Browsing by Author "Torres, Mark"
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Item A Framework for Understanding Whole-Earth Carbon Cycling(Cambridge University Press, 2019) Lee, Cin-Ty A.; Jiang, Hehe; Dasgupta, Rajdeep; Torres, Mark; Orcutt, Beth N.; Daniel, Isabelle; Dasgupta, RajdeepBuilding from the base of knowledge presented in the preceding chapters, this chapter explores how the cycling of carbon in subduction zones and orogenic belts varies with supercontinent cycles and mountain building. It discusses the processes that link short-term and long-term carbon cycling and the timescales of these processes, such as the response times of weathering and atmospheric drawdown at periods of enhanced volcanism. This chapter covers topics of potential fluctuations in the long-term CO2 content of Earth’s atmosphere because of mantle–climate feedback, again taking advantage of the modeling platforms available for further exploration of these topics.Item Embargo Differentiation of a CO2-rich, hydrous alkalic basalt and the genesis of carbonatites(2024-03-20) Rodriguez, Maria Raquel; Dasgupta, Rajdeep; Lee, Cin-Ty; Torres, MarkIntraplate settings almost uniquely host alkaline magmas and carbonatites. Although these magmas are spatially connected, the petrogenetic link between alkali magmas such as ocean island basalts (OIBs) and carbonatites is not well established. While previous studies have sought to identify the source origin of these magmas, the mechanisms behind their differentiation remain poorly understood. To constrain the evolution of alkalic magmas at mid-lithospheric depths, we performed high pressure-temperature, phase equilibria experiments on a hydrous, CO2 rich mantle-derived partial melt composition. The experiments were conducted at 1.5-2.0 GPa and 1200-1500 °C. The experimentally generated samples were studied using electron probe micro-analysis, where phase assemblage consisted of olivine + clinopyroxene + spinel + carbonated-silicate melt ± calcite ± vapor. As the melt composition undergoes evolution, the initial stages of crystallization generate alkalic OIB-like compositions, which subsequently transition towards natural calcio-magnesio carbonatite compositions. Our findings suggest that a single volatile-rich parental melt composition can give rise to OIBs and carbonatites at varying conditions.Item Rainy with a Chance of Sea Salt: Sourcing the Sulfur in Houston's Rainfall(Rice University, 2024) Osorio, Valentina; Torres, MarkAs one of six criteria air pollutants monitored by the US Environmental Protection Agency, sulfur dioxide negatively affects human and environmental health. Upon entering the atmosphere, sulfur dioxide is oxidized and dissolved in water as sulfuric acid; consequently sulfate rains out and can act as a tracer for atmospheric processing of sulfur compounds. Precipitation data were taken in Houston and compared to the Attwater Prairie Chicken National Wildlife Refuge in order to compare sulfur sources in atmospheric deposition between urban and rural regions. Houston rain exhibits chemical sign atures that are suggestive of seawater and dust influences on rain chemistry, but leaves uncertainty in attributions to these sources as well as others expected to be present around Houston. This project evaluates the degree to which solute and water isotope data can be used to source sulfate in rainfall both within the major city of Houston and outside of its large suburban area.Item The hydrochemical signatures of (in) congruent weathering in Iceland(2020-04-21) Cole, Trevor L.; Torres, MarkSilicate weathering is often invoked as the dominant mechanism for sequestering CO2 over geologic timescales, where extrusive lithologies are assumed to disproportionately contribute to global silicate weathering fluxes due to their higher reactivity relative to intrusive substrate. While Iceland is largely considered monolithologic (i.e. basaltic), compiled bedrock and solute measurements herein suggest that river water is enriched in Ca and Na relative to a bedrock array which ranges from basaltic to rhyolitic. To explore this relationship, we evaluate environmental factors that could explain the solute trends including clay precipitation (type-I incongruent weathering), variable dissolution rates of primary minerals (type-II incongruent weathering), and rhyolite dissolution/ groundwater contributions. Through forward models we conclude that the precipitation of high-Mg smectite exerts the most control on solute movement relative to type-II incongruency or dissolution of rhyolite. However, more direct measurements of clay mineralogy and rhyolitic ash dissolution are necessary to better constrain this dataset.Item The Impacts of Concrete on pH and Calcium Concentration in Houston’s Bayous(Rice University, 2021-05) Hale, Meagan; Torres, MarkAs the human population grows, so does the percentage of people living in urban areas. This means that an increasing amount of landmass must be used for urban infrastructure and housing to accommodate a greater number of people. The environmental impacts of urbanization are not completely understood. However, one important aspect that may be impacted is water quality. For instance, the concrete used to construct water transport and drainage systems can leach Ca2+ions into urban rivers and increase water pH. These changes are of concern because pH range is a major factor in determining the toxicity and bioavailability of chemical compounds. Additionally, many aquatic microorganisms can only thrive within certain ranges of pH and Ca concentrations. To investigate how the concrete used in urban infrastructure impacts water quality, I studied two major rivers in Houston, TX, USA. The first, White Oak Bayou, is lined with concrete; the second, Buffalo Bayou, has a natural river bottom. These two rivers were compared with the non-urban but still geographically similar Trinity River, since river chemistry may be affected by the presence of concrete anywhere within a river’s watershed. I collected water samples from Buffalo and White Oak bayous and analyzed their major anions and cations using ion chromatography (IC) and inductively-coupled plasma mass spectrometry (ICP-MS) methods, respectively. In addition, I analyzed roughly 50 years’ worth of public water quality data for each bayou and the Trinity River. The data suggest that the concrete-lined White Oak Bayou has a higher Ca concentration and pH value than Buffalo Bayou. The results of this research expand our knowledge of the environmental impacts of water transport and drainage systems.