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«Strengthening the Nation through Diversity, Innovation & Leadership in STEM San Antonio,Texas · October 3-6, 2013 Get Connected! Connect with the ...»

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1 Leaf area index (LAI), the unit area of leaves per unit area of ground, is an important parameter in many ecological models but is one that is difficult to calculate. Better estimates of LAI would provide scientists the data required to better understand vegetation-atmosphere interactions and other ecological processes. We modeled LAI along a gradient in the Sierra Nevada mountains, beginning at the San Joaquin Experimental Range (SJER) field site in an oak woodland savanna and terminating at the Upper Teakettle (UT) field site in a coniferous forest. We expect that LAI will decrease as we move higher along the elevation transect, and seek to quantify this change using data from NASA’s DC-8 aircraft. Shuttle radar topography mission data will be used as an elevation dataset, and LAI will be analyzed by calculating spectral vegetation indices from reflectance measurements. Using data collected in the field at the SJER and UT field sites, we validated our remote sensing estimates of LAI. There is a known correlation between increasing LAI and higher levels of net primary productivity. We anticipate that knowing the spatial distribution of LAI across the transect will be valuable for scientists to understand ecosystem level interactions and the distribution of primary productivity in the Sierra Nevada mountains.

SAT-177

CAUSES OF INCREASED FLOODING ALONG THE NORTH BRANCH OF THE CHICAGO RIVER

Patricia Jaimes, Laura L. Sanders.

Northeastern Illinois University, Chicago, IL.

This research studies the causes of flooding along the North Branch of the Chicago River. The North Branch watershed encompasses rural, suburban, and urban land use areas bordering and within the City of Chicago. In the past 5 years, 2 100-year floods in this area displaced residents and caused millions of dollars of property damage.

Peak flow and mean discharge data from the 62-year stream-flow record will be analyzed to investigate possible causes of the observed flow increase from the 100-square mile watershed. Population will be used as a proxy for degree of urbanization and will be measured by consulting US Census records for the past 6 decades. An increase in population may correlate with an increase in impervious cover such as buildings, roads, and pavement, as well as an increase in sewerage. These changes create more surface runoff and increased river discharge. Possible correlations between population increase and stream-flow will be investigated. It is also possible that the intensity and depth

252 UNDERGRADUATE POSTER ABSTRACTS

of precipitation has changed over the same time period. Changes in average temperature may lead to changes in evapotranspiration, which also could affect stream flow. These variables will be investigated through collection and analysis of precipitation and temperature data from National Weather Service records. The expected results are that there will be a relationship between population and annual peak flow of the North Branch of the Chicago River.

GEOLOGY

SAT-179

CALCULATION OF SO2 FLUXES FROM ACTIVE VOLCANOES IN EL SALVADOR AND NICARAGUA USING

OZONE MONITORING INSTRUMENT IMAGES

Jose Marrero1, Lizzette Rodríguez1, Gustavo Chigna2.

University of Puerto Rico at Mayagüez, Mayagüez, PR, 2Vulcanologia, Instituto Nacional de Sismologia, 1 Vulcanología, Meteorología e Hidrologia, Guatemala City, GT.

Satellite images from the Ozone Monitoring Instrument (OMI) were downloaded and processed in order to measure the SO2 mass in plumes and then calculate the flux of SO2 produced by the most active volcanoes in El Salvador (Santa Ana and San Miguel) and Nicaragua (San Cristóbal, Masaya, Concepción, and Telica) in the period of 2005 to 2012. We discuss here the degassing activity of each volcano studied based on the OMI results and on groundbased data, which were compared with the volcanic activity in the period. Trajectory models from the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) were used to determine the altitudes of the volcanic plumes. Sounding data were used to determine the wind speed at the respective plume heights. Based on the 25 OMI images processed and analyzed using the smoke estimation technique developed by Ichoku and Kaufman in 2005, the average SO2 flux for El Salvador was 530 t/d, and for Nicaragua it was 610 t/d for the period 2007 to 2012. Santa Ana had the highest degassing event, with an SO2 flux of ~19 kilotons per day on October 2005 during its most recent eruption. The highest emitter for Nicaragua was Masaya volcano, with an average SO2 flux of 650 t/d during the 2007 to 2012 period. The annual contribution of the studied volcanoes in El Salvador and Nicaragua during the 2007 to 2012 period of time to the global sulfur budget is ~0.50 teragrams per year, which represents ~2 to 5% of the global volcanic sulfur budget.

