A model to evaluate internal acid neutralization resistance to soil extraction

Soils aggregates that have been contaminated for a long time often sequester contaminants deep within their internal pore structure. This form of heavy metal sequestering is common in the brownfield soils of Cleveland, Ohio, but may be found in the soils of many of the world's industrial areas. Sequestered contamination can be difficult to analyze with conventional extraction methods because the extractant strength and extraction contact time may not be sufficient to release this portion of the contamination. The model AGGANCi may be used to determine if extractant strength and contact time are sufficient to overcome the internal acid neutralizing capacity of soil aggregates, and mobilize sequestered contaminants. A companion model (SAM&BSD) may then be used to determine if there is sufficient time for the mobilized contaminant to migrate out into the bulk extraction liquid where concentrations are measured. Both AGGANCi and SAM&BSD are formulated to examine contaminant transport at the soil aggregate scale, but both are intended to help improve the quality of data used in models applied at much larger scales to evaluate the environmental impacts of heavy metal contamination.