Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompasses two studies on virus aerosolization and transport in the built environment and the subsequent implications for human health. In the first study, we quantified the impact of a barrier on the spatial distribution of different-sized particles released by speaking in a poorly ventilated room. The room was outfitted with 108 passive sampling sites. The barrier resulted in an increase in 0.5 µm particles deposited on the source-side of the barrier and an increase in 0.5 µm particles at other locations 4-6 m from the source. The barrier had minor impacts on the distribution of 1, 6, 10 and 20 µm particles. The results from this study indicated that barriers may not serve as adequate protection to others in the room, depending on their locations relative to the barrier and the timescale of exposure. In the second study, we reviewed the applications of next-generation sequencing for viruses in water environments. We also characterized the occurrence of two viruses (crAssphage and SARS-CoV-2) from a local wastewater treatment plant (WWTP) in both water and air samples at two locations within the WWTP (influent and aeration basin). We found that crAssphage, a fecal indicator, was quantifiable in most air and water samples, but was not detected in control samples. SARS-CoV-2 N2 RNA was detected in a fraction of the water and air samples but was present in the control water samples, so results for this virus are confounded by laboratory contamination. We also found that there was no correlation between airborne and waterborne SARS-CoV-2 concentrations at the WWTP. A quantitative microbial risk assessment model was constructed to determine inhalation risks associated with airborne SARS-CoV-2 for WWTP operators. The probability of infection ranged from about 2.4 x 10-4 to 5.6 x 10-8 and was heavily dependent on exposure time, airborne concentration and other parameters. / Doctor of Philosophy / Airborne microorganisms, such as bacteria, viruses and fungi, are abundant in the natural and built environments. This research encompassed two studies that evaluated the impact of viruses in the built environment on public health. The first study investigated whether a barrier, like Plexiglas, could protect people from another person's exhaled particles in a poorly ventilated room. The barrier resulted in an increase in the smallest particles (0.5 µm) on the same side of the barrier as the source and an increase in these particles at other locations 4-6 m from the source, indicating that individual exposure depends on their location relative to the barrier. The barrier had minor impacts on larger particles (1, 6, 10, and 20 µm). The second study focused on viruses at wastewater treatment plants (WWTPs). As part of this study, we reviewed how one can use knowledge about the DNA and RNA of viruses in water and wastewater. We also measured the amount of two viruses (crAssphage and SARS-CoV-2) in wastewater and in air surrounding the WWTP. We detected crAssphage, a virus that infects bacteria and a marker for human activity, in most wastewater and air samples. We also detected SARS-CoV-2 in some wastewater and air samples, but this virus was also present in some control samples, so laboratory contamination was an issue. Using the concentrations of airborne SARS-CoV-2, we constructed a computational model to estimate the risk of infection for SARS-CoV-2 inhalation for WWTP employees. Our calculations indicated that the risk of infection ranged from 2.4 x 10-4 to 5.6 x 10-8 and heavily depended on parameters such as exposure time and airborne SARS-CoV-2 concentrations.

Since the early 70's chemistry and transport models (ChTMs) have been proposed and improved. Tropospheric ChTMs for trace species are detailed numerical formulations intended to represent the atmospheric system as a whole, accounting for all the individual processes and phenomena that influence climate changes. The development of computer resources and the retrieval of emission inventories and observational data of the species of interest have enhanced the model evolution towards three-dimensional global models that account for more complicated chemical mechanisms, wet and dry deposition phenomena, and interactions and feedback mechanisms between meteorology and atmospheric chemistry. The purpose of this study is to ascertain the sensitivity of the solar radiative field in the atmosphere to absorption and scattering by aerosols. This effort is preliminary to the study of feedback mechanisms between photolytic processes that create and destroy aerosols and the radiation field itself. In this study, a cloud of water-soluble aerosols, randomly distributed in space within hypothetical 1-cm cubes of atmosphere, is generated. A random radius is assigned to each aerosol according to a lognormal size distribution function. The radiative field characterization is analyzed using a Mie scattering code to determine the scattering phase function and the absorption and scattering coefficients of sulfate aerosols, and a Monte Carlo ray-trace code is used to evaluate the radiative exchange. The ultimate goal of the effort is to create a tool to analyze the vertical distribution of absorption by aerosols in order to determine whether or not feedback between photolytic processes and the radiation field needs to be included in a Third Generation Chemistry and Transport model. / Master of Science

