculated results are in good agreements with experimental observations available. For the OH- ligand, two competitive mechanisms co-exist that respectively produce the U(IV) and U(V) species, and the former is significantly preferred because of lower energy barriers. Instead, the NO3- ligand leads to the formation of U(V) while for the Cl- ligand, the U(VI) surface complex remains very stable and is not likely to be reduced because of very high energy barriers. The U(V) and U(IV) complexes are the predominant products for low and high CO32- contents, respectively. Accordingly, the abiotic reduction processes with humic acid are efficient to manage U(VI) contamination and become preferred under basic conditions or at higher CO32- contents. The U(VI) reduction is further promoted by introduction of electron-donating rather than electron-withdrawing substituents to humic acid. Electronic structure analyses and vibrational frequency assignments are calculated for the various uranium surface complexes of the reduction processes, serving as a guide for future experimental and engineered studies. The molecular-level understanding given in this work offers an abiotic route for efficient reduction of U(VI) and remediation of U(VI)-contaminated sites at ambient conditions.


Assuntos
Substâncias Húmicas , Urânio/química , Poluentes Radioativos da Água/química , Eletroquímica , Elétrons , Ligantes , Minerais , Vibração
5.
J Environ Radioact ; 208-209: 106024, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376730

RESUMO

The disequilibrium of the grandparent-daughter pair 210Pb (t1/2=22.3 years)-210Po (t1/2=138 days) has been used to estimate the export fluxes of particulate organic carbon in the ocean using particulate-matter-associated 210Po. 210Po is produced from 210Bi, not from 210Pb. The half-life of 210Bi (t1/2=5.01 days) is sufficiently long compared to the rates of biological particle formation and decomposition or dissolution occurring at sea. The role of 210Bi has not yet been assessed quantitatively in the apparent disequilibrium between 210Pb and 210Po, partly due to the non-existence of 210Bi depth profile measurements at sea up to now. However, greater affinity of 210Bi over 210Po and 210Pb was found recently in coastal waters and phytoplankton 207Bi uptake experiments. Build upon these findings, we developed a primitive and simple analytical approach to elucidate the role of 210Bi in the 210Po-210Pb pair in the ocean using a simplified two-box irreversible steady-state ocean model. We assumed that the activity concentrations in the dissolved and particulate phases of 210Pb, 210Bi, and 210Po in a given water column are solely determined by the concentration of the particles, their input and output, the distribution coefficients between dissolved and particulate phases, and decay constants of these radionuclides in the steady-state ocean. The 210Bi contribution to the 210Pb-210Po activity difference in seawater is found to be significant, therefore, it needs to be considered in estimating particle fluxes using 210Pb-210Po secular equilibrium at sea.


Assuntos
Bismuto/química , Radioisótopos de Chumbo/química , Polônio/química , Monitoramento de Radiação , Poluentes Radioativos da Água/química , Radioisótopos de Chumbo/análise , Polônio/análise
6.
Environ Pollut ; 254(Pt A): 112891, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31408794

RESUMO

The effluents from nuclear mining processes contain relatively high content of radionuclides (such as uranium), which may seriously threaten the environment and human health. Herein, a novel adsorbent, porous hydroxyapatite, was prepared and proven highly efficient for removal of uranyl ions (U(VI)) given its high U(VI) uptake capacity of 111.4 mg/g, fast adsorption kinetics, and the potential stabilization of adsorbed U(VI). A nearly complete removal of U(VI) was achieved by porous HAP under optimized conditions. Langmuir model could well describe the adsorption equilibrium. The data fit well with pseudo-second-order kinetic model, suggesting that U(VI) adsorption is primarily attributed to chemisorption with porous HAP. Intraparticle diffusion analysis showed that the intraparticle diffusion is the rate-limiting step for U(VI) adsorption by porous HAP. After removal by porous HAP, the adsorbed U(VI) ions were incorporated into tetragonal autunite, which has a low solubility (log Ksp: -48.36). Our findings demonstrate that the porous HAP can effectively remediate uranium contamination and holds great promise for environmental applications.


