The 1-Octanol/Water Partition Coefficient of Mercury

Okouchi, Shoichi; Sasaki, Sokichi

doi:10.1246/bcsj.58.3401

Cited by 14 publications

(7 citation statements)

References 13 publications

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“…Elemental Hg is mildly lipophilic, exhibiting foliage-air exchange via stomata as well as uptake by nonstomatal pathways . Oxidized Hg II compounds that are either wet or dry deposited to leaves from the atmosphere or produced on leaf surface by Hg 0 oxidation, can traverse the underlying cuticle by epocuticular dissolution, and eventually diffuse into the epidermal cells .…”

Section: Resultsmentioning

confidence: 99%

“…30 Therefore, PCs appear to play an important role in the plant tolerance of IHg while their influence on MeHg detoxification in rice plant is unclear and possibly minor. Elemental Hg is mildly lipophilic, 31 exhibiting foliage-air exchange via stomata as well as uptake by nonstomatal pathways. 32 Oxidized Hg II compounds that are either wet or dry deposited to leaves from the atmosphere or produced on leaf surface by Hg 0 oxidation, 33 can traverse the underlying cuticle by epocuticular dissolution, and eventually diffuse into the epidermal cells.…”

Section: Resultsmentioning

confidence: 99%

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Localization and Speciation of Mercury in Brown Rice with Implications for Pan-Asian Public Health

Meng

Qiu

Anderson

et al. 2014

Environ. Sci. Technol.

131

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Cultivation of paddy rice for human consumption is a dominant agricultural activity throughout Asia. High levels of mercury (Hg) in rice grain pose a potential threat to human health, although the extent of risk is dependent on the chemical speciation of Hg inside the grain. We have investigated the speciation and localization of Hg in three fractions of rice grain (hull, bran, and white rice) collected from a Hg-contaminated region in China. On a mass basis, the majority of inorganic mercury (IHg) in a rice grain is found in hull and bran. However, the majority of the more toxic species methyl mercury (MeHg) is found in edible white rice. Our data show that during grain processing, most of the IHg (∼78%) is eliminated, but the majority of the MeHg remains in the food product (∼80%). Synchrotron radiation microscopic X-ray fluorescence (SR-μXRF) mapping shows strong localization of Hg at the surface of brown rice grains, corresponding to the pericarp and aleurone layer. We infer that this Hg is predominantly IHg absorbed from the atmosphere. Based on X-ray absorption near-edge spectroscopy (XANES) data we propose that IHg in bran is primarily bound to cysteine, and is associated with phytochelatins. Consequently, IHg is largely immobile and restricted to the outer layers of rice grain. MeHg in bran is primarily bound to cysteine and is associated with proteins. However, this MeHg-cysteine association behaves like a mobile nutrient and is actively transported to the endosperm during seed ripening. Concentration of MeHg-cysteine in white rice has implications for public health. There is growing evidence for Hg contamination of rice throughout Asia due to point and diffuse sources of Hg pollution. The magnitude of the associated risk must be quantified through better understanding of the localization and speciation of mercury in rice. Our work makes an effort to contribute to this understanding.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Localization and Speciation of Mercury in Brown Rice with Implications for Pan-Asian Public Health

Meng

Qiu

Anderson

et al. 2014

Environ. Sci. Technol.

131

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“…As the dominant form of Hg in the atmosphere (>95%) [26], Hg 0 is a mildly lipophilic compound [27] that could diffuse through the cuticle similar to volatile lipophilic compounds [28]. Moreover, compounds containing Hg(II)-either deposited to leaves from the atmosphere or produced at the leaf surface via Hg 0 oxidation [29]-could traverse the epocuticular dissolution into the underlying cuticle and diffuse to epidermal cells [30].…”

Section: Inorganic Hg In Tissues Of Rice Plants During the Rice-growimentioning

confidence: 99%

Inorganic mercury accumulation in rice (Oryza sativa L.)

Meng

Qiu

Wang

et al. 2012

Environmental Toxicology and Chemistry

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To investigate the source and process of inorganic mercury (IHg) accumulation in rice, we monitored the concentrations of IHg in tissues of rice plants (Oryza sativa L.) from four experimental plantation plots. Biweekly during the rice‐growing season, tissues of rice plants, corresponding soil, precipitation, and irrigation water samples were collected. The sampling data support the following: (1) the atmosphere is the principal source of IHg to the aboveground parts of the rice plant; (2) both the atmosphere and soil contribute to IHg content in stalks, but the former source tends to be more important; and (3) soil is the major source of root IHg content. These observations and the fact that the gradually increasing concentration and mass of IHg in stalks and leaves during the rice‐growing season suggested that atmospheric Hg could be absorbed by and incorporated into the aboveground parts of the rice plant and that limited or no Hg emission to the air or translocation to the soil occurred after deposition of atmospheric Hg. The root surface acted as a potential Hg barrier and consequently reduced the translocation of Hg ion mass through the root system to the aboveground parts. Accumulated IHg in aboveground parts of rice plants cannot be transported to seeds, which is completely different from the case of methylmercury. Environ. Toxicol. Chem. 2012; 31: 2093–2098. © 2012 SETAC

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“…However, the log Ks value in propan-2-ol is fitted reasonably well (observed value 1.42, fitted value 1.53). In addition, Okouchi and Sasaki 53 give the solubility of mercury in dry octanol as ≥ 4.0 ×10 -6 mol dm -3 . When combined with the vapor concentration of mercury at 298K, 1, 2 log Cg = -6.98, this yields an observed value of log Ks in dry octanol as ≥ 1.58, by comparison with a predicted value of 1.59, from the descriptors in Table 7 and the equation in Table 2.…”

Section: Discussionmentioning

confidence: 99%

Solvation parameters for mercury and mercury(ii) compounds: calculation of properties of environmental interest

et al. 2008

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Descriptors have been determined for four inorganic mercury(II) species and for seventeen organic mercury(II) species, using experimental literature data. These descriptors can then be used in equations that we have already set out in order to estimate a large number of physicochemical properties. These include the water to octanol partition coefficient and the gas to water partition coefficient. For the organic mercury(II) species, including dimethylmercury and the methylmercury(II) halides, the latter has been estimated over the temperature range 273-373 K.Eqn ( 2) is used for gas to solvent partitions, as log K s , where K s is defined similarly to K w . Both eqn (1) and eqn (2) can be used for the gas to water partition. The independent variables in eqn (1) and eqn (2) are solute descriptors as follows. 10,11 E is the solute excess molar refraction in units of (cm 3 mol À1 )/10, S is the solute dipolarity/polarizability, A and B are the overall or summation hydrogen bond acidity and basicity, V is the McGowan characteristic volume 27 in units of (cm 3 mol À1 )/100, and L is the logarithm of the gas to hexadecane partition coefficient at 298 K.The use of eqn (1) and eqn (2) in the determination of descriptors has been described in detail, 10,11 and numerous examples are available. [28][29][30][31][32] Equations on the lines of eqn (1) and eqn (2) are set

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The 1-Octanol/Water Partition Coefficient of Mercury

Cited by 14 publications

References 13 publications

Localization and Speciation of Mercury in Brown Rice with Implications for Pan-Asian Public Health

Localization and Speciation of Mercury in Brown Rice with Implications for Pan-Asian Public Health

Inorganic mercury accumulation in rice (Oryza sativa L.)

Solvation parameters for mercury and mercury(ii) compounds: calculation of properties of environmental interest

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