Impacts of Indirect Photochemistry of Brown Carbon and Iron Carboxylate Complexes on Gas and Aerosol Chemistry
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Impacts of indirect photochemistry of Brown Carbon and iron carboxylate complexes on gas and aerosol chemistry Inauguraldissertation der Philosophisch-naturwissenschaftlichen Fakult¨at der Universit¨at Bern vorgelegt von Pablo Corral Arroyo aus Spanien Leiter der Arbeit: Andreas T¨urler Departement f¨ur Chemie und Biochemie Von der Philosophisch-naturwissenschaftlichen Fakult¨at angenommen. August 29, 2018 Bern, 28.09.2018 Der Dekan: Prof. Dr. Z. Balogh CONTENTS 3 Contents 1 Introduction 15 1.1 Atmosphere...................................... ........ 15 1.2 Aerosolparticlesandaerosolaging . ................ 15 1.2.1 Sources of atmospheric aerosol particles . ................ 15 1.2.2 Composition of atmospheric aerosol particles . ................. 17 1.2.3 Aerosolaging.................................. ....... 17 1.2.4 Influence on climate, ecosystems and human health . ................ 19 1.3 Oxidativeradicalsinthetroposphere . ................. 20 1.4 Browncarbon..................................... ........ 21 1.4.1 Propertiesofbrowncarbon . .......... 21 1.4.2 Brown carbon photochemistry and photosensitizers . .................. 21 1.5 Ironinatmosphericparticles . .............. 23 1.5.1 Sourcesandmobilization . .......... 23 1.5.2 Ironspeciation ................................ ........ 24 1.5.3 Radical chemistry and photochemistry . .............. 24 1.6 Halogensintheatmosphere . ............ 27 1.6.1 Activatedhalogenspecies . ........... 27 1.6.2 Feedbacks between photosensitized chemistry and halogenactivation . 27 1.7 Diffusion, viscosity and chemical reactivity. .................... 28 1.8 Motivationandoutline. ............ 30 1.8.1 Motivationoftheproject . .......... 30 1.8.2 Specificgoalsofthisthesis . ........... 32 1.8.3 Outlineofthethesis ............................ ......... 32 2 Chapter 2 35 2.1 Abstract........................................ ........ 36 2.2 Introduction.................................... .......... 36 2.3 Experimentalsection. ............ 38 2.3.1 Coated-wallflowtubeexperiments . ............ 38 2.4 Experimentalconditions . ............. 40 2.4.1 JIC calculations....................................... 41 2.4.2 Aerosolflow-reactorexperiments . ............. 42 2.4.3 Experimentalconditions . ........... 42 2.4.4 Chemicals..................................... ...... 42 2.5 Resultsanddiscussion . ............ 43 2.5.1 Coated-wallflowtube . .. ........ 43 CONTENTS 4 2.5.2 Aerosolflowtube................................ ....... 49 2.5.3 Proposedmechanism. ........ 51 2.6 Atmosphericrelevance . ............ 51 2.7 Conclusion ...................................... ........ 52 2.8 SupportingInformation . ............ 53 2.8.1 NO2 actinometry....................................... 53 3 Chapter 3 59 3.1 Abstract........................................ ........ 60 3.2 Introduction.................................... .......... 60 3.3 Experimental .................................... ......... 62 3.3.1 Coated-wallflowtubeexperiments . ............ 62 3.3.2 Aerosolflowtubeexperiments . .......... 63 3.4 Results......................................... ........ 63 3.4.1 Influence of photosensitizer type and mixing ratio . ................. 63 3.4.2 Influenceofrelativehumidity . ............ 64 3.4.3 Influenceofcompetingdonors. ........... 66 3.5 Discussion...................................... ......... 67 3.6 Upscalingtoatmosphericconditions . ................ 70 3.7 SupportingInformation . ............ 71 3.7.1 Spectra ....................................... ..... 71 3.7.2 NO loss and conversion to HO2 production ........................ 71 3.7.3 Experimentsperformed . ......... 72 3.7.4 Laser flash photolysis (LFP) experiments . .............. 73 3.7.5 Thicknessdependence . ......... 75 3.7.6 Radical production from IC/CA aerosol particles in the aerosol flow tube (AFT) . 75 3.7.7 Modeling ...................................... ..... 77 4 Chapter 4 81 4.1 Abstract........................................ ........ 82 4.2 Introduction.................................... .......... 82 4.3 Experimentalsection. ............ 85 4.3.1 Experimentaldescription . ........... 85 4.4 Results......................................... ........ 86 4.4.1 HO2 production,scavengingandrelease . ...... 86 4.4.2 Iodineactivation .............................. ......... 88 4.5 Conclusions and atmospheric implications . .................. 90 4.6 SupportingInformation . ............ 91 4.6.1 Spectra ....................................... ..... 91 LIST OF FIGURES 5 4.6.2 NO loss and conversion to HO2 production ........................ 91 4.6.3 I2O5 particlesmeasurements . 93 4.6.4 Modelling..................................... ...... 