Temporal Distribution and Gas/Particle Partitioning of Polycyclic Aromatic Hydrocarbons (PAHs) in the Atmosphere of Strasbourg, France

Gas and particulate phase ambient air concentrations of polycyclic aromatic hydrocarbons (Ʃ16PAHs) were determined in Strasbourg, a large city located in the Alsace region of northeastern France, from May 2018 to March 2020, to study the evolution of their temporal variations and their potential origins. The analysis of PAHs was performed using a global analytical method permitting the quantification of pesticides, PAHs, and polychlorobiphenyls (PCBs). Filters and Carbon doped silicon carbide NMC@SiC foams were extracted by accelerated solvent extraction (ASE) followed by a solid-phase extraction (SPE). Afterwards, extracts were analyzed using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Prior to analysis, a pre-concentration step based on solid-phase microextraction (SPME) was used with a polydimethylsiloxane (PDMS) 100 µm fiber. The average total (gas plus particulate) concentration of Ʃ16PAHs varied from 0.51 to 117.31 ng m−3 with a mean of 16.87 ng m−3, with higher concentrations in the cold season of more than 2.5-fold and 6-fold that in the warm season for the gas and particulate phases, respectively. Moreover, low molecular weight (LMW) (2-ring and 3-ring) and medium molecular weight (MMW) (4-ring) PAHs contribute dominantly to the gas phase, while the particulate phase is associated with MMW (4-ring) and high molecular weight (HMW) (5-ring and 6-ring) PAHs. Gas/particle partitioning coefficient (log Kp) was calculated, and values varied between −4.13 and −1.49. It can be seen that the log Kp increased with the molecular weight of the PAHs and that the log Kp is different between cold and warm seasons for HMW PAHs but not for LMW PAHs. Diagnostic ratios of PAHs, which were employed to estimate the primary source of PAHs in Strasbourg, indicate that fuel combustion and biomass/coal burning are the possible origins of PAHs in Strasbourg’s atmosphere.

AMBIENT AIR QUALITY STATUS OF DEWAS INDUSTRIAL AREA OF MADHYA PRADESH, INDIA

A study has been conducted to assess the ambient air quality status of Dewas industrial area of Madhya Pradesh, India. Total nine locations were selected in Dewas industrial area for ambient air quality monitoring. The eleven pollutants mainly particulate matter less than 10 µ size (PM10), particulate matter less than 2.5 µ size (PM2.5), nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), ammonia (NH3), benzene (C6H6), benzo (a) Pyrene (BaP) – particulate phase, lead (Pb), Arsenic (As) and Nickel (Ni) were monitored during different four quarters from April 2019 to March 2020. The study revealed that average concentration of gaseous pollutants viz, NO2, SO2, O3, NH3, C6H6 in ambient air were well within standard limits at all selected locations, however concentration of particulate matter (PM10, PM2.5) and heavy metals (Pb & Ni) except As level were found exceeding the National Ambient Air Quality Standards (NAAQS) 2009, India at few monitoring locations. Benzo (a) Pyrene (BaP) –particulate phase in ambient air was not detected during this study. Ambient air Quality Index was found to be moderate (115.56-198.36) at six locations and satisfactory (17.60-94.94) at three locations in Dewas industrial area. Overall ambient Air Quality Index of Dewas industrial area was observed, satisfactory to moderate during this study w.r.t. Air Quality Index. KEY WORDS: Industrial Area, Ambient Air, Air Pollutants, Air Quality Index

Impact of NO_<i>x</i> on secondary organic aerosol (SOA) formation from <i>α</i>-pinene and <i>β</i>-pinene photooxidation: the role of highly oxygenated organic nitrates

The formation of organic nitrates (ONs) in the gas phase and their impact on mass formation of secondary organic aerosol (SOA) was investigated in a laboratory study for α-pinene and β-pinene photooxidation. Focus was the elucidation of those mechanisms that cause the often observed suppression of SOA mass formation by NOx, and therein the role of highly oxygenated multifunctional molecules (HOMs). We observed that with increasing NOx concentration (a) the portion of HOM organic nitrates (HOM-ONs) increased, (b) the fraction of accretion products (HOM-ACCs) decreased, and (c) HOM-ACCs contained on average smaller carbon numbers. Specifically, we investigated HOM organic nitrates (HOM-ONs), arising from the termination reactions of HOM peroxy radicals with NOx, and HOM permutation products (HOM-PPs), such as ketones, alcohols, or hydroperoxides, formed by other termination reactions. Effective uptake coefficients γeff of HOMs on particles were determined. HOMs with more than six O atoms efficiently condensed on particles (γeff>0.5 on average), and for HOMs containing more than eight O atoms, every collision led to loss. There was no systematic difference in γeff for HOM-ONs and HOM-PPs arising from the same HOM peroxy radicals. This similarity is attributed to the multifunctional character of the HOMs: as functional groups in HOMs arising from the same precursor HOM peroxy radical are identical, vapor pressures should not strongly depend on the character of the final termination group. As a consequence, the suppressing effect of NOx on SOA formation cannot be simply explained by replacement of terminal functional groups by organic nitrate groups. According to their γeff all HOM-ONs with more than six O atoms will contribute to organic bound nitrate (OrgNO3) in the particulate phase. However, the fraction of OrgNO3 stored in condensable HOMs with molecular masses > 230 Da appeared to be substantially higher than the fraction of particulate OrgNO3 observed by aerosol mass spectrometry. This result suggests losses of OrgNO3 for organic nitrates in particles, probably due to hydrolysis of OrgNO3 that releases HNO3 into the gas phase but leaves behind the organic rest in the particulate phase. However, the loss of HNO3 alone could not explain the observed suppressing effect of NOx on particle mass formation from α-pinene and β-pinene. Instead we can attribute most of the reduction in SOA mass yields with increasing NOx to the significant suppression of gas phase HOM-ACCs, which have high molecular mass and are potentially important for SOA mass formation at low-NOx conditions.

