An automated monitoring system for VOC ozone precursors in ambient air: development, implementation and data analysis

Abstract

An automated system for the monitoring of volatile organic compound (VOC) ozone precursors in ambient air is described. The measuring technique consists of subambient preconcentration on a cooled trap followed by thermal desorption and GC/FID analysis. First, the technical development, which permits detection limits below 0.05 ppbv to be reached, proceeded in two steps: (1). the determination of optimum sampling parameters (trap composition and conditioning, outlet split, desorption temperature); (2). the development of a reliable calibration method based on a highly accurate standard. Then, a 4-year field application of the hourly measuring chain was carried out at two urban sites. On the one hand, quality control procedures provided the best VOC identification (peak assignment) and quantification (reproducibility, blank system control). On the other hand, the success and performances of the routine experience (88% of the measurements covered more than 40 target compounds) indicated the high quality and suitability of the instrumentation which is actually applied in several French air quality monitoring networks. Finally, an example of data analysis is presented. Data handling identified important organic compound sources other than vehicle exhaust.

Intercomparison of the comparative reactivity method (CRM) and pump–probe technique for measuring total OH reactivity in an urban environment

“…These two GCs detected more than 34 NMHCs (C 2 -C 10 ) and 22 OVOCs (C 2 -C 10 ), as reported in Table 3. The NMHC-GC has been described elsewhere (Badol et al, 2004). Ambient air is sampled through a NAFION membrane and VOCs are trapped at a temperature of −30 • C inside a quartz tube filled with Carbosieve SIII and Carbopack B. Ambient VOCs are trapped at a sampling flow rate of 20 cm 3 min −1 for a duration of 30 min, leading to a sampling volume of 600 cm 3 .…”

Variability of hydroxyl radical (OH) reactivity in the Landes maritime pine forest: results from the LANDEX campaign 2017

“…Over the past 2 decades, OH reactivity measurements have been conducted in various environments at the ground level using the available techniques: urban and suburban areas, forest areas, and marine areas (Yang et al, 2016;Dusanter and Stevens, 2017). A few aircraft measurements have also been carried out to complete ground-based observations (Brune et al, 2010). Many studies highlighted the interest of investigating OH reactivity in forest areas exhibiting large concentrations of biogenic volatile organic compounds (BVOCs) since BVOC emissions exceed anthropogenic VOCs by a factor of 10 at the global scale (Guenther et al, 1995).…”

Multi-year levels and trends of non-methane hydrocarbon concentrations observed in ambient air in France

“…This study compares 91 the trends in NMHC levels between urban and rural French atmospheres in order to examine 92 the homogeneity of the trends for France and for other neighboring European countries. InBadol et al, 2004). It should be noted that due to the occurrence108 of some public works at the urban site of Les Halles in Paris from 2011 to 2016, the location 109 of the sampling site in 2011 was changed to Siege Airparif (48°51'N, 2°21'E).…”

“…The measurement uncertainty of the NMHCs was in the range of 5 to 13% for hourly 154 on-line measurements (Badol et al, 2004) and in the range of 11 to 28% for off-line weekly 155…”