When Emission Reductions aren't Enough: Increasing Aluminium Levels in Rivers Recovering from Acidification

When Emission Reductions aren't Enough: Increasing Aluminium Levels in Rivers Recovering from Acidification

Dissolved aluminium in freshwaters, caused by chronic acidification of soils, is highly toxic in particular for salmon.  Given the documented recovery from acidification and decreasing aluminum concentration trends in rivers in Europe and the United States the aluminum problem was considered solved. Yet a recent study has shown the salmon populations on the East Coast of Canada are plummeting by 88-99% in the past ten years.  Here we make the first assessment of aluminum trends in a long-term database (1980-2015) in rivers in Nova Scotia and we find, surprisingly, that total aluminum levels have significantly increased in all monitored sites.  We propose a new model to address the mechanisms for the increased aluminum levels in Atlantic Canada, despite acid deposition reductions.