Risk Assessment and Solution Technologies for Soil Contaminated by Harmful Heavy Metals and Other Substances

Background and Objectives

As evidenced by the recent agreement on international standards for cadmium (Cd) concentration in white rice, vegetables, etc. by the Codex Alimentarius Commission (Joint FAO/WHO Food Standards Programme), the issue of food safety is drawing increasingly strong public attention and concern both at home and abroad. There is an impending need for efforts to ensure safety in food production against contamination by harmful heavy metals or radioactive substances. We are investigating the contamination process of agricultural products by cadmium, arsenic (As) and radioactive substances as well as the development of technologies to prevent and remove such contamination.

Project Overview

With respect to soil contamination by cadmium, arsenic, radioactive substances and other harmful substances in the farm environment, chemical forms and the behavior in soil of these substances will be investigated. In addition, technologies to prevent their absorption into agricultural products will be studied, because such absorption could have human health consequences through human intake of contaminated agricultural products. For cadmium, chemical cleaning, phytoremediation and other contamination removal technologies will be developed, with the view to establishing solution technologies in combination with the absorption prevention technologies.

Relevant Outcomes to Date

1. Technologies to remediate cadmium-contaminated soil in a cost-effective and safe manner through chemical cleaning and phytoremediation processes.
2. Differences in cadmium absorption among varieties of rice, soybeans and vegetables have been established. With respect to rice, the gene locus involved in cadmium absorption has been identified, based on which the development of low-absorption varieties is being pursued.
3. A method to accurately trace the behavior of cadmium in soil and the absorption process into crops has been developed by the application of stable isotope techniques.
4. Arsenic absorption of rice has been studied and the possibility of partial transfer of organic arsenic into brown rice has been demonstrated.
5. Absorption by crops of radioactive uranium (U) existing in very small concentration in soil has been demonstrated to be extremely low.