Reversibility of acidification: soils and surface waters

Abstract

SynopsisAs empirical relationships between acidic deposition and its effects on soils and surface waters have become increasingly understood, the focus of attention has shifted to the reversal of acidification in response to decreased amounts of acidic deposition.Recent decreases in acidic deposition, in both North America and parts of Europe, have initiated the reversal of acidification and the recovery of impacted ecosystems. Reversal has also been investigated in large-scale experiments with whole ecosystems. Predictive models can account for much of this empirical and experimental data, at least at the catchment scale, over periods of years.Discrepancies between observed and predicted effects are attributable in part to the increasingly important role of nitrogen in soil and water acidification. ‘Nitrogen saturation’ threatens to offset the incipient recovery following decreases in SO2 emissions. Future climate change might further exacerbate the problem by increasing the rate of mineralisation of soil organic matter and releasing stored nitrogen.