Arsenic immobilization in anaerobic soils by the application of by-product iron materials obtained from the casting industry

ABSTRACT

Reducing the arsenic (As) concentration in rice grains is of great interest from a human health perspective. Iron (Fe) materials immobilize As in soils, thereby effectively reducing the As concentration in rice grains. We investigated the effect of by-product Fe materials obtained from the casting industry on the As mobility in two soils (soil A and soil B) by a long-term (approximately 100 days) flooded soil incubation experiment. The examined Fe materials were spent steel shot (SSS), fine spent casting sand (SCS) containing steel shot, and two kinds of residual Fe materials (RIMs) from steel shot production. Commercial Fe materials used to immobilize As (zero-valent Fe and ferrihydrite) were tested for comparison. The dissolved As in soil solution of controls for soil A and soil B reached approximately 100 and 800 μg L^‒1, respectively. The effect on As immobilization of all the by-product Fe materials increased with time and was comparable to or greater than that of commercial ferrihydrite, except for SCS. The additions of SSS and RIMs decreased by more than 90% of the dissolved As in soil A and decreased by more than 50% in soil B after 100 days incubation. Overall, the effect of the by-product Fe materials on the solubility of silicon and phosphorus was much less than that of the commercial Fe materials. Considering the cost advantage over commercial Fe materials, the Fe materials obtained from the casting industry as by-products are promising amendments for the immobilization of As in paddy soils.

KEY WORDS:

• Anaerobic soil
• arsenic immobilization
• by-product iron
• phosphorus
• silicon

Acknowledgments

We deeply appreciate the dedicated assistance of Mr Taichi Hihara throughout the research. The authors also thank Dr Toshiaki Ohkura (Institute for Agro-Environmental Sciences, NARO) for his support in using the X-ray diffractometer. We thank Dr Tomohito Arao (Central Region Agricultural Research Center, NARO), Dr Akira Kawasaki (Advanced Analysis Center, NARO), Dr Koji Baba, Ken Nakamura (Institute for Agro-Environmental Sciences, NARO), and Mr Satoshi Takamiya (Ministry of Agriculture, Forestry and Fisheries) for their useful suggestions and comments. The XANES measurements were performed with the approval of the High-Energy Accelerator Research Organization, KEK (Proposal No. 2011G016), and the Aichi Synchrotron Radiation Center (Proposal No. 201606072). The ICP-OES and ICP-MS measurements were carried out at the Advanced Analysis Center, NARO.

Main part of this work was supported by the Ministry of Agriculture, Forestry and Fisheries under a Grant-in-Aid for the research project for improving food safety and animal health As-210. Other aspects of this work were conducted under the collaborative research agreement between the Institute for Agro-Environmental Sciences, NARO, and Sintokogio Ltd.

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Funding

Main part of this work was supported by the Ministry of Agriculture, Forestry and Fisheries under a Grant-in-Aid for the research project for improving food safety and animal health As-210.