The paper by a team led by Professor David Fowler of the Centre for Ecology and Hydrology is about to be published in Environmental Pollution. It examines trends in acid deposition since 1986 when international protocols began to reduce industrial emissions of acidic sulphur and nitrogen oxides.
SO2 emissions in the UK and the EU declined by 71% and 72% respectively, between 1986 and 2001. All regions of the UK now show significant declines in sulphur deposition, the scientists found, but they note that the declines were relatively small in high rainfall areas of the West Country, Wales, the Pennines and Scotland.
While land-based sources of SO2 have declined, "emissions from shipping have increased and are now a significant contributor to sulphur deposition in the UK", the scientists conclude.
As emissions have declined, acidity levels in rain have also fallen more slowly than non-rainfall dry deposition. Therefore dry areas of eastern Britain have benefited more than the wetter areas which contain the sites most sensitive to acidification, such as poorly buffered lakes and rivers in Wales and south-west Scotland.
Emissions of nitrogen oxides in the UK and the EU have declined by 35% and 25%, respectively, but declines in nitrogen deposition are only apparent in the east where there has been a statistically significant 20% fall. Trends in the wetter areas are not clear.