Nickel partitioning in acid soils at low moisture content

Nickel sorption at moisture content corresponding to 1.2 times field moisture capacity (soil water potential 7.84 J kg− 1) was studied in 10 non-calcareous soils from different regions of the European Union with pH 3.6 to 6.7 and soil organic carbon (SOC) content 0.25 to 33.1%. Binding of Ni resulted in the displacement of Ca, Mg, and Na into soil solution and decrease in soil solution pH. The amount of cations released was from 0.36 to 1.00 times the amount of Ni sorbed (molc: molc). The ability of Windermere Humic Aqueous Model VI (WHAM VI) to predict Ni concentration in soil solutions was evaluated. In the soils with SOC content > 1% (8 soils), Ni concentration in soil solution calculated with WHAM VI was close to the measured concentration with the root mean squared error of the predicted log [Ni] (RMSElog [Ni]) = 0.25 while for the whole set of 10 soils RMSElog [Ni] = 0.44.