Growing Rice Aerobically Markedly Decreases Mercury Accumulation by Reducing Both Hg Bioavailability and the Production of MeHg

Wang, Xun; Ye, Zhihong; Luo, Bing; Huang, Li-Nan; Meng, Miaojing; Shi, Jianbo; Jiang, Guibin

doi:10.1021/es4038929

Cited by 104 publications

(36 citation statements)

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“…3) of THg in roots showed an increasing trend, suggesting that the entry of THg into the rice plant could be a persistent and continuous process, also indicating that roots play a dominant role in accumulating THg. Similar findings have been reported in previous studies on rice (Meng et al 2010;Wang et al 2014). It has also been reported that rice seed (brown rice) has the highest ability to accumulate MeHg compared to other tissues (Meng et al 2010;Zhang et al 2010a).…”

Section: Discussionsupporting

confidence: 91%

Radial oxygen loss has different effects on the accumulation of total mercury and methylmercury in rice

Wang

Li²,

Tam

et al. 2014

Plant Soil

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Background and Aims Mercury (Hg) pollution in paddy fields and rice has aroused great concern in recent years. This study investigated the dynamic changes of radial oxygen loss (ROL) and Fe plaque formation on roots, and their effects on Hg accumulation in rice plants. Methods A rhizobag experiment was conducted to study temporal variations and correlations between ROL (amounts and rates), Fe plaque formation, total Hg (THg) and methylmercury (MeHg) in plant tissues and in plaque of four rice cultivars during six growth stages.Results ROL amounts and Fe plaque formation increased from tillering to reproductive stages, then ROL amounts gradually decreased until maturation stage, whereas Fe plaque remained relatively stable. ROL rates continued to decline during the entire growth period. Both ROL amounts and Fe concentrations in plaque were positively correlated with THg concentrations in the plaque, whereas negatively correlated with THg in straw and brown rice. However, there were no significant relationships between ROL, Fe in plaque and MeHg in plaque and in plant tissues.Plant Soil (2014) 385:343-355 DOI 10.1007/s11104-014-2239-x Responsible Editor

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Section: Discussionsupporting

confidence: 91%

Radial oxygen loss has different effects on the accumulation of total mercury and methylmercury in rice

Wang

Li²,

Tam

et al. 2014

Plant Soil

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“…Understanding the relationships of the plant life cycle and changes in mercury speciation could have implications for the management of rice production, for example, timing the flooding of fields to reduce the uptake of MeHg from soil before flowering to reduce the translocation of MeHg into grains (Peng et al 2012). Exposing rice paddies to aerobic conditions reduced the uptake of MeHg by plants, perhaps due to a reduction in the amount of SRB in aerobic conditions and water management strategies that include exposing soil to the air during particular phases of growth may lessen the risks of methylation (Wang et al 2014). However, it is unclear whether the effects of re-flooding, which seem to promote methylation in other environments, would negate the benefits of aerobic cultivation.…”

Section: Inundated Environmentsmentioning

confidence: 99%

Recent advances in the study of mercury methylation in aquatic systems

Paranjape

Hall

2017

FACETS

121

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With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.

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“…Changing redox parameters over the rice growing season may affect the process of Hg methylation. Previous studies have observed that in artificially Hg-polluted soil, Hg bioavailability for methylation can be significantly affected by the level of water saturation Wang et al, 2014;Peng et al, 2012). Peng et al (2012) specified that intermittent flooding, as opposed to continuous flooding, could reduce soluble Hg concentrations and inhibit Hg methylation in the rice rhizosphere, subsequently decreasing the accumulation of MeHg in rice grain.…”

Section: Samplingmentioning

confidence: 99%

“…Mercury methylation is largely facilitated by a subset of sulfate-reducing bacteria (SRB; Gilmour et al, 1992) and/or iron-reducing bacteria (Fleming et al, 2006) in anoxic conditions. Specially, the methylation of inorganic Hg (IHg) in paddy soil primarily occurs through a process mediated by sulfate-reducing bacteria (Peng et al, 2012;Rothenberg and Feng, 2012;Wang et al, 2014;Liu et al, 2009Liu et al, , 2014. MeHg accumulated throughout a rice plant during the growing season can be readily translocated to grain during riceseed ripening .…”

Section: Introductionmentioning

confidence: 99%

“…Such studies on MeHg and rice emphasize that factors which control the biochemical cycling of Hg within rice paddy ecosystems are very complex and include the concentration and distribution of Hg in ambient air, wet and dry deposition, irrigation water, and the solid and liquid phases of soil. These factors in turn impact the absorption, transportation, and accumulation of Hg in rice plants (Meng et al, 2010Rothenberg and Feng, 2012;Liu et al, 2012;Wang et al, 2014;Peng et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

et al. 2016

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Abstract. Rice paddy plantation is the dominant agricultural land use throughout Asia. Rice paddy fields have been identified as important sites for methylmercury (MeHg) production in the terrestrial ecosystem and a primary pathway of MeHg exposure to humans in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete ricegrowing season at two different typical Hg-contaminated mining sites in Guizhou province, China: an abandoned site with a high Hg concentration in soil but a low concentration in the atmosphere and a current-day artisanal site with a low concentration in soil but a high concentration in the atmosphere. Our results showed that the flux of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg in soil; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg (IHg). Elevated MeHg concentrations and the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal site demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg in paddy water and surface soil is dependent on elevated Hg in the atmosphere and the consequential deposition of new Hg into a low-pH anoxic geochemical system. The absence of depth-dependent variability in the MeHg concentration in soil cores collected from the abandoned Hg mining site, consistent with the low concentration of Hg in the atmosphere and high pH of the paddy water and irrigation water, suggested that net production of MeHg at this site was limited. We propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

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Growing Rice Aerobically Markedly Decreases Mercury Accumulation by Reducing Both Hg Bioavailability and the Production of MeHg

Cited by 104 publications

References 50 publications

Radial oxygen loss has different effects on the accumulation of total mercury and methylmercury in rice

Radial oxygen loss has different effects on the accumulation of total mercury and methylmercury in rice

Recent advances in the study of mercury methylation in aquatic systems

Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

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