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Soil organic C (SOC) content is one of the most dynamic of soil properties. In this study, we examined the effects of land use change on SOC pools for a single soil series and developed a mapping approach to relate SOC dynamics to land use change. Six paired sites, consisting of adjacent agricultural field and forest within a single delineation, were sampled and the SOC pools determined. The average forest SOC pool (157 Mg ha−1) was significantly higher (P < 0.05) than the field pool (103 Mg ha−1), supporting the importance of land use on SOC pools. We propose the development of a SOC phase based on land use to map such differences. Master O and A horizon data should be used to establish SOC phases. Data can be obtained from existing soil surveys, updates, or C accounting activities. Land use classes can be identified with digital imagery and SOC phases can be assigned to all mapping units. Mapping units sampled for C accounting can be resampled to detect patterns and rates of change. This approach provides a robust data set to effectively map and model SOC pools and change across the landscape.

The mobilization and transport of per-and polyfluoroalkyl substances (PFASs) via surface runoff (runoff) from aqueous film-forming foam (AFFF)-contaminated soils during rainfall, flooding, or irrigation has not been thoroughly evaluated, and the effectiveness of carbonaceous sorbents in limiting PFASs in runoff is similarly unquantified. Here, laboratory-scale rainfall simulations evaluate PFAS losses in runoff and in leaching to groundwater (leachate) from AFFF-contaminated soils varying in texture, PFAS composition and concentration, and remediation treatment. Leaching dominated PFAS losses in soils with a concentration of ∑PFAS = 0.2−2 mg/kg. However, with higher soil PFAS concentrations (∑PFAS = 31 mg/kg), leachate volumes were negligible and runoff dominated losses. The concentration and variety of PFASs were far greater in leachates regardless of the initial concentrations in soil. Losses of PFASs were dependent on the C-chain length for leachates and more on the initial concentration in soil for runoff. Suspended materials did not meaningfully contribute to runoff losses. While concentrations of most PFASs declined significantly after the first rainfall event, desorption and transport in both runoff and leachates persisted over several rainfall events. Finally, results showed that sorption to AC mostly occurred during, not prior to, rainfall events and that 1% w/w AC substantially reduced losses in runoff and leachates from all soils.

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