Gas-particle distribution, neutralization and size of sulfate and nitrate in the southwestern desert aerosol

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:197323

Turpin, B J; Saxena, P; McMurry, P H; Allen, G

Observations made on 47 days during summer 1992 in Meadview, Arizona were used to characterize inorganic ionic and gaseous concentrations near the Grand Canyon. A sampler equipped with denuders to remove alkaline and acidic gases measured gaseous ammonia, sulfur dioxide and nitric acid and fine particulate ammonium, total extractable acidity (TEA), sulfate and nitrate. In addition, a set of impactors measured size-resolved sulfate, nitrate and ammonium. The medium 6-hr average fine particulate sulfate concentration was 1.6 {micro}g/m{sup 3} with about two-thirds of the values below 2. Sulfur dioxide concentrations were comparable to sulfate concentrations. Two-thirds of the particulate-phase nitrate concentrations were less than 0.25 {micro}g/m{sup 3}, and the maximum value was 0.5. However, substantial nitric acid was present in the gas phase (medium concentration of 2 {micro}g/m{sup 3}). In contrast to prior conclusions that sulfate in this region is generally completely neutralized by ammonia, the median ammonium to sulfate ratio in this study was 1.4. Furthermore, sulfate and ammonium concentrations were highly correlated. With one exception sulfate mass median diameters were 0.15--0.27 {micro}m. More than half of the TEA observations were less than 8 nanomoles/m{sup 3}, and the maximum value was 30.

• OSTI ID: 197323
• Report Number(s): CONF-9405167--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
AIR POLLUTION MONITORING
AMMONIA
AMMONIUM COMPOUNDS
ARID LANDS
ARIZONA
ECOLOGICAL CONCENTRATION
NITRATES
NITRIC ACID
PARTICLE SIZE
SULFATES
SULFUR DIOXIDE