Anthropogenic influence on new particle formation in the marine boundary layer atmosphere

The most important parameter for estimates of the anthropogenic induced climate change is the radiative forcing. In a comparison of the earth’s radiative budget in the year 2011 relative to 1750, the intergovernmental panel on climate change concludes that the largest uncertainty in the total radiative forcing derives from aerosol particles and their ability to modify cloud properties as cloud condensation nuclei (CCN). This uncertainty may be reduced from increased knowledge of the spatial and temporal distribution of aerosol particles with CCN properties. In this project, aerosol particles formed in coastal and marine atmospheres through so called new particle formation (NPF) were analysed spatially and temporally and an assessment of the anthropogenic impact on the marine NPF was attempted. A method known as the NanoMap method was applied to infer the frequency of NPF in marine environments in the North Sea, Baltic Sea and the Mediterranean Sea. The results of the NanoMap analysis clearly identifies NPF frequently occurring in all three marine environments. The results suggested furthermore an increased probability of NPF in areas with heavy shipping. If the particles formed by the NPF grow to sizes with diameters larger than 50 nm, these may participate in the formation of clouds as CCN. To assess the anthropogenic impact on marine NPF, aerosol properties and NPF were simulated with the ADCHEM model. The input gas phase emissions to the model were emissions from anthropogenic, biogenic and natural sources. The simulations were carried out mainly over the the North Sea and the model was evaluated against the total particle volume measured in Høvsøre, Denmark. The model results were reasonably consistent with the observations. From the ADCHEM modelling results, it was concluded that anthropogenic marine emissions do influence NPF. The modelled particle size distribution at Høvsøre showed evidence of an increase in the NPF most likely as a result of anthropogenic emissions of condensable gases. However, particulate matter from shipping emissions were in some cases found to suppress the NPF. It was therefore concluded that new marine emission control legislations of sulphur-containing compounds may result in a decrease of marine NPF. If particulate emissions were also to be reduced, the result may instead be an increase of marine NPF. The ADCHEM model results were furthermore compared to the NanoMap analysis of the same period. The comparison showed that the modelled and the inferred NPF in the marine areas coincided to a large extent. The consistency between the modelled and the inferred NPF is an encouraging result and provides a first verification of the NanoMap analysis.Ville Berg Malmborg Skeppstrafiken ökar antalet nanopartiklar i atmosfären I den här studien där aerosoler, luft-partiklar, studerats i marin miljö visar resultaten att utsläpp från skeppstrafiken kan bidra till att öka antalet nanopartiklar i luften. De partiklar som studerats här är i första hand de allra minsta nanopartiklarna som bildas i atmosfären. Dessa bildas vid ungefär 1 nanometer genom nypartikelbildning (NPB) och om dessa växer kan de potentiellt få stor inverkan på klimatet och molnbildning i atmosfären. Skeppspartiklarna bildas framförallt direkt vid förbränning av fossilt bränsle och kallas primärpartiklar. Gasutsläpp från skeppstrafiken kan leda till att partiklar bildas vid ett senare tillfälle i atmosfären, så kallade sekundärpartiklar. Vid NPB bildas enbart sekundärpartiklar. NPB är en process där ett ämne i gas-fas kondenserar till flytande eller fast fas. NPB kan påverka klimatet när de små partiklarna växer till större storlekar och bildar så kallade kondensationskärnor. Kondensationskärnor är partiklar som tillåter vattenånga att kondensera vid de förhållanden som råder i atmosfären. Dessa partiklar är därför nödvändiga för bildandet av moln. Tidigare studier har visat att NPB kan bidra med 5-50 % av alla kondensationskärnor globalt sett och förändringar i NPB kan därför kraftigt påverka klimatet. För att studera den antropogena påverkan på NPB i marina miljöer tillämpades i studien två metoder. Förhållandena för NPB i den marina atmosfären över Nordsjön simulerades med hjälp av en aerosol-modell. Vidare användes en mätbaserad metod som kallas NanoMap för att påvisa var och hur ofta NPB sker i marina miljöer. Resultaten från NanoMap-studien visar att NPB är ett ganska vanligt fenomen i den marina atmosfären i både Nordsjön, Östersjön och Medelhavet. Ett viktigt resultat visar på en anmärkningsvärt hög sannolikhet för NPB i marina områden med kraftig mänsklig aktivitet. Figur 1 visar resultat från NanoMap-studien i östra Medelhavet samt inringade områden med kraftiga utsläpp från skeppstrafiken, enligt den europeiska samarbetsorganisationen EMEP. I modellstudien där NPB simulerades i Nordsjön framkom att stora antropogena utsläpp av primärpartiklar kan leda till mindre NPB. Dock visade resultaten att den sammanlagda effekten av utsläppen av både gaser och primärpartiklar från skeppstrafiken ger en ökning av NPB över hav och i kustnära miljöer. Den internationella sjöfartsorganisationen har möjlighet att reglera utsläppen från skeppstrafiken. Nya regleringar som träder i kraft den 1 januari 2015 skall minska skeppsutsläppen av svaveldioxid i Nordsjön till en tiondel av dagens värde. Enligt resultaten i denna studie kan detta leda till mindre frekvent NPB i Nordsjön. Eftersom den slutgiltiga ökningen eller minskningen i NPB kan få effekter för klimatet, då antalet kondensationskärnor i luften sannolikt kan påverkas, finns ett starkt behov av fler studier av NPB som klarlägger både antropogena och biogena källor till NPB. Handledare: Adam Kristensson, Pontus Roldin och Erik Swietlicki Examensarbete 60 hp i Fysik, 2014 Fysiska institutionen, Lunds Universite

