Effect of Ethanol on Microbial Community Structure and Function During Natural Attenuation of Benzene, Toluene, and \u3cem\u3eo\u3c/em\u3e-Xylene in a Sulfate-reducing Aquifer

Ethanol (EtOH) is a commonly used fuel oxygenate in reformulated gasoline and is an alternative fuel and fuel supplement. Effects of EtOH release on aquifer microbial ecology and geochemistry have not been well characterized in situ. We performed a controlled field release of petroleum constituents (benzene (B), toluene (T), o-xylene (o-X) at ∼1–3 mg/L each) with and without EtOH (∼500 mg/L). Mixed linear modeling (MLM) assessed effects on the microbial ecology of a naturally sulfidic aquifer and how the microbial community affected B, T, and o-X plume lengths and aquifer geochemistry. Changes in microbial community structure were determined by quantitative polymerase chain reaction (qPCR) targeting Bacteria, Archaea, and sulfate reducing bacteria (SRB); SRB were enumerated using a novel qPCR method targeting the adenosine-5′-phosphosulfate reductase gene. Bacterial and SRB densities increased with and without EtOH-amendment (1−8 orders of magnitude). Significant increases in Archaeal species richness; Archaeal cell densities (3–6 orders of magnitude); B, T, and o-X plume lengths; depletion of sulfate; and induction of methanogenic conditions were only observed with EtOH-amendment. MLM supported the conclusion that EtOH-amendment altered microbial community structure and function, which in turn lowered the aquifer redox state and led to a reduction in bioattenuation rates of B, T, and o-X

Groundwater discharge to the western Antarctic coastal ocean

Submarine groundwater discharge (SGD) measurements have been limited along the Antarctic coast, although groundwater discharge is becoming recognized as an important process in the Antarctic. Quantifying this meltwater path-way is important for hydrologic budgets, ice mass balances and solute delivery to the coastal ocean. Here, we estimate the combined discharge of subglacial and submarine groundwater to the Antarctic coastal ocean. SGD, including subglacial and submarine groundwater, is quantified along the WAP at the Marr Glacier terminus using the activities of naturally occurring radium isotopes (223Ra, 224Ra). Estimated SGD fluxes from a 224Ra mass balance ranged from (0.41 ± 0.14)×104 and (8.2 ± 2.3)×104m3 d−1. Using a salinity mass balance, we estimate SGD contributes up to 32% of the total freshwater to the coastal environment near Palmer Station. This study suggests that a large portion of the melting glacier may be infiltrating into the bedrock and being discharged to coastal waters along the WAP. Meltwater infiltrating as groundwater at glacier termini is an import-ant solute delivery mechanism to the nearshore environment that can influence biological productivity. More importantly, quantifying this meltwater pathway may be worthy of attention when predicting future impacts of climate change on retreat of tidewater glaciers

Antología

Introducción de Rubén Jaramillo a los dos textos de Sieyes: La presente selección de sus dos escritos prinipales ha sido tomada de: Emmanuel J. Sieyes, ¿Qué es el Tercer Estado?, seguido de Ensayo sobre los privilegios, en traducción de José Rico Godoy. Colección Nuestos Clásicos, de la Universidad Nacional Autónoma de Mexic

Coastal Septic Systems and Submarine Groundwater Discharge: A Case Study

The focus of this dissertation is submarine groundwater discharge (SGD), the direct flow of groundwater from the seabed to the sea, and onsite wastewater treatment systems in coastal California. The research focuses primarily on a single coastal community in central California, Stinson Beach, where conventional onsite treatment systems, or septic systems, are used exclusively for wastewater disposal. The overarching goal of the work has been to quantify the magnitude and timing of SGD at the site and to provide insight into how onsite wastewater treatment at Stinson Beach affects local groundwater quality and, via SGD, surface water quality, all with the broader goal of informing and guiding future development along the California coast