Arsenic sequestration in iron plaque and its effect on As uptake by rice plants grown in paddy soils with high contents of As, iron oxides, and organic matter

Abstract

The aim of this study is to investigate the effects of the rice (Oryza sativa L.) root's iron (Fe) plaques on arsenic (As) uptake by rice plants grown in As-contaminated soil with high contents of iron oxides and organic matter, from the Guandu Plain of northern Taiwan. The results of the soil incubation study show that both As and Fe concentrations in the soil solutions increased with flooding time due to reductive dissolution of iron oxides induced by the soil's high contents of organic matter. Large Fe plaques were deposited on rice roots and substantial amounts of As were sequestrated in these Fe plaques. About 73.8 to 90.4 % of the total As released from soils was distributed in the iron plaques and only a small proportion was distributed in the rice plants. This study provides evidence that iron plaques are the main controlling factor in limiting the uptake of As into the rice plants grown in the tested soils, and that iron plaque formation enhancement could be used to reduce As uptake by paddy rice grown in As-contaminated soils, thus reducing As toxicity.

Arsenic phytotoxicity and accumulation in rice seedlings grown in arsenic‐contaminated soils as influenced by the characteristics of organic matter amendments and soils

“…In our previous study, it was found that a high content of iron oxides and hydroxides and OM in Gd soils enhance the formation of iron plaque on rice roots under flooding conditions. Iron plaque could act as a barrier and prevent As uptake and accumulation in rice plants ( Syu et al., ). Because Cf soils have low amounts of iron oxides and hydroxides, the amounts of iron plaque formation were the lowest among the three tested soils.…”

Application of iron and silicon fertilizers reduces arsenic accumulation by two Ipomoea aquatica varities

“…At circumneutral pH, hydrated Fe(III) oxide could interact with As(III) and As(V) by forming inner-sphere complexes (Roberts et al 2004;Sarkar et al 2008;Ciftci et al 2011). It is reasonable to suggest that Fe plaque commonly formed on root surfaces could intercept part of As that tended to move into roots Syu et al 2013). The formation of iron plaque on the root surfaces of I. aquatica was not investigated in this study.…”

A Comparative Study to Alleviate Arsenite Accumulation in Hydroponically Grown Oryza sativa Seedlings Through Combinations of Se, P and Fe

“…A number of studies have shown that Fe-plaque could act as a barrier to the uptake of other toxic metals in rice. It is now proven that Fe is deposited on the rice root surface of aquatic plants as Fe-(oxyhydr) oxides (Fe plaques) which reduces the overall root surface area available for As uptake and some amount of As gets adsorbed on the Fe-plaques (Syu et al, 2013;Hu et al, 2015). In agreement with these studies, in the present study, inhibition of iAs uptake was more pronounced in As+Fe treated plants which could be due to the formation of Fe plaque on the root surface which acted as a barrier towards uptake of iAs.…”

“…There have been several studies in recent past involving alleviation of iAs toxicity in rice through essential elements such as Fe, Se and P. Lou-Hing et al (2011) studied the effect of P on iAs uptake, Syu et al (2013) Fe on iAs uptake, Liu et al (2004a) on the combined effect of Fe and P on As uptake in rice. Recently, Kumar et al (2013) has reported that the co-application of Se(IV) and P can reduce iAs uptake in rice seedlings.…”