UPTAKEOF Cd, Cu, Ni AND Zn BY THE WATER HYACINTH, EICHHORNIA CRASSIPES (MART.) SOLMS FROM PULVERISED FUEL ASH (PFA) LEACHATES AND SLURRIES KEVIN B. CORDES 1,∗ , ARADHANA MEHRA 1 , MARGARET E. FARAGO 2 and DIPAK K. BANERJEE 3 1 School of Environmental and Applied Science, University of Derby, Derby, Derbyshire, England; 2 Environmental Geochemistry Research Group, The T. H. Huxley School of The Environment, Earth Science and Engineering, Imperial College of Science, Technology and Medicine, London, England; 3 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India ( ∗ author for correspondence: e-mail: k.b.cordes@derby.ac.uk; fax: +44 1332 622 747) Abstract. The main solid waste product from coal-fired power stations is pulverised fuel ash (PFA), which can be enriched in toxic elements. Disposal of PFA by dry (in landfills) or wet (by slurrying) disposal methods can release these elements into the environment. Thereafter, the contaminants can be taken up by biota such as Eichhornia crassipes, a common aquatic plant, which has the ability to accumulate elements from water. This study investigates the uptake of Cd, Cu, Ni and Zn by E. cras- sipes grown in leachates and slurries prepared from two different PFA samples. PFA samples were obtained from Indraprastha Power Station (IPP Stn.) in New Delhi, India and the Ratcliffe-on-Soar Power Station in the UK. E. crassipes grown in PFA leachates and slurries at 1:5 and 1:50 solid:liquid (PFA:deionised water) ratios show that the plant has a very high accumulation capacity for Cd, Cu, Ni and Zn from both leachates and slurries and the uptake of these metals is stronger in the roots than in the tops of the plant. Metal accumulation, as shown by the accumulation factor (AF) values, is higher from both leachates and slurries for plants grown in the 1:50 (PFA:DIW) ratios than in the 1:5 ratios, initial metal concentrations being higher in the 1:5 ratios than in the 1:50 ratios. Lower metal accumulation in the plants grown in slurries than in leachates is related to the high turbidity of growth medium in slurries resulting in ash particles adhering to the root surfaces thus reducing the surface area of metal absorption. Eichhornia plants are able to reduce the pH of all leachates, especially the highly alkaline Ratcliffe leachates to near neutral conditions. Accumulation of Cd and Zn by the plant is higher from the lower pH IPP leachates than the Ratcliffe leachates, indicating that these metals are more soluble and bioavailable in the acidic medium. However, accumulation of Cu and Ni is independent of the pH of the leachates, indicating that other factors, such as metal species, presence of complexing agents in the growth solutions, and effects of competing metal ions may be contributory factors towards the metal uptake and accumulation by the plant. Key words: accumulation factors (AF), Eichhornia crassipes, leachates, Power Stations, pulverised fuel ash (PFA), slurries 1. Introduction Globally, coal is a major fossil fuel resource which provides the majority of en- ergy consumption for the production of electricity. The use of coal is increasing in countries like China and India whilst decreasing in Britain (IEA, 1992, 1993; DTI, 1994). The main product of coal combustion is Pulverised Fuel Ash (PFA), a fine powdery aluminosilicate glass material (70–80%) containing 1–4% varying oxides Environmental Geochemistry and Health 22: 297–316, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.