The Role of Organic Matter in the Mobility of Metals in Contaminated Catchments

Abstract

We have applied a concept framework for scale-specific processes in order to characterize the role of the organic matter in the mobility of metals. At very small scale, we identified roles by immobilization of metals (immobilization in litter, immobilization in soil aggregates, dissolved organic carbon chelates in fine pores), by mobilization of metals (organochemical weathering, soluble chelates, organocolloids, free enzymatic degradation of immobile organic carbon), and by supporting the mobilization or immobilization of metals by other compartments at the same scale (energy source for microorganisms, buffering of soil solution). These roles have effects on the fluxes of metals and can be characterized at a larger scale: transfer of metals to plants and to lower soil layers by hydrological fluxes. At scales ranging from contaminated sites to watershed, we identified the same roles as above, that however up-scaled differently as a function of the site type (contaminated soil in the slope area, mining dump or tailing dam, contaminated soil in the floodplain, contaminated stream ecotone), with corresponding effects on the fluxes of metals subsoil and groundwater to surface water, on the transfer to surface water by lateral types of flows, transfer to floodplains, and volatilization (also differentiated as a function of the type of site). The literature is comprehensively screened for each case. The extent and consistency of the available scientific knowledge decrease with the increase of the system scale and complexity. Based on this analysis, multiscale biogeochemical and ecotoxicological research directions are suggested.KeywordsOrganic MatterSewage SludgeFulvic AcidAcid Mine DrainageDissolve Organic Carbon ConcentrationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.