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1.
Anal Chem ; 92(5): 3581-3588, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-31916433

RESUMO

In situ monitoring of Sb speciation improves the understanding of Sb biogeochemistry and toxicity in ecosystems. Precise measurement of Sb is a challenge due to its instability of oxidation and ultratrace concentration. The development of simple and reliable methods specific to SbIII measurement is not only appealing but essential for implementing regulations. Here, we present an in situ speciation analysis method for SbIII, using the diffusive gradients in thin films (DGT) technique, combined with mercapto-functionalized SBA-15 mesoporous silica nanoparticles (MSBA). Laboratory performance tests confirmed MSBA-DGT uptake was independent of pH (4-9) and ionic strength (0.1-200 mmol L-1). DGT devices equipped with MSBA-based binding gels showed a theoretically linear accumulation of SbIII and exhibited a high capacity for SbIII at 65 µg/gel disc, with negligible accumulation of SbV over a 72 h deployment. Compared with commercial 3-mercaptopropyl-functionalized silica (MFS), the nanosized MSBA facilitate its even distribution in the binding gels. Furthermore, the good selectivity and high homogeneity of the MSBA gel enabled it to be applied in a rice rhizosphere in conjunction with AgI gel to investigate the effects of sulfur application on the SbIII solubility. In summary, the newly developed MSBA-DGT provides a selective measurement of SbIII, showing potential for environmental monitoring and further application in understanding the biogeochemical process of Sb.

2.
Environ Sci Technol ; 54(6): 3138-3147, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-31968168

RESUMO

Behavior of trace elements in flooded/lowland rice soils is controlled by root-zone iron oxidation. Insoluble iron species bind/capture toxic elements, i.e., arsenic. However, it was recently observed that within this territory of arsenic immobilization lies a zone of prolific iron release, accompanied by a significant flux of arsenic in close proximity to rice root apices. Questions still remain on how common this phenomenon is and whether the chemical imaging approaches or soils/cultivars used influence this event. Here, three types of ultrathin/high-resolution diffusive gradient in thin films (DGT) substrates were integrated with oxygen planar optodes in a multilayer system, providing two-dimensional mapping of solute fluxes. The three DGT approaches revealed a consistent/overlapping spatial distribution with localized flux maxima for arsenic, which occurred in all experiments, concomitant with iron mobilization. Soil/porewater microsampling within the rhizosphere revealed no significant elevation in the solid phase's total iron and arsenic concentrations between aerobic and anaerobic zones. Contrary to arsenic, phosphorus bioavailability was shown to decrease in the arsenic/iron flux maxima. Rice roots, in addition to their role in nutrient acquisition, also perform a key sensory function. Flux maxima represent a significant departure from the chemical conditions of the bulk/field environment, but our observations of a complete rhizosphere reveal a mixed mode of root-soil interactions.


Assuntos
Arsênico , Oryza , Poluentes do Solo , Rizosfera , Solo
3.
Talanta ; 205: 120148, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450468

RESUMO

Spent coffee grounds (SCG) immobilized in agarose gel are proposed as a novel binding agent for application in the Diffusive Gradients in Thin films (DGT) technique for the determination of Cd, Cu, Ni, Pb and Zn in waters. The SCG-agarose gel was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry and Porosimetry by nitrogen adsorption. Elution of analytes from the binding agent was effectively performed with 2 mol L-1 HCl. The effects of key DGT parameters (e.g. immersion time, ionic strength and pH) were evaluated with a deployment of DGT devices (DGT-SCG) in synthetic solutions with ionic strengths between 0.005 mol L-1 and 0.1 mol L-1 and within a pH range of 3.5-8.0. The results were in excellent agreement with the predicted theoretical curve for mass uptake. Consistent results were found for solutions with ionic strengths between 0.005 mol L-1 and 0.1 mol L-1 and within a pH range of 3.5-8.0. The DGT-SCG performance was also evaluated in two spiked river water samples (Corumbataí and Piracicaba river) with satisfactory uptake values (CDGT-SCG/Csol) between 0.74 and 1.53. The proposed DGT-SCG opens opportunities for using residual biomass as binding phase in the DGT technique, showing low costs in production and complying with "green" technology approaches.

