Abstract
This paper presents an evaluation of the consistency of an urban state-of-the-art hydrocarbon (HC) emission inventory. The evaluation was conducted through the comparison of this inventory with hourly HC measurements during two summer months in the centre of Marseille, on the Mediterranean French coast. Factors of under or overestimation could be calculated for each compound on the basis of a systematic HC to HC ratio analysis. These results, associated with a deep analysis of the speciation profiles, show that most of the common and highly concentrated hydrocarbons (such as butanes) are too much predominant in the emission speciation, while the heavy and less common species (branched alkanes, substituted aromatics) are under-represented in the inventory. The urban diffuse sources appear here as one critical point of the inventories. The disagreements were shown to have a strong incidence on the representation of the air mass reactivity. In a last step, the identified uncertainties in emissions were implemented in an air-quality model for sensitivity studies. It was shown that the observed biases in the inventory could affect the regional ozone production, with a probable impact on ozone peaks of 2–10 ppbv over the area.
Highlights
Volatile organic compounds (VOCs) hold a determining place in air-quality-related problems at various scales in the troposphere (Colvile et al, 2001; Friedrich and Obermeier, 1999; Sillman, 1999) due to their intense emission at ground level and their fast reactivity with OH in the presence of nitrogen oxides (NOx) to produce ozone and oxidized species
The present study focuses on the global representativeness of an urban NonMethane HydroCarbon (NMHC) mixture, as provided by a stateof-the-art urban emission inventory compiled by LPCA/CGS
From several sets of NMHC measurements, we propose a critical evaluation of emission speciation profiles
Summary
Volatile organic compounds (VOCs) hold a determining place in air-quality-related problems at various scales in the troposphere (Colvile et al, 2001; Friedrich and Obermeier, 1999; Sillman, 1999) due to their intense emission at ground level and their fast reactivity with OH in the presence of nitrogen oxides (NOx) to produce ozone and oxidized species. It is necessary to complete our knowledge on the mixing of VOC sources to better evaluate the exposure of the population to gaseous pollutants (ORSIF, 2006), and to produce a consistent description of regional anthropogenic plumes and their related ozone formation potential (here called OFP). According to a recent air-quality assessment in North-America (NARSTO, 2005), one delicate stage of the generation of emission inventories is the representation of the wide variety of VOC species emitted by each source, because of the weakness of some existing speciation
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