Assuntos
Durapatita/química , Mineração , Urânio/química , Poluentes Radioativos da Água/química , Adsorção , Difusão , Íons , Cinética , Porosidade , Urânio/análise
7.
Environ Pollut ; 253: 221-230, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31310872

RESUMO

There is a need to develop highly efficient materials for capturing uranium from nuclear wastewater. Here, 5-methylbenzotriazole modified graphene oxide (MBTA-GO) was used to adsorb U(VI) from aqueous solution. By the trials of different conditions, we found that the removal of U(VI) from acidic solution was strongly dependent on pH but independent of ionic strength. The U(VI) adsorption was perfectly conformed to the pseudo-second-order kinetics and the adsorption isotherms were simulated by the Langmuir model well. A high removal capacity (qmax = 264 mg/g) for U(VI) at pH 3.5 was obtained. XPS, EXAFS analyses and DFT calculations revealed that the mechanism of uranium capture was ascribed to (i) the surface complexation by benzotriazole and carboxyl groups (providing lone pair electrons) on MBTA-GO and (ii) enhanced synergistic coordination ability of delocalized π-bond of triazole group toward U due to the transfer of electrons from graphene sheet to benzotriazole. DFT calculations further demonstrated that benzotriazole displayed stronger binding with U(VI) compared to carboxyl group due to higher binding energy of [Side/Surface-U-MBTA-GO] (79.745, 54.986 kcal/mol) than [MBTA-GO-COOH-U] (27.131 kcal/mol). This work will provide valuable insight into designing novel nitrogen-containing adsorbents for practical application in wastewater treatment.


Assuntos
Grafite/química , Triazóis/química , Urânio/química , Poluentes Radioativos da Água/química , Adsorção , Cinética , Concentração Osmolar , Óxidos/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias , Água
8.
Chemosphere ; 231: 405-414, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31146132

RESUMO

The release of uranyl from uranium tailing sites is a widely concerned environmental issue, with limited investigations on the effect of coexistence of various colloids. Gibbsite colloids extensively exist, together with ubiquitous humic substances, in uranium polluted waters at tailing sites, due to high concentration of dissolved Al in acid mine drainage. In this context, we investigated the co-transport of U(VI), gibbsite colloids and humic acid (HA) as a function of pH and ionic strength at a U(VI) concentration (5.0 × 10-5 M) relevant within mine tailings and related waste. It was found that, owing to electrostatic attraction, gibbsite colloids and HA associated with each other and transported simultaneously regardless of U(VI) presence. Besides the impact of pH and ionic strength, whether gibbsite colloids facilitated U(VI) transport depended on HA concentration. Gibbsite colloids impeded U(VI) transport at relatively low HA concentration (≤5 mg L-1), because associated colloids loaded with U(VI) were positively charged which favored colloid retention on negatively charged quartz sand in the column. U(VI) together with gibbsite colloids and low concentration HA was completely blocked at natural pH and/or high ionic strength. At relatively high HA concentration (20 mg L-1), however, the associated colloids showed negative zeta potential which facilitated U(VI) transport because of repulsion between negatively charged colloids and quartz sand. Meanwhile, high concentration of HA dramatically accelerated the transport of gibbsite colloids. These results implied that gibbsite colloids might imped U(VI) migration at uranium tailing sites unless the aquifers are enriched with abundant humic substances.


