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MEASUREMENTS OF NON-METHANE VOLATILE ORGANIC COMPOUNDS IN THE LOWER TROPOSPHERE FROM TETHERED BALLOON AND KITE SAMPLING PLATFORMS BY INTERNAL STANDARD CALIBRATION USING AMBIENT CFC REFERENCE COMPOUNDS
Description:
A new analytical approach for the sampling and analysis of volatile organic compounds (VOCs) from sampling platforms used in the vertical profiling of the lower troposphere, such as kites, balloons, and remotely piloted vehicles will be developed. These sampling platforms are severely limited by size, weight and electrical power constraints. VOCs will be sampled using battery-powered pumps onto multistage solid adsorbent cartridges which contain a series of solid adsorbents and allow the analysis of a wide volatility range of VOCs (approximately C3 to C15). Compounds of particular interest are ozone precursor compounds such as alkanes, alkenes, aromatic compounds and biogenic emissions. Analysis will be performed by temperature controlled thermal desorption, focusing onto a micro-volume freezeout trap and injection onto a gas chromatography (GC) column with multiple detection modes such as flame ionization detection (FID), electron capture detection (ECD) and mass spectrometry (MS).
While in previous adsorbent sampling methods, sampling under precisely controlled flow rates was critical for the accurate quantitative VOC analysis, the use of atmospheric reference compounds, in particular the use of long-lived chlorofluorocarbons (CFCs) for internal standard will be investigated. Compounds that will be considered include F-11, F-12, F-113 and tetrachloromethane. This technique does not require a highly accurate control of the sampling flow rate and sampling volume and, therefore, will significantly reduce the expense and weight for sampling equipment and also the amount of labor required for the sampling and analysis of atmospheric VOCs. Processing of large sample sets will be done at the field site with an automatic thermal desorption systems (Perkin Elmer ATD 400 Thermal Desorber) and temperature-programmed GC/FID/ECD.
The use of kites and tethered balloons for vertical profiling of chemical species and meteorological parameters in the troposphere is a research priority of this group. The VOC analysis technique will be added to the kite/balloon instrument package and be used to measure vertical profiles of VOCs. The instruments will be field tested in close collaboration with EPA and NOAA coordinated field campaigns on tropospheric ozone formation and transport. These measurements will be an important contribution to experiments aimed at elucidating the role of VOCs in the atmospheric formation of oxidants, such as ozone and aerosols.
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