Light-duty passenger cars and large ocean-going vessels represent two particle emission sources that have the ability to affect human health, climate change and air quality in local communities and worldwide. Driving speed and engine technology are two factors that can affect vehicle emissions. In California, drivers can drive upwards of 70% at speeds above the posted limits. This can cause high uncertainty when modeling vehicle emissions. The first part of this thesis examines both high-speed driving and direct-injection effects on particle concentration and composition while the second part examines the effectiveness of a scrubber technology to remove particulate matter (PM) from large ocean-going vessel emissions. The results show that high-speed driving can affect both total particle count and composition significantly as well as direct-injection technology. Ocean-going vessels equipped with a scrubber are effective at removing gaseous SO2, however, they are not as effective at removing PM or black carbon (BC).

Light-duty vehicles emit gaseous and particle emissions that have the ability to effect climate, human health, and air quality. Vehicle technologies are changing rapidly due to the need to increase fuel efficiency. The use of biofuels (i.e., ethanol and iso-butanol) may increase due to the desire to reduce the use of fossil fuels. The changes in fuels and vehicle technologies may change the resulting emissions and need to be assessed. For instance, the water-soluble and water-insoluble particle composition could have detrimental health effects. This dissertation investigates the emissions of PM and gaseous emissions from current and emerging vehicle technologies.

The first section of the dissertation discusses a novel technique developed to determine the real-time Water-Insoluble Mass (WIM) fractions of vehicle emissions. The technique is then implemented in the following sections to infer the WIM fraction of vehicle emissions. The next section investigated the PM emissions from a number of hybrid, PFI, and GDI vehicle technologies on ranging aromatic concentrations and octane rating. The next section evaluated the gaseous and particulate emissions from PFI and GDI vehicles on varying concentrations of ethanol and iso-butanol fuels. Ethanol concentration ranged from E10 to E20 and iso-butanol fuels ranged from B16 to B32. The last section of this dissertation examined the gaseous and particle emissions from GDI and FFV technologies from vary concentrations of ethanol and iso-butanol fuels. For the GDI vehicles, ethanol concentration ranging from E10 to E20 and iso-butanol concentrations of B16 to B32 were used. The FFVs used ethanol concentrations were E10, E51, and E83 with an addition iso-butanol blend of B55. PM mass, Particle Size Distributions (PSDs), Particle Number (PN), BC/soot, Water-Soluble Organic Carbon (WSOC), and real-time WIM fractions were measured for the last three sections mentioned. Significant results on particle composition effects from vehicles, fuels, and driving conditions were found. Increasing vehicular speed increased particle hygroscopicity and decreased the WIM fraction. Alcohol concentration decreases the fraction of soot to the total PM mass for the GDI vehicles tested. Generally, increased ethanol concentration decreased the PN and PM mass.

Aerosols can indirectly effect the radiative balance of the environment by acting as Cloud Condensation Nuclei (CCN) and modifying the microphysical properties of clouds by forming droplets which can either scatter solar radiation back into space, or allow it to pass through and reach the surface of the earth. The potential to activate as CCN and form cloud droplets in the atmosphere is primarily a function of chemical composition and size, and can vary with the aerosol source (i.e. combustion, sea salt, etc.). However, information in regards to the CCN activity of different primary and secondary aerosol sources is limited and not always well defined due to the complexity of the particles. As a result, the aerosol-cloud-climate relationship is not well understood and is the largest source of uncertainty in radiative forcing estimates.

Unique methods to estimate the CCN potential of aerosols derived from different emission sources will be presented. First, a method of analysis to observe and predict the aerosol morphology in CCN activation data for various aerosol compositions representative of emissions sources was developed to investigate the effect of mixing states on aerosol hygrosocopicity. Next, a method of characterizing rapidly changing particle hygroscopicity generated by vehicles operating over transient drive cycles was developed and utilized to gain information related to the hygroscopicity of emissions derived from the use different biofuels in modern gasoline vehicles. This study was extended to investigate the effect of using biodiesel and renewable diesel fuels in modern diesel vehicles equipped with advanced emissions control technologies on aerosol hygroscopicity and CCN activity. Although modeling atmospheric interactions is highly dependent on source emissions data such as that provided in this work, aerosol emissions from vehicles may be subject to rapid physical and chemical changes during atmospheric aging which can modify the hygroscopic properties. Thus, to assess the effect of atmospheric interactions on chemical and physical CCN transformations a new mobile atmospheric chamber was developed to age and characterize fresh vehicle emissions derived from modern gasoline vehicles. By investigating both fresh and aged emissions, this work presented provides a comprehensive understanding of the aerosol hygroscopicity from the emissions source to its aged state in the atmosphere.