5.
Environ Sci Technol ; 53(13): 7288-7295, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31187619

RESUMO

The speciation of arsenic in wet and dry deposition are ambiguously described in current literature. Presented here is a 2 year study quantifying arsenic species in atmospheric deposition collected daily from an E. Atlantic coastal, semirural site, with comparative urban locations. Inorganic arsenic (Asi) was the principal form of arsenic in wet deposition, with a mean concentration of 0.54 µmol/m3. Trimethylarsine oxide (TMAO) was found to be the dominant form of organic arsenic, determined as above the LoD in 33% of wet deposition samples with a mean concentration of 0.12 µmol/m3. Comparison with codeposited trace elements and prevailing weather trajectories indicated that both anthropogenic and marine sources contribute to atmospheric deposition. Analysis of dry deposition revealed it to be a less significant input to the land-surface for Asi, contributing 32% of that deposited by wet deposition. Dry deposition had a larger proportion of Asi than that found in wet deposition, with TMAO making up only 12% of the sum of species. In comparison, urban sites showed large spatial and temporal variations in organic arsenic deposition, indicating that local sources of methylated species may be likely and that further understanding of biogenic arsine evolution and degradation are required to adequately assess the atmospheric arsenic burden and subsequent contribution to terrestrial ecosystems.


Assuntos
Poluentes Atmosféricos , Arsênico , Oligoelementos , Ecossistema , Monitoramento Ambiental , Tempo (Meteorologia)
6.
Sci Total Environ ; 650(Pt 1): 546-556, 2019 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-30205344

RESUMO

Manganese oxides are naturally occurring powerful oxidants and scavengers, which can control the mobility and bioavailability of arsenic (As). However, the effect of synthetic nanostructured manganese oxides on the mobilization and transportation of As at actual paddy soils are poorly understood, especially in soils with low or medium background Mn concentration. In the present study, a novel nano manganese oxide with superior reactivity and surface area has been synthesized. A 90-d soil incubation experiment combined with pot and field rice cultivation trials were designed to evaluate the effectiveness of exogenous α-MnO2 nanorods on the mobilization and transportation of As in soil-rice systems. Our results proved that the addition of α-MnO2 nanorods can effectively control the soil-to-solution partitioning of As under anaerobic conditions. After treatment with different amounts of α-MnO2 nanorods, the content of effective As decreased, offset by an increase in residual As and insoluble binding As (Ca-As and Fe-As). Enhancing the oxidation of As(III) into As(V), the α-MnO2 nanorods increased the adsorption of As onto indigenous iron (hydr)oxides which greatly reduced the soil porewater As content. In addition, pot experiments and field applications revealed that the influx of As into the aerial parts of rice plants (stems, husk and leaves) was strictly prohibited after treatments with different amount of α-MnO2 nanorods; more interestingly, significantly negative correlations have been observed between As and Mn in rice, which indicated that as Mn is increased in soil, As in brown rice decreases. Our results demonstrated that the use of α-MnO2 nanorods in As polluted paddy soil containing low levels of background Mn oxides can be a promising remediation strategy.


Assuntos
Arsênico/metabolismo , Recuperação e Remediação Ambiental/métodos , Compostos de Manganês/química , Nanotubos/química , Oryza/metabolismo , Óxidos/química , Poluentes do Solo/metabolismo , Adsorção , Arsênico/química , Disponibilidade Biológica , China , Compostos Férricos/química , Nanotubos/ultraestrutura , Oryza/química , Oxirredução , Componentes Aéreos da Planta/química , Componentes Aéreos da Planta/metabolismo , Solo/química , Poluentes do Solo/química
7.
Anal Chem ; 91(2): 1344-1352, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30560662

