Chemical and Physical Properties of Reconstructed Mineral Sand Mine Soils in Southeastern Virginia

Abstract

The mining of heavy mineral sands will result in the disturbance of more than 2500 ha of prime farmland in Virginia and North Carolina during the next 20 years. The physical and chemical properties of the mine soils that result from the mining and reclamation process were studied in a replicated small-plot experiment on pilot mining pits. Separation of sandy tailings from slimes (silt and clay) in dewatering pits led to significant lateral and vertical differentiation in soil texture, density, and seasonal wetness across the final reclamation surface. There were significant differences in chemical and physical properties between the mine soils and the adjacent undisturbed soil. There were also differences between the two mining pits along with significant variability within the mine pits. This variability was directly related to the mining and reclamation methods used. The variability was expressed as differences in texture, effective cation exchange capacity, bulk density, water-holding capacity, and associated chemical properties. The presence of a high bulk density and low water holding in the subsoils of the mined areas would prevent plants from obtaining sufficient water through a combination of mechanical impedance and low water-holding capacity. Compaction of the surface and subsurface also limited rooting in nonsandy reclaimed areas. Freshly deposited materials were low in pH (≤5.2) and plant-available nutrients because of the highly weathered nature of the original deposit and the mineral separation processes.