Characterization of gaseous and particulate phase organic compounds during a winter-time air pollution event

&lt;p&gt;&lt;strong&gt;&amp;#160;Abstract&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Atmospheric particles are known to cause adverse health effects and premature deaths in European cities. To improve air quality, a detailed understanding of particle sources is thus essential in order to reduce their emissions. Secondary organic aerosols (SOA) produced from the oxidation of volatile organic compounds emitted by anthropogenic sources such as road vehicles and solid fuel combustion is an important air pollution source in urban areas. It is demonstrated that SOA contribute significantly to the atmospheric particle loading, and could even be the major contributor at specific locations. Yet, state of the art models are still not able to reproduce SOA formation despite recent advances. Clearly, further work is needed to improve our understanding of the processes related to SOA formation.&lt;/p&gt;&lt;p&gt;In this context, a field campaign has been conducted at a monitoring station in Cork City, Ireland during winter 2019 (26&lt;sup&gt;th&lt;/sup&gt; January to 8&lt;sup&gt;th&lt;/sup&gt; February). The chemical composition of organic compounds in both gas and particle phases was investigated online using a Time-of-Flight Chemical Ionisation Mass Spectrometer (ToF-CIMS) coupled with a Filter Inlet for Gases and Aerosols (FIGAERO). PM&lt;sub&gt;2.5&lt;/sub&gt; concentration, ozone and nitrogen oxides (NO&lt;sub&gt;x&lt;/sub&gt;) were also monitored during the campaign, as well as meteorological parameters. Finally, air mass backward trajectories were computed using the HYSPLIT model.&lt;/p&gt;&lt;p&gt;A strong night-time air pollution event was observed during the field campaign, characterized by PM&lt;sub&gt;2.5&lt;/sub&gt; concentrations up to 180 &amp;#181;g m&lt;sup&gt;-3&lt;/sup&gt;. Using iodide as reagent, the FIGAERO-ToF-CIMS detected hundreds of ions simultaneously in gas and particulate phases. Among the identified compounds were a range of well-known atmospheric tracers of solid fuel burning, including phenolic compounds such as guaiacol and catechol, and numerous oxygenated polycyclic aromatic hydrocarbons (OPAHs). A number of nitrated aromatic compounds were also detected. In this work, the gas/particle partitioning of some of these key compounds has been investigated to provide information on phase transfer of solid fuel emissions over time. The thermograms produced by the FIGAERO analysis are also used to determine the volatility of the species detected. Finally, the FIGAERO-ToF-CIMS data is used to explore the extent to which oxidation of the gaseous emissions by the nitrate radical (NO&lt;sub&gt;3&lt;/sub&gt;) leads to the formation of nitrated compounds in the particulate phase. This work thus provides unique insights into the night-time oxidation processes that can lead to SOA formation from anthropogenic sources.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;This work was supported by the Irish Research Council (GOIPG/2017/1364) and by the European Union&amp;#8217;s Horizon 2020 research and innovation programme (EUROCHAMP-2020, grant no.&amp;#160;730997; Marie Sk&amp;#322;odowska-Curie grant agreement No. 751527).&lt;/p&gt;

River bed-load sediments and suspended particles: two different worlds for trace metals

&lt;p&gt;Anthropogenic activities release many types of contaminants, such as trace metals, in the environment. For recent decades, numerous studies investigated their behavior, particularly in the dissolved phase. The transfer of contaminants adsorbed on the particulate phase received less attention although particulate matter also plays a key role in their propagation. One first difficulty is the variability of adsorption and releasing processes driven by both water physico-chemical conditions and contaminants properties. Secondly, there are different compartments in particulate phases, e.g. bed-load sediments and suspended particles, and the proportion of these two worlds is highly variable according to climate conditions (temperature, rainfall) and stream (hydro)geomorphological characteristics. In this context, our study investigates trace metal dynamics (Pb, Zn, Cu) in bed-load sediments and suspended particles from a small tributary of the Loire River, the Egoutier stream (Loiret, France). High spatial and temporal sampling frequency of the two fractions allowed to understand the patterns of trace metals transfer. Trends of trace metals contents observed in the particulate phase correspond to those in the dissolved one, except for Pb, the most insoluble compound. Contaminants concentrations and behaviors are driven both by trace metals order of solubility in bed-load sediments and suspended particles, and by external factors such as meteorological conditions, stream geochemistry and geomorphology. Besides, they are mostly adsorbed on iron and manganese oxides from suspended particles and on organic compounds from the bed-load sediments. Their temporal dynamics are controlled by seasons variabilities, notably rain amounts and humid periods, whereas their spatial distribution essentially reflects stream geomorphology, notably by the presence of a small pond creating a disconnection between the upstream and the downstream part of the watercourse and therefore two different patterns of transfert. Upstream, bed-load sediments contamination presents large fluctuations regulated by anthropogenic releases during dry periods and organic supplies during the humid ones, whereas homogeneous levels were observed downstream. In the suspended particles fraction, upstream higher contents are only correlated to humid periods, where more oxides are transported, while downstream transport is amplified by higher rain amounts.&lt;/p&gt;