Aerosols show type-specific characteristics, which depend on intensive aerosol optical and microphysical properties that influence the radiation processes in the atmosphere in several ways. There are still large uncertainties in the calculation of the aerosol direct radiative effect. The classification of aerosols and the characterization of the vertical aerosol distribution is needed in order to provide more accurate information for radiative-transfer simulations. In the framework of the present thesis, the vertical and spatial distribution as well as optical properties of atmospheric aerosols over the European continent were investigated based on lidar measurements. Possibilities for an aerosol classification or so-called aerosol typing were presented and major aerosol types were specified. Former studies about the classification of aerosols were summarized and representative values for aerosol-type-dependent parameters were given. Case studies were used to demonstrate how observations of the European lidar network EARLINET from 2008 until 2010 were analyzed for aerosol layers and how model simulations and auxiliary data including the assessment of meteorological conditions were applied to determine the origin of each single aerosol layer. Thus, aerosol-type dependent parameters were evaluated and a novel method for the typing of aerosols was developed, which can be used, e.g., within algorithms of satellite data retrievals. Additionally, conversion factors were determined, which are needed for the harmonization of satellite data of present and upcoming missions. Furthermore, findings of the aerosol typing based on EARLINET data were compared to results of the aerosol classification scheme for satellite-borne lidar measurements onboard CALIPSO. It could be shown that deficient classifications of the aerosol type emerged systematically within the automated CALIPSO algorithm. Those wrong classification leads to an underestimation of the single-scattering albedo and hence to an overestimation of the warming effect of the respective aerosol layer. This overestimated warming effect has to be kept in mind for simulations of the global aerosol radiative effect based on CALIPSO data. / Die Bestimmung des direkten Strahlungsantriebs von Aerosolen ist mit großen Unsicherheiten behaftet. Inwiefern Aerosole die Strahlungsprozesse in der Atmosphäre beeinflussen ist abhängig von ihren optischen und mikrophysikalischen Eigenschaften. Zur Optimierung von Strahlungstransfersimulationen werden daher ergänzende Informationen über typspezifische Aerosoleigenschaften sowie die vertikale Aerosolverteilung benötigt. Im Rahmen der vorliegenden Arbeit wurden anhand von Lidarmessungen die vertikale und räumliche Verteilung atmosphärischer Aerosole über Europa analysiert sowie deren optische Eigenschaften ermittelt. Einleitend werden Möglichkeiten der Aerosolklassifizierung erläutert und Aerosoltypen spezifiziert, die über Europa beobachtet werden können. Vorherige Studien zur Aerosolklassifizierung sind in einer Literaturübersicht zusammengefasst. Anhand von Fallstudien wurde zunächst die Analyse von Beobachtungen des europäischen Lidarnetzwerkes EARLINET von 2008 bis 2010 auf das Vorhandensein von Aerosolschichten verdeutlicht. Die Herkunft jeder einzelnen Aerosolschicht wurde anschließend unter Verwendung von Modellrechnungen sowie weiteren Informationen bestimmt und aerosoltypspezifische Kenngrößen berechnet. Mit Hilfe dieser Kenngrößen ist es möglich, den Typ des Aerosols abzuleiten. Daraus wurde eine neuartige Methode zur Typisierung von Aerosolen entwickelt, die z.B. in Algorithmen zur Verarbeitung von Satellitendaten verwendet werden kann. Zusätzlich wurden Umrechnungsfaktoren bestimmt, die zur Zusammenführung und zum Vergleich von Daten aktueller und zukünftiger Satellitenmissionen benötigt werden. Die Ergebnisse der Aerosoltypisierung auf Basis von EARLINET-Daten wurden anschließend mit Ergebnissen der automatischen Typisierung weltraumbasierter Lidarmessungen des CALIPSO-Satelliten verglichen. Es konnte gezeigt werden, dass innerhalb des CALIPSO-Algorithmus systematisch fehlerhafte Klassifizierungen des Aerosoltyps auftreten. Diese falsche Klassifizierung führt zu einer Unterschätzung der Einfachstreualbedo und zu einer Überschätzung der erwärmenden Wirkung der betreffenden Aerosolschicht. Die überschätzte Wärmewirkung hat wiederum fehlerhafte Ergebnisse bei Strahlungstransferrechnungen, die auf CALIPSO-Daten basieren, zur Folge.

