Nitrogen Oxides Emissions, Chemistry, Deposition, and Export Over the Northeast United States During the WINTER Aircraft Campaign

[摘要] We examine the distribution and fate of nitrogen oxides (NOx) in the lower 36 troposphere over the Northeast United States (NE US) using aircraft observations from the 37 Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign in February-March 2015, as well as the GEOS-Chem chemical transport model and concurrent ground-based observations. We find that the National Emission Inventory (NEI) from the US Environmental Protection Agency (EPA) is consistent with WINTER observations of total reactive nitrogen (TNOy) to within 10% on average, in contrast to the significant overestimate reported in past studies under warmer conditions. Updates to the dry deposition scheme and dinitrogen pentoxide (N2O5) reactive uptake probability, ɣ(N2O5), result in an improved simulation of gas-phase nitric acid (HNO3) and submicron particulate nitrate (pNO3⁻), reducing he longstanding factor of 2-3 overestimate in wintertime HNO3+pNO3⁻ to a 50% positive bias. We find a NOx lifetime against chemical loss and deposition of 22 hours in the lower troposphere over the NE US. Chemical loss of NOx is dominated by N2O5 hydrolysis (58% of loss) and reaction with OH (33%), while 7% of NOx leads to the production of organic nitrates. Wet and dry deposition account for 55% and 45% of TNOy deposition over land, respectively. We estimate that 42% of the NOx emitted is exported from the NE US boundary layer during winter, mostly in the form of HNO3+pNO3⁻ (40%) and NOx (38%).

[发布日期] 2018-11-05

[学科分类] 污染

[关键词] DEPOSITION;NITROGEN OXIDES;LOSSES;NITRIC ACID;REACTIVITY;WINTER;TROPOSPHERE;UNITED STATES