Submitted to: United States Department of Agriculture Natural Resources Conservation Service
Publication Type: Abstract Only
Publication Acceptance Date: July 4, 2002
Publication Date: July 24, 2002
Selection of appropriate methods for remediation of soil metals requires careful evaluation of whether the soil contaminant is sufficiently bioavailable or phytoavailable to require remediation. Extensive study of soil Cd risk has recently demonstrated that the high prevalence of renal tubular dysfunction in aged subsistence rice farmers in Japan and China occurred because of two properties of paddy rice: 1) Even though soil Zn was 100-fold higher than soil Cd, grain Cd was increased up to 200-fold above background but grain Zn was not increased (very different from crops grown in aerobic soils); and 2) subsistence rice consumption induces Fe, Zn, and Ca malnutrition, each of which promotes Cd absorption by animals; malnutrition interactions cause even greater Cd absorption. This has broad implications regarding previous fears about Cd in biosolids and other soil amendments. Phytoextraction of soil Cd may be needed to protect consumers and wildlife at some locations. Because most plants accumulate Cd and Zn at about the same ratio found in the soil, an effective phytoextraction technology must have plants which can accumulate very high amounts of Cd regardless of the presence of Zn. We found ecotypes of Thlaspi caerulescens which accumulate over 10-times higher levels of Cd normal T. caerulescens. Soil acidification substantially increased annual Cd phytoextraction. Cd phytoextraction can only be practical with hyperaccumulator plants. We are presently working to combine the Super-Cd-Accumulator and high yield traits to breed commercially useful Cd phytoextraction cultivars. Present lines offer large cost reduction for remediation of soils which caise Cd risks.