Non-methane hydrocarbon
The Continuous Non-Methane Hydrocarbon (NMHC) Measurements Study is an ongoing sampling program at the Centre for Atmospheric Research Experiments (CARE) at Egbert, ON. Approximately 30 C2 to C8 hydrocarbons are collected and analyzed every three hours by an automated, in-situ gas chromatograph system. Data has been collected continuously since March, 2001. The intent of the program is to provide speciated hydrocarbon data for assessing the clean and polluted air masses which arrive at the site, tracking long term trends in NMHC mixing ratios in this quickly developing rural area, providing input for modellers and other special studies carried out at the site, and providing a long term intercomparison data set with co-located NMHC canister sampling carried out every third day by the National Air Pollution Surveillance Network.
The suite of measured compounds includes C2 to C6 alkanes, alkene, and alkynes, plus the C6 to C8 light aromatic species (BTEX). Samples are collected every three hours and represent a 20 minute sample integration period. Air samples are cryogenically concentrated after passing through a water trap and are then injected into a gas chromatograph system. Compound separation is by means of a pre-column with its effluent sequentially switched from a column for separating low boiling point species (C2 and C3) to another column for separating higher boiling point compounds (C4 - C8). Detection and quantification is by means of dual flame ionization detectors. Approximately once per day a surrogate air sample (secondary standard) is analyzed followed by a blank analysis to verify instrument performance. Data is processing is partly automated and partly manual. Results are normally posted on the internal CARE web site within two weeks of sampling and database results are updated approximately annually. This instrument system is currently (2009) the only North American site of the World Meteorological Organization's Global Atmosphere Watch (GAW) VOC in-situ monitoring network and, as such, has been audited by that organization (Nov.2008)
출처: <http://www.ec.gc.ca/natchem/default.asp?lang=En&n=A81EEC5B-1>
NMVOC is the abbreviation for non-methane volatile organic compounds.[1]
It is a generic term for a large variety of chemically different compounds, like for example, benzene, ethanol, formaldehyde, cyclohexane, 1,1,1-trichloroethane or acetone. Essentially, NMVOCs are identical to VOCs, but with methane excluded.
Sometimes NMVOC is also used as a sum parameter for emissions, where all NMVOC emissions are added up per weight into one figure. In absence of more detailed data, this can be a very coarse parameter for pollution, e.g. for summer smog or indoor air pollution.
출처: <http://en.wikipedia.org/wiki/NMVOC>
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