Alexandre Albinet

Diurnal/nocturnal concentrations and sources of particulate-bound PAHs, OPAHs and NPAHs at traffic and suburban sites in the region of Paris (France).

Particulate concentrations of polycyclic aromatic compounds (PACs) including, 17 polycyclic aromatic hydrocarbons (PAHs), 9 oxygenated PAHs (OPAHs) and 18 nitrated PAHs (NPAHs) were determined at traffic and suburban sites located in the region of Paris. A 12 h sampling basis time resolution was applied in order to study their diurnal and nocturnal variations. Observed concentrations were about 10 times higher at the traffic site for all compounds and were higher during the night-time for both sites (except for NPAHs at the traffic site). No significant differences in PAH and OPAH profiles were observed at both sites whereas, for NPAHs, 1-nitropyrene (diesel source) was the most abundant at the traffic site and 2+3-nitrofluoranthene (secondary formed by gas-phase reaction) was predominant at the suburban site. The study of the specific ratio 2-nitrofluoranthene/1-nitropyrene (2-NFlt/1-NP) showed a local formation of NPAHs in gaseous phase at the suburban site. A detailed analysis showed that atmospheric humidity and rainfalls modified differently PAH and NPAH profiles, in comparison to OPAH. A difference of the scale variability of water solubility between, light (MW≤228 g mol(-1)) and heavy compounds (MW≥273 g mol(-1)), could explain these observations. The specific study of the relationships between PACs and other measured pollutants highlighted that particle resuspension could constitute a significant source of PM on the traffic site. Even if NPAH formation seemed clearly evident at the suburban site during periods characterised by high O(3) and NO(2) concentration levels, results showed also that the primary and/or secondary origins of OPAHs and NPAHs were strongly dependent on the sampling site and on sampling conditions. Finally, we conclude that higher time sampling resolutions would be helpful in investigating the atmospheric chemistry and behaviours of PACs in correlation with the local meteorological variations and the daily cycle of human activities.

Photochemical generation of reactive species upon irradiation of rainwater: negligible photoactivity of dissolved organic matter.

This paper focuses on the study of the photochemical activity of dissolved organic matter present in rainwater. Formation rates of the reactive species hydroxyl radical (OH(*)), singlet oxygen ((1)O(2)) and dissolved organic matter triplet states ((3)DOM()) were determined by irradiation (UV-A) of wet-only rainwater samples collected in Turin (Italy) in the presence of specific scavengers (benzene, furfuryl alcohol and phenol, respectively). Photo-formation rates of OH(*) ( approximately 3.10(-)(11)Ms(-)(1)) and (1)O(2) ( approximately 10(-)(14)Ms(-)(1)) were lower (1 or 2 orders of magnitude) or largely lower (4 to 10 orders of magnitude) than those determined for fog and cloud samples in previous studies. (3)DOM() formation rate values were either negligible or quite low ( approximately 10(-)(12)Ms(-)(1)) by comparison with those evaluated for surface water samples. Deduced steady-state [OH(*)] were in the same range as those reported for fog samples in the literature (8.7.10(-)(16) to 1.5.10(-)(15)M), while [(1)O(2)] was often several orders of magnitude lower and, therefore, could be considered as negligible. Nitrite (NO(2)(-)) constituted the main source of OH(*) (69 + or - 21 to 138 + or - 36%), and the deduced contribution of DOM was low or nil. All the results obtained in this study tend to demonstrate that DOM (including HUmic LIke Substances, HULIS) present in rainwater is poorly or not photoactive. Therefore, there could be considerable difference between rainwater DOM (HULIS included) and the organic matter present in surface waters, particularly the humic substances, as far as the photochemical activity is concerned.

A really quick easy cheap effective rugged and safe (QuEChERS) extraction procedure for the analysis of particle-bound PAHs in ambient air and emission samples.

