Assessing the biological reactivity of organic compounds on volcanic ash: implications for human health hazard

Exposure to volcanic ash is a long-standing health concern for people living near active volcanoes and in distal urban areas. During transport and deposition, ash is subjected to various physicochemical processes that may change its surface composition and, consequently, bioreactivity. One such process is the interaction with anthropogenic pollutants; however, the potential for adsorbed, deleterious organic compounds to directly impact human health is unknown. We use an in vitro bioanalytical approach to screen for the presence of organic compounds of toxicological concern on ash surfaces and assess their biological potency. These compounds include polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dlPCBs). Analysis of ash collected in or near urbanised areas at five active volcanoes across the world (Etna, Italy; Fuego, Guatemala; Kelud, Indonesia; Sakurajima, Japan; Tungurahua, Ecuador) using the bioassay inferred the presence of such compounds on all samples. A relatively low response to PCDD/Fs and the absence of a dlPCBs response in the bioassay suggest that the measured activity is dominated by PAHs and PAH-like compounds. This study is the first to demonstrate a biological potency of organic pollutants associated with volcanic ash particles. According to our estimations, they are present in quantities below recommended exposure limits and likely pose a low direct concern for human health

Uptake and surface chemistry of SO2 on natural volcanic dusts

V-dust (v-dust) is a highly variable source of natural particles in the atmosphere, and during the period of high volcanic activity it can provide a large surface for heterogeneous interactions with other atmospheric compounds. Icelandic v-dust was chosen as a case study due to frequency of volcanic eruptions and high aeolian activity in the area. In this study, we focus on the kinetics and mechanism of the reaction of sulfur dioxide (SO2) with natural v-dust samples under atmospheric conditions using coated wall flow tube reactor and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Steady state uptake coefficients determined are in the range of 10−9 to 10−8 depending on the considered v-dust. Concomitantly with SO2 uptake, both sulfites and sulfates are monitored on the surface of v-dust, with sulfates being the final oxidation product, attesting of SO2 surface reaction. Surface hydroxyl groups play a crucial role in the conversion of SO2 to sulfites as evidenced from both flow tube and DRIFTS experiments. Based on these experimental results, a mechanism for SO2 interaction with different surface sites of v-dust is proposed and discussed. This study provides original insights in the kinetics of SO2 uptake under simulated atmospheric conditions and its mechanism and transformation on volcanic material. To that regards, it brings an accurate perspective on SO2 heterogeneous sinks in the atmosphere.The authors acknowledge Mr Vincent Gaudion and Dr Mohamad Zeineddine (SAGE, IMT Lille Douai) for their assistance in the lab. We are grateful to Mr Bruno Malet and Dr Laurent Alleman (SAGE, IMT Lille Douai) for conducting the ICP-MS experiments. This work was achieved in the frame of Labex CaPPA, funded by ANR through the PIA under contract ANR-11-LABX-0005-01, and CPER CLIMIBIO project, both funded by the Hauts-de-France Regional Council and the European Regional Development Fund (ERDF). J. Lasne acknowledges support from the Labex CaPPA and CPER CLIMIBIO projects and the Hauts-de-France Regional Council for his post-doctoral fellowship.Peer Reviewe

