It has been long known that colloidal particles move in the subsurface in different environmental systems. For example, metal colloids can cause contamination, clay particles can move from one horizon to another in soils, and organic matter can create colloidal particles through agglomeration. We have investigated the movement of particles in the subsurface of two critical zone observatories and discovered that such particle movement can change the chemistry of rock at depth in a shale in humid temperate climates and can move significant fluxes of material out of weathering corestones in quartz diorite lithologies under rain forest conditions. In particular, loss of micron-sized K-containing particles in weathering rock at meters depth, well below the soil, has been documented in the Rose Hill shale of central Pennsylvania while sub-millimeter-sized particles have been observed to move in large voids in the subsurface in weathering quartz diorite in the Luquillo Mountains of Puerto Rico. The former particles are almost exclusively illite in composition. In contrast, the particles moving through the quartz diorite consist of weathered biotite, weathered plagioclase, and quartz. In both cases, the weathered rock material that remains after particle movement is chemically different from the original (unaltered) rock. Such subsurface particulate transport may be geomorphologically important during weathering reactions especially in shale lithologies (where particle sizes are small) and in granitic rocks in the tropics (where large voids can form between corestones).

Nanoparticle (and macroparticle) movement in the subsurface changes regolith chemistry

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.