A quick easy cheap effective rugged and safe (QuEChERS) like extraction procedure is presented for the measurement of polycyclic aromatic hydrocarbons (PAHs) associated to particulate matter from ambient air or combustion process. The procedure is based on a short mechanical agitation (vortex during 90 s) using a small volume of acetonitrile (7 ml) as extraction solvent. Equivalent extraction efficiencies were obtained when comparing the QuEChERS and the traditional pressurized solvent extraction (ASE) procedures for ambient air and emission (wood combustion) filter samples. The developed QuEChERS extraction protocol was validated with the analysis of a standard reference material (NIST SRM 1649a, urban dust). By comparison to other extraction methods including ASE, the simplicity of the QuEChERS protocol allows to minimize experimental errors, to decrease about a factor 5 the cost per extraction and to increase the productivity per working day by a 10-fold factor. This paper constitutes the first report on the applicability of a QuEChERS-like approach for the quantification of PAHs or other organic compounds in atmospheric particulate matter.

Phototransformation processes of 2,4-dinitrophenol, relevant to atmospheric water droplets

This paper shows that the polychromatic quantum yield for the photolysis of 2,4-dinitrophenol (24DNP) in the wavelength interval of 300-500 nm is (8.1+/-0.4) x 10(-5) for the undissociated phenol, and (3.4+/-0.2) x 10(-5) for the phenolate. The second-order rate constants for reaction with ()OH were determined here as (1.76+/-0.05) x 10(9) M(-1) s(-1) and (2.33+/-0.11) x 10(9) M(-1) s(-1) for the phenol and the phenolate, respectively. By combining laboratory results and a simple modelling approach of the atmospheric aqueous phase, this work shows that the direct photolysis and the reaction with ()OH would play a comparable role in the degradation of 24DNP at pH>4. The ()OH reaction would prevail for pH<4. Both pathways would be more important than the night-time reaction with *NO(3) as removal processes for 24DNP in the atmospheric waters.

UVA irradiation induces direct phototransformation of 2,4-dinitrophenol in surface water samples

Lake water samples spiked with 2,4-dinitrophenol (24DNP) were irradiated under artificial UVA irradiance. It was found that the direct photolysis is the main photodegradation pathway of 24DNP in lake water. On the lake water samples it was also determined the formation and consumption rates of *OH, by means of the transformation reaction of benzene into phenol. It was found that the rate of direct photolysis prevails over the *OH phototransformation rate by one-two orders of magnitude. Moreover, the excited triplet states of chromophoric dissolved organic matter and singlet oxygen are expected to play a negligible role in the photodegradation of 24DNP. By modelling the direct photolysis of 24DNP in surface water bodies, one gets a half-life time of 2-10 summer sunny days for water-column depths up to 10 m. This would make the direct photolysis a major pathway for the transformation of 24DNP in freshwaters.

Limited formation of isoprene epoxydiols‐derived secondary organic aerosol under NOx‐rich environments in Eastern China

Secondary organic aerosol (SOA) derived from isoprene epoxydiols (IEPOX) has potential impacts on regional air quality and climate yet is poorly characterized under NOx-rich ambient environments. We report the first real-time characterization of IEPOX-derived SOA (IEPOX-SOA) in Eastern China in summer 2013 using comprehensive ambient measurements, along with model analysis. The ratio of IEPOX-SOA to isoprene high-NOx SOA precursors, e.g., methyl vinyl ketone and methacrolein, and the reactive uptake potential of IEPOX was lower than those generally observed in regions with prevailing biogenic emissions, low NOx levels, and high particle acidity, elucidating the suppression of IEPOX-SOA formation under NOx-rich environments. IEPOX-SOA showed high potential source regions to the south with large biogenic emissions, illustrating that the interactions between biogenic and anthropogenic emissions might have played an important role in affecting the formation of IEPOX-SOA in polluted environments in Eastern China.

