Doctor of Philosophy

dissertationThis study provides a holistic view of dust storms and transport in the eastern Great Basin, and is the first to analyze the meteorological, source, and chemical characteristics of dust production in this region. First, the climatology of dust storm events affecting Salt Lake City, Utah (SLC) was assessed, and the controls on atmospheric dust generation and transport documented. Records indicate seasonal and diurnal patterns, with dust storms typically occurring in spring months during the afternoon. Since 1930, SLC had 379 dust event days (DEDs), averaging 4.7 per year, with elevated PM10 exceeding National Ambient Air Quality Standards (NAAQS) on 16 days since 1993, or 0.9 per year. Strengthening cyclonic systems are the primary producer of these dust storms. Next anthropogenically disturbed areas and barren playa surfaces were identified as the primary dust source types contributing to dust storms in the region. Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery during DEDs was analyzed to identify dust plumes, and assess the characteristics of dust source areas, which produce dust during the spring and fall and during drought. Most plumes originate from playas, classified as Barren land cover, with a silty clay soils; they often have anthropogenic disturbances, including military operations and water withdrawal. Disturbance is necessary to produce dust from vegetated landscapes in the region, evidenced by the new dust source active from 2008-2010 in the 2007 Milford Flat Fire scar, which underwent postfire land treatments. Finally, the elemental composition of dust in the region was characterized. Dust and surface soil samples were collected, resuspended, and analyzed with Sychrotron XRay Fluorescence (SXRF). Dust and soil from the eastern Great Basin are distinctly different, and identifiable. Within the dust and soil groups, however, large differences are not seen and individual samples cannot be identified by their elemental composition. Dust and soil from the eastern Great Basin tends to not be enriched in most major soil elements, excepting a large enrichment of Na in dust samples. Trace elements, however, show very large enrichment values for both dust and soil. The enrichment of dust samples has notable importance for ecosystem functioning and human health

Midweek Intensification of Rain in the U.S.: Does Air Pollution Invigorate Storms?

The effect of pollution on rainfall has been observed to depend both on the type of pollution and the precipitating environment. The climatological consequences of pollution for rainfall are uncertain. In some urban areas, pollution varies with the day of the week because of weekly variations in human activity, in effect providing a repeated experiment on the effects of pollution. Weekly variations in temperature, pressure, cloud characteristics, hails and lightning are observed in many areas. Observing a weekly cycle in rainfall statistics has proven to be more difficult, although there is some evidence for it. Here we examine rainfall statistics from the Tropical Rainfall Measuring Mission (TRMM) satellite over the southern U.S. and adjacent waters, and find that there is a distinct, statistically significant weekly cycle in summertime rainfall over the southeast U.S., as well as weekly variations in rainfall over the nearby Atlantic and the Gulf of Mexico. Rainfall over land peaks in the middle of the week, suggesting that summer rainfall on large scales may increase as pollution levels rise. Both rain statistics over land and what appear to be compensating effects over adjacent seas support the suggestion that air pollution invigorates convection and outflow aloft

Plastic Rain in Protected Areas of the United States

Eleven billion metric tons of plastic are projected to accumulate in the environment by 2025. Because plastics are persistent, they fragment into pieces that are susceptible to wind entrainment. Using high-resolution spatial and temporal data, we tested whether plastics deposited in wet versus dry conditions have distinct atmospheric life histories. Further, we report on the rates and sources of deposition to remote U.S. conservation areas. We show that urban centers and resuspension from soils or water are principal sources for wet-deposited plastics. By contrast, plastics deposited under dry conditions were smaller in size, and the rates of deposition were related to indices that suggest longer-range or global transport. Deposition rates averaged 132 plastics per square meter per day, which amounts to \u3e1000 metric tons of plastic deposition to western U.S. protected lands annually

Impacts of Water Development on Great Salt Lake and the Wasatch Front

Although droughts and floods produce short‐term fluctuations in the elevation of Great Salt Lake, water diversions since the arrival of 19th Century pioneers represent a persistent reduction in water supply to the lake, decreasing its elevation by 11 feet and exposing much of the lake bed. As Utah moves forward, we need to be aware of the impacts of lowered lake levels and make decisions that serve the interests of all Utahns. In particular, proposals to further develop the water supply of the Great Salt Lake should carefully consider potential impacts to the health of the lake and examine the tradeoffs. There are no water rights to protect Great Salt Lake, so water development currently focuses solely on whether there is water upstream to divert. If future water projects reduce the supply of water to the lake, its level will continue to drop.1 Although water conservation has reduced urban per capita use by 18 percent, overall municipal water use has increased by 5 percent because of our growing population.2 To significantly reduce water use, a balanced conservation ethic needs to consider all uses, including agriculture, which consumes 63 percent of the water in the Great Salt Lake Basin. Increased awareness of how water use is lowering Great Salt Lake will help us avoid the fate of other salt lakes such as the Aral Sea in Central Asia or California’s Owens Lake, both of which have been desiccated and now cause severe environmental problems. We must look beyond the next few decades and decide how we value the lake for future generations. Lower lake levels will increase dust pollution and related human health impacts, and reduce industrial and environmental function of Great Salt Lake. We must be willing to make decisions now that preserve Great Salt Lake’s benefits and mitigate its negative impacts into the coming centuries

