Arsenic Speciation and Volatilization from Flooded Paddy Soils Amended with Different Organic Matters

Huang, Hai; Jia, Yan; Sun, Guoxin; Zhu, Yan

doi:10.1021/es203635s

Cited by 158 publications

(102 citation statements)

References 33 publications

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“…The positive correlation with DOC is consistent with previous reports that additions of organic matter stimulated As methylation and the volatilization of methylated As species. 20,21,46,47 Furthermore, arsM copy number was found to be significantly higher in the rhizosphere soil than in the bulk soil and to be enhanced by the addition of rice straw, 36 both suggesting a positive effect of organic substrate addition possibly due to increased food source for the As methylation microbes. Soil flooding was found to enhance As methylation in soil 21,48 and to increase the concentration of DMA in rice grain.…”

Section: ■ Discussionmentioning

confidence: 96%

Arsenic Methylation in Soils and Its Relationship with Microbial arsM Abundance and Diversity, and As Speciation in Rice

Zhao

Harris

Jia

et al. 2013

Environ. Sci. Technol.

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187

125

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Methylation of arsenic in soil influences its environmental behavior and accumulation by plants, but little is known about the factors affecting As methylation. As speciation was determined in the pore waters of six soils from diverse geographical locations over 54 days of incubation under flooded conditions. The concentration of methylated As (monomethylarsonic acid, MMA, and dimethylarsinic acid, DMA) varied from 0 to 85 μg L −1 (0 − 69% of the total As in pore water). Two Bangladeshi paddy soils contaminated by irrigation of As-laden groundwater produced large concentrations of inorganic As but relatively little methylated As. Two contaminated paddy soils from China produced a transient peak of DMA during the early phase of incubation. Methylated As represented considerable proportions of the total soluble As in the two uncontaminated soils from the UK and U.S. The copy number of the microbial arsenite methyltransferase gene (arsM) correlated positively with soil pH. However, pore-water methylated As correlated negatively with pH or arsM copy number, and positively with dissolved organic C. GeoChip assay revealed considerable arsM diversity among the six soils, with 27−35 out of 66 sequences in the microarray being detected. As speciation in rice plants grown in the soils generally mirrored that in the pore water. The results suggest that methylated As species in plants originated from the soil and As methylation in soil was influenced strongly by the soil conditions. ■ INTRODUCTIONArsenic (As) is a ubiquitous contaminant in the environment originating from both natural and anthropogenic sources. Because its biogeochemical behavior and toxicity vary greatly among different chemical species, it is important to understand how the speciation of As changes in the environment and what drives such changes. A particularly important case is the paddy rice system because it is now recognized that rice is a major source of As in the human diet. 1 The anaerobic conditions in paddy soils are conducive to the mobilization of arsenite, 2,3 which is taken up inadvertently by rice roots through the strong uptake pathway for silicic acid. 4 Rice grain contains both inorganic As (arsenate and arsenite) and organic As (mostly dimethylarsinic acid, DMA; occasionally also trace amounts of monomethylarsonic acid, MMA, and tetramethylarsonium). 5−9 As speciation in rice varies widely among different riceproducing regions. Market-basket surveys show that Asian rice generally is dominated by inorganic As with DMA typically accounting for about 20% of the total As. [5][6][7]10 In contrast, rice produced in the U.S. and Europe is more variable in As speciation with many samples containing more organic than inorganic As. 5,7,8,10 It is possible that that this geographical pattern reflects the relative bioavailability of inorganic versus organic As in different paddy environments. 10 Compared with inorganic As, methylated As species are more easily accumulated in rice grain. 10 Although pentavalent methylated As species are ...

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Section: ■ Discussionmentioning

confidence: 96%

Arsenic Methylation in Soils and Its Relationship with Microbial arsM Abundance and Diversity, and As Speciation in Rice

Zhao

Harris

Jia

et al. 2013

Environ. Sci. Technol.

