In-situ Soil Solution Extraction with Polyacrylonitrile Hollow-Fibers

Hollow-fiber samplers permit the non-destructive extraction of the soil solution from the soil matrix. Samplers constructed from polyacrylonitrile filter elements were successfully used to extract solution from a range of soil types. Preliminary testing showed that the filter elements did not retain any of the major anions or cations present in soil solution. Inorganic ions capable of specific adsorption (PO₄ and Cu) were not retained, but phytate concentration was reduced by passage through the filter. Comparison with centrifuge drainage extraction showed that soil solution obtained from hollow-fiber samplers had a higher pH, as a result of CO₂ degassing, and lower elemental concentrations. It was concluded that the hollow-fiber samplers were preferentially extracting solution from the larger pores, and that this solution may better represent that extracted by plants.