Forescasting chemical recovery from acidification

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Acid deposition is recognised as a major regional pollutant that has had negative impacts on sensitive terrestrial and aquatic ecosystems across eastern North America. Deposition of strong acids has accelerated base cation leaching from soils, and there is increasing concern that declining soil base saturation could result in a decline in forest health and productivity. Acidic deposition to base poor soils has resulted also in decreases in surface water pH and increases in the concentration of inorganic monomeric aluminium. A number of dynamic process-oriented models have been developed to investigate the response of surface waters to acid deposition. Dynamic acidification models can be readily used to provide an estimate of the future soil or surface water chemistry. As such, dynamic models are being increasingly applied on a regional basis to assess the benefits of reduced acid deposition and predict times to recovery. The proposed research program will contribute to the better prediction of the future chemical status of soils and waters under proposed future emission reductions. The research is innovative and novel in that predictive modelling tools will be developed to determine environmental risk from anthropogenic impacts. The research will principally focus on acid deposition, although the influence of land-use change and climate will be considered. The methodology will focus on linking or nesting existing biogeochemical and hydrological models. Novel statistical and modelling techniques will be utilised to quantify uncertainty in model predictions. The research program will focus principally on established long-term monitoring sites. Existing information for these sites will be supplemented with measurements of additional state variables with the objective to develop an integrated monitoring network for the application of computer models. This type of network approach is essential for synthesising the results of individual sites and for providing a coherent message to policy makers. It is anticipated that the results of the research program will provide the scientific underpinning for the development and implementation of future emission reduction polices.