A review of coarse mineral dust in the Earth system

Mineral dust particles suspended in the atmosphere span more than three orders of magnitude in diameter, from <0.1 µm to more than 100 µm. This wide size range makes dust a unique aerosol species with the ability to interact with many aspects of the Earth system, including radiation, clouds, hydrology, atmospheric chemistry, and biogeochemistry. This review focuses on coarse and super-coarse dust aerosols, which we respectively define as dust particles with a diameter of 2.5–10 µm and 10–62.5 µm. We review several lines of observational evidence indicating that coarse and super-coarse dust particles are transported farther than previously expected and that the abundance of these particles is substantially underestimated in current global models. We synthesize previous studies that used observations, theories, and model simulations to highlight the impacts of coarse and super-coarse dust aerosols on the Earth system, including their effects on dust-radiation interactions, dust-cloud interactions, atmospheric chemistry, and biogeochemistry. Specifically, coarse and super-coarse dust aerosols produce a net positive direct radiative effect (warming) at the top of the atmosphere and can modify temperature and water vapor profiles, influencing the distribution of clouds and precipitation. In addition, coarse and super-coarse dust aerosols contribute a substantial fraction of ice-nucleating particles, especially at temperatures above –23 °C. They also contribute a substantial fraction to the available reactive surfaces for atmospheric processing and the dust deposition flux that impacts land and ocean biogeochemistry by supplying important nutrients such as iron and phosphorus. Furthermore, we examine several limitations in the representation of coarse and super-coarse dust aerosols in current model simulations and remote-sensing retrievals. Because these limitations substantially contribute to the uncertainties in simulating the abundance and impacts of coarse and super-coarse dust aerosols, we offer some recommendations to facilitate future studies. Overall, we conclude that an accurate representation of coarse and super-coarse properties is critical in understanding the impacts of dust aerosols on the Earth system

Newly identified climatically and environmentally significant high-latitude dust sources

Dust particles from high latitudes have a potentially large local, regional, and global significance to climate and the environment as short-lived climate forcers, air pollutants, and nutrient sources. Identifying the locations of local dust sources and their emission, transport, and deposition processes is important for understanding the multiple impacts of high-latitude dust (HLD) on the Earth\u27s systems. Here, we identify, describe, and quantify the source intensity (SI) values, which show the potential of soil surfaces for dust emission scaled to values 0 to 1 concerning globally best productive sources, using the Global Sand and Dust Storms Source Base Map (G-SDS-SBM). This includes 64 HLD sources in our collection for the northern (Alaska, Canada, Denmark, Greenland, Iceland, Svalbard, Sweden, and Russia) and southern (Antarctica and Patagonia) high latitudes. Activity from most of these HLD sources shows seasonal character. It is estimated that high-latitude land areas with higher (SI ≥0.5), very high (SI ≥0.7), and the highest potential (SI ≥0.9) for dust emission cover >1 670 000 km$^{2}$, >560 000 km$^{2}$, and >240 000 km$^{2}$, respectively. In the Arctic HLD region (≥60$^{∘}$ N), land area with SI ≥0.5 is 5.5 % (1 035 059 km$^{2}$), area with SI ≥0.7 is 2.3 % (440 804 km$^{2}$), and area with SI ≥0.9 is 1.1 % (208 701 km$^{2}$). Minimum SI values in the northern HLD region are about 3 orders of magnitude smaller, indicating that the dust sources of this region greatly depend on weather conditions. Our spatial dust source distribution analysis modeling results showed evidence supporting a northern HLD belt, defined as the area north of 50$^{∘}$ N, with a “transitional HLD-source area” extending at latitudes 50–58∘ N in Eurasia and 50–55$^{∘}$ N in Canada and a “cold HLD-source area” including areas north of 60$^{∘}$ N in Eurasia and north of 58$^{∘}$ N in Canada, with currently “no dust source” area between the HLD and low-latitude dust (LLD) dust belt, except for British Columbia. Using the global atmospheric transport model SILAM, we estimated that 1.0 % of the global dust emission originated from the high-latitude regions. About 57 % of the dust deposition in snow- and ice-covered Arctic regions was from HLD sources. In the southern HLD region, soil surface conditions are favorable for dust emission during the whole year. Climate change can cause a decrease in the duration of snow cover, retreat of glaciers, and an increase in drought, heatwave intensity, and frequency, leading to the increasing frequency of topsoil conditions favorable for dust emission, which increases the probability of dust storms. Our study provides a step forward to improve the representation of HLD in models and to monitor, quantify, and assess the environmental and climate significance of HLD

