Solubility equilibria controlling solution phosphorus concentration in minesoils in Galicia, Spain

Solution P control through dissolution/precipitation equilibria was studied in coal mine soils in Galicia, NW Spain. Soil solution was obtained by a column displacement method and analysed for pH, Eh, electrical conductivity, and most common anions and cations. Ionic activities were calculated using the program SOLMINEQ and saturation indexes determined for several phosphate minerals. Strengite, variscite, fluorapatite or MnPO4.1.5H2O appeared to control phosphorus solubility, depending on Eh, pH and ionic strength conditions.