Environmental change in aquatic systems; Impacts of air pollution and climate change on the ecosystems of upland, arctic and alpine lakes and streams using hydrochemical models, stable isotope techniques and palaeolimnology; Multiple pressures on aquatic systems in Southern Africa, including acid mine drainage, eutrophication and acid deposition; Biogeochemical studies of nitrogen and carbon (deposition, soils, vegetation, waters, trace gases); Modelling critical loads for fresh waters; Aquatic monitoring of air pollution and climate change impacts; Nitrogen stable isotope tracer experiments and natural abundance studies; Acidification and eutrophication caused by nitrogen deposition; Acidification and palaeolimnology in remote mountain lakes.