An investigation into the tropospheric chemistry of acidic aerosols and ammonia in the laboratory

This thesis describes a broad range of experiments based on an aerosol flow-tube system to probe the interactions between atmospherically relevant aerosols with trace gases. This apparatus was used to obtain simultaneous optical and size distribution measurements using FTIR and SMPS measurements respectively as a function of relative humidity and aerosol chemical composition. Heterogeneous reactions between various ratios of ammonia gas and acidic aerosols were studied in aerosol form as opposed to bulk solutions. The apparatus is unique, in that it employed two aerosol generation methods to follow the size evolution of the aerosol while allowing detailed spectroscopic investigation of its chemical content. A novel chemiluminescence apparatus was also used to measure [NH4+]. SO2.H2O is an important species as it represents the first intermediate in the overall atmospheric oxidation process of sulfur dioxide to sulfuric acid. This complex was produced within gaseous, aqueous and aerosol SO2 systems. The addition of ammonia, gave mainly hydrogen sulfite tautomers and disulfite ions. These species were prevalent at high humidities enhancing the aqueous nature of sulfur (IV) species. Their weak acidity is evident due to the low [NH4+] produced. An increasing recognition that dicarboxylic acids may contribute significantly to the total acid burden in polluted urban environments is evident in the literature. It was observed that speciation within the oxalic, malonic and succinic systems shifted towards the most ionised form as the relative humidity was increased due to complete protonisation. The addition of ammonia produced ammonium dicarboxylate ions. Less reaction for ammonia with the malonic and succinic species were observed in comparison to the oxalic acid system. This observation coincides with the decrease in acidity of these organic species. The interaction between dicarboxylic acids and ‘sulfurous’/sulfuric acid has not been previously investigated. Therefore the results presented here are original to the field of tropospheric chemistry. SHO3-; S2O52-; HSO4-; SO42- and H1,3,5C2,3,4O4-;C2,3,4O4 2- were the main components found in the complex inorganic-organic systems investigated here. The introduction of ammonia produced ammonium dicarboxylate as well as ammonium disulfite/sulfate ions and increasing the acid concentrations increased the total amount of [NH4+].

Characteristics of the wave energy resource at the Atlantic marine energy test site

The wave energy industry is progressing towards an advanced stage of development, with consideration being given to the selection of suitable sites for the first commercial installations. An informed, and accurate, characterisation of the wave energy resource is an essential aspect of this process. Ireland is exposed to an energetic wave climate, however many features of this resource are not well understood. This thesis assesses and characterises the wave energy resource that has been measured and modelled at the Atlantic Marine Energy Test Site, a facility for conducting sea trials of floating wave energy converters that is being developed near Belmullet, on the west coast of Ireland. This characterisation process is undertaken through the analysis of metocean datasets that have previously been unavailable for exposed Irish sites. A number of commonly made assumptions in the calculation of wave power are contested, and the uncertainties resulting from their application are demonstrated. The relationship between commonly used wave period parameters is studied, and its importance in the calculation of wave power quantified, while it is also shown that a disconnect exists between the sea states which occur most frequently at the site and those that contribute most to the incident wave energy. Additionally, observations of the extreme wave conditions that have occurred at the site and estimates of future storms that devices will need to withstand are presented. The implications of these results for the design and operation of wave energy converters are discussed. The foremost contribution of this thesis is the development of an enhanced understanding of the fundamental nature of the wave energy resource at the Atlantic Marine Energy Test Site. The results presented here also have a wider relevance, and can be considered typical of other, similarly exposed, locations on Ireland’s west coast.