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Significant uncertainty exists in the seasonal distribution of NH 3 emissions since the predominant sources are animal husbandry and fertilizer application. Previous studies that estimated bottom–up and top–down NH 3 emissions have provided the most comprehensive information available about the seasonality of NH 3 emissions. In this study, this bottom–up(More)
Unbiased symmetric metrics to quantify the relative bias and error between modeled and observed concentrations, based on the factor between measured and observed concentrations , are introduced and compared to conventionally employed metrics. Application to the evaluation of several data sets shows that the new metrics overcome concerns with the(More)
The temporal and spatial distributions of primary and secondary organic carbon aerosols (OC) over the continental US from 15 June–31 August 1999, were estimated by using observational OC and elemental carbon (EC) data from Interagency Monitoring of Protected Visual Environments (IMPROVE) and Southeastern Aerosol Research and Characterization project(More)
[1] The partitioning of total nitrate (TNO 3) and total ammonium (TNH 4) between gas and aerosol phases is studied with two thermodynamic equilibrium models, ISORROPIA and the aerosol inorganics model (AIM), and three data sets: high time resolution measurement data from the 1999 Atlanta Supersite Experiment (summer case) and the 2002 Pittsburgh Air Quality(More)
Biogeosciences Discussions This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Abstract Atmospheric ammonia (NH 3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH 3 contributes to surface water(More)
The University of California at Davis (UCD) aerosol module, an internally mixed, sectional aerosol model with dynamic mass transfer between the gas and particle phases, has been coupled to the Community Multiscale Air Quality (CMAQ) model. This paper describes the application of the CMAQ-UCD model to simulate air quality in Tampa, a large city with a(More)
[1] Significant uncertainty exists in the magnitude and variability of ammonia (NH 3) emissions. NH 3 emissions are needed as input for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH 3 emissions are estimated to come from agricultural nonpoint sources, which are suspected to have a strong seasonal pattern.(More)
Introduction Human population growth and urban, industrial , and agricultural expansion have profoundly im-pacted the quantities and composition of nitrogen (N)-containing pollutants released to the environment (Vitousek et al. 1997). In particular, human encroachment on the coastal zone has been accompanied by a precipitous rise in land-based N nutrients(More)
[1] Recent regulations require large-scale emission reductions of NO x and SO 2 in the eastern United States. These emission changes will alter the partitioning of ammonia between the gas and particle phases. Furthermore, ammonia emissions are expected to increase in the future. How will these changes impact the contribution of ammonia to inorganic(More)
The inorganic aerosol system of sulfate, nitrate, and ammonium can respond non-linearly to changes in precursor sulfur dioxide (SO 2) emissions. The potential increase in nitrate, when sulfate is reduced and the associated ammonia is released, can negate the sulfate mass reduction. Current regional-scale air quality models do not reproduce the present-day(More)