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Effect of ambient NH"3 levels on PM"2"."5 composition in the Great Smoky Mountains National Park [An article from: Atmospheric Environment]
Book Details
PublisherElsevier
ISBN / ASINB000RR7VGC
ISBN-13978B000RR7VG1
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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:
Continuous measurements were made of gaseous NH"3, gaseous HNO"3, PM"2"."5 sulfate, aerosol mass, air temperature, and relative humidity (RH), and 24-h filter samples of PM"2"."5 aerosols were analyzed to determine the effects of ambient NH"3 levels on PM"2"."5 aerosol composition. These measurements were conducted from 2 to 15 August 2002, at Look Rock, TN, at an air monitoring station located on a mountain ridge (elevation ~800m MSL) on the southwestern edge of the Great Smoky Mountains National Park. A strong diurnal pattern was observed for gaseous NH"3 levels at this site with higher daytime and much lower NH"3 during the night hours. The diurnal variability of both gaseous NH"3 concentrations and RH suggests that conditions controlling aerosol nitrate formation and acidic aerosol neutralization are complex. The observations during this 2-week long sampling period showed that measurable NH"4NO"3 aerosol was not present under the ambient conditions encountered. However, modest perturbations from observed ambient conditions could have enabled NH"4NO"3 aerosol production. The extent of neutralization of sulfate aerosol collected on filters indicates that there was insufficient regional NH"3 to neutralize the acidic sulfate aerosols to the degree predicted from local NH"3 and RH conditions. Incomplete neutralization of acidic sulfate could also result if neutralization proceeds more slowly under field conditions compared to laboratory conditions or model predictions. Continuous measurements of aerosol ammonium and/or acidity are needed to determine if ammonia availability or kinetic limitations (or both) restrict neutralization of acidic sulfate aerosols, a key factor for modeling and exposure studies.
Description:
Continuous measurements were made of gaseous NH"3, gaseous HNO"3, PM"2"."5 sulfate, aerosol mass, air temperature, and relative humidity (RH), and 24-h filter samples of PM"2"."5 aerosols were analyzed to determine the effects of ambient NH"3 levels on PM"2"."5 aerosol composition. These measurements were conducted from 2 to 15 August 2002, at Look Rock, TN, at an air monitoring station located on a mountain ridge (elevation ~800m MSL) on the southwestern edge of the Great Smoky Mountains National Park. A strong diurnal pattern was observed for gaseous NH"3 levels at this site with higher daytime and much lower NH"3 during the night hours. The diurnal variability of both gaseous NH"3 concentrations and RH suggests that conditions controlling aerosol nitrate formation and acidic aerosol neutralization are complex. The observations during this 2-week long sampling period showed that measurable NH"4NO"3 aerosol was not present under the ambient conditions encountered. However, modest perturbations from observed ambient conditions could have enabled NH"4NO"3 aerosol production. The extent of neutralization of sulfate aerosol collected on filters indicates that there was insufficient regional NH"3 to neutralize the acidic sulfate aerosols to the degree predicted from local NH"3 and RH conditions. Incomplete neutralization of acidic sulfate could also result if neutralization proceeds more slowly under field conditions compared to laboratory conditions or model predictions. Continuous measurements of aerosol ammonium and/or acidity are needed to determine if ammonia availability or kinetic limitations (or both) restrict neutralization of acidic sulfate aerosols, a key factor for modeling and exposure studies.
