Inorganic mercury accumulation in rice (Oryza sativa L.)

Abstract

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

Prediction of methylmercury accumulation in rice grains by chemical extraction methods

“…Besides, recent studies revealed that IHg accumulated in rice grains could be mainly from the atmosphere but not soil (Greger et al, 2005;Lodenius et al, 2003;Mao et al, 2013;Meng et al, 2012), and thus it could be less possible to find any significant relationship between extractable IHg and grain IHg levels. However, it would also be interesting to explore the possibility of using (NH 4 ) 2 S 2 O 3 extraction to predict IHg uptake or bioaccumulation from soils, which may help understand the mechanisms of IHg uptake by rice plants.…”

Investigation of Hg uptake and transport between paddy soil and rice seeds combining Hg isotopic composition and speciation

“…It evidences the complexity of the Hg accumulation process in rice seeds and the influence of several environmental factors. Among the variables that affect such mechanisms there is the rice cultivar (Horvat et al, 2003;Li et al, 2013) and the contribution from atmospheric deposition (Horvat et al, 2003;Meng et al, 2010Meng et al, , 2012Yin et al, 2013a). The latter one principally influenced the top soil (0-10 cm) of rice paddies (Li et al, 2008b), which is evidenced by one order of magnitude decrease of Hg concentration with in 1km distance from the artisanal Hg mining sites (Meng et al, 2011).…”

“…A contrasting pattern of uptake and plant distribution of Hg species has been largely documented (Horvat et al, 2003;Meng et al, 2010Meng et al, , 2011Meng et al, , 2012Rothenberg et al, 2011). Soil contribution appears as the main source of iHg in roots .…”

The Bioaccumulation and Migration of Inorganic Mercury and Methylmercury in the Rice Plants

“…MeHg in soil was first absorbed by roots and then translocated to the above-ground parts (leaves and stalk, [9]). However, IHg accumulated in rice plants could mainly come from the atmosphere through leaf uptake, but not from soil [10][11], because the root surface, acting as IHg barrier, could inhibit the translocation of IHg through the root system to the aboveground parts, but could not inhibit MeHg transfer [12]. Meanwhile, recently rice leaves and stalk burial is being encouraged all over the world as an economical and environmentally friendly method to get rid of rice residuals.…”