Nadine Locoge

An investigation into the traffic-related fraction of isoprene at an urban location

Abstract Continuous hourly measurements of isoprene and 30 other hydrocarbons were performed at an urban centre site in Lille, France, from May 1997 to April 1999. Parallel mass emissions of the same hydrocarbons from in-service passenger vehicles were determined from measurements made on a chassis dynamometer using the European MVEG driving cycle. On the one hand, descriptive statistics and principal component analysis revealed the strong traffic origin of isoprene in winter months and its double biogenic and anthropogenic origin during the summer. On the other hand, the emission measurements of individual hydrocarbons in exhaust gases confirmed the presence of isoprene in petrol fuelled (with or without catalytic converters) and diesel car exhausts. Finally, the isoprene/acetylene ratios, both of them derived from ambient concentrations and emission factors, were compared. No statistically significant difference was found in winter, indicating the strict traffic origin of isoprene during that period. For the winter period, a simple regression analysis was performed on daily isoprene concentrations vs. those of acetylene and three other exhaust gases tracers—propene, ethylene and 1,3-butadiene. The established regression equations, together with the four tracer concentrations, were used to estimate the vehicle exhaust fractions of isoprene. From November to March, vehicle exhaust explained the totality of isoprene levels. While traffic remained the major source of isoprene with a contribution greater than 50% during the growing season, it still constituted a non-negligible source of isoprene in summer, anti-correlated to temperature and fluctuating between 10% and 50%. The application with 1,3-butadiene gives the greatest estimation of the anthropogenic fraction of isoprene. Other sources of 1,3-butadiene, acetylene, ethylene and propene were suspected in addition to their known traffic origin.

Characterisation of NMHCs in a French urban atmosphere: overview of the main sources.

Continuous hourly air quality data involving 37 C2-C9 non-methane hydrocarbons (NMHC) over 4 years are reported for the first time in Lille metropol, northern France, at two urban roadside and background sites. The data have been analysed in two complementary steps: univariate statistics which define the spatial and temporal characteristics of NMHC by constructing the seasonal and daily concentration profiles, and multivariate statistics based on principal component analysis (PCA). A number of important sources have been clearly identified depending on the season: (1) motor vehicle exhaust, which dominates the NMHC distribution and particularly in winter, even for isoprene; (2) wintertime stationary combustion and activities related to fossil fuel consumption in general, such as natural gas leakage of ethane and propane; (3) summertime evaporative emissions from fuel and solvent; and (4) summertime biogenic emissions through isoprene behaviour and their dependence on temperature.

VOC in an urban and industrial harbor on the French North Sea coast during two contrasted meteorological situations

Two measurement campaigns of volatile organic compounds (VOC) were carried out in the industrial city of Dunkerque, using Radiello passive samplers during winter (16-23 January) and summer (6-13 June) 2007. 174 compounds were identified belonging to six chemical families. Classifying sampling sites with similar chemical profiles by hierarchical ascending classification resulted in 4 groups that reflected the influence of the main industrial and urban sources of pollution. Also, the BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) quantification allowed us to map their levels of concentration. Benzene and toluene (BT) showed high concentrations in Northern Dunkerque reflecting the influence of two industrial plants. Differences among spatial distributions of the BT concentrations over contrasted meteorological conditions were also observed. An atypical ratio of T/B in the summer samples led us to investigate the BTEX origins shedding light on the contribution of pollutants transported across various zones of VOC emissions situated in Europe.

Developing receptor-oriented methods for non-methane hydrocarbon characterisation in urban air: Part I: source identification

Abstract The identification of non-methane hydrocarbons (NMHC) main sources is described at urban scale including their spatial and temporal variations. It is based on a receptor-oriented methodology derived from 4-year continuous and hourly measurements of nearly 40 C2–C9 ambient NMHC carried out at two urban sites of the medium-sized city of Lille, northern France. The methods devoted to sources identification included three complementary approaches: univariate statistics through the analysis of the ambient level time series, bivariate statistics through an original NMHC/acetylene Graphical Ratio Analysis which consisted in the study of the temporal evolution of the ambient level ratios and their comparison with those derived from vehicle exhaust emission factors, and multivariate statistics through various summertime and wintertime principal component analysis. Four main categories of sources were consistently identified: (1) motor vehicle exhaust, which dominates the NMHC distribution and particularly in winter, even for isoprene (2) wintertime stationary combustion and activities related to fossil fuel consumption in general (3) summertime evaporative emissions from fuel and solvent (4) summertime biogenic emissions for isoprene and their dependence on temperature and insolation.