RESUMO

Thallium (Tl) has been identified as a priority contaminant because of its severe toxic effects. Exact measurement of Tl is a challenge because it is difficult to avoid altering the element's chemical speciation during sampling, transport, and storage. In situ measurement may be a good choice. Based on the in situ technique of diffusive gradients in thin films (DGT), new DGT devices equipped with novel laboratory-synthesized manganese oxide (δ-MnO2) binding gels were developed and systematically validated for the measurement of Tl, including Tl(I) and Tl(III) species, in water. Comparison between Chelex binding gel and δ-MnO2 gel on the uptake kinetics of Tl demonstrated that δ-MnO2 binding gels could adsorb Tl rapidly and effectively. Removal of Tl from the δ-MnO2 gels was achieved by use of 1 mol·L-1 oxalic acid, yielding elution efficiencies of 1.0 for Tl(I) and 0.86 for TI(III). Theoretical responses from DGT devices loaded with δ-MnO2 gel (δ-MnO2-DGT) were obtained irrespective of pH (4-9) and ionic strength (0.1-200 mmol·L-1 NaNO3). δ-MnO2-DGT showed good potential for long-term monitoring of Tl due to its high adsorption capacity of 27.1 µg·cm-2 and the stable performance of δ-MnO2 binding gel kept in solution, containing only 10 mmol·L-1 NaNO3, for at least 117 days. Field deployment trials confirmed that δ-MnO2-DGT can accurately measure the time-averaged concentrations of Tl in fluvial watercourses. In summary, the newly developed δ-MnO2-DGT technique shows potential for environmental monitoring and biogeochemical investigation of Tl in waters.

8.
Environ Sci Technol ; 52(24): 14140-14148, 2018 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-30431268

RESUMO

The speciation of selenium (Se) controls its fate and behavior, determining both its biological and environmental activities. However, in situ monitoring of SeIV presents a significant challenge due to its sensitivity to redox change. A novel diffusive gradients in thin films (DGT) technique containing mercapto-, amino-bifunctionalized SBA15 mesoporous silica nanoparticles was developed and evaluated in a series of laboratory and field deployment tests. The SBA-DGT exhibited a linear accumulation of SeIV ( r2 > 0.997) over a 72 h deployment, with negligible accumulation of SeVI(<5%). Consistent prediction of SeIV occurred within ionic strength and pH ranges of 0.1-200 mmol L-1 and 3.6-8, respectively. Limits of detection of the SBA-DGT were 0.03 µg SeIV L-1, which is suitable for natural waters. Moreover, the properties of the bifunctionalized SBA15 enable it to be fabricated within ultrathin (0.05 mm) gel layers for use in conjunction with O2 planar optode imaging. This new sandwich sensor technology with SBA-DGT was validated by mapping the two-dimensional distribution of SeIV and oxygen simultaneously in rice rhizospheres. This study shows that SBA-DGT provides a selective measurement of SeIV in situ, demonstrating its potential for both environmental monitoring and as a research tool for improving our understanding of Se biogeochemical processes.


Assuntos
Nanopartículas , Selênio , Monitoramento Ambiental , Dióxido de Silício , Solo
9.
Environ Sci Technol ; 52(21): 12098-12107, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30247023

RESUMO

A method using miniaturized arrayed DGT-probes (PADDI) for high-frequency in situ sampling with LA-ICPMS and CID analysis was developed to measure the field-scale heterogeneity of trace-element bioavailability. Robust calibrations (R2 > 0.99) combined with high-sensitivity (LOD = 0.35 ng cm-2), multielemental detection, and short measurement times were achieved using a new LA-ICPMS microDGT analysis. In the studied paddy-site (size: ∼2500 m2), total element concentrations across the field were approximately uniform (R.S.D. < 10%), but bioavailability was shown to vary significantly as determined from 864 microgel measurements housed within 72 PADDI arrays. Porewater As measurements were unable to differentiate the top/rhizosphere and bulk/deeper-soil layers. However, dynamic sampling with DGT revealed significant differences. Heterogeneity behaviors varied greatly between the different elements. Arsenic bioavailability was stable laterally across the field, but varied with depth, which was in contrast to the trends for Pb. Fe/S(-II) change was bidirectional, differing horizontally and vertically throughout the field. The heterogeneity in Pb bioavailability, due to the high frequency of hotspot maxima that were discretely dispersed across the paddy, proved the most difficult to simulate requiring the greatest number of probe deployments to determine a reliable field-average. The DGT-PADDI system provides a new characterization of infield trends for improved trace-inorganics' management in agricultural wetlands.