–  –  –

Vulcanología, Meteorología e Hidrologia, Guatemala City, GT.

Monitoring volcanic emissions is crucial to understanding volcanic behavior and the different influences these materials exert over the atmosphere, land, and on human health. Studying SO2 emissions through satellite remote sensing techniques with sensors such as the Ozone Monitoring Instrument (OMI) is economically beneficial and workwise efficient since it can be done for extended periods of time with the analyst in a safe place, away from risk. The SO2 emission trends in this study showed that there was an increase in SO2 flux before significant eruptive events and a decrease after. The average SO2 fluxes for Pacaya, Fuego, and Santiaguito volcanoes were 750 tonnes per day (t/d), 259 t/d, and 660 t/d, respectively. The highest flux was measured at Pacaya volcano, with 23 kilotons/ day emitted on May 29, 2010, during its most recent paroxysmal eruption. Although Pacaya showed the highest flux during the study period based on the data and comparing with previous fluxes, Fuego is the most consistent SO2 emitter of the Guatemalan volcanoes, since it is constantly degassing detectable fluxes of SO2 which was not observed for either Pacaya or Santiaguito volcanoes. Ash is also a very important volcanic material that needs to be detected due to the risk it poses for crops (by damaging them and consequently affecting livestock) as well as air traffic because it can be interrupted by ash clouds. OMI’s aerosol index images (AI) were used to detect ash content in plumes, but in general, most AIs did not show good results.





253 UNDERGRADUATE POSTER ABSTRACTS

FRI-178

CARBON ISOTOPE CHEMOSTRATIGRAPHY OF LOWER CEDAR MOUNTAIN FORMATION, UTAH

Jose Salazar-Verdin, Marina Suarez.

University of Texas at San Antonio, San Antonio, TX.

The Cedar Mountain Formation in Utah is important to improve our understanding of the Early Cretaceous continental climate. Recent discoveries also make this formation important to understanding the evolution of dinosaurs in the Early Cretaceous. The age of these rocks is still unclear and more studies need to be done to establish a more accurate chronostratigraphy. Vertebrate paleontologists argue that this section is no older than Barremian (130 to 125 Ma) while ostrocode and pollen biostratigraphers suggest dates as old as Berriasian (145 to 140). By using organic carbon isotope chemostratigraphy we expect to improve stratigraphic context. In 2007, 57 samples were collected, and this summer they were prepared by crushing them into a fine powder and decarbonated using 3M hydrochloric acid (HCl). The samples were then weighed and analyzed on a Delta + XP IRMS connected to a Costech element analyzer and reported relative to Vienna Pee Dee Belemnite (VPDB). The δ13Corg values average 26.5 ‰ and range from -28.8 ‰ to -24.3 ‰. Previous data (U-Pb dates from a carbonate sample of 119 Ma and preliminary paleomagnetic signatures) suggested we could expect to see the global C3 negative isotope excursion followed by a positive excursion. While the curve does vary by about 2 ‰, no significant excursions are recognized, and we therefore conclude the age to be Barremian which, in other carbon isotope curves, show smaller variations. Additional magnetostratigraphic data may clarify this conclusion as will continued stratigraphic research in near localities.

FRI-180

CARBONATE IDENTIFICATION USING X-RAY DIFFRACTION AND ORGANIC CARBON CHEMOSTRATIGRAPHY

OF THE RUBY RANCH MEMBER WITHIN THE CEDAR MOUNTAIN FORMATION NEAR MOAB, UTAH

Elizabeth Montgomery, Marina Suarez.

University of Texas at San Antonio, San Antonio, TX.

The Cedar Mountain Formation (CMF) represents the earliest deposition of terrestrial Cretaceous strata in the United States and records significant changes in biota and climate. The goal of this project is to interpret paleoclimate from one of the few well-exposed lacustrine sequences in the CMF through lithologic, mineralogic, and stable isotope geochemical analysis. The Lake Carpenter lacustrine sequence in the Ruby Ranch Member of the CMF is located near Moab, Utah, and was sampled from 4 trenches at 25 cm increments for lithologic description, carbon isotope chemostratigraphy, and carbonate stable isotope analysis. Mineralogy was determined through powdered X-ray diffractometry using a Scintag XDS 2000 XRD. Silicate mineralogy consists of clays and quartz. Carbonate mineralogy fluctuates between calcite, high magnesium calcite, and dolomite. High Mg calcite and dolomite likely indicate arid conditions. The δ13 C composition of sedimentary organic carbon was determined by powdering the sample, decarbonating the sample with 0.5 M HCl at 60 °C, rehomogonizing the sample, and combusting in a Costech elemental analyzer at 1000 °C. Resulting CO2 is analyzed on a delta+XP continuous flow mass spectrometer.