OCEAN ACIDIFICATION

Ocean acidification is a consequence of the anthropogenic release of carbon dioxide (CO2) to the atmosphere. When CO2 is dissolved in water it affects the composition of ions and lowers the pH of the water. As the partial CO2 pressure in the atmosphere increases a new balance is reached with the surface waters which causes the pH of the surface oceans to decrease. For small shallow seas this effect may be worse than in the oceans because of the limited vertical mixing of deep water and the limited buffering capability (alkalinity). A decrease in ocean pH may have direct effects on ecosystems and indirect effects where the saturation states of calcium carbonates are the most important. This project aims to model projections of future pH of the Baltic Sea surface waters from several CO2 scenarios suggested by the IPCC. A predictive, deterministic model was constructed to project future changes in pH based on the atmospheric CO2 partial pressure, alkalinity and the equilibrium of ions. From the model the ion concentrations can be calculated and used to calculate projections of the saturation state of calcite and aragonite of the Baltic Sea surface waters. Projections of Baltic Sea pH during the 21st century have been made using the model and the CO2 scenarios A1FI, A2 and B2 described by the IPCC. For these scenarios the projections show a decrease in pH by 0.2-0.4 units. If possible changes in alkalinity, which may be a result of changes in river run off to the Baltic Sea, are included the decrease in pH may be as large as 0.5 units. Projections for calcium carbonate indicate that it is possible that calcite becomes under saturated in spring and autumn during the 2050's but is not likely to become under saturated during summers. Aragonite is in our model projected to become under saturated in all seasons already in the 2040's. The magnitude of our projected changes in pH and saturation states of calcite and aragonite has been reported by SMHI to cause negative effects on calcifying organisms and may have effects on the ecosystem as a whole

Biomass burning emissions and influence of combustion variables in the cone-calorimeter