To date, no observation-based proxy for climate change has been successful in quantifying the feedbacks between clouds and climate. The most promising, yet demanding, avenue to gain confi dence in cloud–climate feedback estimates is to utilize observations and large-eddy simulations (LES) or cloud-resolving modeling (CRM) to improve cloud process parameterizations in large-scale models. Sustained and improved satellite observations are essential to evaluate large-scale models. A reanalysis of numerical prediction models with assimilation of cloud, aerosol, and precipitation observations would provide a valuable dataset for examining cloud interactions. The link between climate modeling and numerical weather prediction (NWP) may be exploited by evaluating how accurate cloud characteristics are represented by the parameterization schemes in NWP models. A systematic simplifi cation of large-scale models is an important avenue to isolate key processes linked to cloud–climate feedbacks and would guide the formulation of testable hypotheses for fi eld studies. Analyses of observation-derived correlations between cloud and aerosol properties in combination with modeling studies may allow aerosol–cloud interactions to be detected and quantifi ed. Reliable representations of cloud dynamic and physical processes in large-scale models are a prerequisite to assess aerosol indirect effects on a large scale with confi dence. To include aerosol indirect effects in a consistent manner, we recommend that a “radiative fl ux perturbation” approach be considered as a complement to radiative forcing.

Aerosols are thought to have a large effect on the climate, especially through their interactions with clouds. The magnitude and in some cases the sign of aerosol effects on cloud and precipitation are highly uncertain. Part of the uncertainty comes from the multiple competing effects that aerosols have been proposed to have on cloud properties. In addition, covariation of clouds and aerosol properties with changing meteorological conditions has the ability to generate spurious correlations between cloud and aerosol properties. This work presents a new way to investigate aerosol-cloud-precipitation interactions while accounting for the influence of meteorology on cloud and aerosol. The clouds are separated into cloud regimes, which have similar retrieved cloud properties, to investigate the regime dependence of aerosol-cloud-precipitation interactions. The strong aerosol optical depth (AOD)- cloud fraction (CF) correlation is shown to have the ability to generate spurious correlations. The AOD-CF correlation is accounted for by investigating the frequency of transitions between cloud regimes in different aerosol environments. This time-dependent analysis is also extended to investigate the development of precipitation from each of the regimes as a function of their aerosol environment. A modification of the regime transition frequencies consistent with an increase in stratocumulus persistence over ocean is found with increasing AI (aerosol index). Increases in transitions into the deep convective regime and in the precipitation rate consistent with an aerosol invigoration effect are also found over land. Comparisons to model output suggest that a large fraction of the observed effect on the stratocumulus persistence may be due to aerosol indirect effects. The model is not able to reproduce the observed effects on convective cloud, most likely due to the lack of parametrised effects of aerosol on convection. The magnitude of these effects is considerably smaller than correlations found by previous studies, emphasising the importance of meteorological covariation on observed aerosol-cloud-precipitation interactions.

