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Estimation of contributions of NO"2 and PAN to total atmospheric deposition of oxidized nitrogen across Eastern Canada [An article from: Atmospheric Environment]
Description
This digital document is a journal article from Atmospheric Environment, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.
Description:
Total oxidized nitrogen (N) dry deposition fluxes have been estimated for a 1-year period at seven eastern Canadian rural sites using observed air concentrations of nitric acid (HNO"3) and particle nitrate (NO"3^-), modelled air concentrations of nitrogen dioxide (NO"2) and peroxyacetyl nitrate (PAN), and modelled dry deposition velocities. The calculated annual dry N deposition fluxes range from 0.8 to 4kgNha^-^1 depending on location. HNO"3 is estimated to contribute at most 47-68% of the total, while conservative estimates for NO"2 indicate it contributes 12-36% of the total. Smaller contributions are from NO"3^- (12-20%) and PAN (3-16%). The NO"2 contribution to total N dry deposition is higher at locations closer to NO"x emission sources (e.g., over and downwind of urban areas) than that at remote locations. Available rural NO"2 measurements indicate that the modelled NO"2 concentrations (from which dry deposition of NO"2 is calculated) are low. With adjustments for this bias, the NO"2 contribution to total dry N flux can be higher than 50%, implying that NO"2 dry deposition is more important over a greater land area than previously believed and likely more important than HNO"3 over some areas. Combining our calculated dry deposition totals with monitored wet deposition produces an estimate of total annual N deposition ranging from 3 to 8kgNha^-^1, depending on location, with 25-60% contributed by dry deposition. If NO"2 and PAN dry deposition are excluded, then total N deposition is underestimated by 7-30%, depending on location, suggesting that previous estimates that have not included NO"2 have underestimated dry and total N deposition substantially.
Description:
Total oxidized nitrogen (N) dry deposition fluxes have been estimated for a 1-year period at seven eastern Canadian rural sites using observed air concentrations of nitric acid (HNO"3) and particle nitrate (NO"3^-), modelled air concentrations of nitrogen dioxide (NO"2) and peroxyacetyl nitrate (PAN), and modelled dry deposition velocities. The calculated annual dry N deposition fluxes range from 0.8 to 4kgNha^-^1 depending on location. HNO"3 is estimated to contribute at most 47-68% of the total, while conservative estimates for NO"2 indicate it contributes 12-36% of the total. Smaller contributions are from NO"3^- (12-20%) and PAN (3-16%). The NO"2 contribution to total N dry deposition is higher at locations closer to NO"x emission sources (e.g., over and downwind of urban areas) than that at remote locations. Available rural NO"2 measurements indicate that the modelled NO"2 concentrations (from which dry deposition of NO"2 is calculated) are low. With adjustments for this bias, the NO"2 contribution to total dry N flux can be higher than 50%, implying that NO"2 dry deposition is more important over a greater land area than previously believed and likely more important than HNO"3 over some areas. Combining our calculated dry deposition totals with monitored wet deposition produces an estimate of total annual N deposition ranging from 3 to 8kgNha^-^1, depending on location, with 25-60% contributed by dry deposition. If NO"2 and PAN dry deposition are excluded, then total N deposition is underestimated by 7-30%, depending on location, suggesting that previous estimates that have not included NO"2 have underestimated dry and total N deposition substantially.