Biomass burning is one of the largest contributors of particles and trace gases to the atmosphere. This work focuses on constraining the impacts that biomass burning has on Earth's climate through two effects: scattering or absorption of light by particles and particle impacts on cloud formation. To explore biomass burning light interaction and hygroscopicity, a series of environmental chamber experiments were carried out using fuels common to the southwest U.S. This work includes the effects that photochemical aging has on the emissions to provide a realistic assessment of the emissions' lifetime in the atmosphere.

The work done on the cloud formation properties of the emissions shows that two common assumptions applied to the emissions misrepresent their cloud forming abilities. The first assumption, that surface active compounds are negligible in cloud activation, is shown to not apply to biomass burning aerosols. Not accounting for the presence of surface active compounds over estimates the hygroscopicity of the aerosols by up to 30%. The second assumption, that the volume of the particles is well characterized by the electrical mobility diameter, is also shown to not apply to the system. Making the second assumption when parameterizing the hygroscopicity of the aerosols underestimates the hygroscopicity by up to 50%. Accounting for both assumptions is shown to have a greater impact at the point of emission than after six hours of photochemical aging. Therefore, the age of the aerosols must be taken into account when predicting the indirect effects of biomass burning aerosol.

This work also explores the light absorption of biomass burning aerosol and its reaction to photochemical aging. The results indicate that the aerosol is light absorbing and the magnitude of absorption can change with photochemical exposure. This work also shows that the absorption of the aerosol evolves with the volatility and surface active compounds present in the aerosol.

The final part of this work demonstrates that the local air quality that biomass is grown in can have an impact when that biomass is burned. Biomass grown in a polluted area is shown to emit more NOx than biomass grown in a clean area and that the aerosols are less volatile.

Aerosols have a direct effect on climate, through reflection of solar radiation and indirectly as seeds for cloud formation; cloud condensation nuclei (CCN). There is however, a large uncertainty in our understanding of the contributions of aerosols to climate change. It is therefore imperative to explore the chemical and physical properties of aerosol that influence CCN activity and droplet kinetics. This dissertation investigates the effects of aerosol mixing states, chemical composition and photochemical aging on the CCN forming potential of ambient salts and combustion aerosol. Using customized instrumentation and algorithms, the CCN droplet kinetics of inorganic salts and photochemically aged combustion aerosol is also evaluated.

The droplet growth of inorganic and organic salts and the effects of cloud condensation nuclei concentrations on the final droplet sizes were explored with a modified, higher sensitivity optical particle counter (OPC). From the higher sensitivity OPC data, the final droplet diameters of CCN appear independent of aerosol hygroscopicity but strongly dependent on the CCN concentration. We also evaluated the effects of excess non-condensable gases on the CCN activation and droplet kinetics in a cloud condensation nuclei counter (CCNc). Excess, heavier gases increased mass transfer of water vapor and modified the supersaturation in the CCNc column.

The CCN activity and droplet kinetics of aged anthropogenic primary and biogenic aerosol was evaluated. CCN activity and droplet kinetics of α-pinene SOA formed in an atmospheric reactor and mixed with diesel or motor oil-fuel primary organic aerosol (POA) was characterized by the single parameter κ-hygroscopicity. Results showed that a similarity in the CCN activity of organic aerosol may indicate a propensity for mixing. An empirical model developed using unit mass resolution (UMR) aerosol mass spectrometer data captures the complex CCN activity of the mixed systems. The hygroscopicity and droplet kinetics of fresh and aged emissions from new generation gasoline direct injection engines retrofitted with a gasoline particulate filter (GPF) was also evaluated. Photochemical aging and subsequent condensation of the SOA formed from the co-emitted gas phase SOA precursors increased the hygroscopicity of gasoline emissions.

This body of work provides new insights into the current understanding of the effects of aerosol chemical composition, mixing state and hygroscopicity. The findings will help reduce the prevailing uncertainty in estimating anthropogenic radiative forcing

The cloud condensation nuclei (CCN) activity of both primary and secondary sources of aerosol was studied to gain a deeper understanding of how aerosols affect climate and health. CCN from secondary organic aerosol (SOA) was studied in four different systems: longifolene, isoprene, amines and uncombusted gasoline. Primary aerosol from electronic cigarette (E-cig) liquids was also studied.

The CCN activity of longifolene SOA increased over time, but could not be seen with the use of the typical κ-hygroscopicity parameter. To further investigate the cause of this, volatility data was taken at various thermodenuder temperatures and then used to model the formation of reaction products. Modeling showed that extremely low volatility organic compounds (ELVOCs) are produced via this pathway.

