scholarly journals Modes in the size distributions and neutralization extent of fog-processed ammonium salt aerosols observed at Canadian rural locations

2012 ◽  
Vol 12 (2) ◽  
pp. 5519-5550
Author(s):  
X. H. Yao ◽  
L. Zhang
Keyword(s):  
Ammonium Sulfate ◽  
Ammonium Salt ◽  
Inorganic Ions ◽  
Dominant Mode ◽  
Water Soluble ◽  
Size Distributions ◽  
Minor Mode ◽  
Water Soluble Inorganic Ions ◽  
Acidic Conditions ◽  
A Minor

Abstract. Among the 192 samples of size-segregated water-soluble inorganic ions collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at eight rural locations in Canada, ten samples were identified to have gone through fog processing. The supermicron particle modes of ammonium salt aerosols were found to be the fingerprint of fog processed aerosols. However, the patterns and the sizes of the supermicron modes varied with ambient temperature (T) and particle acidity and also differed between inland and coastal locations. Under T > 0 °C condition, fog-processed ammonium salt aerosols were completely neutralized and had a dominant mode at 1–2 μm and a minor mode at 5–10 μm if particles were in neutral condition, and ammonium sulfate was incompletely neutralized and only had a 1–2 μm mode if particles were in acidic conditions. Under T < 0 °C at the coastal site, fog-processed aerosols exhibited a bi-modal size distribution with a dominant mode of incompletely-neutralized ammonium sulfate at about 3 μm and a minor mode of completely-neutralized ammonium sulfate at 8–9 μm. Under T < 0 °C condition at the inland sites, fog-processed ammonium salt aerosols were sometimes completely neutralized and sometimes incompletely neutralized, and the size of the supermicron mode was in the range from 1 to 5 μm. Overall, fog-processed ammonium salt aerosols under T < 0 °C condition were generally distributed at larger size (e.g., 2–5 μm) than those under T > 0 °C condition (e.g., 1–2 μm).

scholarly journals Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

2008 ◽  
Vol 8 (4) ◽  
pp. 13801-13845 ◽  
Author(s):  
L. Zhang ◽  
R. Vet ◽  
A. Wiebe ◽  
C. Mihele ◽  
B. Sukloff ◽  
...  
Keyword(s):  
Warm Season ◽  
Inorganic Ions ◽  
Base Cations ◽  
Bimodal Distribution ◽  
Cold Season ◽  
Water Soluble ◽  
The Other ◽  
Size Distributions ◽  
Order Of Magnitude ◽  
Water Soluble Inorganic Ions

Abstract. Size-segregated water-soluble inorganic ions, including particulate sulphate (SO42-), nitrate (NO3-), ammonium (NH4+), chloride (Cl-) and base cations (K+, Na+, Mg2+, Ca2+), were measured using a Micro-Orifice Uniform Deposit Impactor (MOUDI) during fourteen short-term field campaigns at eight locations in both polluted and remote regions of eastern and central Canada. The size distributions of SO42- and NH4+ were unimodal, peaking at 0.3–0.6 μm in diameter, during most of the campaigns, although a bimodal distribution was found during one campaign and a trimodal distribution during another campaign made at a coastal site. The size distributions of NO3- were unimodal, peaking at 4.0–7.0 μm, during the warm-season campaigns and bimodal, with one peak at 0.3–0.6 μm and another at 4–7 μm, during the cold-season campaigns. A unimodal size distribution, peaking at 4–6 μm, was found for Cl-, Na+, Mg2+ and Ca2+ during approximately half of the campaigns and a bimodal distribution, with one peak at 2 μm and the other at 6 μm, was found during the rest of the campaigns. For K+, a bimodal distribution, with one peak at 0.3 μm and the other at 4 μm, was observed during most of the campaigns. The measured ion concentrations varied by one order of magnitude across the various sites. The air-mass origins and meteorological conditions both played important roles in formulating the observed geographical and seasonal patterns of these ion species concentration levels, size distributions and fine particle acidity.

scholarly journals Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

2008 ◽  
Vol 8 (23) ◽  
pp. 7133-7151 ◽  
Author(s):  
L. Zhang ◽  
R. Vet ◽  
A. Wiebe ◽  
C. Mihele ◽  
B. Sukloff ◽  
...  
Keyword(s):  
Inorganic Ions ◽  
Bimodal Distribution ◽  
Meteorological Conditions ◽  
Water Soluble ◽  
The Other ◽  
Submicron Particles ◽  
Emission Sources ◽  
Size Distributions ◽  
Nucleation Mode ◽  
Water Soluble Inorganic Ions