Assuntos
Arsênico , Oryza , Poluentes do Solo , Disponibilidade Biológica , Ferro , Solo , Enxofre
10.
J Agric Food Chem ; 66(18): 4710-4715, 2018 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-29633616

RESUMO

Shrimp, a popular and readily consumed seafood, contains high concentrations of arsenic. However, few studies have focused on whether arsenic in the shrimp could be transformed during the cooking process and gastrointestinal digestion. In this study, a combined in vitro model [Unified Bioaccessibility Research Group of Europe (BARGE) Method-Simulator of Human Intestinal Microbial Ecosystem (UBM-SHIME)] was used to investigate arsenic bioaccessibility and its speciation in raw and cooked shrimps. The results showed that the cooking practices had little effect on the arsenic content and speciation. Bioaccessibility of arsenic in raw shrimp was at a high level, averaging 76.9 ± 4.28 and 86.7 ± 3.74% in gastric and small intestinal phases, respectively. Arsenic speciation was stable in all of the shrimp digestions, with nontoxic arsenobetaine (AsB) being the dominated speciation. The cooking practice significantly increased the bioaccessibility of arsenate ( p < 0.05) in shrimp digests, indicating the increase of the potential health risks.


Assuntos
Arsênico/química , Arsênico/metabolismo , Frutos do Mar/análise , Animais , Disponibilidade Biológica , Culinária , Crustáceos/metabolismo , Digestão , Mucosa Gástrica/metabolismo , Temperatura Alta , Humanos , Mucosa Intestinal/metabolismo , Modelos Biológicos
11.
Water Res ; 137: 281-289, 2018 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-29554532

RESUMO

Phosphite (P+III) is of emerging chemical interest due to its importance within the global phosphorus cycle. Yet, to date, precise/accurate measurements of P+III are still lacking due to the inherent analytical challenges linked to its instability/ease of oxidation and ultra-trace concentration. Here, we present the first in-situ sampling and speciation analysis method, for dissolved P+III, using the diffusive-gradients-in-thin-films (DGT) technique, combined with capillary-column-configured-dual-ion-chromatography (CC-DIC). Method optimization of the DGT elution regime, to simultaneously maximize desorption efficiency and CC-DIC sensitivity, along with the characterization of diffusion coefficients for P+III, were undertaken before full method validation. Laboratory-performance testing confirmed DGT-P+III acquisition to be independent of pH (3.0-10.0) and ionic strength (0-500 mM). The capacity for P+III was 45.8 µg cm-2, while neither P+V (up to 10 mg L-1) nor As+V (up to 1 mg L-1) impacted the DGT-P+III measurement. This novel method's functionality stems from the herein confirmed speciation preservation and double pre-concentration of P+III, resulting in quantification limits as low as 7.44 ng L-1 for a 3-day deployment. Applications of this method in various terrestrial/aquatic environments were demonstrated and simultaneous profiles of P+III and P+V across a sediment-water interface were captured at mm resolution in two contrasting redox-mesocosm systems.


Assuntos
Poluentes Ambientais/análise , Fosfitos/análise , Monitoramento Ambiental/métodos , Água Doce/análise , Concentração Osmolar , Solo/química , Águas Residuárias/análise
12.
Environ Sci Technol ; 52(7): 3968-3974, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29505707

RESUMO

Marine sources of arsenic to the atmosphere are normally dismissed as minor. Here we show that arsenic can be biovolatilized from seawater, and that biovolatilzation is based on organic arsenic species present in the seawater. Even though inorganic arsenic is in great excess in seawaters, it is trimethylarsine (TMA) that is the primary biovolatilized product, with dimethylarsine (DMA) also observed if dimethylarsinic acid (DMAA) is spiked into seawaters. With respect to budgets, 0.04% of the total arsenic in the seawater was biovolatilized over a 2-week incubation period. To test the environmental significance of this finding, wet deposition was analyzed for arsenic species at coastal locations, one of which was the origin of the seawater. It was found that the oxidized product of TMA, trimethylarsine oxide (TMAO), and to a less extent DMAA were widely present. When outputs for arsines (0.9 nmol/m2/d) from seawater and inputs from wet deposition (0.3-0.5 nmol/m2/d) were compared, they were of the same order of magnitude. These findings provide impetus to reexamining the global arsenic cycle, as there is now a need to determine the flux of arsines from the ocean to the atmosphere.