Newly identified climatically and environmentally significant high-latitude dust sources

Peer reviewe

Heterogeneous interactions kinetic investigation for volatile compounds of atmospheric interest on pure and HNO3 duped ice surfaces, in the region of upper troposphere / Lower stratosphere

The primary goal of the present PhD dissertation, was to investigate The Heterogeneous Interactions of Volatile Organic Acids with Pure (H2O) and Doped with Nitric Acid (HNO3) Ice Surfaces. Heterogeneous processes over ice surfaces are of significant importance in the Upper Troposphere/Lower Stratosphere (UTLS) chemistry and hence they play a central role in Air Quality and Climate Change issues. In order to carry out the proposed work, the Continuous Flow - Effusive Molecular Beam Technique of Very Low Pressure Reactor (VLPR) equipped with a properly modified Knudsen Reactor was employed. Ice surfaces were formed with gradual water vapors deposition on a cryostatted metal surface. In the present work the heterogeneous interaction of methanoic (HC(O)OH), propanoic (CH3CH2C(O)OH) and butanoic (CH3CH2CH2C(O)OH) acid with pure and doped with various concentrations (wt %) of nitric acid, ice surfaces was studied. Experiments performed over several substrate temperature range Τ: 209 - 196 Κ, while gas phase concentrations varied over 1x1010 - 1x1012 molecule cm-3. Under these conditions initial uptake coefficients (γ) as well as their dependence on substrate temperature, the coverage (θ), the maximum substrate available sites (Nmax) and the binding probability (NS) of carboxylic acids on the various ice surfaces were measured. Subsequently, the relative strength of the various acids interactions with the different ice surfaces (ΚLang), as well as its dependence on substrate temperature was determined via fitting experimental data with the Langmuir isotherm model, at the different temperatures experiments performed (ΚLang(T)). Measurements carried out with pure ice surfaces fingerprint, quantitatively, the relative reactivity for the studied carboxylic acids, while at the same time they provided us with useful information regarding the mechanism of the heterogeneous interaction. The corresponding experiments performed with nitric acid doped ice surfaces showed both that HNO3 plays a critical role on enhancing their storage efficiency, converting them in very strong sinks of volatile organic acids and that heterogeneous processes have a generic and most likely determinative significance in Atmospheric Chemistry. Finally, the atmospheric lifetime of carboxylic acids due to their heterogeneous loss, as well as, the fraction of molecules that interact with cirrus clouds as a function of Surface Area Density (SAD, cm2 cm-3) were determined. The thorough knowledge of the above two parameters is very crucial to the overall assessment of the carboxylic acids Impact in the AtmosphereΚατά την εκπόνηση της παρούσας διδακτορικής διατριβής διερευνήθηκε η Ετερογενής Αλληλεπίδρασης Πτητικών Οργανικών Οξέων με Επιφάνειες καθαρού (Η2Ο) και εμπλουτισμένου με νιτρικό οξύ (H2O/HNO3) Πάγου. Οι συγκεκριμένες διεργασίες κατέχουν