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Development of a NO2 scrubber for accurate sampling of ambient levels of terpenes
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2002 (English)In: Atmospheric Environment, ISSN 1352-2310, Vol. 36, no 9, 1443-1452 p.Article in journal (Refereed) Published
Abstract [en]

The result of pumping air containing 56 ppb NO2 through a terpene-spiked adsorbent (90–130 ng, 90–100 ml min−1), Tenax TA, for 20 min (1.8–2.0 l) was that 8% of α-pinene, 7% of β-pinene, 21% of Δ3-carene and 5% of limonene were oxidised. In similar experiments with air containing 56 ppb O3, 3% of α-pinene, 4% of β-pinene, 10% of Δ3-carene and 38% of limonene were oxidised. Sampling a mixture of a terpene and NO2 using Tenax TA can give unwanted overestimation of the amount of reaction products from the terpene–NO2 reaction or underestimation of the original terpene levels. A scrubber was needed to reduce the problems caused by interfering reactions on the adsorbent of NO2 and to reduce discrimination of reactive compounds due to their relatively fast decay on the adsorbent. Several chemicals have been tested for their ability of removing NO2 and our objective was to develop a well functioning, reusable, easy to handle, easy manufactured NO2 scrubber. The result of the experiments was a scrubber consisting of two glass fibre filters coated with Na2SO3 assembled in a dust collector. The recovery of the terpenes through the scrubber varied between 75% and 97% at 15–75% relative humidity, and the scrubber is a one-use scrubber due to memory effects. The Na2SO3 scrubber could be stored in room air for at least one month without loosing the capacity of removing NO2.

Place, publisher, year, edition, pages
2002. Vol. 36, no 9, 1443-1452 p.
Keyword [en]
Nitrogen dioxide; Scrubber; Tenax TA; Terpene; Sodium sulphite
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:umu:diva-8842DOI: doi:10.1016/S1352-2310(01)00581-7OAI: oai:DiVA.org:umu-8842DiVA: diva2:148513
Available from: 2008-02-18 Created: 2008-02-18 Last updated: 2012-06-26Bibliographically approved
In thesis
1. Oxidation of terpenes in indoor environments: A study of influencing factors
Open this publication in new window or tab >>Oxidation of terpenes in indoor environments: A study of influencing factors
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis the oxidation of monoterpenes by O3 and NO2 and factors that influenced the oxidation were studied. In the environment both ozone (O3) and nitrogen dioxide (NO2) are present as oxidising gases, which causes sampling artefacts when using Tenax TA as an adsorbent to sample organic compounds in the air. A scrubber was developed to remove O3 and NO2 prior to the sampling tube, and artefacts during sampling were minimised when using the scrubber. The main organic compounds sampled in this thesis were two monoterpenes, alfa-pinene and delta-3-carene, due to their presence in both indoor and outdoor air. The recovery of the monoterpenes through the scrubber varied between 75-97% at relative humidities of 15-75%.

The reactions of alfa-pinene and delta-3-carene with O 3, NO2 and nitric oxide (NO) at different relative humidities (RHs) and reaction times were studied in a dark reaction chamber. The experiments were planned and performed according to an experimental design were the factors influencing the reaction (O3, NO2, NO, RH and reaction times) were varied between high and low levels. In the experiments up to 13% of the monoterpenes reacted when O3, NO2, and reaction time were at high levels, and NO, and RH were at low levels. In the evaluation eight and seven factors (including both single and interaction factors) were found to influence the amount of alfa-pinene and delta-3-carene reacted, respectively. The three most influencing factors for both of the monoterpenes were the O 3 level, the reaction time, and the RH. Increased O3 level and reaction time increased the amount of monoterpene reacted, and increased RH decreased the amount reacted.

A theoretical model of the reactions occurring in the reaction chamber was created. The amount of monoterpene reacted at different initial settings of O3, NO2, and NO were calculated, as well as the influence of different reaction pathways, and the concentrations of O3 and NO2, and NO at specific reaction times. The results of the theoretical model were that the reactivity of the gas mixture towards alfa-pinene and delta-3-carene was underestimated. But, the calculated concentrations of O3, NO2, and NO in the theoretical model were found to correspond to a high degree with experimental results performed under similar conditions. The possible associations between organic compounds in indoor air, building variables and the presence of sick building syndrome were studied using principal component analysis. The most complex model was able to separate 71% of the “sick” buildings from the “healthy” buildings. The most important variables that separated the “sick” buildings from the “healthy” buildings were a more frequent occurrence or a higher concentration of compounds with shorter retention times in the “sick” buildings.

The outcome of this thesis could be summarised as follows;

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Place, publisher, year, edition, pages
Umeå: Ekologi och geovetenskap, 2003. 84 p.
Keyword
Environmental chemistry, Monoterpene, Ozone (O3), Nitrogen dioxide (NO2), Nitrogen oxide (NO), Relative humidity (RH), Modelling, Scrubber, Experimental design, Interaction, Volatile organic compounds (VOC), Sick buildings syndrome (SBS), Principal component analysis (PCA), Indoor air, Ventilation, Tenax TA, Sodium sulphite, Miljökemi
National Category
Environmental Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-29 (URN)91-7305-313-9 (ISBN)
Public defence
2003-04-29, Umeå, 10:00
Available from: 2003-04-29 Created: 2003-04-29 Last updated: 2017-01-24Bibliographically approved

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