Spatial-temporal Analysis of Ammonia Emission Potentials in the Canadian Great Lakes

Abstract:

The ammonia emission potential (molar ratio of dissolved [NH4+] / [H+]) can be used to characterize the propensity of a water body to act as a source or sink of atmospheric ammonia. Using the Great Lakes Water Quality Monitoring and Surveillance dataset (2000 – present) published by Environment and Climate Change Canada, NH₃ emission potentials were calculated across the four Canadian Great Lakes. Significant spatial variability in the calculated emission potentials were revealed between the 4 lakes studied, as well as between different measurement sites on each lake, suggesting contributions from local sources and runoff from differing land-use types. Trends through time at individual sites were normalized and aggregated to evaluate the long-term trend in the emission potentials over the region. The magnitude of the calculated emission potentials suggests that ammonia in the Canadian Great Lakes participates in bidirectional exchange with the atmosphere, being both a source and a sink for atmospheric ammonia.