Browsing University of Alaska Fairbanks by Subject "groundwater"
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Geology and Geochemistry of the Ship Creek and Monashka Creek reservoirs, Southcentral AlaskaGraywacke from the Ship Creek watershed, dissolves incongruently in distilled water. The dissolution appears to follow a first-order rate law which in integrated form is: k = -2.303/t log No-Q/No where No is the concentration in ppm of Ca, Mg, Na or K in the graywacke, Q is the total quantity of these ions leached in time t(days), k is the rate constant in days-1. Experimentally derived rate constants for the dissolution of graywacke in distilled water at 5oC are log k+2CA, -4.128 day-1; log k+2Mg, -6.174 day-1; log k+Na, -5.800 day-1; and log k+K, -5.249 day-1. The above constants are for 40 to +100 mesh graywacke. A surface area correction term must be inserted in the above equation if it is applied to a different size fraction. Using the above equation and rate constants, the chemical composition of a water in contact with graywacke was calculated. With the exception of magnesium, the agreement between the calculated composition and that of Ship Creek water was good. Assuming that the groundwater in the Ship Creek watershed contacts about 1.5X104cm2 graywacke per liter, 120 to 360 days are required at 5oC to produce the concentration of ions observed in Ship Creek. Release of exchangeable H+ from the soil mat to the reservoir water will not significant1y lower the pH of the water. Leaching of heavy metals from sulfides contained in the bedrock of the two watersheds does not pose a water quality hazard. Lineaments in the bedrock at Monashka Creek may provide channels through which water may seep from the reservoir. These are not expected to pose a problem in retaining water in the reservoir, but they may result in small, new springs down grade from the reservoir.
Microbial ecology and biodegradation potential of a sulfolane-contaminated, subarctic aquiferContaminant biodegradation is one of many ecosystem services aquifer microbiota can provide to humans. Sulfolane is a water-soluble emerging contaminant that is associated with one of the largest contaminated groundwater plumes in the state of Alaska. Despite being widely used, the biodegradation pathways and environmental fate of sulfolane are poorly understood. In this study, we investigated the biodegradation of sulfolane by the microbial community indigenous to this contaminated subarctic aquifer in order to better understand the mechanisms and rates of loss, as well as the environmental factors controlling them. First, we conducted aerobic and anaerobic microcosm studies to assess the biodegradation potential of contaminated subarctic aquifer substrate and concluded that the aquifer microbial community can readily metabolize sulfolane, but only in the presence of oxygen, which is at low concentration in situ. We also investigated the impacts of nutrient limitations and hydrocarbon co-contamination on sulfolane biodegradation rates. To identify exactly which community members were actively degrading sulfolane, we combined DNA-based stable isotope probing (SIP) with genome-resolved metagenomics methods. We found a Rhodoferax sp. to be the primary sulfolane degrading microorganism in this system and obtained a near-complete genomic sequence of this organism, which allowed us to propose a new metabolic model for sulfolane biodegradation. Finally, we assessed the distribution of sulfolane-degrading bacteria throughout the contaminated subarctic aquifer by sequencing 16S rRNA genes from 100 groundwater samples and two sulfolane treatment systems and screening for the sulfolane degrader previously identified using SIP. This assessment revealed that sulfolane biodegradation potential is widespread throughout the aquifer but is not likely occurring under normal conditions. However, the sulfolane-metabolizing Rhodoferax sp. was the most dominant microbe in an effective experimental air-sparge system, suggesting that injecting air into the aquifer can stimulate sulfolane biodegradation in situ. These studies are the first to investigate sulfolane biodegradation potential in a subarctic aquifer. Through this work, we learn there are several important factors limiting biodegradation rates, we expand the known taxonomic distribution of sulfolane biodegradation, and we shed insights into the mechanisms underlying an effective in situ sulfolane remediation system.
North Slope Borough water study: a background for planningThe Planning and Research Section of Alaska Dept. of Natural Resources initiated this pilot water study with the North Slope Borough and the University of Alaska's Arctic Environmental Information and Data Center and Institute of Water Resources. Traditional and present water uses in the eight North Slope Borough villages are examined to assist in evaluating and planning for present and future water use, treatment, and disposal requirements.