Practical phytoextraction in cadmium-polluted paddy fields using a high cadmium accumulating rice plant cultured by early drainage of irrigation water

Abstract

Some indica rice varieties are potential phytoextractors for paddy fields polluted with Cd because of their high biomass and because they can accumulate Cd to moderate levels in their shoots. To establish a practical phytoextraction system, phytoextraction using two indica rice cultivars (MORETSU and IR-8) was carried out in a paddy field polluted with moderate Cd levels (2.91 and 2.52 mg kg -1 , respectively). The Cd concentration and Cd uptake of MORETSU increased when irrigation water was drained at the maximum tillering stage, and the paddy soil was under oxidative conditions until harvesting. The Cd uptake of MORETSU and IR-8 increased and reached 516 and 657 g ha -1 , respectively, at the beginning of October. After phytoextraction using these high Cd accumulating rice varieties for 2 years, the Cd concentration in the paddy field decreased by 18% compared with the initial Cd concentration. The Cd concentration in the rice grains of a japonica ordinary rice variety (HINOHIKARI) subsequently grown on the field after the phytoextraction was lower than the concentration in rice grown on a nonphytoextracted field. These results suggest that phytoextraction using high Cd accumulating rice varieties with early drainage of irrigation water is a practical remediation system for moderate Cd polluted paddy fields in southwest Japan.

Phytoextraction by high-Cd-accumulating rice to reduce Cd in wheat grains grown in Cd-polluted fields

“…3). However, the plant height of "IR8" was short, and it was assumed to have lodging tolerance (Ibaraki et al 2009). Because several typhoons pass through southwest Japan each year, lodging tolerance is an important characteristic for phytoextractor plants grown in this area.…”

“…We used "IR8", "CHOKOUKOKU", "MORETSU" and "MINAMIYUTAKA" indica rice varieties, which have been previously reported to accumulate high amounts of Cd (Azuma et al 2003;Ibaraki et al 2009;Murakami et al 2009). The experimental plots (5 × 5 m) were located in field A.…”

“…Each sample was ground to a powder. Two grams of the powdered sample was digested in 40 mL of nitric acid (HNO 3 )-perchloric acid (HClO 4 )-sulfuric acid (H 2 SO 4 ) (5:1:1) mixed solution (Ibaraki et al 2009). The Cd concentration of this digested solution was determined using a flame atomic absorption spectrophotometer (FAAS; AA-6800, Shimadzu, Kyoto, Japan).…”

Cadmium Phytoremediation Potential of Napiergrass Cultivated in Kyushu, Japan

“…The pH and the electric conductivity (EC) of the surface soil at 0-15 cm depth were examined by twin compact pH meter (B-212, Horiba Co. Ltd., Tokyo, Japan) and twin conductivity meter (B-173, Horiba Co. Ltd, Tokyo, Japan), respectively, on 5 June, 2010, and 23 November, 2010. The total C and total N content of the soil in these fields were reported to be 24 g kg −1 and 1.9 g kg −1 , respectively, by Ibaraki et al [14]. The crops cultivated before the previous [11] and present trials were sorghum as a summer crop and winter wheat as a winter crop.…”

“…Wruk Wona was subjected to field trials in Cd-contaminated paddy fields (gray lowland soil) in 2011 in Kyushu, Japan, where the previous research was carried out in 2010 [11]. The source of Cd contamination in the soil was fallout dust from a neighboring zinc-refining plant [13,14]. The soil in these fields consists of clay loam (clay content 25%, silt content 22%, and sand content 53%).…”