New frontiers in elucidating the kinetics and mechanisms of metal and oxyanion sorption at the soil mineral/water interface

An understanding of the kinetics and mechanisms of metal and oxyanion sorpt ion on soil minerals and soils is fundamental in assessing the speciation, mobility, and bioavailability of metals and oxyanions in natural systems. T raditionally, sorption has been studied using macroscopic equilibrium appro aches. It is now well recognized that the kinetics of metal and oxyanion so rption/release must be understood if accurate predictions are to be made ab out metal/oxyanion fate/mobility and soil remediation. This paper covers as pects of kinetic models acid their applicability to heterogenous systems an d the rates and mechanisms of rapid and slow metal and oxyanion sorption re actions. With some metals (e.g. Co, Ni, Zn) residence lime affects the rate of metal release with other metals such as Pb, there is little effect of r esidence time, To definitively understand the dynamics of sorption mechanis ms, one must employ molecular scale approaches. Over the past decade, with the advent of cutting-edge molecular-scale in-situ analytical techniques, s ignificant advances have occurred in determining the speciation and sorptio n/release mechanisms of and oxyanions in the subsurface environment. These in environmental science have major impacts on: soil frontiers on strategie s, development of predictive models, and contaminant/bioavailability assess ments. Frontiers in metal sorption at the soil mineral/water interface are highlighted in this review.