A new retrieval algorithm has been developed based on the Optimal Estimation (OE) approach, which retrieves lognormal aerosol size distribution parameters from multiwavelength aerosol extinction data, as measured by the Stratospheric Aerosol and Gas Experiment (SAGE) II in the lower stratosphere. Retrieving these aerosol properties becomes increasingly more difficult under aerosol background conditions, when tiny particles (« 0.1 µm) prevail, to which the experiment is nearly or entirely insensitive. A successful retrieval algorithm must then be able (a) to fill the 'blind spot' with suitable information about the practically invisible particles, and (b) to identify 'the best' of many possible solutions. The OE approach differs from other previously used aerosol retrieval techniques by taking a statistical approach to the multiple solution problem, in which the entire range of possible solutions are considered (including the smallest particles) and characterized by probability density functions. The three main parts of this thesis are (1) the development of the new OE retrieval algorithm, (2) the validation of this algorithm on the basis of synthetic extinction data, and (3) application of the new algorithm to SAGE II measurements of stratospheric background aerosol. The validation results indicate that the new method is able to retrieve the particle size of typical background aerosols reasonably well, and that the retrieved uncertainties are a good estimate of the true errors. The derived surface area densities (A), and volume densities (V ) tend to be closer to the correct solutions than the directly retrieved number density (N), median radius (R), and lognormal distribution width (S). Aerosol properties as retrieved from SAGE II measurements (recorded in 1999) are observed to be close to correlative in situ data. In many cases the OE and in situ data agree within the (OE and/or the in situ ) uncertainties. The retrieved error estimates are of the order of 69% (σN), 33% (σR), 14% (σS), 23% (σA), 12% (σV), and 13% (σReff ). The OE number densities are generally larger, and the OE median particle sizes are generally smaller than those N and R retrieved by Bingen et al. (2004a), who suggest that their results underestimate (N) or overestimate (R) correlative in situ data due to the 'small particle problem'. The OE surface area estimates are generally closer to correlative in situ profiles (courtesy of T. Deshler, University of Wyoming), and larger than Principal Component Analysis (PCA) retrieval solutions of A (courtesy of L. W. Thomason, NASA LaRC) that have been observed to underestimate correlative in situ data by 40-50%. These observations suggest that the new OE retrieval algorithm is a successful approach to the aerosol retrieval problem, which is able to add to the current knowledge by improving current estimates of aerosol properties in the lower stratosphere under low aerosol loading conditions.

Aerosols play important roles in atmospheric and environmental processes. Not only do they impact human health, they also affect visibility and climate. Despite recent advances made to under their sources and fate, there remains a limited understanding of the mechanisms that lead to the formation of aerosols and their ultimate fate in the atmosphere. These knowledge gaps provide the crux of the research reported herein, which has focused on identifying novel sources of atmospheric aerosol, characterizing its physical and optical properties, and rationalizing these properties using an in-depth knowledge of the molecular level mechanisms that led to its formation. Upon mowing, turfgrasses emit large amounts of green leaf volatiles which can then be oxidized by ozone to form SOA. Overall, the mowing of lawns has the potential to contribute nearly 50 µg SOA per square meter of lawn mowed. This SOA contribution is on the same order of magnitude as other predominant SOA sources (isoprene, monoterpenes, sesquiterpenes). Turfgrasses represent an interesting and potentially meaningful SOA source because they contribute to SOA and also because they cover large land areas in close proximity to oxidant sources. Another related SOA precursor is sugarcane, which is in the same family as turfgrass and is among the largest agricultural crops worldwide. Globally, the ozonolysis of sugarcane has the potential to contribute 16 Mg SOA to the atmosphere, compared to global estimates of SOA loading that range from 12-70 Tg SOA. In order to fully understand the role of atmospheric SOA on the radiative budget (and therefore climate), it is also important to understand its optical properties; its ability to absorb vs scatter light. Turfgrass and sugarcane produced SOA that was weakly absorbing while its scatter efficiency was wavelength and size-dependent. Interestingly, SOA formed under both dry (10% RH) and wet (70% RH) conditions had the same bulk chemical properties (O:C), yet significantly different optical properties, which was attributed to differences in molecular-level composition. The work presented herein represents a unique, inclusive study of SOA precursors. A complete understanding of the chemistry leading to SOA formation is used to understand its physical and optical properties and evaluate these large-scale effects of SOA from these precursors.