Assuntos
Coloides/química , Substâncias Húmicas/análise , Modelos Químicos , Urânio/química , Poluentes Radioativos da Água/química , Adsorção , Água Subterrânea/química , Concentração Osmolar , Porosidade , Quartzo , Dióxido de Silício , Simportadores , Urânio/análise , Água
9.
Environ Pollut ; 250: 196-205, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30995573

RESUMO

In recent years, water pollution caused by radionuclides has become a rising concern, among which uranium is a representative class of actinide element. Since hexavalent uranium, i.e. U(VI), is biologically hazardous with high migration, it's essential to develop efficient adsorbents to minimize the impact on the environment. Towards this end, we have synthesized a novel material (GO/PEDOT:PSS) by direct assembling graphene oxide (GO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) through a facile ball milling method, which shows impressing performance for the immobilization of U(VI). On the basis of the batch experiments, GO/PEDOT:PSS exhibits ionic strength-independent sorption edges and temperature-promoted sorption isotherms, revealing an inner-sphere complexation with endothermic nature. The sorption kinetics can be illustrated by the pseudo-second-order model, yielding a rate constant of 1.09. × 10-2 g mg-1∙min-1, while the sorption isotherms are in coincidence with the Langmuir model, according to which the maximum sorption capacity is measured to be 384.51 mg g-1 at pH 4.5 under 298 K, indicating a monolayer sorption mechanism. In the light of the FT-IR and XPS investigations, the surface carboxyl/sulfonate group is responsible to the chelation of U(VI), indicating that the enhanced sorption capacity may be ascribed to the PSS moiety. These findings can greatly contribute to the design strategy for developing highly efficient adsorbents in the field of radioactive wastewater treatment.


Assuntos
Nanocompostos/química , Urânio/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Radioativos da Água/química , Adsorção , Compostos Bicíclicos Heterocíclicos com Pontes/química , Grafite/química , Concentração de Íons de Hidrogênio , Cinética , Polímeros/química , Poliestirenos/química , Temperatura
10.
Environ Pollut ; 248: 332-338, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30802747

RESUMO

The decontamination of U(VI) on graphene oxide/nano-alumina (GO/Al2O3) composites were investigated by batch, XRD, FT-IR and XPS techniques. The characterization results showed that GO/Al2O3 composites presented a variety of oxygen-containing functional groups, which provided the more surface reactive sites. The batch experiments indicated that sorption equilibrium of U(VI) on GO/Al2O3 composites was achieved within 30 min, and the maximum sorption capacity derived from Langmuir model was 142.8 mg/g at pH 6.5. In addition, the slight decrease of sorption capacity was observed even after fifth recycling times. These results indicated that GO/Al2O3 composites displayed the fast sorption rate, high sorption capacity and good regeneration performance. No effect of ionic strength revealed the inner-sphere surface complexation of U(VI) on GO/Al2O3 composites. FT-IR and XPS analysis demonstrated that the high adsorption of U(VI) on GO/Al2O3 was attributed to the various oxygen-bearing functional groups. In addition, the nano Al2O3 was transferred to amorphous AlO(OH) mineral phase by XRD pattern, which provided the additional reactive sorption sites. These observations indicated that GO-based composites can be regarded as a promising adsorbent for immobilization and pre-concentration of U(VI) from aqueous solutions in the environmental remediation.


Assuntos
Descontaminação/métodos , Recuperação e Remediação Ambiental/métodos , Grafite/química , Urânio/química , Poluentes Radioativos da Água/química , Adsorção , Óxido de Alumínio , Concentração Osmolar , Óxidos/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
11.
Environ Sci Pollut Res Int ; 26(7): 7115-7122, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30652269

RESUMO

The analyzed sediments were taken from the man-made reservoirs (Velka Richnava, Rozgrund and Vindsachta) located in an area intensively mined for polymetallic ores since the end of the eleventh century (Banska Stiavnica region, Central Europe). The aims of this study were to determine the radioactivity of natural (226Ra, 228Th, 210Pb) and artificial (137Cs and 241Am) radionuclides, compare the radionuclides' distribution, and indicate the correlation of radioisotopes and their origin related to sediment properties. Two analytical techniques were used. 228Th, 226Ra, 241Am, and 137Cs were measured by means of gamma spectrometry and 210Pb was determined by its daughter radionuclide 210Po using alpha spectrometry. The results showed that the highest mean level of 226Ra (42.6 Bq·kg-1), 228Th (49.7 Bq·kg-1) and 210Pb (75.2 Bq·kg-1) was in the sediments collected from Rozgrund. The radioactivity of 137Cs and 241Am were present at a higher level in the layer related to Chernobyl (1986) accident and nuclear weapon test (1950/1960). The distribution of natural radionuclides was quite similar in all reservoirs. Chemometric analysis confirmed the radionuclides' origin and correlation between the analyzed parameters.