Midweek Increase in U.S. Summer Rain and Storm Heights, Suggests Air Pollution Invigorates Rainstorms

Tropical Rainfall Measuring Mission (TRMM) satellite data show a significant midweek increase in summertime rainfall over the southeast U.S., due to afternoon intensification. TRMM radar data show a significant midweek increase in rain area and in the heights reached by afternoon storms. Weekly variations in model-reanalysis wind patterns over the region and in rain-gauge data are consistent with the satellite data. A midweek decrease of rainfall over the nearby Atlantic is also seen. EPA measurements of particulate concentrations show a midweek peak over much of the U.S. These observations are consistent with the theory that anthropogenic air pollution suppresses cloud-drop coalescence and early rainout during the growth of thunderstorms over land, allowing more water to be carried above the 0 C isotherm, where freezing yields additional latent heat, invigorating the storms--most dramatically evidenced by the shift in the midweek distribution of afternoon-storm heights--and producing large ice hydrometeors. The enhanced convection induces regional convergence, uplifting and an overall increase of rainfall. Compensating downward air motion suppresses convection over the adjacent ocean areas. Pre-TRMM-era data suggest that the weekly cycle only became strong enough to be detectable beginning in the 1980's. Rain-gauge data also suggest that a weekly cycle may have been detectable in the 1940's, but with peak rainfall on Sunday or Monday, possibly explained by the difference in composition of aerosol pollution at that time. This "weekend effect" may thus offer climate researchers an opportunity to study the regional climate-scale impact of aerosols on storm development and monsoon-like circulation

Enhancement of FGF-like polypeptides in the retinae of newborn mice exposed to hyperoxia

AbstractRetinae from neonatal mice exposed to prolonged hyperoxia (100% oxygen), show marked vasoproliferation. Extracts of such retinae were chromatographed on a heparin-Sepharose column and the absorbed material subjected to HPLC fractionation. Two components, approx. 10 and 18 kDa, respectively, were found to have angiogenic activity, which was higher than in corresponding extracts from animals exposed to air. Both fractions and an additional 5 kDa component reacted with an antibody to basic fibroblast growth factor (bFGF) and showed higher levels in hyperoxia. The data suggest that hyperoxia activates angiogenic factors belonging to the heparin binding family

Breaking the HAC Barrier: Histone H3K9 acetyl/methyl balance regulates CENP-A assembly

Establishment of Human Artificial Chromosomes (HACs) depends on an interplay of H3 lysine 9 modifications at centromeres, providing insights into the pathways that control incorporation of the kinetochore-specificing histone H3 variant CENP-A

Evaporative sodium salt crust development and its wind tunnel derived transport dynamics under variable climatic conditions

Playas (or ephemeral lakes) can be significant sources of dust, but they are typically covered by salt crusts of variable mineralogy and these introduce uncertainty into dust emission predictions. Despite the importance of crust mineralogy to emission potential, little is known about (i) the effect of short-term changes in temperature and relative humidity on the erodibility of these crusts, and (ii) the influence of crust degradation and mineralogy on wind speed threshold for dust emission. Our understanding of systems where emission is not driven by impacts from saltators is particularly poor. This paper describes a wind tunnel study in which dust emission in the absence of saltating particles was measured for a suite of climatic conditions and salt crust types commonly found on Sua Pan, Botswana. The crusts were found to be non-emissive under climate conditions characteristic of dawn and early morning, as compared to hot and dry daytime conditions when the wind speed threshold for dust emission appears to be highly variable, depending upon salt crust physicochemistry. Significantly, sodium sulphate rich crusts were found to be more emissive than crusts formed from sodium chloride, while degraded versions of both crusts had a lower emission threshold than fresh, continuous crusts. The results from this study are in agreement with in-situ field measurements and confirm that dust emission from salt crusted surfaces can occur without saltation, although the vertical fluxes are orders of magnitude lower (∼10 μg/m/s) than for aeolian systems where entrainment is driven by particle impact

Epigenetic regulation of centromeric chromatin: old dogs, new tricks?

The assembly of just a single kinetochore at the centromere of each sister chromatid is essential for accurate chromosome segregation during cell division. Surprisingly, despite their vital function, centromeres show considerable plasticity with respect to their chromosomal locations and activity. The establishment and maintenance of centromeric chromatin, and therefore the location of kinetochores, is epigenetically regulated. The histone H3 variant CENP-A is the key determinant of centromere identity and kinetochore assembly. Recent studies have identified many factors that affect CENP-A localization, but their precise roles in this process are unknown. We build on these advances and on new information about the timing of CENP-A assembly during the cell cycle to propose new models for how centromeric chromatin is established and propagated