Measuring VOCs in Christchurch ambient air : using SIFT-MS technique (2002)
AuthorsChalermot, Warawanshow all
The project is aimed at monitoring the volatile organic compounds (VOCs) that may be regarded as undesirable in Christchurch's ambient air. Nine VOCs viz NH₃ (ammonia), C₂H₄ (acetylene), C₃H₆ (propene), CH₃OH (methanol), C₂H₅OH (ethanol), CH₃CHO (acetaldehyde), C₆H₆ (benzene), C₇H₈ (toluene) and C₈H₁₀ (xylene) were selected to be examined diurnally and seasonally. The samples were taken from various areas around the city. The selected ion flow tube mass spectrometry (SIFT-MS) technique was chosen as the analytical technique for the study as its fast analysis time and high sensitivity (10 ppb to 40 ppm) give it a significant advantage over more conventional methods. Among the results found were unexpected converse behaviour of the dominant species C₃H₆ (propene) and CH₃OH (ethanol). In winter, C₃H₆ (propene) was the dominant pollutant of the nine selected VOCs whereas in summer it was C₂H₅OH (ethanol). Further, the concentration ratios of C₆H₆ (benzene) to C₇H₆ (toluene) are different from the value reported in other cities for urban atmospheric air. The presence of these species at the concentration levels found in the atmospheric conditions prevailing here are sufficiently high to be of concern and a monitoring program is advised.