Zero-valent iron reduces cadmium and arsenic accumulation in spinach (Spinacia oleracea L.)

Abstract

Cadmium (Cd) and arsenic (As) soil contamination poses significant problems for crop production worldwide. Zero-valent iron (Fe⁰) is a reactive material with reducing power capable of stabilizing toxic elements, including heavy metals and metalloids. In this study, we examined the effect of Fe⁰ application on Cd and As accumulation in spinach (Spinacia oleracea L.) grown in Cd- or As-contaminated soil. Fe⁰ soil application reduced Cd and As concentrations in spinach shoots and/or roots, and decreased their availability in soil, which may have affected their accumulation in spinach. Additionally, we examined the forms of soil Cd and As using the sequential extraction method. The potential availability of Cd and As forms in soils for plant root is: exchangeable > iron-manganese-oxide-bound > organic-matter-bound > free-oxide-occluded > residual. Fe⁰ application increased Cd and As distribution in the free-oxide-occluded fraction. Additionally, Fe⁰ application decreased As distribution in the iron-manganese-oxide-bound fraction while tended to decrease Cd in the organic-matter-bound fraction and increase it in the iron-manganese-oxide-bound fraction. Thus, Fe⁰ application can be effective in reducing Cd and As availability in their contaminated soils. Meanwhile, this study showed that Fe⁰ application inhibited the growth of spinach in Cd-contaminated soil. The unfavorable alterations caused by Fe⁰ in the contaminated soil should also be investigated in the future.

Keywords:

• Arsenic
• cadmium
• sequential extraction method
• spinach
• zero-valent iron

Disclosure statement

The authors report no potential conflict of interest.

Additional information

Funding

This study was partly supported by the Steel Industry Foundation for the Advancement of Environmental Protection Technology (Grant No. 07/08_suishitsu_waka-290).