Reducing Cadmium Phytoextactability by Coal Bottom Ash

Coal bottom ash is generally considered to be a ferro-aluminosilicate mineral and has a higher pH. In acidic and cadmium (Cd) contaminated soil, the coal bottom ash can be a good amendment for increasing Cd immobilization and for decreasing Cd uptake of crop plants. In addition compost having very high indigenous negativity can contribute on increasing Cd holding capacity of soil and then on decreasing Cd uptake of plant. The objectives of this study are to evaluate the effect of  coal bottom ash on Cd phytoextractbility in a gold mine tailing affected soil. Bottom ash was applied at 4 levels of 0, 20, 40, and 80 Mg·ha^-1 and compost at 2 levels of 0 and 30 Mg·ha^-1. A radish cultivar (Raphanus sativa L.) was sown by hand in the experimental field on August 27, 2005, and harvested on October 29, 2005. Radish yield was increased slightly with increasing application of bottom ash. It was maximized at level of BA 40 Mg·ha^-1. Radish yield was more effectively increased by compost addition. Cd uptake by  radish was significantly reduced with increasing application of bottom ash. Addition of bottom ash and compost more significantly decreased exchangeable Cd concentration than addition of bottom ash. The water soluble + exchangeable Cd fraction was significantly decreased with increasing application of bottom ash, but residual fraction was increased. Soil pH and negativity were highly increased by addition of bottom ash. Reducing Cd phytoavailability can be attributed primarily to immobilization of Cd by enhanced pH-induced increases in negative charge. Conclusively, bottom ash could be good amendment to reduce Cd phytoavailability and extractability in Cd contaminated arable soil.