Emissions from biomass burning are highly variable and depend on combustion conditions as well as fuel properties. Simultaneous emissions from pyrolysis, smouldering, and combustion of the biomass material(s) burning leads to uncertainties in how these processes contribute to emissions of individual or groups of compounds as well as to total particle emissions. These uncertainties are difficult to constrain when analysing real-world emissions but also when performing laboratory studies of e.g., cook-stove emissions in more controlled environments. This study was designed to reduce some of this variability by enabling highly reproducible conditions by controlling combustion via adjustment of a few key factors. The aim of this study was to identify how these factors influenced emissions, and how different pyrolysis and burn conditions in turn contributed to the particle emissions.In this study, we used a controlled atmosphere cone calorimeter according to ISO 5660‐5. We controlled fuel moisture content, the air flow to the combustion and O2 available for combustion, and the total heat flux (HF) to the fuel to study the independent effect of combustion variables on the aerosol emissions. In each experiment a small 10x10x1 cm piece of Birch-wood was put in a sample holder and combusted under controlled conditions. We conducted over 40 experiments, varying HF and flow conditions while monitoring fuel mass loss to quantify emission yields. An Aerosol Mass Spectrometer (AMS, Aerodyne Billerica, USA), a multi‐wavelength aethalometer (AE33, Magee Sci., USA) and a particle size spectrometer (DMS5000, Cambustion, UK) measured time‐resolved evolution in particle properties during burns. Our results showed that pyrolysis conditions in the absence of O2 resulted in organic aerosol (OA) emissions with mass yields (g/g fuel) from a few percent at the lowest HF and up to ten percent at the highest HF. During combustion in air, equivalent black carbon (eBC) emissions were found to moderately increase with increasing HF. eBC was also found to increase when the O2 availability or combustion was reduced (O2 deficient combustion). Polycyclic aromatic hydrocarbon (PAH) was here defined separately from OA in the AMS analysis. PAH emissions were low for pyrolysis and combustion at high air flows (excessive O2 availability). In contrast, O2 deficient combustion conditions resulted in dramatically increased PAH emissions, with yields as high as to 0.5% (g/g fuel). The relationship between PAH emissions and availability of air and O2 during combustion is illustrated in Figure 1. Future analyses include a more detailed PAH analysis including off-line GC-MS, thermal-optical carbon analysis, UV-VIS absorption of MeOH soluble OA. We will parameterize emissions based on the initial conditions such as HF, moisture content, air flow rate (cooling) and O2 availability. A mechanistic understanding of relationships between combustion variables and emissions can aid the development of cleaner biomass combustion technologies and will improve fire emission models

Fire-induced radiological integrated assessment : aerosol characterization

This report on detailed aerosol characterization of fire smoke emissions is part of the Fire-Induced Radiological Integrated Assessment (FIRIA; CERN, Switzerland). In this study, carried out at Lund University, a number of materials were combusted in a cone calorimeter at varied heat fluxes. In a few experiments, the effect of reduced O2 content of supply air was investigated (vitiated conditions). The materials included electrical components, magnets, plastic components, oil and cables and were selected due to their high probability of experiencing ionizing radiation in the research facilities at CERN. The aerosol particle yield in the combustion emissions was determined in terms of number and mass emissions. In addition, the particle physical properties in terms of size distributions, the mass - mobility relationship, and the black carbon fraction of emitted particles was determined. Finally, the particle morphology was determined with transmission electron microscopy (TEM) and elemental composition of trace elements by ICP-MS. The total range of aerosol mass yields spanned from approximately 0.005 (g/g fuel) to 0.23 (g/g fuel). Electrical components and magnets were identified as the combustibles with highest mass yields. Mass yields for cables spanned from 0.005-0.09 g/g fuel. The emissions were highly dynamic, with rapid shifts in concentrations and the particle number size distribution as measured with a fast mobility spectrometer (DMS500). The number yields ranged from approximately 0.05*10^14 to 2*10^14 emitted particles per gram of fuel and was measured within the size range 5-1000 nm. The emissions could be parameterized for future modelling applications into nucleation mode particles (with geometric mean diameter that varied between 20-50 nm) and accumulation mode particles (with geometric mean diameter 100-230 nm). The aerosol mass yields were governed primarily by the concentration and size distribution of accumulation mode particles. Mass yields were determined from 1) Impactor measurements (Dekati Gravimetric Impactor) and 2) Simultaneous measurements of the electrical mobility size distribution (DMS500) and effective density distribution (DMA-APM). The general agreement between the two techniques was good (R2=0.93). Black carbon is indicative of refractory carbonaceous particles which form in fuel rich conditions of the hot flame environment and associated with the black color of soot (smoke). Black carbon yields were for most experiments similar to the derived mass yields. TEM images showed typical refractory black carbon aggregates at high BC fractions. The primary particle size was larger than for diesel exhaust. However, at reduced heat flux and during vitiated combustion (reduced O2 concentration), black carbon yields were sometimes much lower than the derived particle mass yields. TEM analysis for a sample with low BC fraction showed only very few particles and those that were found had distinctly different properties to the high BC fraction sample. We hypothesize that particles emitted under these conditions were dominated by low volatility organic matter formed in the pyrolysis of the materials. Such components were likely co-emitted with black carbon also in conventional experiments, although in minor mass fractions. Based on previous studies it can be hypothesized that H:C ratios are low for the cases with high BC fraction