93 5 Chapter 5 97 5.1 Abstract........................................ ........ 98 5.2 Introduction.................................... .......... 98 5.3 ExperimentalSection. ............ 101 5.4 Resultsanddiscussion . ............ 102 5.5 Conclusions and atmospheric implications . ..................108 5.6 SupportingInformation . ............ 109 5.6.1 PTR normalization for different RH ............................109 5.6.2 Modelling..................................... 110 6 Chapter 6 113 6.1 Abstract........................................ ........ 114 6.2 Introduction.................................... .......... 114 6.3 Experimental .................................... ......... 117 6.4 Results......................................... ........ 118 6.4.1 STXMresults................................... 118 6.4.2 HPLC-MSresults................................ ....... 121 6.4.3 PTR-MSresults ................................. 124 6.5 Conclusions ..................................... ......... 125 7 Conclusions and outlook 127 7.1 Conclusions ..................................... ......... 127 7.2 Outlook ......................................... ....... 129 8 References 133 9 Acknowledgements 149 List of Figures 1.1 Overview of AMS datasets of non-refractory PM1. Pie charts show the average mass con- centration and chemical composition with the following color code: organics (green), sulfate (red), nitrate (blue), ammonium (orange), and chloride (purple). Colors for the study labels indicate the type of sampling location: urban areas (blue), < 100 miles downwind of major cites (black), and rural/remote areas > 100 miles downwind (pink). Reproduced from Zhang et al. 1.................................................. 18 LIST OF FIGURES 6 1.2 Radiative forcing induced by greenhouse gases, stratospheric water vapour, surface albedo, aerosol particles, between 1750 and 2005. Reproduced from IPCC, AR5 (2013) 2. ....... 19 1.3 Catalytic mechanism of a photosensitizer (P). The initial step is the excitation step leading to the singlet state (P∗(s)) production followed by the singlet to triplet (P∗(t)) intersystem crossing. P∗(t) can react with oxygen producing singlet oxygen or with an organic molecule producing an intermediate radical (PH·) which can react the a electron/H atom acceptor leadingtotheproductionofP. .......... 22 1.4 Proposed reaction pathways for imidazole formation in the glyoxal/ammonium sulfate system are shown. Green colored compounds were previously described in literature 3,4; orange colored compounds were identified in this work. Reproduced from Kampf et al. 5 ............ 23 1.5 Photochemical catalytic cycle of an iron-carboxylate complex in a particle. FeIIICA (iron citrate) is photolyzed leading to the reduction of iron to Fe2+ and the decarboxylation of the ligand and the production of an organic radical. The latter reacts with oxygen leading to HOx 3+ and a new stable molecule, which can further react with HOx or by cycling with Fe , leading to the decomposition of citric acid to oxygenated volatile organic compounds (OVOC). HO2 reduces Fe2+ back into Fe3+,whichcanbecomplexedagainbycitricacid. 26 1.6 Classification into solid, semi-solid and liquid states of various substances as a function of dynamic viscosity. For organic liquids the molecular diffusion coefficient Dorg can be inferred from the viscosity via the Stokes-Einstein relation (eq. 5). In the bottom panel we show the corresponding e-folding times of equilibration for various particle diameters according to Shiraiwa et al. 6. Reproduced from Koop et al. 7 .......................... 29 2.1 Sketch of the photochemical flow tube reactor setups at PSI for (a) Setup 1 in 2013 measuring NO2 generation and (b) forSetup2in2014measuringNOloss. 38 2.2 NO2 profile for a 0.025 M IC bulk solution, whose concentration increases to ∼ 0.2 M of IC in the film due to the citric acid hygroscopic properties. The gray shaded areas indicate periods where NO was exposed in the dark. The yellow shaded areas indicates the period of irradiation; the decrease in the intensity of yellow represents 2.26 × 1016, 1.47 × 1016, 1.14 × 1016 and 3.94 × 1015 photons cm−2 s−1 for seven, five, three and one lamp, respectively. This time series clearly indicates the light dependence production of HO2 radicals from the photosensitizationofICinaCAfilm. ........... 44 2.3 A linear correlation of HO2 as a function of IC concentration. The left y axis represents the values for Setup 1, while the right y axis represents the values for Setup 2 (an order of magnitude difference for both scales). The Setup 2 data fall between a factor of 2 and 3 from Setup 1 after accounting for differences between Setup 1 and 2;seeSect. 3.1.1. 45 −2 −1 2.4 HO2 fluxes in molecules cm min as a function of actinic flux for a 300 − 420 nm range (solid symbols). The data are plotted as a concentration