Browsing by Subject "Volatile organic compounds"
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Item Impact of variable emissions on ozone formation in the Houston area(2009-12) Pavlovic, Radovan Thomas, 1971-; Allen, David T.; McDonald-Buller, ElenaGround level ozone is one of the most ubiquitous air pollutants in urban areas, and is generated by photochemical reactions of oxides of nitrogen (NOx) and volatile organic compounds (VOCs). The effectiveness of emission reduction strategies for ozone precursors is typically evaluated using gridded, photochemical air quality models. One of the underlying assumptions in these models is that industrial emissions are nearly constant, since many industrial facilities operate continuously at a constant rate of output. However, recent studies performed in the Houston-Galveston-Brazoria area indicate that some industrial emission sources exhibit high temporal emission variability that can lead to very rapid ozone formation, especially when emissions are composed of highly reactive volatile organic compounds. This work evaluates the impact of variable emissions from industrial sources on ground-level ozone formation in Houston area, utilizing a unique hourly emission inventory, known as the 2006 Special Inventory, created as a part of the second Texas Air Quality Study. Comparison of the hourly emissions inventory data with ambient measurements indicated that the impact of the variability of industrial source emissions on ozone can be significant. Photochemical modeling predictions showed that the variability in industrial emissions can lead to differences in local ozone concentrations of as much as 27 ppb at individual ozone monitor locations. The hourly emissions inventory revealed that industrial source emissions are highly variable in nature with diverse temporal patterns and stochastic behavior. Petrochemical and chemical manufacturing flares, which represent the majority of emissions in the 2006 Special Inventory, were grouped into categories based on industrial process, chemical composition of the flared gas, and the temporal patterns of their emissions. Stochastic models were developed for each categorization of flare emissions with the goal of simulating the characterized temporal emission variability. The stochastic models provide representative temporal profiles for flares in the petrochemical manufacturing and chemical manufacturing sectors, and as such serve as more comprehensive input for photochemical air quality modeling.Item Indoor air quality in retail stores(2011-05) Rhodes, Joshua Daniel; Siegel, Jeffrey A.; Xu, YingRetail stores are understudied given the energy, occupant health, and potential sales impacts associated with poor indoor air quality (IAQ). There is also evidence of elevated pollutants in retail environments. This thesis is an exploration of the indoor air quality of retail stores. The first section of this thesis is a literature review on field investigations of the indoor air quality in retail buildings. Sixteen investigations report different measurements in 17 specific types of retail environments. Measurements vary depending on the specific investigation, but include VOCs, SVOCs, particles, microbiological species, and radon. When reported, indoor to outdoor ratios of almost all pollutants are greater than unity, suggesting the importance of indoor sources in retail environments. The second section of this thesis is an analysis of the whole store net emission factor for different retail environments. From the types of pollutants found in the retail store investigations, VOCs were the only pollutant group studied frequently enough to merit this analysis. The final section is an analysis of the potential for pollutant remediation strategies. Two methods, increasing air change rate and air cleaning, are considered with an analysis of the energy penalties associated with each.Item Smoking bans as particle source control and HVAC component loading due to airborne particle mass deposition(2006-12) Waring, Michael Shannon.; Siegel, Jeffrey A.This first part of this study assessed differences in the indoor air quality and occupancy levels in seventeen bars due to a city-wide smoking ban that took effect on September 1, 2005 in Austin, Texas, USA. The following were measured in each venue before and after the smoking ban: mean number of occupants, mean number of lit cigarettes, temperature, relative humidity, room volume, and PM2.5, CO, and CO2 concentrations. Additionally, VOC measurements were conducted at three of the venues. There was not a statistically significant change in occupancy, but the best estimate PM2.5 concentrations in the venues decreased 71 – 99%, a significant reduction in all venues, relative to the pre-ban levels; CO concentrations decreased significantly in all but one venue; and concentrations of VOCs known to be emitted from cigarettes decreased to below the detection limit for all but two common compounds. These results suggest that the smoking ban has effectively improved indoor air quality in Austin bars without an associated decrease in occupancy. The second part of this study modeled the amount of mass deposited on HVAC components for a month of operation (i.e., the loading rate) due to airborne particulate matter. The rate at which HVAC components load due to particle deposition is important from both an indoor air quality and energy perspective. The parameters that have the largest influence on the loading rates depend heavily on whether the building is residential or commercial. For the residential cases, the parameters that influenced the filter, coil, and supply-side duct loading rates the most were the Filtration and bypass, Coil properties, and Duct complexity parameters, respectively. For the commercial cases, which always employed some sort of intentional ventilation, the Ambient parameter was the most influential for all loading rates but the return-side ducts, for which the Emissions parameter was the most influential. Additionally, the Ambient and Emissions parameters ranked near the top of the most important parameters for many scenarios. For both the residential and commercial cases, the median over all cases for the filter loading rate was an order of magnitude larger than the median for the coil loading rate, which was an order of magnitude over the duct loading rates. The residential and commercial loading rates compare as follows: for median loading rates over all modeled scenarios, the commercial case for filter loading is approximately a factor of 89 over the residential case (65.39 versus 0.731 g/mo.); the commercial coil loading is approximately a factor of 39 over the residential case (1.83 versus 0.0468 g/mo.); and the commercial supply-side duct loading is approximately 114 times over the residential case (0.58 versus 0.0051 g/mo.). HVAC component loading causes higher pressure drops in the system, which can lead to reduced flow and reduced heating and cooling capacity for residential systems and increased fan energy usage for commercial systems. The results herein could be used to estimate filter changing and coil cleaning schedules with more information about how filter and coil loading affect pressure drop over time in real indoor environments. Additionally, the loading can have indoor air quality implications in the form of secondary pollutant formation or resuspension of biologically active material.