To further investigate changing hygroscopicity of SOA, isoprene SOA and isoprene + longifolene SOA was studied in addition to longifolene. The CCN/CN ratio of 100 nm particles at ~0.2% supersaturation was plotted, resulting in a sigmoid indicative of a critical time, at which 50% of the particles activated. This plot and critical time were then recreated using gas-phase decay data of the precursors, resulting in a similar sigmoid that predicted the critical time within 0.15 hours of the initial critical times. This indicates that gas phase vapors may influence CCN activation and changing hygroscopicity.

The potential health effects of aerosols produced by electronic cigarettes was studied by atomizing dilute E-cig liquid into a scanning mobility particle sizer (SMPS) coupled with a CCN counter. Flavorings were found to effect the enhanced condensational growth (ECG) potential, and mass spectra of the liquids also showed significant differences in the composition of the liquids.

The hygroscopity of amines was studied in 2 methods: temperature changes and alcohol amines. Temperature effects the evaporation of salts that form from amine oxidation. Hygroscopicity cannot be predicted using average molecular weights from the PiLS-ToF-MS.

The CCN potential of uncombusted gasoline was studied relative to commercial blends. Hygroscopicity was dependent on blend and changed over time for one commercial blend, but not the other, indicating not all fuel blends have the same CCN activity.

A majority of atmospheric aerosol in urban areas is attributed to transportation emissions, and particularly, gasoline vehicle emissions. The particulate matter (PM) emitted directly from the tailpipe consists of primary organic aerosol (POA) and black carbon. In addition to the particulate emissions, common gaseous pollutants include, nitrogen oxides (NOx), and non-methane organic gases (NMOG), which can photochemically react in the atmosphere to produce secondary organic aerosol (SOA).

SOA formation from gasoline vehicles has received considerable attention in recent years, with the majority of studies focusing on older technology port-fuel injection (PFI) engines. There is limited information on the SOA formation from current technology gasoline direct injection (GDI) engines, despite the abundance of information on the primary emissions from these engines. GDI technology is considered a major pathway to reduce greenhouse gas emissions. However, GDI engines have been measured to emit increased PM mass when compared to similar PFI engines. To counteract the increased PM emissions, manufacturers and regulators may need to utilize various emission control strategies. The goal of this work was to investigate the effects of select emission control strategies on the secondary aerosol potential of newer technology GDI vehicles.

First, the effects of a catalyzed gasoline particulate filter (GPF) were explored. The addition of a GPF has shown drastic reduction in tailpipe PM mass for GDI vehicles, however its effect on secondary emissions were unknown. This study aided to understand if a catalyzed GPF is effective in the removal of secondary aerosol precursors, thus increasing the significance of the after-treatment technology. Next, the impacts of high ethanol fuel blends, and varying driving conditions on secondary aerosol were assessed. This study analyzed the variations in composition and morphology of the emissions from vehicles operated on 10% to 78% ethanol fuels (% volume). In addition to the effects of vehicle exhaust from high ethanol fuel blends, this study investigated how a controlled surrogate environment can affects the reaction potential of vehicle exhaust. The effects of aromatic and ethanol content were further explored with lower ethanol blends (0%-20% by volume). These fuels were more similar to current commercial fuel blends and focused on the effects of smaller variations in ethanol and aromatic content on the physicochemical properties of the secondary aerosol. Finally, connections between the different vehicle certification standards, fuels, driving cycles, and reaction conditions were explored to form relationships between measured tailpipe emission concentrations and the resulting SOA formation potential from vehicles.

In this study, the authors evaluate the hygroscopicity and droplet kinetics of fresh and aged emissions from new generation gasoline direct injector engines retrofitted with a gasoline particulate filter (GPF). Furthermore, ageing and subsequent secondary aerosol formation is explored in (NH4)2SO4-seeded and non-seeded experiments. The authors explore the impacts on measured and predicted hygroscopicity, CCN-activity, and droplet kinetics of secondary aerosol mixed with initially insoluble carbonaceous materials versus very soluble (NH4)2SO4 seed. The chemical composition and density of the secondary aerosol (SA) formed from aging is measured with an HR-TOF-AMS and a custom-built APM-SMPS system. The supersaturated and subsaturated hygroscopicity of the fresh and aged emission is measured with a DMT Streamwise Thermal Gradient CCN counter and a hygroscopicity tandem differential mobility analyzer (HTDMA), respectively. The measurements show that the fresh gasoline emissions are only slightly hygroscopic in both supersaturated and subsaturated environments. Photochemical aging and subsequent condensation of the secondary aerosol formed from the co-emitted gas phase precursors increases the hygroscopicity of gasoline emissions. Without the GPF, both subsaturated and supersaturated hygroscopicity. When the engine was retrofitted with the GPF, the secondary aerosol (SA) experiments were seeded with (NH4)2SO4. In these experiments the presence of the condensing SA depresses the hygroscopicity of the salt-secondary aerosol mixture. The hygroscopicity was also depressed in the subsaturated regime with time. These changes in the hygroscopicity with aging were additionally sensitive to aerosol dry size distribution. The authors also used threshold droplet growth analysis (TDGA) to evaluate the effects of the condensing SA on droplet kinetics. These results have important implications for the assessment of cloud-aerosol indirect effects of salt-seeded and black carbonaceous aerosol cores. The authors concluded that in the new generation GDI vehicles the point of aerosol emissions will have significant influence on the impacts of the secondary and primary aerosols on climate.