Assuntos
Mineração , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , Radioisótopos de Césio , Europa (Continente) , Sedimentos Geológicos , Radioatividade , Radioisótopos/análise , Eslováquia , Espectrometria gama , Poluentes Radioativos da Água/química
12.
J Water Health ; 16(4): 542-548, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30067237

RESUMO

An analytical study was carried out to determine the level of uranium in the soil and rock and associate it with the levels in surface and underground water, which are the main sources of drinking water in Singida Urban District, Tanzania. Fifteen water samples, 12 soil samples and nine rock samples were collected in Singida Urban District in February 2016. Water samples were analysed by the Government Chemist Laboratory Agency using inductively coupled plasma optical emission spectrometry (ICP-OES) (2007) and analyses for soil and rock samples were carried out through total X-ray fluorescence (XL3 ANALYSER) at Sokoine University of Agriculture in the Department of Soil and Geological Sciences. Uranium levels in the soils and rocks samples found ranged from 3.744 to 8.754 mg kg-1, SE ± 0.849 and P-value <0.001 for soil and 20.01-31.57 mg kg-1, SE ± 2.474 and P-value 0.077 for rocks respectively. The levels in soil and rock influences the levels in surface and underground water which were between 0.087 and 1.097 mg L-1 for surface water and <0.01-0.46 mg L-1 for underground water, respectively. Singida Urban District has higher uranium levels in the soil and rock with a consequence of high levels in drinking water sources.


Assuntos
Água Potável/química , Solo/química , Urânio/química , Poluentes Radioativos da Água/química , Água/química , Água Subterrânea/química , Humanos , Tanzânia
13.
J Environ Radioact ; 192: 505-512, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30114621

RESUMO

Radioiodine (present mostly as 129I) is difficult to remove from waste streams or contaminated groundwater because it tends to exist as multiple anionic species (i.e., iodide (I-), iodate (IO3-) and organo-iodide) that do not bind to minerals or synthetic materials. In this work, the efficacy of organoclay OCB and OCM, and granular activated carbon (GAC) as sorbents to bind I- and IO3- from artificial groundwater (AGW) was examined. These sorbents were highly effective at removing I- and IO3- from AGW under oxic condition, with the adsorption capacity up to 30 mg I/g sorbent. Based on X-ray spectroscopy measurements, I- was bound to organic ligands in organoclays OCB and OCM, but when GAC was exposed to I- in groundwater, the sequestered I species was molecular I2. For IO3- interacting with organoclay OCB and GAC, the adsorbed I species remained being IO3-, but when organoclay OCM that contains both quaternary amine and sulfur was exposed to IO3-, the sulfur compound would reduce IO3- to I- that was then bound to organic ligands. Thus, the inexpensive and high-capacity organoclays and GAC may provide a practical solution for removing 129I contaminant from environmental systems and liquid nuclear wastes.


Assuntos
Carvão Vegetal/química , Recuperação e Remediação Ambiental/métodos , Radioisótopos do Iodo/análise , Poluentes Radioativos da Água/análise , Adsorção , Silicatos de Alumínio/química , Argila , Água Subterrânea/química , Radioisótopos do Iodo/química , Poluentes Radioativos da Água/química
14.
J Environ Radioact ; 192: 376-384, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30048900

