ACID LEACHING OF METALS FROM ENVIRONMENTAL PARTICLES - EXPRESSING RESULTS AS A CONCENTRATION WITHIN THE LEACHABLE FRACTION

The merits of expressing the results obtained following an acid extrac tion (EPA leaching method 3051) of environmental particles as the meta l concentration within the leachable fraction only were examined for s amples collected in a small agricultural watershed (southern Quebec, C anada). The concentration of Fe, Al, Cr, Ni, Cu, Zn, Cd, and Pb in sed iments, suspended solids, and soil was calculated using the leached ma ss instead of the total mass of the starting material to eliminate bia s introduced by the variable amount of nonreactive residual material. A mass balance calculation was performed on a sediment sample, and fou r different applications are given to illustrate the advantages of thi s method compared to the conventional way of reporting leach data. Aci d leaching methods will be used more extensively as leach information data for reference materials are published because they fulfill an imp ortant need, in particular for environmental monitoring programs. Howe ver, we believe that the approach reported here generates results that have more scientific meaning and usefulness. It is not affected by gr ain size or composition, it does not need data correction, it provides the true metal concentrations of the leachable fraction, and more imp ortantly, it offers a direct link between environmental particles of d ifferent nature (sediment, soil, and suspended solids).