Long-term trends in atmospheric reactive nitrogen across Canada: 1988-2007

► Atmospheric NO3−, pNH4+ and HNO3 significantly decreased across Canada (1988-2007). ► No trend in atmospheric NH4+ concentrations across Canada (1988-2007). ► Decreases in atmospheric reactive nitrogen follow NOx and SO2 emission reductions. ► Greatest decreases in reactive nitrogen concentrations in southern Ontario. ► Reduced NOx emissions are predicted to decrease environmental impacts of N deposition.