Assuntos
Arsênico , Arsenicais , Atmosfera , Ácido Cacodílico , Água do Mar
13.
Sci Total Environ ; 612: 1365-1372, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-28898943

RESUMO

Rice plants grown on soils with elevated arsenic have been shown to have increased arsenic content in their grains. To gain a better understanding of the likelihood of high grain arsenic in rice grown in different soils, it is important to understand the factors affecting the bioavailability and mobility of arsenic. Paddy soils from six different physiographic regions of Bangladesh were collected, and diffusive gradients in thin-films (DGT) were used to assess the porewater and solid phase arsenic. While significant differences were identified in total soil arsenic (1.4-9.8mg/kg), porewater arsenic (AsCsoln) (5.6-64.7µg/l), labile arsenic (AsCDGT) (6.3-77.6µg/l), and solid phase pool of arsenic (AsKd) (52-1057l/kg), importantly arsenic resupply capacity was not different between the physiographic regions. All soils had a high ratio of DGT to porewater arsenic (~1), this in conjunction with the porewater arsenic values and the high AsKd values suggesting a large solid phase pool of arsenic capable of contributing towards the resupply/transport of the labile pool of arsenic in the soil porewater. This indicates that there is less difference in soil arsenic availability than might be predicted based solely on total soil arsenic content between the physiographic regions.


Assuntos
Arsênico/química , Poluentes do Solo/química , Solo/química , Bangladesh , Monitoramento Ambiental , Oryza
14.
Environ Sci Technol ; 51(21): 12210-12218, 2017 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-28977751

RESUMO

For arsenic speciation, the inputs for wet deposition are not well understood. Here we demonstrate that trimethylarsine oxide (TMAO) and inorganic arsenic are the dominant species in monsoonal wet deposition in the summer Indian subcontinent, Bangladesh, with inorganic arsenic dominating, accounting for ∼80% of total arsenic in this medium. Lower concentrations of both species were found in monsoonal wet deposition in the winter Indian subcontinent, Sri Lanka. The only other species present was dimethylarsinic acid (DMAA), but this was usually below limits of detection (LoD). We hypothesize that TMAO and inorganic arsenic in monsoonal wet deposition are predominantly of marine origin. For TMAO, the potential source is the atmospheric oxidation of marine derived trimethylarsine. For inorganic arsenic, our evidence suggests entrainment of water column inorganic arsenic into atmospheric particulates. These conclusions are based on weather trajectory analysis and on the strong correlations with known wet deposition marine derived elements: boron, iodine, and selenium. The finding that TMAO and inorganic arsenic are widely present and elevated in monsoonal wet deposition identifies major knowledge gaps that need to be addressed regarding the understanding of arsenic's global cycle.


Assuntos
Arsênico , Arsenicais , Bangladesh , Ácido Cacodílico , Sri Lanka
15.
Anal Chim Acta ; 983: 54-66, 2017 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-28811029

RESUMO

Chemical fractionation, speciation analysis and bioavailability of metals and metalloids in waters have received increased attention in recent years. However, this interest is not matched by progress in improving species integrity during standard 'grab' sample collection, processing and storage. Time-averaged, low disturbance sampling, in situ, of trace element species, in particular, is a more reliable approach for environmental chemical surveillance and methods based on the diffusive gradients in thin films (DGT) technique stand out as one of the most widely used of the passive sampler classes, and hence will be the primary focus of this review. The DGT technique was initially developed to sample metals and semi-metals in freshwaters, and later was extended to include marine settings as well as the measurement of metal fluxes in sediments/soils. Nowadays, DGT based technologies are used extensively in a variety of geochemical and environmental health research disciplines. This review specifically surveys the application of the DGT measurement for fractionation and speciation analysis (as defined by IUPAC) of metal or metalloids in aqua. Use of DGT in fresh, estuarine and marine waters, as well as effluents has improved the knowledge base of in situ data related to fractionation processes (e.g. labile and inert species; organic and inorganic species; dissolved and nanoparticles), and speciation analysis. This supports not only the calculations underpinning numerous software speciation models for cation and anion behavior, but also our understanding of the bioavailability and toxicity of these species. The measurement of metals by DGT are easy to obtain, which is core to its popular use, but often the results require sophisticated interpretation and a wide spectrum of chemical knowledge to really explain in full, which is why the method has and continues to capture the interest of researchers.


