abstract / Public Health / Master / Master of Philosophy

The focus of this research was the examination of the emission and transformation of nitrogen oxides emitted from vehicles. Measured data for this experiment were collected from May 1 thru May 31, 2002, and were compared to values modeled with CALINE4. CALINE4 is a photochemical and dispersive model used to predict concentrations of NOX (NO+NO2) from line sources. The measurement campaign was coincident with the Bay Regional Atmospheric Chemistry Experiment (BRACE). An ambient air quality monitoring site was constructed adjacent to Gandy Boulevard, in Tampa, FL. When comparisons of measured and modeled NO and NO2 values were made it was found that CALINE4 underpredicted NO2; i.e., underpredicted the conversion of NO, for both daytime and nighttime conditions. Possible causes of this bias were investigated and it was found that the simple kinetic mechanism present in CALINE4 was not sufficient to account for all of the reactions occurring. A simulation was run with a more comprehensive NO conversion mechanism and it was found that the reactions containing peroxy radicals affected the conversion rate but were not present in the simple CALINE4 mechanism. The simulation runs suggested that the ratio of radicals to O3 remained nearly constant during the course of the reaction. This pointed to an improved mechanism where the photolytic rate constant in CALINE4 could be replaced with a new constant, keff. This brought theday time calculations within reasonable agreement of the measured values, including an unexpected improvement in nighttime concentrations. Specifically, this modification eliminated the negative fractional bias in calculated daytime NO2 concentrations, moving it from -0.16 to 0.043. The fractional bias in nighttime calculations was improved from -0.17 to -0.036. Average hourly traffic counts were then used as inputs to the model to compare to the entire month of May 2002 data and it was found that the daytime fractional bias was improved from -0.27 to -0.06 and the nighttime from -0.35 to -0.24

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Problems associated with instruments used to measure low levels of NO₂ include non-specificity, low sensitivity, and an uncharacterized dependence on environmental conditions. MDA Scientific has recently introduced a continuous colorimetric tape technique (chemcassette) to monitor for pollutant gases. Advantages of this technology include ease of use, fast-response alarm capability, and adaptability to measure different pollutants. This research characterized and compared chemcassette performance for NO₂ with other low-level NO₂ monitoring technologies including the luminox LMA-3 monitor and the EPA reference CSI chemiluminescnt monitor. The test protocol was based on EPA procedures. The chemcassette was found to be sensitive to temperature and relative humidity effects. The chemiluminescent monitor had the best overall performance. The luminox monitor displayed temperature dependence. Variation in stability of the chemcassette optical system, tape paper uniformity, and possible interference from ozone were characterized. (Abstract shortened with permission of author.)

Measurement error is an important issue in studies of environmental epidemiology. We considered the effects of measurement error in environmental covariates in several important settings affecting current public health research. Throughout this dissertation, we investigate the impacts of measurement error and consider statistical methodology to fix that error.

INTRODUCTION: Syndromic surveillance is a method of rapid disease detection based on categories of syndromes, or signs, experienced before the full onset of disease. It is increasingly being used by government agencies and health departments to identify disease outbreaks in a timely manner. Environmental exposures are known to induce respiratory and gastrointestinal symptoms, tend to have a seasonality component, and adversely affect the health of millions of people. OBJECTIVE: In this study, we assess the availability of environmental exposure data for air pollution (PM2.5, ozone, and NO2), pollen, and water contaminant exposure for use in a syndromic surveillance project. We also evaluate: 1) the general proximity of HMO populations to monitors, and 2) distribution of SES characteristics of the area populations with respect to monitor locations. METHODS: We collected exposure data, patient population data, and Census tract SES data for two metropolitan areas where Kaiser Permanente (KP) provides medical services: Atlanta, Georgia and the northern Virginia, District of Columbia (DC), and Baltimore area. Exposure data for air pollution and pollen were collected for 2013-2014. Straight-line distance from a monitor to the nearest KP clinic, and from each Census tract centroid, to the nearest air pollution or pollen monitor was computed using the Euclidean distance formula. RESULTS: Air pollution is routinely monitored by a Federal mandate, is universally available, and easily obtained. Pollen data is collected by private entities, which in some cases hinders access. Water quality data is generally publically available, but it is collected at the source and not easily traceable to water delivery endpoints. In both Atlanta and DC, Maryland, and Virginia most of the clinics (78% and 94%, respectively) are located within 10 miles of an air pollution monitor; approximately 83% and 94% of the KP populations were located within 10 miles of an air pollution monitor. SES populations differ substantially by race, age, income, and education with respect to the nearest monitor. However, the median and interquartile range of various air pollutants does not differ much across the monitors – indicating that, on average, there is little SES gradient in type of level of air pollution exposure. CONCLUSIONS: Overall, this study adds knowledge regarding future considerations about the coverage of environmental monitors and to what extent exposure measure estimates can be assigned to certain populations located near monitors.

