title: Simulating the long-term chemistry of an upland UK catchment: major solutes and acidification.
abstract: CHUM-AM was used to investigate changes in soil and water chemical variables in four moorland sub-catchments in Cumbria UK, to which non-marine S deposition has declined by 65% since the 1970s. The principal processes represented in the model comprise N and S uptake and release, water movements, the binding of cations by soil organic matter, chemical interactions in solution, and chemical weathering. CHUM-AM reproduced reasonably well the current soil pH and pools of N and S, and changes in streamwater chemistry over the period 1970-2000, notably decreases in the concentrations of alkaline earth cations and sulphate, and increases in pH. The model also predicts streamwater pH-Al relationships in agreement with observations. Predictive calculations suggest that constant atmospheric deposition of N at present rates will lead to N saturation and re-acidification, whereas a 50% reduction in N would stabilise soil and streamwater pH at about the present levels.
authors.affiliation: Centre for Ecology and Hydrology (Lancaster), Library Avenue, Bailrigg, Lancaster LA1 4AP, United Kingdom. et@ceh.ac.uk
authors.forename: E
authors.initials: E
authors.lastname: Tipping
authors.forename: A J
authors.initials: AJ
authors.lastname: Lawlor
authors.forename: S
authors.initials: S
authors.lastname: Lofts
mesh_terms: D000393:Air Pollutants; D002412:Cations; D003198:Computer Simulation; D004739:England; D004782:Environmental Health / Q000706:statistics & numerical data; D004784:Environmental Monitoring / Q000379:methods*; D005843:Geography; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D009584:Nitrogen; D013455:Sulfur; D014872:Water Movements; D014874:Water Pollutants, Chemical; D014887:Weather
chemical_list: D000393:Air Pollutants; D002412:Cations; D014874:Water Pollutants, Chemical; D013455:Sulfur; D009584:Nitrogen