View the NCST Project Webpage

The risks associated with exposure to emissions from wastewater treatment plants (WWTP) are currently uncertain and require more research, stronger regulatory frameworks and safer design consideration. Known toxic compounds, bacteria, fungi, endotoxins and viruses have been observed near WWTP the past, but their concentration and classification are still dubious. The airborne exposure route is also still poorly established due to the lack of information on aerosol characterization and transport.

The first portion of this dissertation attempts to fill some of the gaps in scientific literature by establishing a relationship between WWTP aerated basin coverage, source emission flux, particle composition, size and distribution as well as the dispersion of aerosolized particulates in Southern California. On-line measurements and filter sample collection were executed at Orange County Sanitation District (OCSD) and at two other locations along the Santa Ana River Watershed; Redlands Wastewater Treatment Plant (RWWTP) and Western Municipal Wastewater Treatment Plant (WMWWTP) for comparison. A laboratory bioreactor was also created to measure Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) and Total Suspended Solids (TSS) and consequently develop a theoretical model, which will later serve as a guide to estimate real world WWTP aerosol number emission fluxes from laboratory data. In addition, the role of hygroscopic growth (CCN activity) in viral wet deposition was investigated at a relative humidity representative of the respiratory system (the upper airways and lungs). The outcome of this analysis provided critical information to further understand the probability of disease via inhalation of pathogens in WWTP aerosol. Results will provide science to aid the design of potential regulatory laws to further implement a safe and non-polluting environment when treating wastewater.

The last chapter of this dissertation provides a phytotoxic assessment on four major crops (wheat, maize, sorghum and soybean) in Mpumalanga province, the fourth-biggest contributor to South Africa's GDP and a region with a horticultural industry that the country heavily relies on. This work highlights the importance of sulfur dioxide emissions and ozone formation in the Highveld Priority Area (HPA) in terms of stressors on agriculture and food security (measured as crop yield losses). The study also compares the phytotoxic results with the potential risk to human health through the inhalation of these pollutants and it presents a monetary value for the total revenue loss within the region.

A study on secondary organic aerosol (SOA) was conducted with a focus on correlating the chemical and physical characteristics with aerosol's ability acting as cloud condensation nuclei (CCN). The work focuses on three types of aerosol: beta-caryophyllene ozonolysis SOA, aliphatic amine SOA, and cigarette environmental tobacco smoke. The work on beta-caryophyllene ozonolysis SOA enhances our understanding of the CCN activity of SOA formed with and without the presence of isoprene, by probing the effects of a series of environmental parameters on the formation and properties of SOA with more ambient-relevant precursor concentrations. This study demonstrates that aerosol formed from ozonolysis of a mixture of low and high molecular weight terpenes can be hygroscopic and can contribute to the global biogenic SOA CCN budget.

The aliphatic amine work explores the atmospheric behaviors of amines with typical atmospheric oxidants, e.g. nitrate radical, hydroxyl radical and ozone. This study shows that night time chemistry of aliphatic amines can produce secondary organic and inorganic aerosol mixtures, and the relative contribution of each component depends on the environment relative humidity. Thus, modelers need to include as much ambient data as possible in order to mimic the amine behavior in the real atmosphere. The hygroscopicity of aliphatic amine secondary aerosol is also investigated, focusing on the correlation between complex composition and aerosol CCN activity. Despite of measurement artifacts, primary aliphatic amine aerosol is composed of highly volatile components with high hygroscopicity.

The third part of the work characterizes the environmental tobacco smoke (ETS) from research cigarettes, with an emphasis on enhanced condensational growth (ECG), represented by CCN activity and droplet formation properties. Changes in smoke particle size, chemistry, and volatility are correlated to changes in droplet behavior from offline and online chemical and physical measurements. The study shows that reference cigarette ETS are hygroscopic and will have similar lung deposition rates despite source.