Emissions of ammonia (NH3) into the atmosphere, principally from agricultural sources, have been implicated in the pollution of forests, moorlands and grasslands, through the subsequent deposition of reduced nitrogen (NH,, -N). Consequently, legislation has been implemented to control both the transboundary transport and local environmental impacts of NH,,. This thesis investigates the emission, dispersion and local deposition of N113 from two sources that are major components of national N113 emissions inventories, slurry applied to grassland and naturally ventilated cattle buildings. AN balance method was identified for determining the time-average deposition of N113 downwind of a farm building, whilst an adapted micrometeorological flux-gradient technique was developed for estimating local deposition downwind of slurry spreading. This method used an analytical atmospheric dispersion model to provide advection corrections to the standard flux-gradient method. The UK-ADMS model, which incorporates a reasonably detailed treatment of building effects, was identified for use in determining the near-field dispersion from naturally ventilated farm buildings. Eight field experiments were conducted to determine the emission, dispersion and local deposition of N113 volatilised from slurry applications. Emission fluxes during the initial runs following slurry spreading were found to depend on friction velocity, relative humidity and rainfall. Local deposition, at sufficient rates to affect local deposition budgets, was not found to occur during near-freezing conditions or following the application of fertilisers. Local deposition velocities during other periods were found to depend on the latent heat flux, temperature and the roughness length. During such periods, 14 - 18 % of the emitted NH3 was estimated to deposit within 50 rn of the source. Experiments were also conducted at two naturally ventilated farm buildings, the Silsoe Research Institute Structures Building and a working dairy farm. Ammonia emission factors were determined for the main building and slurry lagoon at the dairy farm. A novel application of a model back-calculation method was applied to determine the emission from the lagoon. Dispersion of NH3 from both sites was found to be adequately modelled using UK-ADMS. Approximately 2% of the emitted NH3 deposited within 100 - 150 rn of each building. Time averaged deposition velocities calculated from the farm building studies confirmed that NH3 was deposited to the leaf surfaces and uptaken across the leaf cuticle. Temperature dependent exchange rates were also indicated by the results of the farm building experiments, With NH3 uptake being regulated by the assimilation potential of the plant. The experimental results demonstrated that deposition around both sources could lead to local critical load exceedancesT. hese were only estimatedt o occur within a few tens of metres downwind of slurry spreading whilst critical load exceedancesw ere predicted at distanceso f up to 100 m or more downwind of the farm building. The temporal variability in local recapture found in these experiments, particularly for farm buildings, suggests that seasonal variability in the treatment of N113 eniission and deposition should be included in atmospheric transport models. Furthermore, it is possible that transboundary transport of NHx may increase during winter periods with peak housing emissions.

This thesis presents data from an integrated study of precip~tation, ground and surface water chemistry from 460 km of the Peak District, between May 1987 and April 1988. All samples have been analysed for a suite of nine major ions. Data have been used to: (1) describe temporal and spatial variability of acid precipitation and deposition; (2); examine the controls on precipitation chemistry; (3) describe the chemistry of sampled waters and elucidate catchment processes; and (4) examine the impact of bulk deposition on ground and surface water chemistry. The dense network of collectors has clearly identified significant small scale variability of precipitation chemistry across the study area. However, temporal variability is consistent with observations of other workers. It has been statistically demonstrated that calcium and non-marine sulphate have a close temporal and spatial association. This is hypothesised as being the result of atmospheric reactions between regional gaseous sulphur dioxide and extractive industry derived calcium. The resultant calcium sulphate is prinCipally removed by below cloud scavenging and dry deposition. All sampled groundwaters bave .a high acid neutralising capacity which illustrates the dominance of limestone solutional processes. Surface waters have relatively high concentrations of base cations indicating some buffering potential. However, high variability of bo~~ hydrogen and aluminium suggests a limited buffering capability during storm events. Advanced statistical techniques have demonstrated a complex association between surface water acidification and the bulk deposition of marine ions. This is consistent with the findings of other researchers. Cross and partial correlation have shown the mobility of aluminium in acid sensitive waters to be related to elevated loadings of hydrogen. This research has demonstrated the importance of finescale resolution in precipitation chemistry monitoring networks. Advanced statistical techniques have identified relationships between precipitation chemistry and ground and surface water quality in a geologically complex ..environment.

This research presents the development and application of generic methodologies for the production of a spatially resolved emissions inventory for the North West region of England. The overall purpose of the estimates is to provide emissions data for use within air quality management applications. The North West region is used as the basis of the work due to being composed of a number of administrative units and providing the regional context for local air quality management in the main urban areas of Greater Manchester and Merseyside. Estimates are made for the key urban pollutants (CO, NOx, VOCs, PM and S02) from anthropogenic sources in 1994 and are shown at a variety of spatial scales. Data are available in terms of a regional 5 x 5 km grid, a sub-regional 1 x 1 km grid or at the scale of the original data source. Source categories, which correspond to broad management groupings, comprise road transport; rail transport; airports; shipping; industry; (Part A and Part B); and other (domestic and commercial) sources. Estimation procedures are developed in relation to readily available data sources and are applied within a GIS environment. The use of GIS has been shown to be an appropriate tool for the development of spatially resolved inventories and has further potential in relation to additional applications of the resultant emissions data. The requirements of producing a generic methodology which uses readily available data sources has been found to limit the degree of detail with which it is possible to develop estimation procedures. One of the principal limitations is the availability of comparable activity data for a number of administrative units. However, the results of the inventory are shown to be useful for a number of air quality management activities, including the identification of patterns of emissions at different scales of investigation and the identification of the location and causality of emission 'hotspots'.