Influence of zero-valent iron and rice husk on As and Cd uptake in rice

Abstract

Zero-valent iron (ZVI) and rice husk (RH) have potential as adsorbents for heavy metals; however, their effects on iron plaque formation and heavy metal uptake by plants are still unclear. In this study, the impacts of ZVI, RH and their combinations on iron plaque formation on the root surface and the uptake of As and Cd by rice plants were investigated. A pot experiment was performed under waterlogged conditions using As<sup>(III)</sup>- or Cd<sup>(II)</sup>-spiked soil. The results showed that ZVI (0.05% or 0.2%) with or without RH significantly increased iron plaque formation and Fe contents in rice plants and pore water. Under As treatment, ZVI (0.05% or 0.2%) without or with RH obviously increased the As content in plaques and reduced the As content in grains by 67% and 66% and 19% and 24%, respectively. The Cd content was markedly increased in iron plaques and reduced in roots, shoots and grains by ZVI and RH. ZVI (0.05% or 0.2%), RH and their combinations reduced the grain Cd content by 61, 62, 60, 68 and 69%. These findings suggest that ZVI is effective in hindering As and Cd uptake by rice with or without RH in paddies contaminated with As or Cd.