RESUMO

The uptake and depuration kinetics of dissolved 109Cd, 57Co and 134Cs were determined experimentally in the European flat oyster Ostrea edulis (Linnaeus, 1758) under different pH conditions (i.e., 8.1, 7.8 and 7.5) for 59 days. Uptake and depuration rates were variable within these elements; no effects were observed under different pH conditions for the uptake biokinetics of 109Cd and 57Co and depuration of 109Cd and 134Cs in oyster. The uptake and depuration rate constants of 134Cs differed during the exposure phase between treatments, while the steady state concentration factors (CFss) were similar. The resulting Cs activity that was purged during short- and long-term depuration phases differed, while the remaining activities after thirty-nine days depuration phase (RA39d) were similar. Co-57 depuration was affected by pCO2 conditions: RA39d were found to be significantly higher in oysters reared in normocapnia (pCO2 = 350 µatm) compared to high pCO2 conditions. Co-57 tissue distribution did not differ among the variable pCO2 conditions, while 109Cd and 134Cs accumulated in soft tissue of oysters were found to be higher under the highest pCO2. Additionally, Cd, Co and Cs were stored differently in various compartments of the oyster cells, i.e. cellular debris, metal-rich granules (MRG) and metallothionein-like proteins (MTLP), respectively. The subcellular sequestration of the elements at the end of the depuration phase did not differ among pH treatments. These results suggest that bioconcentration and tissue/subcellular distribution are element-specific in the oyster, and the effects of higher pCO2 driven acidification and/or coastal acidification variably influence these processes.


Assuntos
Radioisótopos de Cádmio/metabolismo , Radioisótopos de Césio/metabolismo , Radioisótopos de Cobalto/metabolismo , Ostrea/fisiologia , Poluentes Radioativos da Água/metabolismo , Animais , Radioisótopos de Cádmio/análise , Radioisótopos de Cádmio/química , Dióxido de Carbono/química , Radioisótopos de Césio/análise , Radioisótopos de Césio/química , Radioisótopos de Cobalto/análise , Radioisótopos de Cobalto/química , Concentração de Íons de Hidrogênio , Cinética , Metalotioneína/metabolismo , Oceanos e Mares , Água do Mar/química , Distribuição Tecidual , Poluentes Radioativos da Água/química
15.
J Environ Radioact ; 192: 279-288, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29990775

RESUMO

Short chain carbon-14 (14C) containing organic compounds can be formed by abiotic oxidation of carbides and impurities within nuclear fuel cladding. During fuel reprocessing and subsequent waste storage there is potential for these organic compounds to enter shallow subsurface environments due to accidental discharges. Currently there is little data on the persistence of these compounds in such environments. Four 14C-labelled compounds (acetate; formate; formaldehyde and methanol) were added to aerobic microcosm experiments that contained glacial outwash sediments and groundwater simulant representative of the Sellafield nuclear reprocessing site, UK. Two concentrations of each electron donor were used, low concentration (10-5 M) to replicate predicted concentrations from an accidental release and high concentration (10-2 M) to study the impact of the individual electron donor on the indigenous microbial community in the sediment. In the low concentration system only ∼5% of initial 14C remained in solution at the end of experiments in contact with atmosphere (250-350 h). The production of 14CO2(g) (measured after 48 h) suggests microbially mediated breakdown is the primary removal mechanism for these organic compounds, although methanol loss may have been partially by volatilisation. Highest retention of 14C by the solid fractions was found in the acetate experiment, with 12% being associated with the inorganic fraction, suggesting modest precipitation as solid carbonate. In the high concentration systems only ∼5% of initial 14C remains in solution at the end of the experiments for acetate, formate and methanol. In the formaldehyde experiment only limited loss from solution was observed (76% remained in solution). The microbial populations of unaltered sediment and those in the low concentration experiments were broadly similar, with highly diverse bacterial phyla present. Under high concentrations of the organic compounds the abundance of common operational taxonomic units was reduced by 66% and the community structure was dominated by Proteobacteria (particularly Betaproteobacteria) signifying a shift in community structure in response to the electron donor available. The results of this study suggest that many bacterial phyla that are ubiquitous in near surface soils are able to utilise a range of 14C-containing low molecular weight organic substances very rapidly, and thus such substances are unlikely to persist in aerobic shallow subsurface environments.