Aerosol formation and emissions from realistic compartment fires

Firefighters are occupationally exposed to a large number of toxic compounds (IARC 2010). The occupational exposure of firefighters has been classified as potentially carcinogenic (class 2B, IARC; (Straif K. et al. 2007)). Poorly quantified emission factors and low understanding of when various aerosol emissions are likely to form during a fire event (initiation, combustion, extinguishing) inhibit efforts to reduce exposure by interventions to the firefighting strategy. The study was designed to evaluate firefighters’ exposure to air pollutants and to allow identification of how aerosol emissions respond to burning conditions and interventions of the firefighting. The study was conducted at the MSB firefighter training facility in Revinge outside Lund, Sweden. Eight small (5x3x2 m) sheds were built to imitate small compartment environments: apartment, bedroom, workshop, etc. These sheds were ignited under realistic fire scenarios (e.g., accident, arson) and later used for training new fire investigators (forensic police). Firefighter students and teachers monitored and extinguished the fires in similar procedures to real fire events. A supervisor monitored the combustion conditions, allowing or restricting fresh-air flow into the fire by opening or closing of the main door.Fire emissions were extracted from the fire through a 10 m (Ø 6 mm) stainless steel pipe, diluted ~1:50 with HEPA and active charcoal filtered air. The diluted emissions were monitored with a battery of aerosol monitoring instruments. Instrumentation included an aerosol mass spectrometer (Aerodyne SP-AMS, Billerica USA), an aethalometer (AE33, Magee Sci. USA), a differential mobility spectrometer (DMS500, Cambustion, UK), CO2 monitor (LI-COR, USA), and a NO/NO2 monitor (2BTech, USA). Complementary background measurements were positioned downwind or sidewind of the fires. With this equipment we collected data with the aim to resolve relationships between combustion conditions and pollution formation during different phases of a fire response. The results showed that total particle mass (PM1) emissions correlated with CO2 emissions and thus fire intensity. The emissions were speciated according to equivalent black carbon (eBC), organic aerosol (OA) and polycyclic aromatic hydrocarbon (PAH) derived from AMS data. When speciated, different particle emissions were found to depend on activities of the firefighting and the supervisor responsible for allowing or restricting fresh air into the combustion environment. Most evidently, we found that restricting the access to O2 by closing the door resulted in a sharp increase of OA and even more pronounced, PAH. PAH increased by several orders of magnitude, suggesting that PAH exposure-risks may increase drastically when fires become under-ventilated. Extinguishing the fire with water quickly decreased all particle emissions. The results described are illustrated in Figure 1.Further analysis involves additional off-line analyses, derivation of emission factors, time-resolved speciated emission analysis and evaluation of relationships between emissions, burning conditions and firefighting strategies

A comparison of carbon monoxide yields and particle formation at various global equivalence ratios in vitiated and under-ventilated conditions