Volatile organic compounds sources in Paris in spring 2007. Part II: source apportionment using positive matrix factorisation

Environmental context Volatile organic compounds are key compounds in atmospheric chemistry as precursors of ozone and secondary organic aerosols. To determine their impact at a megacity scale, a first important step is to characterise their sources. We present an estimate of volatile organic compound sources in Paris based on a combination of measurements and model results. The data suggest that the current emission inventory strongly overestimates the volatile organic compounds emitted from solvent industries, and thus needs to be corrected. Abstract A positive matrix factorisation model has been used for the determination of volatile organic compound (VOC) source contributions in Paris during an intensive campaign (May–June 2007). The major sources were traffic-related emissions (vehicle exhaust, 22% of the total mixing ratio of the measured VOCs, and fuel evaporation, 17%), with the remaining emissions from remote industrial sources (35%), natural gas and background (13%), local sources (7%), biogenic and fuel evaporation (5%) and wood-burning (2%). It was noted that the remote industrial contribution was highly dependent on the air-mass origin. During the period of oceanic influences (when only local and regional pollution was observed), this source made a relatively low contribution (<15%), whereas the source contribution linked to traffic was high (54%). During the period of continental influences (when additional continental pollution was observed), remote industrial sources played a dominant role, contributing up to 50% of measured VOCs. Finally, the positive matrix factorisation results obtained during the oceanic air mass-influenced period were compared with the local emission inventory. This comparison suggests that the VOC emission from solvent industries might be overestimated in the inventory, consistent with findings in other European cities.

Volatile organic compounds sources in Paris in spring 2007. Part I: qualitative analysis

Environmental context Megacities are huge hotspots of pollutants that have an impact on atmospheric composition on local to larger scales. This study presents for the first time detailed results of measurements of volatile organic compounds in Paris and shows that, whereas non-methane hydrocarbons are mainly of local and regional origin associated with traffic emissions, a significant part of oxygenated volatile organic compounds originates from continental import. This highlights the importance of measuring volatile organic compounds instead of non-methane hydrocarbons alone in source classification studies. Abstract High-time-resolution measurements of volatile organic compounds (VOCs) were performed in the Paris city centre in spring 2007. The studied region was influenced mainly by air masses of two origins: (1) from the Atlantic Ocean, and (2) from north-eastern Europe. Although the baseline levels (i.e. those not influenced by local emissions) of non-methane hydrocarbons (NMHC) and CO were only slightly impacted by changes in the air-mass origin, oxygenated compounds such as acetone and methanol showed much higher baseline levels in continentally influenced air masses. This suggests that NMHC and CO mixing ratios were mainly influenced by local-to-regional-scale sources whereas oxygenated compounds had a more significant continental-scale contribution. This highlights the importance of measuring VOCs instead of NMHC alone in source classification studies. The period of Atlantic air influence was used to characterise local pollution, which was dominated by traffic-related emissions, although traffic represents the source of only one third of total VOCs emissions in the local inventory. In addition to traffic-related sources, additional sources were identified; in particular, emissions from dry-cleaning activities were identified by the use of a specific tracer (i.e. tetrachloroethylene).