Abstract. Size-segregated water-soluble inorganic ions, including particulate sulphate (SO42-), nitrate (NO3-), ammonium (NH4+), chloride (Cl-), and base cations (K+, Na+, Mg2+, Ca2+), were measured using a Micro-Orifice Uniform Deposit Impactor (MOUDI) during fourteen short-term field campaigns at eight locations in both polluted and remote regions of eastern and central Canada. The size distributions of SO42- and NH4+ were unimodal, peaking at 0.3–0.6 µm in diameter, during most of the campaigns, although a bimodal distribution was found during one campaign and a trimodal distribution was found during another campaign made at a coastal site. SO42- peaked at slightly larger sizes in the cold seasons (0.5–0.6 µm) compared to the hot seasons (0.3–0.4 µm) due to the higher relative humidity in the cold seasons. The size distributions of NO3- were unimodal, peaking at 4.0–7.0 µm during the warm-season campaigns, and bimodal, with one peak at 0.3–0.6 µm and another at 4–7 µm during the cold-season campaigns. A unimodal size distribution, peaking at 4–6 µm, was found for Cl-, Na+, Mg2+, and Ca2+ during approximately half of the campaigns and a bimodal distribution, with one peak at 2 µm and the other at 6 µm, was found during the rest of the campaigns. For K+, a bimodal distribution, with one peak at 0.3 µm and the other at 4 µm, was observed during most of the campaigns. Seasonal contrasts in the size-distribution profiles suggest that emission sources and air mass origins were the major factors controlling the size distributions of the primary aerosols while meteorological conditions were more important for the secondary aerosols. The dependence of the particle acidity on the particle size from the nucleation mode to the accumulation mode was not consistent from site to site or from season to season. Particles in the accumulation mode were more acidic than those in the nucleation mode when submicron particles were in the state of strong acidity; however, when submicron particles were neutral or weakly acidic, particles in the nucleation mode could sometimes be more acidic. The inconsistency of the dependence of the particle acidity on the particle size should have been caused by the different emission sources of all the related species and the different meteorological conditions during the different campaigns. The results presented here at least partially explain the controversial phenomenon found in previous studies on this topic.

Water-soluble inorganic ions of size-differentiated atmospheric particles from a suburban site of Mexico City

2017 ◽  
Vol 75 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Telma Castro ◽  
Oscar Peralta ◽  
Dara Salcedo ◽  
José Santos ◽  
María I. Saavedra ◽  
...  
Keyword(s):  
Mexico City ◽  
Inorganic Ions ◽  
Atmospheric Particles ◽  
Water Soluble ◽  
Water Soluble Inorganic Ions ◽  
Suburban Site

scholarly journals The sensitivity of PM<sub>2.5</sub> acidity to meteorological parameters and chemical composition changes: 10-year records from six Canadian monitoring sites

2019 ◽  
Author(s):  
Ye Tao ◽  
Jennifer G. Murphy
Keyword(s):  
Chemical Composition ◽  
Meteorological Parameters ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Seasonal Cycles ◽  
Accuracy And Precision ◽  
Different Seasons ◽  
Water Soluble Inorganic Ions ◽  
Composition Changes

Abstract. Aerosol pH is difficult to measure directly but can be calculated if the chemical composition is known with sufficient accuracy and precision to calculate the aerosol water content and the H+ concentration through ion balance. In practical terms, simultaneous measurements of at least one semi-volatile constitute, e.g. NH3 or HNO3, are required to provide a constraint on the calculation of pH. Long-term records of aerosol pH are scarce due to the limited monitoring of NH3 in conjunction with PM2.5. In this study, 10-year (2007–2016) records of pH of PM2.5 at six eastern Canadian sites were calculated using the E-AIM II model with the input of gaseous NH3, gaseous HNO3 and major water-soluble inorganic ions in PM2.5 provided by Canada's National Air Pollution Surveillance (NAPS) Program. Clear seasonal cycles of aerosol pH were found with lower pH (~2) in summer and higher pH (~3) in winter consistently across all six sites, while the day-to-day variations of aerosol pH were higher in winter compared to summer. Tests of the sensitivity of aerosol pH to meteorological parameters demonstrate that the changes in ambient temperature largely drive the seasonal cycle of aerosol pH. The sensitivity of pH to chemical composition shows that pH has different responses to the changes in chemical composition in different seasons. During summertime, aerosol pH was mainly determined by temperature with limited impact from changes in NHx or sulfate concentrations. However, in wintertime, both meteorological parameters and chemical composition contribute to the variations in aerosol pH, resulting in the larger variation during wintertime. This study reveals that the sensitivity of aerosol pH to chemical composition is distinctly different under different meteorological conditions and needs to be carefully examined for any particular region.

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