A large array of biogeochemical processes control the cycling and fate of chemicals in soil systems; these include sorption, precipitation, and partitioning reactions that may retain chemicals in the soil matrix and render them unavailable for biological transformation. The release of retained chemicals from the soil matrix may occur gradually over decades or longer, exceeding practical timescales used for field or laboratory measurement, or conversely, remain immobilized. Also, the rate and extent of release will determine whether a chemical will reach environmentally relevant concentrations in soil porewater and groundwater. Challenges associated with predicting the long-term release of chemicals associated with the solid-phase in soil systems include the use of chemical extractions that may not accurately target the labile fraction of a retained chemical (i.e., inadvertent extraction of immobilized chemicals), non-linear rates of slow release over time, and variable rates of release under different hydrologic flow regimes (i.e., variable Darcy flux). Here, challenges associated with evaluating and predicting the long-term release, fate and transport of retained chemicals are discussed, with emphasis placed on the behavior of inorganic constituents. Case studies that highlight these challenges also illustrate the utility of models for evaluating the long-term behavior of chemicals retained in soil.

Challenges associated with predicting the release, fate, and transport of chemicals retained in soil

ACS Fall 2021

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