This master thesis was tasked to find out how the parameter of interior atmosphere changes at student's club "Mrtvá Ryba", that means atmospheric aerosols sized from 0,524 to 20 micrometers. This work tries to show indoor aerosols before and after the smoking ban and its comparison. This work describes concentrations PM1 and PM10, and their behavior per day. Concentrations was measured by APS (Aerodynamic particle sizer). The measurement was the first step in the non-smoking club, then processing with retrieved informations in CoPlot, CoStat and Excel, where the statistical method has done, and comparison with previous values. T-tests was used for statistics and linear regresion. The result confirms, what was it supposed to, so concentracion values are significantly different. The average concentration of all measured days (six) of smoking campaign was at PM1 13,28 µg.m-3 and at PM10 23,38 µg.m-3. The average concentration of all measured days (thirty six) of non-smoking campaign was at PM1 4,88 µg.m-3 and at PM10 24,61 µg.m-3. Resulting concentration of aerosol particles was explicity lower at non-smoking period than at smoking period. Contamination of interior enviroment is influenced by many factors. The most important factor is presence of persons and their number, concentration of outdoor...

The Highveld region of South Africa contributes substantially to the aerosol loading over southern Africa because of its importance as an industrial, mining and farming base. Aerosols affect climate by absorbing or reflecting incoming solar radiation, and by affecting cloud microphysics, cloud albedo and precipitation. The physical and optical properties of industrial/urban aerosols over the Highveld region of South Africa were analysed during a 32-day winter sampling period (21 May to 21 June) in 2002; a 32-day summer sampling period (21 October to 21 November) in 2002, and a second 32-day winter sampling period (19 May to 19 June) in 2003. Synoptic circulation systems were examined in as far as they affect the horizontal transport of aerosols over the Highveld region. Measurements of aerosol optical thickness (AOT) from the ground to the top of the atmosphere and aerosol size distribution characteristics over the Highveld region were taken using hand-held hazemeters and a CIMEL sun photometer. The AOT observed over the region during the winter 2002 and 2003 sampling periods and during the summer 2002 sampling period indicated high turbidity. In the 2002 winter sampling period, the AOT530nm ranged between 0.05 to 0.7 with an average of 0.14. In the 2002 summer sampling period, the AOT530nm ranged between 0.05 to 0.6, with an average of 0.24. In the 2003 winter sampling period, the AOT500nm ranged between 0.06 to 0.6, with an average of 0.21. The Ångström exponent value had a wide range, 0.8 to 2.4 in the 2002 winter and summer sampling periods and also in the 2003 winter sampling period, indicating that a range of particle sizes was present over the Highveld region. The Ångström exponent values obtained were derived from the influences of Aeolian dust, coarse-mode industrial particles and, to a small extent, fine-mode biomassburning aerosols. Case studies, based on trajectory analysis and meteorology of the sampling area, were made of the aerosols emanating from the township sites during each of the three sampling periods to observe the build-up and dispersion of aerosols at that time.

Research into indoor environment has shown that schools are buildings with high- levels of particulate matter concentrations. This is especially the case of schools situated in high-density traffic or in industrial areas. Several studies have also proven the impact of PM on the teenage generation's health. So far no detailed study has been performed to cover the environment of school gyms where the PM dynamics are different from other indoor microenvironments. This different dynamics relates to the gym environment heterogeneity and to the human activities taking place in it. Due to higher pulmonary ventilation, the exposure of the exercising pupils can reach levels possibly noxious to their health. Size resolved mass concentrations of aerosol were measured in three elementary Schools in Prague. One school was situated in the city centre with high traffic density. The second school was situated on a plateau on the periphery with a medium level traffic. The third school can be found in Prague south-western suburbia, in an open landscape, with low traffic density. PM concentrations were measured simultaneously in naturally ventilated gyms and outdoors ajacent to the particular school building. Two pairs of monitors were used throughout the study: A DustTrak Aerosol Monitor and a Personal Cascade...