Abstract:
To investigate the regulation effect of ferrihydrite (Fh) on the uptake of arsenic (As) and cadmium (Cd) by different rice varieties, we conducted pot trials with conventional rice Huanghuazhan (H) and hybrid rice Y Liangyou 9918 (Y) as the test rice. Two groups of treatments were set up according to whether Fh was applied or not,one group was the control soil planted with conventional rice Huanghuazhan (H-CK) and hybrid rice Y Liangyou 9918 (Y-CK); The other group applied Fh at 1% soil weight ratio and consisted of planting conventional rice Huanghuazhan (H-Fh) and hybrid rice Y Liangyou 9918 (Y-Fh).The results showed that: Fh was relatively stable throughout the growth period of rice, not easy to be reduced and dissolved, and As and Cd in pore water could be effectively adsorbed by Fh; compared with H-CK, the As and Cd concentrations of pore water under the H-Fh treatment were reduced by 76.3% and 31%, respectively, and compared with Y-CK, the As and Cd concentrations of pore water under the Y-Fh treatment were reduced by 73.7% and 57.8%. The application of Fh could promote the transformation of As and Cd in rhizosphere soil from unstable fraction to stable fraction, and the stabilization effect of Fh on As and Cd in rhizosphere soil of conventional rice Huanghuazhan was more significant. Under H-Fh treatment, the content of As in unstable fraction (non-specific adsorption fraction, specific adsorption fraction and weakly crystalline iron oxide bound fraction) was decreased by 100%, 30.8% and 14.7%, respectively, compared with H-CK, while the content of As in crystalline iron oxide bound fraction was increased by 36.7%. Compared with Y-CK, Y-Fh treatment reduced the content of unstable As by 9.9%, 18.2% and 14.9%, respectively, and increased the content of crystalline iron oxide bonded As by 29.2%. Compared with H-CK, the content of exchangeable Cd under H-Fh treatment was significantly reduced by 31.5%, while the content of all Cd fractions under Y-Fh treatment had no significant change compared with Y-CK. The application of Fh significantly reduced the As content of the polished rice of the conventional rice Huanghuazhan by 44.6% compared with its CK, but did not significantly inhibit the accumulation of As in the polished rice of the hybrid rice Y Liangyou 9918, and Fh had no significant effect on the Cd content of the polished rice of the two rice varieties. Therefore, Fh can be used as an effective amendment to reduce and control the accumulation of As in rice during the safe utilization of As and Cd complex contaminated rice fields, but the effect varies significantly with the availability of As in the rhizosphere of different rice varieties.