Submitted to: International Journal of Phytoremediation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/2/2013
Publication Date: 2/12/2014
Citation: Simmons, R., Chaney, R.L., Angle, J.S., Kruatrachue, M., Klinphoklap, S., Reeves, R.D., Bellamy, P. 2014. "Towards practical cadmium phytoextraction with Thlaspi caerulescens". International Journal of Phytoremediation. DOI:10.1080/15226514.2013.876961. Interpretive Summary: Cadmium contaminated rice paddies produce rice grain with excessive cadmium which may harm humans who consume the grain over decades. Methods to remove cadmium from such soils are being researched. One possible method to remediate these problems is growing the cadmium hyperaccumulator, alpine pennycress (Thlaspi caerulescens) from southern France which can accumulate over 1000mg Cd/kg dry shoot biomass in health plants. But this species from northern Europe was not able to survive during the monsoon growing season in Mae Sot, Thailand, where zinc mine wastes contaminated rice paddy soils and is causing adverse human health effects. Methods were tested to allow growth of Thlaspi at Mae Sot by using soil ridges to improve drainage, and a fungicide to support growth under the warm conditions. Growing Thlaspi during late Fall, Winter thru early Spring allowed strong biomass production with high cadmium concentration. Acidification of the neutral pH soils allowed greater cadmium accumulation in plant shoots as expected based on greenhouse pot trials previously reported. Potential cadmium removals were modeled for different Thlaspi production methods, showing that much of the contaminated land with <10 mg/kg soil Cd could be phytoremediated within a few years, such that the process would be cost effective. This approach could be applied at many Asian cadmium contaminated rice fields, as well as cadmium contaminated soils in the US requiring remediation.
Technical Abstract: During 2005-2007, a series of field trials were conducted to investigate the potential of Thlapsi caerulescens ecotypes derived from southern France to phytoextract localized Cd/Zn contamination in Thailand. Soil treatments included pH variation and fertilization level. T. caerulescens ecotypes were transplanted to the field plots three months after germination and harvested in May prior to the onset of seasonal rains. During this three month cultivation period, the growth of T. caerulescens ecotypes was rapid with shoot biomass (DW) ranging from 0.928-2.17 g/plant (278-651 kg/ha (DW)). Shoot Cd and Zn concentrations for the four ecotypes evaluated ranged from 457-597 and 2645-2899 mg/kg (DW). Cadmium and Zn translocation factors (shoot/root) for the ecotypes tested ranged from 0.911-1.06 and 1.65-2.06, and Cd and Zn bioaccumulation factor ranged from 11.5-15.1 and 1.16-1.32, respectively. Over 47% of the paddy fields in the affected area have total soil Cd concentrations ranging from 0.3 to <10.0 mg/kg. In such situations it is envisaged that optimizing the use of fungicidal sprays, acidic soil pH, planting density and prolonging the effective cropping period will enhance rates of Cd and Zn removal to levels that facilitate practical Cd phytoextraction.