A model to evaluate a soil’s bulk solid phase resistance to extraction analysis

Measurements of soil contamination are essential to environmental models that function at many scales. For old contamination soils, contamination measurements can be significant sources of error. Often, soils that have been contaminated for a long time sequester contaminants deep within aggregates where they are difficult to measure and difficult to remove. Heavy metal sequestering is very common in the soils of Cleveland, Ohio, but may be found in many of the world’s industrial areas. Sequestered contamination can be difficult to measure with conventional laboratory extractions because contact times may not be sufficient to allow removal of this fraction of the contamination. This manuscript presents a model (SAM&BSD) designed to examine the degree to which liquid phase diffusion within the internal pore structure of soil aggregates and/or solid state diffusion within aggregates resist the release of contaminants during laboratory extractions. The results may be used to improve the accuracy of soil contamination measurements, or to assess the reliability of values measured by standard extraction techniques. A companion model (AGGANCi) may be used to determine if the extraction acidity and duration are sufficient to overcome the internal acid neutralization capacity of the soil and allow transport to be dominated by diffusion. The goal of both analysis tools is to improve the quality of data used in environmental models that address the impacts of soil contamination.