Assuntos
Monitoramento Ambiental , Metais/análise , Poluentes Químicos da Água/análise , Disponibilidade Biológica , Fracionamento Químico , Difusão , Água Doce/análise , Água do Mar/análise
16.
Chemosphere ; 184: 812-819, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28645085

RESUMO

The monitoring of oxyanions in waters, presents significant challenges due to their relatively low concentrations, and a characteristically changeable/unstable/reactive geochemistry with high spatial and temporal turnover. This results in a very heterogeneous pattern of mobility and bioavailability, which is difficult to capture reliably and in a cost effective manner. The diffusive gradients in thin-films (DGT) technique is a popular analytical tool for testing water quality, primarily because it provides a time-integrated measurement. However, to date, the most widely used DGT configuration for oxyanion sampling, the slurry ferrihydrite binding layer (SF-DGT) has only been fully characterized for phosphate. Confirmatory testing of the functional range of ionic strengths, pH, deployment times and ionic competition effects, that the SF-DGT's operates within has not been carried out, but is addressed in this study for VV, AsV, SbV, and MoVI. In this study SF-DGT SbV measurements functioned over the largest range of conditions (ionic strength, 0.1-500 mM; pH 3.86-9.90), while ionic strengths above 100 and 500 mM were found to be problematic for AsV and MoVI, respectively. Low pH (below 4) caused inferences with VV, conversely AsV and MoVI determination faltered/deviated from predicted responses in pH conditions of ∼9. SF-DGT measurements adequately predicted up to weeklong averaged in situ metal oxyanion concentrations in a freshwater river. This study concludes that the SF-DGT configuration is highly suitable for pollution monitoring applications in freshwater systems for key oxyanion species.


Assuntos
Monitoramento Ambiental/métodos , Compostos Férricos/química , Poluentes Químicos da Água/análise , Arseniatos/análise , Difusão , Metais , Molibdênio/análise , Concentração Osmolar , Vanadatos/análise , Água
17.
Sci Total Environ ; 590-591: 406-415, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28285852

RESUMO

While the impact of arsenic in irrigated agriculture has become a major environmental concern in Bangladesh, to date there is still a limited understanding of arsenic in Bangladeshi paddy soils at a landscape level. A soil survey was conducted across ten different physiographic regions of Bangladesh, which encompassed six types of geomorphology (Bil, Brahmaputra floodplain, Ganges floodplain, Meghna floodplain, Karatoya-Bangali floodplain and Pleistocene terrace). A total of 1209 paddy soils and 235 matched non-paddy soils were collected. The source of irrigation water (groundwater and surface water) was also recorded. The concentrations of arsenic and sixteen other elements were determined in the soil samples. The concentration of arsenic was higher in paddy soils compared to non-paddy soils, with soils irrigated with groundwater being higher in arsenic than those irrigated with surface water. There was a clear difference between the Holocene floodplains and the Pleistocene terraces, with Holocene floodplain soils being higher in arsenic and other elements. The results suggest that arsenic is most likely associated with less well weathered/leached soils, suggesting it is either due to the geological newness of Holocene sediments or differences between the sources of sediments, which gives rise to the arsenic problems in Bangladeshi soils.

18.
Chemosphere ; 175: 497-504, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28249191

RESUMO

Arsenic (As)-contaminated agricultural soils threaten crop yields and pose a human health risk. Augmentation of exogenous microorganisms exhibiting plant-growth promoting and As speciation changing shows potential to improve crop growth and change soil As availability. Trichoderma asperellum SM-12F1 exhibiting both traits was developed into chlamydospores to improve its persistence in contaminated soils. After inoculation, As availability and enzyme activity in two types of soils and the growth as well as As uptake of water spinach (Ipomoea aquatic Forsk.) were investigated. The results indicated that inoculation significantly improved water spinach growth in both soils. Inoculating chlamydospores at 5% significantly increased As concentration (139%), bioconcentration factor (150%), and translocation factor (150%) in water spinach grown in Chenzhou (CZ) soils, while no significant change for these in Shimen (SM) soils. Inoculating chlamydospores at 5% caused a significant increase (16%) of available As content in CZ soils, while a significant decrease (13%) in SM soils. Inoculation significantly caused As methylation in both soils, while significant As reduction merely observed in CZ soils. The differential changes in available As contents in both soils were attributed to the soil pH, As fractionations and speciation characteristics. Furthermore, Inoculating chlamydospores at 5% significantly improved the activities of ß-glucosidase (155%), chitinase (211%), and phosphatase (108%) in SM soils, while significant decreases in ß-glucosidase (81%), phosphatase (54%), aminopeptidase (60%), and catalase (67%) in CZ soils. Bioaugmentation and As availability change were responsible for this result. These observations will be helpful for the application of fungal chlamydospores in the future bioremediation.