There have been previous studies comparing experimental methods for the purpose of capturing gaseous yields at a range of global equivalence ratios. However, no work has investigated the capability of the open controlled atmosphere cone calorimeter for collecting such data where its two modes of operation are directly compared. The aim of this study is to compare carbon monoxide yields collected using vitiated and under-ventilated modes of atmospheric control in order to identify the preferable method of replicating carbon monoxide yields reported from larger scale enclosure fire experiments. Cone irradiances of 30, 50 and 65 kW/m2 were applied to PMMA and plywood samples. Vitiated tests were conducted using a mixed air/diluent gas, with an inflow rate of either 100, 150 or 180 L/min, resulting in a reduced oxygen concentration of 17.5 vol. %. Under-ventilated tests were conducted using flow rates of 5, 10 and 20 L/min in an air atmosphere. Particle formations and emissions were also measured using a particle analyser and have been reported herein. Results indicate that the under-ventilated mode of equivalence ratio control offers a more promising method of capturing species yields with favourable comparisons to other bench scale methods

Evolution of In-Cylinder Diesel Engine Soot and Emission Characteristics Investigated with Online Aerosol Mass Spectrometry

To design diesel engines with low environmental impact, it is important to link health and climate-relevant soot (black carbon) emission characteristics to specific combustion conditions. The in-cylinder evolution of soot properties over the combustion cycle and as a function of exhaust gas recirculation (EGR) was investigated in a modern heavy-duty diesel engine. A novel combination of a fast gas-sampling valve and a soot particle aerosol mass spectrometer (SP-AMS) enabled online measurements of the in-cylinder soot chemistry. The results show that EGR reduced the soot formation rate. However, the late cycle soot oxidation rate (soot removal) was reduced even more, and the net effect was increased soot emissions. EGR resulted in an accumulation of polycyclic aromatic hydrocarbons (PAHs) during combustion, and led to increased PAH emissions. We show that mass spectral and optical signatures of the in-cylinder soot and associated low volatility organics change dramatically from the soot formation dominated phase to the soot oxidation dominated phase. These signatures include a class of fullerene carbon clusters that we hypothesize represent less graphitized, C5-containing fullerenic (high tortuosity or curved) soot nanostructures arising from decreased combustion temperatures and increased premixing of air and fuel with EGR. Altered soot properties are of key importance when designing emission control strategies such as diesel particulate filters and when introducing novel biofuels

Investigation of late-cycle soot oxidation using laser extinction and in-cylinder gas sampling at varying inlet oxygen concentrations in diesel engines

[EN] This study focuses on the relative importance of O-2 and OH as oxidizers of soot during the late cycle in diesel engines, where the soot oxidation is characterized in an optically accessible engine using laser extinction measurements. These are combined with in-cylinder gas sampling data from a single cylinder engine fitted with a fast gas-sampling valve. Both measurements confirm that the in-cylinder soot oxidation slows down when the inlet concentration of O-2 is reduced. A 38% decrease in intake O-2 concentration reduces the soot oxidation rate by 83%, a non-linearity suggesting that O-2 in itself is not the main soot oxidizing species. Chemical kinetics simulations of OH concentrations in the oxidation zone and estimates of the OH-soot oxidation rates point towards OH being the dominant oxidizer.The authors gratefully acknowledge the Swedish Energy Agency, the Competence Center for Combustion Processes KCFP (Project number 22485-3), and the competence center METALUND funded by FORTE for financially supporting this research. The authors acknowledge Volvo AB for providing the gas-sampling valve and personally Jan Eismark (Volvo AB) and Mats Bengtsson (Lund University) for their technical support.Gallo, Y.; Malmborg, VB.; Simonsson, J.; Svensson, E.; Shen, M.; Bengtsson, P.; Pagels, J.... (2017). Investigation of late-cycle soot oxidation using laser extinction and in-cylinder gas sampling at varying inlet oxygen concentrations in diesel engines. Fuel. 193:308-314. https://doi.org/10.1016/j.fuel.2016.12.013S30831419

Characteristics of Particulate Emissions from Low Temperature Combustion and Renewable Fuels : Aerosol Mass Spectrometry of Refractory Carbonaceous Particles

