Insights into atmospheric oxidation

Forests emit biogenic volatile organic compounds (BVOCs) that, together with e.g. sulfuric acid, can operate as aerosol precursor compounds when oxidised. Aerosol particles affect both air visibility, human health and the Earth s radiative budget, thus making the emission inputs and oxidation mechanisms of VOCs absolutely crucial to understand. This thesis discusses the life cycle of compounds in the atmosphere. Specifically, we studied the representations of emission of BVOCs, the atmosphere s oxidation ability along with the sources and sinks of sulfuric acid. The main tool to achieve this was numerical modelling, often compared to field observations. Additionally, we performed computational chemistry simulations in order to calculate transitions in sulfuric acid. The main findings of this thesis can be summarised into the following: (1) Biological understanding of VOC emission processes needs to be enhanced in order to predict VOC concentrations with a high precision. (2) The unexplained fraction of the total OH reactivity in the boreal forest is larger than the known fraction and known secondary organic oxidation products of primary emitted terpenes cannot explain the missing reactivity. (3) OH is the main oxidation agent of organic compounds in the boreal atmosphere. (4) Criegee Intermediates, produced from unsaturated hydrocarbons, can oxidise SO2 effectively in order to provide as an essential source of sulfuric acid in areas with high VOC concentrations. (5) Two-photon electronic excitation did not turn out to be a significant sink of gaseous sulfuric acid in the stratosphere. This thesis closes a large part of the sulfuric acid concentration gap in VOC rich environments. Further, this thesis raises awareness of the fact that we still do not fully comprehend the mechanisms leading to BVOC emissions nor the organic atmospheric chemistry in the boreal forest. Finally, this work encourage to study alternative BVOC emission sources as well as alternative atmospheric oxidants.Skogar avger utsläpp av flyktiga organiska molekyler, så-kallade VOC. Oxidationsprodukterna av dessa molekyler kan, tillsammans med bl.a. svavelsyra, både skapa nya aerosolpartiklar i atmosfären, samt öka storleken av existerande partiklar. Aerosolpartiklarna i atmosfären påverkar både jordens klimatsystem, sikten och människors hälsa. Det är därför helt avgörande att förstå VOC-molekylernas källor och oxidationsmekanismer. Denna avhandling diskuterar och studerar molekylers livscykel i atmosfären. De specifika studieobjekten var 1) representationen av utsläppen av VOCs i atmosfärkemimodeller, 2) atmosfärens oxidationsförmåga, och 3) källorna och sänkor för svavelsyra i luften. Det viktigaste verktyget i studierna var numeriska simuleringar, som ofta jämfördes med fältobservationer. Dessutom utförde vi beräkningskemiska simuleringar för att beräkna elektroniska transitioner i svavelsyramolekylen. De viktigaste resultaten av denna avhandling är: (1) Biologisk förståelse av utsläppsprocesserna för VOC bör stärkas för att kunna förutsäga VOC koncentrationer med en hög precision. (2) Den oförklarliga andelen av den totala OH reaktiviteten i taigaskogsområden är större än den kända andelen. Dessutom kan kända sekundära organiska oxidationsprodukter av primärt utsläppta terpener inte förklara den saknade reaktiviteten. (3) OH är huvudoxidanten av organiska molekyler i atmosfären ovanför taigaskog. (4) Criegee intermediärer, reaktionsprodukter av omättade organiska föreninger, kan oxidera SO2 effektivt, och därmed producera svavelsyra i områden med höga VOC-koncentrationer. (5) Två-foton elektronisk excitation är inte en betydande sänka för svavelsyra i stratosfärens gasfas. Denna avhandling överbygger en stor del av klyftan mellan uppmätta och beräknade svavelsyrakoncentrationer i VOC-rika miljöer. Dessutom ökar denna avhandling medvetenheten om att vi fortfarande inte helt förstår de mekanismer som leder till VOC-utsläpp, samt den organiska atmosfärskemin, i taigaskogsområden. Slutligen uppmuntrar detta arbete till att att studera alternativa VOC utsläppskällor i skogen, samt alternativa atmosfäriska oxidanter

Calculated two-photon electronic transitions in sulfuric acid and its atmospheric relevance

Non Peer reviewe

Case report:Evolution of pulmonary manifestations and virological markers in critical COVID-19 infection in Bruton's agammaglobulinemia

Despite several reports and small case series on the disease course of SARS-CoV-2 infection in patients with inborn errors of immunity (IEI), including X-linked agammaglobulinemia (XLA), this topic remains incompletely described. Here we present the case of a 38-year-old unvaccinated man with XLA, who acquired SARS-CoV-2 infection and experienced a protracted disease course with 47 days of SARS-CoV-2 positivity, critical COVID-19 with respiratory insufficiency necessitating intensive care and ventilatory support, and prompting repeated intensified treatments with remdesivir, dexamethasone, and monoclonal antibodies to eventually control infection. We describe the disease course and treatment and review the current literature on COVID-19 susceptibility and evidence for vaccine efficacy in patients with XLA

SOSAA — a new model to simulate the concentrations of organic vapours, sulphuric acid and aerosols inside the ABL — Part 2: Aerosol dynamics and one case study at a boreal forest site

Natural and anthropogenic aerosols may have a great impact on climate as they directly interact with solar radiation and indirectly affect the Earth’s radiation balance and precipitation by modifying clouds. In order to quantify the direct and indirect effects, it is essential to understand the complex processes that connect aerosol particles to cloud droplets. Modern measurement techniques are able to detect particle sizes down to 1 nm in diameter, from ground to the stratosphere. However, the data are not sufficient in order to fully understand the processes. Here we demonstrate how the newly developed one-dimensional column model SOSAA was used to investigate the complex processes of aerosols at a boreal forest site for a six-month period during the spring and summer of 2010. Two nucleation mechanisms (kinetic and organic) were tested in this study, and both mechanisms produced a good prediction of the particle number concentrations in spring. However, overestimation of the particle number concentration in summer by the organic mechanism suggests that the OH oxidation products from monoterpenes may not be the essential compounds in atmospheric nucleation. In general, SOSAA was correct in predicting new particle formation events for 35% of the time and partly correct for 45% of the time.Peer reviewe

Oxidation of SO2 by stabilized Criegee intermediate (sCI) radicals as a crucial source for atmospheric sulfuric acid concentrations

The effect of increased reaction rates of stabilized Criegee intermediates (sCIs) with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012) increases sulfuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO) with SO2 according to the values recommended by Welz et al. (2012) increases the H2SO4 yield by 3–6%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 33–46% to atmospheric sulfuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that the contribution from sCI reactions to sulfuric acid production is most important in the canopy, where the concentrations of organic compounds are the highest, but can have significant effects on sulfuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism could be crucial in regional as well as global models.Peer reviewe