Grant: Discovery Grants Program - Individual

Increased release of aluminium (Al) from soils to freshwaters is one of the most toxic impacts of chronic terrestrial acidification, and has been responsible for the extirpation of native salmon populations in Europe and the USA in the 1980s. The Al problem was widely considered solved following the success of acid emission legislation in the 1990s; the harmful effects of freshwater acidification were shown to be reversible and Al levels in freshwaters decreased. However, our laboratory has discovered that there are widespread increases in Al levels in lakes and rivers since 2000 across eastern North America and Europe, with hotspots in southeastern Sweden and NS. Our identification of this unpredicted change in freshwater chemistry has illuminated an urgent international issue, not only for salmon populations that currently are declining to near extirpation levels, but forest ecosystem productivity, biodiversity, water treatment and, potentially, human health. My research programme will use a combination of database and field studies to assess the extent and causes of Al trends, and hence risk from acidification, in over 500 field sites across North America and Europe. We will develop new predictive approaches for determining which catchments are likely to have high and increasing Al levels. Key mechanisms will be evaluated with respect to drivers of Al both on an inter-annual, seasonal and event scales. We will employ field and statistical analysis of long-term stream chemistry databases to test our hypotheses on the causes of increasing Al levels and to develop new theoretical models to explain this unexpected trend. We will also map the extent of the toxic form of Al, based on field experiments across NS to determine where and in what conditions the lakes and river chemistry exceeds toxic thresholds for Al. Finally, we will test the efficacy of methods of delivery of calcium and alkalinity to forest soils through enhanced weathering: applying crushed rock onto forest soils. evaluating the role of different types of rock application, and the ability of this method to reduce Al levels. Since calcium limitations are a widespread problem across eastern North America and Europe, and catchments in NS are an excellent model system for testing/monitoring strategies for Al mitigation, contributions from my research programme will have international impact. My research program will support the training of several HQP including 2 doctoral, 2 masters and 4 undergraduate students.