Irreversible Impacts of Micro-Pollutants On Natural Soils.

By integrating results available in the literature and from our own laboratory investigations, we argue that chemical pollution under specific conditions may lead to irreversible changes in soils. These changes may cause the formation of contemporary soils characterized by regimes different than those of natural soils. As a result the natural soils become parent materials for contemporary, Anthropocene soils. Unlike the natural soil genesis process that is measured in geological time scales, the chemically-induced formation of the contemporary soil occurs within a much shorter "life time" scale. In this presentation we discuss changes induced to the natural soil matrix and its properties at the molecular level following irreversible interactions with anthropogenic micro-pollutants. In particular, the effect of exposure of clays and humic substances to pollutants such as heavy metals, organic pesticides, persistent hydrocarbons, and engineered nanomaterials is examined, and micro-pollutant induced changes in the soil properties are explored. The contaminants induce structural modifications of clay minerals and organic matter, as observed by spectroscopic and electron microscopy analyses. Additional examples of changes in soil surface composition, as identified by chromatography and elemental analysis, with consequences for soil water transmission are discussed. Finally, the indirect implications of contamination on soil microbiological activity are shown. These examples support our claim that chemical contaminants are an additional factor in the formation of Anthropocene soils.