Characterising sources and sinks of rural VOC in eastern France.
Fifty non-methane hydrocarbons (NMHC) and seventeen carbonyl compounds were measured at a French rural site from 1997 to 2001, as part of the EMEP programme. Data handling was based on an original source-receptor approach. First, the examination of the levels and trends was completed by the comparison of the seasonal distribution of rural and urban VOC/acetylene ambient ratios. This analysis has shown that most of the compounds derived from mixing and photochemical transformation of mid-range transported urban pollutants from the downwind urban area. Then, identified sources and sinks were temporally apportioned. Urban air masses mixing explains, at least, 80% of the wintertime levels of anthropogenic NMHC and isoprene. In summer, photochemistry dominates the day-to-day distribution of anthropogenic NMHC whilst summertime isoprene is also controlled by in-situ biogenic emissions. Then, the results of C(1)-C(3) carbonyls were discussed with respect to their direct biogenic and anthropogenic emissions and photochemical production through the [carbonyl/auto-exhaust tracers] emission ratio. Diluted vehicle exhaust emissions mainly contribute to the total content of lower aldehydes in winter while other processes control lower ketones. Secondary production is predominant in summer with at least a 50% high intensity. Its dependence upon temperature and radiation is also demonstrated. Finally, the importance of the primary and secondary biogenic production of acetone and formaldehyde is assessed. In particular, biogenic contribution would explain 37 +/- 25% of acetone levels in summer.
Laboratoire Interuniversitaire des Systèmes Atmosphériques, Faculté des Sciences et Technologies, Université Paris XII, 61, avenue du Général de Gaulle, 94010 Créteil Cedex, France. borbon@lisa.univ-paris12.fr
Agnès
A
Borbon
Patrice
P
Coddeville
Nadine
N
Locoge
Jean-Claude
JC
Galloo
D000393:Air Pollutants / Q000032:analysis*; D002849:Chromatography, Gas; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D005602:France; D009930:Organic Chemicals / Q000032:analysis*; D012621:Seasons; D001335:Vehicle Emissions / Q000032:analysis; D014835:Volatilization
D000393:Air Pollutants; D009930:Organic Chemicals; D001335:Vehicle Emissions