Recovery from episodic acidification delayed by drought and high sea salt deposition

摘要

For the prediction of episodic acidification large uncertainties areconnected to climatic variability and its effect on drought conditions andsea-salt episodes. In this study data on 342 hydrological episodes in 25Swedish streams, sampled over 10 years, have been analyzed using a recentlydeveloped episode model. The results demonstrate that drought is the mostimportant factor modulating the magnitude of the anthropogenic influence onpH and ANC during episodes. These modulating effects are especiallypronounced in southern and central Sweden, where the historically high aciddeposition has resulted in significant S pools in catchment soils. Theresults also suggest that the effects of episodic acidification are becomingless severe in many streams, but this amelioration is less clear in coastalstreams subject to high levels of sea-salt deposition. Concurrently with theamelioration of the effects of episodic acidification, regional climatemodels predict that temperatures will increase in Sweden during the comingdecades, accompanied by reductions in summer precipitation and more frequentstorms during fall and winter in large areas of the country. If thesepredictions are realized delays in streams' recovery from episodicacidification events can be expected.