Speciation of organic fraction does matter for source apportionment. Part 1: A one-year campaign in Grenoble (France)

PM10 source apportionment was performed by positive matrix factorization (PMF) using specific primary and secondary organic molecular markers on samples collected over a one year period (2013) at an urban station in Grenoble (France). The results provided a 9-factor optimum solution, including sources rarely apportioned in the literature, such as two types of primary biogenic organic aerosols (fungal spores and plant debris), as well as specific biogenic and anthropogenic secondary organic aerosols (SOA). These sources were identified thanks to the use of key organic markers, namely, polyols, odd number higher alkanes, and several SOA markers related to the oxidation of isoprene, α-pinene, toluene and polycyclic aromatic hydrocarbons (PAHs). Primary and secondary biogenic contributions together accounted for at least 68% of the total organic carbon (OC) in the summer, while anthropogenic primary and secondary sources represented at least 71% of OC during wintertime. A very significant contribution of anthropogenic SOA was estimated in the winter during an intense PM pollution event (PM10>50μgm-3 for several days; 18% of PM10 and 42% of OC). Specific meteorological conditions with a stagnation of pollutants over 10days and possibly Fenton-like chemistry and self-amplification cycle of SOA formation could explain such high anthropogenic SOA concentrations during this period. Finally, PMF outputs were also used to investigate the origins of humic-like substances (HuLiS), which represented 16% of OC on an annual average basis. The results indicated that HuLiS were mainly associated with biomass burning (22%), secondary inorganic (22%), mineral dust (15%) and biogenic SOA (14%) factors. This study is probably the first to state that HuLiS are significantly associated with mineral dust.

Atmospheric reactions of 9,10-anthraquinone

The probably carcinogenic compound 9,10-anthraquinone is mainly existing in the atmosphere in the particulate phase and is often detected and measured among other oxygenated PAHs in atmospheric samples. Its fate, once released or formed in the atmosphere, still remains unknown. In this work, heterogeneous chemical oxidation processes of 9,10-anthraquinone were investigated with ozone (O3), nitrogen dioxide (NO2) and hydroxyl radical (OH). The study of 9,10-anthraquinone adsorbed on silica particles showed no reactivity with O3 and NO2. On the other hand, the reaction with OH radicals was observed and led to the formation of 1-hydroxy-9,10-anthraquinone, another oxidation product recognized as possibly carcinogenic to humans. This study showed that reactions with ozone and nitrogen dioxide are unlikely to contribute to atmospheric degradation of 9,10-anthraquinone, whereas reactions with OH radicals could be involved in 9,10-anthraquinone degradation processes, even if such reaction is probably very slow under ambient conditions.

Speciation of organic fractions does matter for aerosol source apportionment. Part 2: Intensive short-term campaign in the Paris area (France)

The present study aimed at performing PM10 source apportionment, using positive matrix factorization (PMF), based on filter samples collected every 4h at a sub-urban station in the Paris region (France) during a PM pollution event in March 2015 (PM10>50μgm-3 for several consecutive days). The PMF model allowed to deconvolve 11 source factors. The use of specific primary and secondary organic molecular markers favoured the determination of common sources such as biomass burning and primary traffic emissions, as well as 2 specific biogenic SOA (marine+isoprene) and 3 anthropogenic SOA (nitro-PAHs+oxy-PAHs+phenolic compounds oxidation) factors. This study is probably the first one to report the use of methylnitrocatechol isomers as well as 1-nitropyrene to apportion secondary OA linked to biomass burning emissions and primary traffic emissions, respectively. Secondary organic carbon (SOC) fractions were found to account for 47% of the total OC. The use of organic molecular markers allowed the identification of 41% of the total SOC composed of anthropogenic SOA (namely, oxy-PAHs, nitro-PAHs and phenolic compounds oxidation, representing 15%, 9%, 11% of the total OC, respectively) and biogenic SOA (marine+isoprene) (6% in total). Results obtained also showed that 35% of the total SOC originated from anthropogenic sources and especially PAH SOA (oxy-PAHs+nitro-PAHs), accounting for 24% of the total SOC, highlighting its significant contribution in urban influenced environments. Anthropogenic SOA related to nitro-PAHs and phenolic compounds exhibited a clear diurnal pattern with high concentrations during the night indicating the prominent role of night-time chemistry but with different chemical processes involved.