Initial results show a range of values between -27.9 ‰ (VPDB) at the base to -22.5 ‰ (VPDB) at the top of the sections. These results are still too preliminary to correlate with existing C-isotope records; however, we expect the sequence to correlate to carbon isotope excursions Ap7 to Al1.

SAT-180

ISOTOPIC AND CHEMICAL VARIABILITY OF CALCIUM CARBONATE MICROFACIES IN EARLY TO MIDDLE

TRIASSIC LIMESTONES

Yesenia Herrera1, Adam B. Jost2, Kimberly V. Lau2, Daniel J. Lehrmann3, Meiyi Yu4, Jonathan L. Payne.

Northeastern Illinois University, Chicago, IL, 2Stanford University, Stanford, CA, 3Trinity University, San Antonio, TX, 1 College of Resource and Environment Engineering, Guizhou University, Guizhou Province, CN.

4 The chemical composition and isotopic signature of calcium carbonate (CaCO3) microfacies reflect the fluids from which they precipitated (e.g., seawater, early diagenetic fluids, or deep burial diagenetic fluids). Consequently, the chemistry of each microfacies provides a fingerprint of the fluids from which it formed. However, the influence of these different microfacies on the bulk composition of CaCO3 is not well understood. In this study, we will sample carbonate muds, fossil grains, and void filling cements from 2 limestone rock samples that contain a variety of common depositional microenvironments. One sample is a Tubiphytes reef boundstone of Middle Triassic age (~247 Mya) containing multiple generations of CaCO3 cement. The other sample is a thrombolitic microbialite of Early Triassic age (~252 Mya) containing micritic sediment, microbial framework, aragonite crystal fans, and sparry calcite cement.

We will analyze CaCO3 powders from each microfacies in each sample for major and minor elements, including

254 UNDERGRADUATE POSTER ABSTRACTS

redox-sensitive trace metals, as well as δ13C and δ18O ratios, using an inductively-coupled plasma optical emission spectrometer (ICP-OES), an inductively-coupled plasma mass spectrometer (ICP-MS), and an isotope ratio mass spectrometer (IRMS), respectively. An improved understanding of the geochemical differences among microfacies and their source fluids will aid the interpretation of bulk rock geochemical records for samples in which analysis of individual carbonate phases is not feasible.

FRI-177

AQUEOUS ALTERATION OF AMORPHOUS FE:SI SYNTHETIC SMOKES WITH MG-RICH SOLUTION TO

SIMULATE HYDRATION RELATED TO CM METEORITES

Doris J. Rivera-Santiago, Lysa Chizmadia, Sully Lebron.

University of Puerto Rico at Mayagüez, Mayagüez, PR.

Goddard Space Flight Center has created amorphous silicate smokes through vapor deposition that have infrared reflectance spectra similar to materials observed in circumstellar disks and in cometary tails. Detailed examinations of primitive meteorites reveal significant volumes of amorphous nonstoichiometric silicate materials, similar to smokes.

Consequently, these smokes are the best analogs available for experimental studies to better understand asteroidal aqueous alteration. The vital goal for this current research is to reconstruct the textures/grains present in chondritic meteorites in a laboratory and to try understanding the basic structures in the field of planetary science. In past hydration experiments with deionized H2O, Fe-smokes resulted in very acidic pHs while Mg-smokes became very alkaline. Therefore, this study is an attempt to understand the interrelationship between Fe and Mg during aqueous alteration. A series of hydration reactions were conducted using Fe-silicate smokes with 3 different Fe:Si ratios. All 3 Fe:Si smokes were reacted with an aqueous solution of Mg(OH)2 over a period of 30 minutes and pH and T were measured with an OakTron Testr30 every 10 seconds. Hydration of the FeSiOx smokes with Mg(OH)2 (aq) became alkaline immediately and converged on pH of ~10.2 in 30 s. Higher Fe:Si resulted in less alkaline solutions. In conclusion, the reaction’s pHs decreased as the ratio increased. These results are consistent with the types of secondary minerals observed in primitive meteorites.

OCEANOGRAPHY

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