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187

125

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“…The organic constituents can be regarded as nutritional supplements to significantly increase the microbial activity (Laird et al, 2009). Huang et al (2012) demonstrated that organic matter addition (i.e., clover or dried distillers grain) increases As methylation and volatilization from paddy soils. In our study, the presence of more or fewer organic constituents for the UBM and SBRC methods resulted in corresponding As methylation percentages for the colon digests.…”

Section: Arsenic Speciation In the Colon Phasementioning

confidence: 99%

Variability of arsenic bioaccessibility and metabolism in soils by human gut microbiota using different in vitro methods combined with SHIME

Yin

Zhang

et al. 2016

Science of The Total Environment

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• Five in vitro gastrointestinal methods combined with SHIME (colon phase) were used.• As bioaccessibility varied in the colon phase among these methods.• Plenty of As(III) and methylated arsenicals by microbial transformation were observed.• As bioaccessibility in PBET/SBRC-SHIME colon phase were closer to in vivo results for NIST 2710a. Arsenic (As) speciation analysis is essential when evaluating the risks upon oral exposure to As-contaminated soils. In this study, we first investigated the variability in the As bioaccessibility and speciation using a combination of five common in vitro methods (SBRC, PBET, DIN, UBM and IVG) (gastric and small intestinal phases) and the SHIME model (colon phase). Our results indicate that the As bioaccessibility varies in the colon phase. An increase in the As bioaccessibility for SBRC and PBET, and a decrease for UBM and IVG were observed in the colon phase. In addition, we found different extents of methylation and large amounts of arsenite [As(III)] due to microbial reduction in the colon digests. The UBM-SHIME method displayed a higher methylation percentage of 13.5-82.1%, but a lower methylation percentage of 0.2-21.8% was observed in the SBRC-SHIME method. Besides, The MMA V levels in the colon digests were positively correlated with those of As(III) and DMA V , so DMA V can be considered an indicator to evaluate the As metabolic speed of in vitro cultured human gut microbiota. Based on the standard reference soil of NIST 2710a, the As bioaccessibility in the colon phase of PBET-SHIME and SBRC-SHIME were the closest to the in vivo results. Combining in vitro methods and SHIME will remarkably affect the accurate assessment of potential risks to human health associated with oral exposure to soil As.

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“…The application of OM (as exogenous nutrition) stimulates the growth of various indigenous microorganisms, including As methylaters which facilitate As methylation and volatilization from soil, and the "volatilization ability" varied between the types of organic matters [13,20]. As mentioned above, the addition of organic matters will enhance the mobilization of As thus increasing its bioavailability for methylaters, and favoring methylation processes.…”

Section: Interactions Of Microorganisms With Organic Mattersmentioning

confidence: 99%

“…As mentioned above, the addition of organic matters will enhance the mobilization of As thus increasing its bioavailability for methylaters, and favoring methylation processes. In addition, OM amendment changes the physicochemical properties (such as pH, Eh) of paddy soils, which can also affect communities and activities of microorganisms, further influence As methylation and subsequent volatilization [13]. It was reported that pH changes can influence the microbial process to affect As methylation or volatilization: a decrease in soil pH enhanced microbial-mediated As volatilization [71].…”

Section: Interactions Of Microorganisms With Organic Mattersmentioning

confidence: 99%

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Effects of microbial processes on the fate of arsenic in paddy soil

2012

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Arsenic (As) is a metalloid toxic to organisms including humans. Arsenic in rice represents a significant exposure pathway for the general population, particularly for those subsisting on rice. Arsenic transformation, namely reduction, oxidation and methylation, in soil-rice systems has fundamental impacts on its mobility and toxicity. In addition to soil chemical properties (pH, Eh, metallic oxides, organic matter), microorganisms play critical roles in As transformation and mobility in paddy soil, such as through ArsM (As(III) S-adenosylmethyltransferase) and interactions with iron oxides or organic matters. Arsenic species in paddy soil directly influence As speciation in rice grain because the methylated As species in rice are mainly derived from microbial methylation in paddy soil. This paper aims to provide an overview on the status of the knowledge and gaps on the chemical aspects of As transformation in soil-rice system in conjunction with microbial ecology and functional genes. In addition, potential pathways (manipulation of microorganisms in paddy soil and genetic engineering) to decrease total As and/or inorganic As in rice grain are proposed.

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Arsenic Speciation and Volatilization from Flooded Paddy Soils Amended with Different Organic Matters

Cited by 158 publications

References 33 publications

Arsenic Methylation in Soils and Its Relationship with Microbial arsM Abundance and Diversity, and As Speciation in Rice

Arsenic Methylation in Soils and Its Relationship with Microbial arsM Abundance and Diversity, and As Speciation in Rice

Variability of arsenic bioaccessibility and metabolism in soils by human gut microbiota using different in vitro methods combined with SHIME

Effects of microbial processes on the fate of arsenic in paddy soil

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