Assuntos
Radioisótopos de Carbono/análise , Água Subterrânea/química , Poluentes Radioativos da Água/análise , Aerobiose , Radioisótopos de Carbono/química , Peso Molecular , Microbiologia da Água , Poluentes Radioativos da Água/química
16.
J Water Health ; 16(3): 476-486, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29952336

RESUMO

Systematic studies were carried out to understand the distribution of natural radionuclides in sediments and radon in water in the riverine environs of Cauvery, one of the major rivers of South India. The activity of radionuclides in the sediment was measured by gamma ray spectrometry. The radon emanation from the sediment was measured by the sealed 'can technique' and the radon in the water was measured using the RAD-7 instrument. The mean values of 40 K, 226Ra, and 232Th in the sediment samples were found to be 297.3 ± 4.16 Bq kg-1, 75.1 ± 2.64 Bq kg-1, and 85.5 ± 2.62 Bq kg-1, respectively. The mean activity of radon, radon exhalation rate, and radium content were found to be 135.68 Bq m-3, 327.1 mBq m-1 h-1, and 133.03 mBq kg-1, respectively. The radon in the water ranged from 0.19 kBq m-3 to 1.40 kBq m-3. The hyper pure germanium gamma spectroscopy measured via 226Ra activity and the radon activity measured by the passive can technique showed good correlation. The mean value of radon in the water was within the internationally recommended level. The sediment was considered safe for the purpose of construction, except for some extreme values, and the water was deemed safe for drinking.


Assuntos
Radioisótopos/química , Radônio/química , Rios , Radiação de Fundo , Sedimentos Geológicos/química , Índia , Monitoramento de Radiação/métodos , Poluentes Radioativos do Solo/química , Poluentes Radioativos da Água/química
17.
J Environ Manage ; 223: 108-114, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29908396

RESUMO

Temporary base treatment is a potential remediation technique for heavy metals through adsorption, precipitation, and co-precipitation with minerals. Manipulation of pH with ammonia gas injection may be especially useful for vadose zone environments as it does not require addition of liquids that would increase the flux towards groundwater. In this research, we conducted laboratory batch experiments to evaluate the changes in uranium mobility and mineral dissolution with base treatments including sodium hydroxide, ammonium hydroxide, and ammonia gas. Our data show that partitioning of uranium to the solid phase increases by several orders of magnitude following base treatment in the presence of different minerals and natural sediments from the Hanford site. The presence of dissolved calcium and carbonate play an important role in precipitation and co-precipitation of uranium at elevated pH. In addition, significant incongruent dissolution of bulk mineral phases occurs and likely leads to precipitation of secondary mineral phases. These secondary phases may remove uranium via adsorption, precipitation, and co-precipitation processes and may coat uranium phases with low solubility minerals as the pH returns to natural conditions.


Assuntos
Urânio/isolamento & purificação , Poluentes Radioativos da Água/isolamento & purificação , Adsorção , Animais , Sedimentos Geológicos , Água Subterrânea , Minerais , Suínos , Urânio/química , Poluentes Radioativos da Água/química
18.
J Environ Radioact ; 192: 10-13, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29870834

RESUMO

Ocean acidification have been shown to not affect the capacity of bivalves to bioaccumulation 134Cs in their tissue; but as this was studied on only one species to date. There is therefore a need to verify if this holds true for other bivalve species or other marine invertebrates. The present short communication confirms that in the scallop Mimachlamys varia and the prawn Penaeus japonicus, two species that supposedly have a record to preferentially concentrates this radionuclide, that bioconcentration of 134Cs was shown not to be influenced by a decreasing pH (and thereby increasing seawater pCO2). Although the dissolved 134Cs was taken up in a similar manner under different pH values (8.1, 7.8, and 7.5) in both species, being described by a saturation state equilibrium model, the species displayed different bioconcentration capacities of 134Cs: CFss in the prawns was approximately 10-fold higher than in scallops. Such results suggest that the Cs bioconcentration capacity are mainly dependent of the taxa and that uptake processes are independent the physiological ones involved in the biological responses of prawns and scallops to ocean acidification.


