ARTIFACTS IN SORPTION EXPERIMENTS WITH TRACE-METALS

Laboratory studies of trace metal sorption by natural and synthetic particles are frequently unrealistic due to the concentrations of sorbate and sorbent being orders of magnitude above those found in nature. Undertaking such experiments under more realistic conditions requires careful quality assessment of the methods used. A series of systematic sorption experiments, based on filtration and measurement by atomic absorption spectrometry (AAS), showed that metal losses to container walls and filters were unavoidable in solutions which emulate freshwaters. These errors can be corrected by using multiple control solutions which estimate metal losses at the appropriate pH and solution concentrations. Without such corrections, sorption can be appreciably overestimated.