Assuntos
Arsênico/análise , Ipomoea/crescimento & desenvolvimento , Poluentes do Solo/análise , Solo/normas , Trichoderma/crescimento & desenvolvimento , Agricultura , Arsênico/metabolismo , Biodegradação Ambiental , Humanos , Ipomoea/metabolismo , Metilação , Solo/química , Poluentes do Solo/metabolismo , Esporos Fúngicos/crescimento & desenvolvimento
19.
Anal Chem ; 89(2): 1178-1184, 2017 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-27936613

RESUMO

Nitrate (NO3-N), the main plant/microbial nitrogen source, has a fast turnover in soil driven by species transformation (nitrification/denitrification) and phyto/microbiota assimilation. The technique of diffusive gradients in thin films (DGT) is capable of a robust, low disturbance measurement of NO3-N but has not been implemented due to the absence of a binding layer suitable for deployment in soils. In this study, a new styrene divinylbenzene-based absorbent with amine functional groups (SIR-100-HP) was cast into an agarose gel support. The NO3-N ion selectivity of the SIR-100-HP/agarose binding layer was retained in the presence of high multivalent ion concentrations and was used successfully to acquire in situ NO3-N measurements in bulk soil. The kinetics of binding and the maximum binding capacity were determined. The total capacity of the DGT containing the SIR-100-HP/agarose binding phase was 667 µg of NO3-N. The performance of DGT was not affected by varying pH (3-8) or ionic strength (0-0.018 mol L-1), while anion competition effects at concentrations reflecting those in common agricultural soils were found to be negligible. Complete elution (100% efficiency) of NO3-N from the binding phase was achieved using a solution of 5% NaCl. This technique was validated in three contrasting soils. CDGT measurements were in excellent agreement with pore water NO3-N values. Two-dimensional NO3-N mapping of a profile of flooded rice paddy soil demonstrated the potential of this novel methodology for improved characterization of in situ N speciation for further understanding of bioavailability and biogeochemical processes of NO3-N in soils.


Assuntos
Resinas de Troca de Ânions/química , Nitratos/análise , Solo/química , Estireno/química , Compostos de Vinila/química , Adsorção , Agricultura , Difusão , Monitoramento Ambiental/métodos , Cinética , Concentração Osmolar , Sefarose/química
20.
Water Res ; 99: 200-208, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27161886

RESUMO

Natural mineral-water interface reactions drive ecosystem/global fluoride (F(-)) cycling. These small-scale processes prove challenging to monitoring due to mobilization being highly localized and variable; influenced by changing climate, hydrology, dissolution chemistries and pedogenosis. These release events could be captured in situ by the passive sampling technique, diffusive gradients in thin-films (DGT), providing a cost-effective and time-integrated measurement of F(-) mobilization. However, attempts to develop the method for F(-) have been unsuccessful due to the very restrictive operational ranges that most F(-)-absorbents function within. A new hybrid-DGT technique for F(-) quantification containing a three-phase fine particle composite (FeAlCe, FAC) adsorbent was developed and evaluated. Sampler response was validated in laboratory and field deployments, passing solution chemistry QC within ionic strength and pH ranges of 0-200 mmol L(-1) and 4.3-9.1, respectively, and exhibiting high sorption capacities (98 ± 8 µg cm(-2)). FAC-DGT measurements adequately predicted up to weeklong averaged in situ F(-) fluvial fluxes in a freshwater river and F(-) concentrations in a wastewater treatment flume determined by high frequency active sampling. While, millimetre-scale diffusive fluxes across the sediment-water interface were modeled for three contrasting lake bed sediments from a F(-)-enriched lake using the new FAC-DGT platform.


Assuntos
Fluoretos , Concentração de Íons de Hidrogênio , Metais , Concentração Osmolar , Água
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