Characterization and Risk Evaluation of Tea Industry Coal Ash for Environmental Suitability

Overload of coal ash (CA) generated from several coal fired plants poses acute problems of disposal and contamination of soil and water resources. Since CA generated from tea factories has not yet been characterized from environmental viewpoints, we attempted to critically characterize the agro-ecological compatibility of CA samples (CA1, CA2, CA3, and CA4) collected from four distantly located tea factories. Among these samples, we found CA3 and CA4 to have low pH and high metal content. Accordingly, we restricted our study to predict the solubility pattern of non-metal and metal ions in CAs by adopting a geochemical model (Visual MINTEQ). Various fractions of metals like Fe, Mn, Cu, Zn, Cr, Ni, and Pb were studied to figure out the mobility pattern of metals in the environment. The results clearly indicate that tea industry derived CA substantially differs from thermal power plant CA as regards several physico-chemical properties, for example, sandy texture, low pH and high nutrient content. Risk evaluation of human exposure to trace elements and the metal fractionation study led us to conclude that CA1 and CA2 are highly compatible with agricultural use.