κεντρικό ρόλο στη χημεία της Ανώτερης Τροπόσφαιρας/Χαμηλώτερης Στρατόσφαιρας (UTLS), ενώ συγχρόνως επιδρούν σημαντικά στην Ποιότητα της Ατμόσφαιρας και τις συντελούμενες Κλιματικές Μεταβολές. Για τη διεκπεραίωση της προτεινόμενης μελέτης, χρησιμοποιήθηκε η ευρείας μοριακής δέσμης τεχνική συνεχούς ροής του Αντιδραστήρα Πολύ Χαμηλής Πίεσης (Very Low Pressure Reactor, VLPR) εφοδιασμένη με κατάλληλα τροποποιημένο για τις ανάγκες των πειραμάτων, Knudsen αντιδραστήρα. Οι επιφάνειες των υποστρωμάτων πάγου σχηματίστηκαν κλιμακωτά με την εναπόθεση ατμών νερού σε κρυοστατούμενη μεταλλική επιφάνεια. Στην παρούσα εργασία μελετήθηκε η ετερογενής αλληλεπίδραση του μεθανοϊκού (HC(O)OH), προπανοϊκού (CH3CH2C(O)OH) και βουτανοϊκού (CH3CH2CH2C(O)OH) οξέος με επιφάνειες καθαρού και εμπλουτισμένου με νιτρικό οξύ, διαφόρων κατά βάρος αναλογιών, πάγου. Τα πειράματα διεξήχθησαν σε θερμοκρασιακό εύρος υποστρώματος Τ: 209 - 196 Κ, ενώ οι συγκεντρώσεις των υπερκείμενων αερίων κυμάνθηκαν από 1x1010 έως 1x1012 molecule cm-3. Για τις συγκεκριμένες συνθήκες μετρήθηκαν οι συντελεστές αρχικής κατακράτησης των οξέων (γ) και η εξάρτηση τους από τη θερμοκρασία υποστρώματος, το ποσοστό επικάλυψης του υποστρώματος (θ), ο αριθμός διαθέσιμων θέσεων του υποστρώματος (Nmax) και η πιθανότητα πρόσδεσης των καρβοξυλικών οξέων στις διάφορες επιφάνειες πάγου (NS). Εν συνεχεία, προσδιορίστηκε η σχετική ισχύς της αλληλεπίδρασης των διαφόρων οξέων με τις διάφορες επιφάνειες πάγου (ΚLang), μέσω της προσαρμογής των πειραματικών δεδομένων με το θεωρητικό μοντέλο ισόθερμης Langmuir και η εξάρτησή της από τη θερμοκρασία (ΚLang(T)). Τα πειράματα που διεξήχθησαν με επιφάνειες καθαρού πάγου αποτύπωσαν, ποσοτικά, τη σχετική δραστικότητα των προς μελέτη καρβοξυλικών οξέων, ενώ συγχρόνως παρήγαγαν χρήσιμες πληροφορίες σχετικές με το μηχανισμό της ετερογενούς αλληλεπίδρασης. Τα αντίστοιχα πειράματα που πραγματοποιήθηκαν σε επιφάνειες πάγου εμπλουτισμένες με HNO3 κατέδειξαν, αφενός τον κρίσιμο ρόλο του HNO3 στην προσαύξηση της απόδοσης αποθήκευσης απλών σωματιδιακών μορφών πάγου και τη μετατροπή τους σε ισχυρές δεξαμενές πτητικών οργανικών οξέων και αφετέρου τη γενικότερη και ενδεχομένως καθοριστική σημασία των ετερογενών διεργασιών στη χημεία της Ατμόσφαιρας. Τέλος, προσδιορίστηκε ο ατμοσφαιρικός χρόνος ζωής της ετερογενούς κατανάλωσης των καρβοξυλικών οξέων και το αντίστοιχο κλάσμα των μορίων που αλληλεπιδρούν, με τις επιφάνειες των συννέφων συναρτήσει της επιφανειακής του πυκνότητας (Surface Area Density cm2 cm-3). Με τον τρόπο αυτόν είναι εφικτή, ποσοτικά, η συνολική αποτίμηση της επίδρασης των καρβοξυλικών οξέων στην Ατμόσφαιρ

Kinetics and Products of the Reactions of F 2 with Br-Atom and Br 2

International audienc

Rate Constants of the Reactions of O( 3 P) Atoms with Ethene and Propene over the Temperature Range 230-900 K

International audienc

Kinetics and Products of the Reactions of Ethyl and n -Propyl Nitrates with OH Radicals

International audienc

Reactions of OH radicals with 2-methyl-1-butyl, neopentyl and 1-hexyl nitrates. Structure-activity relationship for gas-phase reactions of OH with alkyl nitrates: An update

International audienc