Soil acidity status in polluted and non-polluted areas in southern Finland

From 359 study plots on coniferous forest soil in southern Finland, 232 humus and 359 mineral soil (top 5 cm) samples were taken in 1991 and analyzed for their cation exchange capacity, base saturation, pH, total S content (humus samples only), and extractable Al, Fe and Mn concentrations in order to assess the impact of acidic air pollution on soil acidity. The main sources of local air pollutants (SO2 and NOx) were from the capital region and an oil refinery. Although concentrations of S in the humus layer were 8% higher near the emission sources, it was concluded that air pollution has not resulted in a detectable increase in soil acidity. Mean values for humus layer pH (BaCl2), cation exchange capacity (CEC), base saturation, and extractable Al concentration for the overall study area were 2.9 (0.2), 310 (50) meq kg-1, 48 (12)% of CEC, and 530 (340) mg kg-1. The respective values for the mineral soil layer were 3.3 (0.3), 56 (19) meq kg-1, 13 (8)% of CEC, and 320 (130) mg kg-1. Standard deviations are given in parentheses. 24 refs, 2 figs, 5 tabs