Mineral dust photochemistry induces nucleation events in the presence of SO2

Large quantities of mineral dust particles are frequently ejected into the atmosphere through the action of wind. The surface of dust particles acts as a sink for many gases, such as sulfur dioxide. It is well known that under most conditions, sulfur dioxide reacts on dust particle surfaces, leading to the production of sulfate ions. In this report, for specific atmospheric conditions, we provide evidence for an alternate pathway in which a series of reactions under solar UV light produces first gaseous sulfuric acid as an intermediate product before surface-bound sulfate. Metal oxides present in mineral dust act as atmospheric photocatalysts promoting the formation of gaseous OH radicals, which initiate the conversion of SO(2) to H(2)SO(4) in the vicinity of dust particles. Under low dust conditions, this process may lead to nucleation events in the atmosphere. The laboratory findings are supported by recent field observations near Beijing, China, and Lyon, France

FORESAIL-1 cubesat mission to measure radiation belt losses and demonstrate de-orbiting

Abstract Today, the near-Earth space is facing a paradigm change as the number of new spacecraft is literally sky-rocketing. Increasing numbers of small satellites threaten the sustainable use of space, as without removal, space debris will eventually make certain critical orbits unusable. A central factor affecting small spacecraft health and leading to debris is the radiation environment, which is unpredictable due to an incomplete understanding of the near-Earth radiation environment itself and its variability driven by the solar wind and outer magnetosphere. This paper presents the FORESAIL-1 nanosatellite mission, having two scientific and one technological objectives. The first scientific objective is to measure the energy and flux of energetic particle loss to the atmosphere with a representative energy and pitch angle resolution over a wide range of magnetic local times. To pave the way to novel model - in situ data comparisons, we also show preliminary results on precipitating electron fluxes obtained with the new global hybrid-Vlasov simulation Vlasiator. The second scientific objective of the FORESAIL-1 mission is to measure energetic neutral atoms (ENAs) of solar origin. The solar ENA flux has the potential to contribute importantly to the knowledge of solar eruption energy budget estimations. The technological objective is to demonstrate a satellite de-orbiting technology, and for the first time, make an orbit manoeuvre with a propellantless nanosatellite. FORESAIL-1 will demonstrate the potential for nanosatellites to make important scientific contributions as well as promote the sustainable utilisation of space by using a cost-efficient de-orbiting technology.Peer reviewe

Hight induced nucleation in the interaction of SO2 and mineral dust.

internationa

New particle formation from the interaction of SO2 and mineral dust under light irradiation

AIR+YDU:CGO:BD

Minéral dust photochemistry induces nucleation events in the presence of SO2

National @ AIR+YDU:CGO:BDAInternational audienceNon

Heterogeneous uptake of NO2 on Arizona Test Dust under UV-A irradiation: An aerosol flow tube study

SSCI-VIDE+ATARI:CARE:+YDU:LFI:BDA:CGOInternational audienceThe uptake rate of NO2 on Arizona Test Dust aerosols was measured using an aerosol flow tube (AFT). While the uptake rate in the dark could not be measured, the uptake under UV-A irradiation was enhanced, with values in the range from (0.6 +/- 0.3) x 10(-8), (2.4 +/- 0.4) x 10(-8). The observed gas phase products were HONO and NO, with yields of at 30% and 9.6%, respectively. The difference between these measurements and those previously reported on macroscopic films are discussed and differences highlighted. Interestingly, a reasonable agreement is observed between the uptake kinetics of NO2 on Arizona Test Dust macroscopic films and aerosols, despite the different experimental approaches. The simplest approach i.e. thin films having a significant porosity, provides similar uptake kinetics to the more complex and realistic AFT approach. (C) 2013 Elsevier B.V. All rights reserved

SO2 addition to alkenes: a new formation mechanism of organosulfates in the atmosphere

