Reliability of nitrogen dioxide passive diffusion tubes for ambient measurement: in situ properties of the triethanolamine absorbent

Citation
C. Kirby et al., Reliability of nitrogen dioxide passive diffusion tubes for ambient measurement: in situ properties of the triethanolamine absorbent, J ENVIR MON, 2(4), 2000, pp. 307-312
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF ENVIRONMENTAL MONITORING
ISSN journal
1464-0325 → ACNP
Volume
2
Issue
4
Year of publication
2000
Pages
307 - 312
Database
ISI
SICI code
1464-0325(2000)2:4<307:RONDPD>2.0.ZU;2-O
Abstract
Factors concerning NO2 uptake by the absorbent triethanolamine (TEA) in NO2 diffusion tubes are examined. Although the nominal freezing point of TEA i s 17.9-21.2 degrees C, we show that, for a range of aqueous TEA solutions ( 0-20% H2O), no freezing occurs even at -10 degrees C. Therefore NO2 collect ion efficiency is unlikely to be impaired by low temperature exposure. The recovery of TEA from the meshes of exposed samplers is determined as simila r to 98%, even after 42 days, showing that the stability in situ of TEA is unaffected by long-term exposure. A model of a diffusion tube sampling arra y for simultaneous exposures, with a 0.1 m sampler spacing, shows that NO2 uptake by individual samplers is not affected by the presence of neighbouri ng tubes in the array. This is confirmed by sampler precision at two Cambri dge sites. Four sampler preparation methods are compared for differences in NO2 uptake of exposed samplers. All methods employ TEA as absorbent, trans ferred by either dipping meshes in a TEA-acetone solution or pipetting aliq uots of a TEA-H2O solution onto the meshes. For samplers prepared by three of the methods, no difference in NO2 uptake is found, but for samplers prep ared using a 50% v/v TEA-H2O solution, a mean reduction of 18% is found. St udent's t-tests show that the difference is highly significant (P less than or equal to 0.001). Reasons for the difference are discussed.