POTENTIAL UTILIZATION OF COFFEE GROUND MATERIAL AS CADMIUM AND ZINC STABILIZING AMENDMENTS : A CASE STUDY OF MAE TAO, TAK, THAILAND

Abstract

The present research studied the potential utilization of untreated coffee ground (UCG) and carbonized coffee ground (CCG) as Cd and Zn stabilizing amendments in Cd contaminated soil collected from Mae Sot, Tak. Soil was determined with the average Cd and Zn concentrations of 47.2 and 1,660 mg kg-1, respectively. After preparation, UCG and CCG was separately mixed into the contaminated soil with the mixing ratio of 2.5%, 5%, 10% and 20% (w/w). All amended soils were incubated for a total of eight weeks. At the end of incubation period, BCR sequential extraction, DTPA extraction, and plant toxicity test were conducted in order to assess the mobility, plant availability, and toxicity of Cd and Zn in amended soils. The results revealed that the addition of UCG and CCG to contaminated soil resulted in the increase in soil nutrients and OM concentrations. In terms of Cd and Zn distribution, the exchangeable and reducible Cd were found to be decreased with the increasing mixing ratio of UCG. Similar results of Cd and Zn fractionations were observed in all mixing ratio of both UCG and CCG amended soils. In addition, the major Cd fractions during the whole aging process were exchangeable and reducible fractions. Whereas, Zn were mainly found in the forms of reducible and oxidizable fractions. In term of plant availability, Cd was found to be decreased by an average of 1.98% and 2.80% in UCG and CCG amended soil, respectively. At the same time, an increase in Zn plant availability was found in both types of amended soils. The results of phytotoxicity on rice germination, an increase in CCG mixing ratio could improve the possibilities of seed germination as well as root growth. The overall findings indicated that CCG can be considered as Cd immobilizing amendment to the contaminated soil.