Particulate air pollution is one of the major causes of premature death in the world, and combustion-derived soot emissions contribute strongly to the particulate pollution to which humans are exposed. Black carbon (BC) is one such emission and denotes soot with strong light absorption in the ultraviolet to infrared spectrum. Combustion can also generate brown carbon (BrC) particles, with absorption confined to shorter wavelengths than BC and absorption Ångström exponents (AAEs) significantly higher than 1. When emitted to the atmosphere, BC and BrC can accelerate global warming by absorbing incoming solar radiation. The overall aim of this thesis is to improve the understanding of relationships between combustion conditions, physicochemical soot properties, and parameters which are of relevance for adverse health effects and climate impact.Soot emissions were studied from a miniCAST soot generator, a heavy-duty diesel engine, and from traditional and modern biomass based cook stoves. The soot particles were characterized for their optical properties, chemical composition, size, and carbon nanostructure (soot maturity). Soot formation and oxidation processes were studied by extracting particles from the cylinder of a heavy-duty diesel engine. The diesel engine was equipped with an exhaust gas recirculation system, and used either Swedish MK1 fossil diesel, a rapeseed methyl ester (RME) biodiesel, or a renewable hydrotreated vegetable oil (HVO) fuel. Immature soot was characterized by short and amorphous nanostructures, BrC absorption, high polycyclic aromatic hydrocarbon (PAH) fractions, and refractory organic carbon that partially formed pyrolytic carbon during thermal-optical analysis. Mature soot was characterized by ordered nanostructures, BC absorption, low PAH mass fractions, and mass dominated by elemental carbon. A novel methodology was introduced to investigate differences in soot maturity using a soot particle aerosol mass spectrometer (SP AMS). Mature soot, characterized by long fringe lengths, generated mainly low molecular weight carbon cluster fragments (C1-5+). In addition to C1-5+, immature soot with shorter fringe lengths produced signals from midcarbon and fullerene carbon clusters (C≥6+). The new methodology and interpretation can improve methods that use aerosol mass spectrometry for the source apportionment of combustion emissions. It can also aid in the development of new emission mitigation strategies, for example, with respect to the soot oxidation reactivity of relevance for diesel particulate filters. The results show that low temperature combustion conditions result in soot with immature characteristics, while higher temperatures result in more mature soot. The elevated AAEs and a major fraction of the BrC absorption were assigned to refractory soot components. Specifically, the analysis suggested that the progression from BrC to BC absorption as soot maturity increased was caused primarily by the growth of refractory aromatic units, which are the soot building blocks. This description of how combustion conditions may control soot properties can improve our understanding of processes related to light absorption in the atmosphere.The renewable HVO and RME fuels reduced particulate matter and BC emissions; the RME, in addition, reduced PAH emissions compared to fossil diesel. The formation of reactive oxygen species (ROS) is an important mechanism in particle-induced toxicity. The ability of soot particles to form ROS increased with increasing combustion temperatures. It was hypothesized from the analysis of soot properties that the diesel soot potential to form ROS with increasing combustion temperature in the first step increased due to more mature soot nanostructures, and in the second step due to increased oxidation and altered surface oxygen functional groups. This hypothesis can form a basis for future evaluations of drivers of soot particle toxicity that are of relevance for global air pollution problems

Potential air-quality improvements with future energy carriers in transportation

AimOur aim is to provide a-priori information on air-quality implications of potential future energy carriers in transportation relevant for sustainability, life cycle and health-impact assessments.MethodologyInformation on air- and climate-pollutant formation from energy carriers is collected in detailed laboratory assessments on heavy-duty combustion engines as well as on non-tailpipe emissions. We target energy efficiency, characteristics of primary pollutants, characteristics after atmospheric transformation (ageing), and toxicological relevance.Key results/conclusions Emissions from renewable energy carriers for heavy-duty transportation that exist on the markets today (alcohols, FAME, HVO) have been reported by our groups. The results show a need for new future energy carriers with inherent low pollution formation potential and a production potential for electrofuels (e-fuels). Non-tailpipe emissions may increase for certain energy carriers. Knowledge on health and climate implications of different emissions mitigating strategies is necessary to ensure a sustainable path forward for the transport sector