SSCI-VIDE+CARE+MPI:SPR:CGOInternational audienceSecondary organic aerosol (SOA) formation and composition have received increasing attention in the last years due to their impact on climate, air quality and human health. Organosulfates have been increasingly and widely detected in tropospheric particles and has been suggested to arise as side products from SOA production (Tolocka, 2012). Therefore, they have also been identified as SOA tracers (Zhang, 2012). Originally, the production of organosulfates was explained by the esterification reaction of alcohols, but this reaction in atmosphere is kinetically negligible. Other formation pathways have been suggested such as hydrolysis of peroxides and reaction of organic matter with sulfite and sulfate radical anions (SO3-", SO4-") (Nozière, 2010), but it remains unclear if these can completely explain atmospheric organo-sulfur aerosol loading.Figure 1. A possible formation pathway of organosulfates in atmosphere.We have investigated a new formation pathway of organo-sulfur compounds: the addition of SO2 to alkenes (Figure 1). The sulphur dioxide addition to double bond can occur with different mechanisms (photoreaction, ene-reaction, cycloaddition) (Jones, 1974; Vogel, 2007; Lan, 2011). Differently to ozone, sulphur dioxide is a 1,3-dipole with a strong zwitterion character and the most favourable cycloaddition to double bond is a 2+2 addition. On the other hand, O3 adds to alkenes by a well-known 3+2 cycloaddition (Lan, 2011). In order to better understand this reaction and its environmental impact we have studied the reactivity of SO2 with respect to different alkenes (cis/trans, terminal/internal alkenes). The experiments were carried out at the solid (or liquid)-gas interface. A custom built coated-wall flow tube reactor was developed to control relativity humidity, SO2 concentration, temperature and gas flow rate. The uptake coefficients of SO2 on organic films were calculated and resulting products were identified using liquid chromatography coupled with an orbitrap mass spectrometer (LC-HR-MS).The results show that surprisingly SO2 reacts efficiently with alkenes to form organulfates. For examples, the experiments carried out on 1-dodecene highlighted a rapid SO2 uptake and the efficient formation of C12H24O4S, which could be a cyclic organosulfate (Figure 1). Moreover, we have observed that the reaction is acid-catalysed, a faster uptake of SO2 is observed in presence of an acid function. Indeed, it was observed that unsaturated acids (oleic acid) are very sensitive to SO2 addition. These preliminary results tend to elucidate the role of organo-sulfates interfacial chemistry, as a significant pathway for understanding of atmospheric SOA formation

Mineral dust photochemistry induces nucleation events in the presence of SO2

International @ AIR+YDU:CGO:BDAInternational audienceNon

Reactions of SIV species with organic compounds: formation mechanisms of organo-sulfur derivatives in atmospheric aerosols

@ CARE+MPI:JSH:YDU:SPR:CGOInternational audienceSecondary organic aerosol (SOA) have an important impact on climate, air quality and human health. However the chemical reactions involved in their formation and growth are not fully understood or well-constrained in climate models. It is well known that inorganic sulfur (mainly in oxidation states (+IV) and (+VI)) plays a key role in aerosol formation, for instance sulfuric acid is known to be a good nucleating gas. In addition, acid-catalyzed heterogeneous reactions of organic compounds has shown to produce new particles, with a clear enhancement in the presence of ozone (Iinuma 2013). Organosulfates have been detected in tropospheric particles and aqueous phases, which suggests they are products of secondary organic aerosol formation process (Tolocka 2012). Originally, the production of organosulfates was explained by the esterification reaction of alcohols, but this reaction in atmosphere is kinetically negligible. Other formation pathways have been suggested such as hydrolysis of peroxides and reaction of organic matter with sulfite and sulfate radical anions (SO3-•, SO4-•) (Nozière 2010), but it remains unclear if these can completely explain atmospheric organo-sulfur aerosol loading.To better understand the formation of organo-sulfur compounds, we started to investigate the reactivity of SIV species (SO2 and SO32-) with respect to specific functional groups (organic acids and double bonds) on atmospherically relevant carboxylic acids and alkenes. The experiments were carried out in the homogeneous aqueous phase and at the solid-gas interface. A custom built coated-wall flow tube reactor was developed to control relativity humidity, SO2 concentration, temperature and gas flow rate. Homogeneous and heterogeneous reaction kinetics were measured and resulting products were identified using liquid chromatography coupled with an orbitrap mass spectrometer (LC-HR-MS). The experiments were performed with and without the presence of ozone in order to evaluate any impact on the SIV oxidation and product formation. Preliminary results reveal that oxidation of SIV species can occur under a variety of atmospherically relevant conditions. Furthermore, LC-HR-MS analysis confirms the formation of organo-sulfur compounds that could derive from sulfate and/or the sulfite radical anion. These results elucidate the role of organo-sulfates aqueous and interfacial chemistry, important for our scientific understanding of atmospheric SOA formation

Photochemistry of Airborne Dust Produces Nucleation Events in the Troposphere

International @ AIR+YDU:BDA:CGOInternational audienceDust particles acts as a sink for many gases, such as sulfur dioxide. It is well known that SO2 reacts on dust particle surfaces leading to the production of SO4--. It is known that light-driven reactions on dust particles containing TiO2 or Fe(III) oxides produce OH radicals from water. These radicals can convert SO2 adsorbed onto the particles into H2SO4, which stays on the particles. Here, we show that OH radicals may leave the dust particles and go on to initiate gas-phase chemistry with gaseous SO2. To simulate such conditions, we shone light into a flow tube containing low concentrations of dust, along with water vapor and SO2, and monitored the particle concentrations inside the tube. Low dust concentrations are necessary for new particle nucleation; high dust concentrations would provide enough surface area for sulfuric acid to adsorb onto the dust, instead of nucleating aerosol. These findings are supported by recent field observations near Beijing and Lyon