edu.ucar.opensky::articles:17191 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T14:59:32.731820 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7cr5vmf Observations of heterogeneous reactions between Asian pollution and mineral dust over the Eastern North Pacific during INTEX-B 2009-11-03T00:00:00Z publication https://n2t.org/ark:/85065/d7cr5vmf https://doi.org/10.5194/acp-9-8283-2009 McNaughton, C. author Clarke, A. author Kapustin, V. author Shinozuka, Y. author Howell, S. author Anderson, B. author Winstead, E. author Dibb, J. author Scheuer, E. author Cohen, R. author Wooldridge, P. author Perring, A. author Huey, L. author Kim, S. author Jimenez, J. author Dunlea, E. author DeCarlo, P. author Wennberg, P. author Crounse, J. author Weinheimer, Andrew author Flocke, Frank M. author UCAR/NCAR - Library publisher In-situ airborne measurements of trace gases, aerosol size distributions, chemistry and optical properties were conducted over Mexico and the Eastern North Pacific during MILAGRO and INTEX-B. Heterogeneous reactions between secondary aerosol precursor gases and mineral dust lead to sequestration of sulfur, nitrogen and chlorine in the supermicrometer particulate size range. Simultaneous measurements of aerosol size distributions and weak-acid soluble calcium result in an estimate of 11 wt% of CaCO₃ for Asian dust. During transport across the North Pacific, ~5–30% of the CaCO₃ is converted to CaSO₄ or Ca(NO₃)₂ with an additional ~4% consumed through reactions with HCl. The 1996 to 2008 record from the Mauna Loa Observatory confirm these findings, indicating that, on average, 19% of the CaCO₃ has reacted to form CaSO₄ and 7% has reacted to form Ca(NO3)2 and ~2% has reacted with HCl. In the nitrogen-oxide rich boundary layer near Mexico City up to 30% of the CaCO₃ has reacted to form Ca(NO₃)₂ while an additional 8% has reacted with HCl. These heterogeneous reactions can result in a ~3% increase in dust solubility which has an insignificant effect on their optical properties compared to their variability in-situ. However, competition between supermicrometer dust and submicrometer primary aerosol for condensing secondary aerosol species led to a 25% smaller number median diameter for the accumulation mode aerosol. A 10–25% reduction of accumulation mode number median diameter results in a 30–70% reduction in submicrometer light scattering at relative humidities in the 80–95% range. At 80% RH submicrometer light scattering is only reduced ~3% due to a higher mass fraction of hydrophobic refractory components in the dust-affected accumulation mode aerosol. Thus reducing the geometric mean diameter of the submicrometer aerosol has a much larger effect on aerosol optical properties than changes to the hygroscopic:hydrophobic mass fractions of the accumulation mode aerosol. In the presence of dust, nitric acid concentrations are reduced to <50% of total nitrate (nitric acid plus particulate nitrate). NOy as a fraction of total nitrogen (NOy plus particulate nitrate), is reduced from >85% to 60–80% in the presence of dust. These observations support previous model studies which predict irreversible sequestration of reactive nitrogen species through heterogeneous reactions with mineral dust during long-range transport. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. None eng geoscientificInformation