Assuntos
Organismos Aquáticos/metabolismo , Dióxido de Carbono/química , Radioisótopos de Césio/metabolismo , Água do Mar/química , Poluentes Radioativos da Água/metabolismo , Animais , Bivalves , Radioisótopos de Césio/química , Concentração de Íons de Hidrogênio , Penaeidae , Poluentes Radioativos da Água/química
19.
Chemosphere ; 205: 627-634, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29715677

RESUMO

To assess radium (226Ra) as a potential indicator of impact in well waters, we investigated its behavior under natural conditions using a case study approach. 226Ra geochemistry was investigated in 67 private wells of southeastern New Brunswick, Canada, a region targeted for potential shale gas exploitation. Objectives were to i) establish 226Ra baseline in groundwater; ii) characterize 226Ra spatial distribution and temporal variability; iii) characterize 226Ra partitioning between dissolved phase and particulate forms in well waters; and iv) understand the mechanisms controlling 226Ra mobility under natural environmental settings. 226Ra levels were generally low (median = 0.061 pg L-1, or 2.2 mBq L-1), stable over time, and randomly distributed. A principal component analysis revealed that concentrations of 226Ra were controlled by key water geochemistry factors: the highest levels were observed in waters with high hardness, and/or high concentrations of individual alkaline earth elements (i.e. Mg, Ca, Sr, Ba), high concentrations of Mn and Fe, and low pH. As for partitioning, 226Ra was essentially observed in the dissolved phase (106 ±â€¯19%) suggesting that the geochemical conditions of groundwater in the studied regions are prone to limit 226Ra sorption, enhancing its mobility. Overall, this study provided comprehensive knowledge on 226Ra background distribution at local and regional scales. Moreover, it provided a framework to establish 226Ra baselines and determine which geochemical conditions to monitor in well waters in order to use this radionuclide as an indicator of environmental impact caused by anthropogenic activities (e.g. unconventional shale gas exploitation, uranium mining, or nuclear generating power plants).


Assuntos
Meio Ambiente , Monitoramento Ambiental/métodos , Rádio (Elemento)/química , Poluentes Radioativos da Água/química , Poluentes Radioativos da Água/análise , Poços de Água
20.
Chemosphere ; 207: 130-138, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29793024

RESUMO

Plutonium (Pu) isotopes were first determined in surface and core sediment samples collected from the northern North Yellow Sea (NYS) to elucidate their source terms and deposition process as well as the response to catchment environmental changes of inflow rivers. 240Pu/239Pu atom ratios in all sediments showed the typical global fallout value of ∼0.18 without any influences from the nuclear weapons tests conducted recently in the North Korea or early in the Pacific Proving Ground. The large variation of 239+240Pu activities (0.022-0.515 mBq/g) observed in surface sediments should be mainly attributed to the re-suspension and transportation of fine sediments influenced by the Liaonan Costal Current. Based on the two 239+249Pu depth profiles with easily observed onset fallout levels (1952) and global fallout peaks (1963), 239+240Pu served as a valid time mark in the coastal sedimentary system. Riverine input Pu contributed only 15-27% to the total global fallout inventory (92.5-108.8 Bq/m2) in the northern NYS, much lower than that in the Yangtze River estuary (77-80%), indicating a better soil conservation in the northeast China due to higher forest coverage compared to the Yangtze River's drainage basin. The increase of riverine input Pu after 1980s reflected the more intense soil erosion degree caused by the land use and cover change due to the increment of human activities in the northeast China at the same period. Our results demonstrated that plutonium is a good indicator for studying sedimentary process and its response to the environment in the coastal area.


Assuntos
Poluentes Ambientais/química , Sedimentos Geológicos/química , Plutônio/química , Rios/química , Poluentes Radioativos da Água/química , China
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