T. A. Clair, N. Pelletier, S. Bittman, A. Leip, P. Arp, M. D. Moran, I. Dennis, D. Niemi, S. Sterling, C. F. Drury, J. Yang
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Global Biogeochemical Cycles 28, 1343–1357

This paper uses a budget approach to compile information on excess reactive nitrogen (Nr) flows for Canada. Canada is a net receptor of Nr air pollution from the United States, receiving approximately 20% of the Nr leaving the U.S. airshed. Overall, terrestrial natural ecosystems as well as the atmosphere were found to be in balance between Nr inputs and outputs when all N reactive and nonreactive fluxes are included. However, when only reactive forms are considered, almost 50% of N entering the Canadian atmosphere is assumed to be lost to the oceans or to unmeasured dry deposition. Data suggest that denitrification in soils and aquatic systems is larger than what models predict.