Developing receptor-oriented methods for non-methane hydrocarbon characterisation in urban air. Part II: source apportionment

The methods and the results of non-methane hydrocarbon (NMHC) source apportionment are described at urban scale on a spatial and temporal basis. Here, hourly ambient concentrations of nearly 40 C2–C9 NMHC are used. Methods are based on the knowledge of the wintertime NMHC vehicle-exhaust emission ratio generally determined by simple regression analysis taking acetylene, ethylene, propene and 1,3-butadiene as auto-exhaust tracers. The RSD of the estimated source contributions is lower than 20%; the developed receptor-oriented methods are flexible and easily transposable to other areas. In winter, vehicle-exhaust emissions explain 100% of the NMHC majority levels and even isoprene. From May to November, our models revealed the temperature-dependent contribution of additional sources (0.71<r<0.90). On the one hand, the evaporation of fuel and solvent affects the whole C4–C9 NMHC fraction, and fluctuates between 20% and 50%, even for a northern France urban area. On the other hand, both vehicle-exhaust and biogenic emissions control the highly photoreactive isoprene distribution whatever the site; the traffic is responsible for a third of its levels in summer. Finally, the particular behaviour of the C2–C4 compounds pointed out dominant contributions, generally other than traffic. Suspected sources are numerous: natural gas leakage for ethane and propane, wintertime fuel evaporation for butanes and butenes, non-automotive combustion for ethylene and acetylene. Ethane and propane also showed that long-range advective transport, responsible for background concentrations, could significantly contribute to the hydrocarbon levels with a high atmospheric residence time (from 20% to 50%).

Determination of 14 amines in air samples using midget impingers sampling followed by analysis with ion chromatography in tandem with mass spectrometry

An Ion Chromatography-Mass Spectrometry (IC-MS) method was developed for the simultaneous quantification of 14 volatile amines in air. The method includes collection of compounds into two midget impingers in a row filled with 15 ml of ultrapure water. The analytical performances with mass spectrometry detection were compared to those obtained with classical conductivity detection. The use of mass spectrometry detection (in SIM mode) overcomes most of the coelutions encountered with conductivity detection. Although the linearity domain of calibrations is reduced for the MS detection as compared with the CD detection, the detection limits in MS detection are highly lowered allowing the quantification of amines at the levels of μg m(-3) in air with a good accuracy for most compounds (RSD of less than 10%). This method was successfully applied to the analysis of amines released from polyurethane foams. Seven amines were identified and some in high concentrations, like dimethylaminoethanol, NIAX and TEDA.

Development of a methodology examining the behaviours of VOCs source apportionment with micro-meteorology analysis in an urban and industrial area

During summer 2009, online measurements of 25 Volatile Organic Compounds (VOCs) from C6 to C10 as well as micro-meteorological parameters were simultaneously performed in the industrial city of Dunkerque. With the obtained data set, we developed a methodology to examine how the contributions of different source categories depend on atmospheric turbulences, and the results provided identification of emission modes. Eight factors were resolved by using Positive Matrix Factorization model and three of them were associated with mixed sources. The observed behaviours of contributions with turbulences lead to attribute some factors with sources at ground level, and some other factors with sources in the upper part of surface layer. The impact of vertical turbulence on the pollutant dispersion is also affected by the distance between sources and receptor site.

Quantitative cancer risk assessment and local mortality burden for ambient air pollution in an eastern Mediterranean City

Health risks posed by ambient air pollutants to the urban Lebanese population have not been well characterized. The aim of this study is to assess cancer risk and mortality burden of non-methane hydrocarbons (NMHCs) and particulates (PM) based on two field-sampling campaigns conducted during summer and winter seasons in Beirut. Seventy NMHCs were analyzed by TD-GC-FID. PM2.5 elemental carbon (EC) components were examined using a Lab OC-EC aerosol Analyzer, and polycyclic aromatic hydrocarbons were analyzed by GC-MS. The US EPA fraction-based approach was used to assess non-cancer hazard and cancer risk for the hydrocarbon mixture, and the UK Committee on Medical Effects of Air Pollutants (COMEAP) guidelines were followed to determine the PM2.5 attributable mortality burden. The average cumulative cancer risk exceeded the US EPA acceptable level (10−6) by 40-fold in the summer and 30-fold in the winter. Benzene was found to be the highest contributor to cancer risk (39–43%), followed by 1,3-butadiene (25–29%), both originating from traffic gasoline evaporation and combustion. The EC attributable average mortality fraction was 7.8–10%, while the average attributable number of deaths (AD) and years of life lost (YLL) were found to be 257–327 and 3086–3923, respectively. Our findings provide a baseline for future air monitoring programs, and for interventions aiming at reducing cancer risk in this population.