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Investigation of water vapor effects on the detection of nitric acid vapor with the tungstic acid technique

Thesis/Dissertation ·
OSTI ID:6532107

An automated tungstic acid technique (TAT) has been successfully used to measure gaseous HNO/sub 3/ in the presence of water vapor. The TAT is based on the diffusion of gaseous HNO/sub 3/ to the interior walls of a tube coated with tungsten VI oxide (WEO/sub 3/), where it is selectively chemisorbed. The collected HNO/sub 3/ sample is thermally desorbed from the WO/sub 3/ surface, as NO, and measured by a chemiluminescent oxides of nitrogen analyzer. The integrated analyzer response is directly proportional to the nitric acid collected. This study emphasizes the effect of water vapor as a potential interferent for HNO/sub 3/ collection with the TAT system. The effect of water vapor (<78% RH) on the collection efficiency for HNO/sub 3/ with the tungstic acid technique is negligible at 25/sup 0/C, but is significant only at elevated sampling temperatures. This threshold effect is further substantiated and eliminated when a modified sampling collection system was designed with coolant capabilities. The new design has been tested to sub-part-per billion levels with minimal loss of gaseous HNO/sub 3/ signal, thereby increasing sensitivity to atmospheric HNO/sub 3/ concentrations and maintaining the gas/aerosol sample integrity.

Research Organization:
Virginia Polytechnic Inst. and State Univ., Blacksburg (USA)
OSTI ID:
6532107
Country of Publication:
United States
Language:
English

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Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring &amp; Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
AEROSOL MONITORING
AIR POLLUTION
AIR POLLUTION MONITORING
AIR SAMPLERS
CHALCOGENIDES
CHEMILUMINESCENCE
DESIGN
DIFFUSION
ECOLOGICAL CONCENTRATION
EQUIPMENT
FLUIDS
GASES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
LUMINESCENCE
MONITORING
NITRIC ACID
OXIDES
OXYGEN COMPOUNDS
POLLUTION
REFRACTORY METAL COMPOUNDS
SAMPLERS
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
TUNGSTEN OXIDES
VAPORS
WATER VAPOR