Browsing by Subject "particulate organic carbon"
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Item Paleoreconstruction of Particulate Organic Carbon Inputs to the High-Arctic Colville River Delta, Beaufort Sea, Alaska(2013-01-09) Schreiner, Kathryn 1983-High Arctic permafrosted soils represent a massive sink in the global carbon cycle, accounting for twice as much carbon as what is currently stored as carbon dioxide in the atmosphere. However, with current warming trends this sink is in danger of thawing and potentially releasing large amounts of carbon as both carbon dioxide and methane into the atmosphere. It is difficult to make predictions about the future of this sink without knowing how it has reacted to past temperature and climate changes. This dissertation summarizes the results of the first study to look at long term, fine scale organic carbon delivery by the high-Arctic Colville River into Simpson?s Lagoon in the near-shore Beaufort Sea. Modern delivery of organic carbon to the Lagoon was determined to come from a variety of sources through the use of a three end-member mixing model and sediment biomarker concentrations. These sources include the Colville River in the western area of the Lagoon near the river mouth, marine sources in areas of the Lagoon without protective barrier islands, and coastal erosional sources and the Mackenzie River in the eastern area of the Lagoon. Downcore organic carbon delivery was measured on two cores in the Lagoon, one taken near the mouth of the Colville River (spans about 1800 years of history) and one taken on the eastern end of the Lagoon (spans about 600 years of history). Bulk organic parameters and biomarkers were measured in both cores and analyzed with Principle Component Analysis to determine long-term trends in organic carbon delivery. It was shown that at various times in the past, highly degraded organic carbon inputs of what is likely soil and peat carbon were delivered to the Lagoon. At other times, inputs of fresher, non-degraded, terrestrially-derived organic carbon inputs of what are likely higher amounts of plant and vegetative material was delivered to the Lagoon. Inputs of degraded soil carbon were also shown to correspond to higher temperatures on the North Slope of Alaska, likely indicating that warmer temperatures lead to a thawing of permafrost and in turn organic carbon mobilization to the coastal Beaufort Sea.Item The Relationships of Particulate Matter and Particulate Organic Carbon with Hypoxic Conditions Along the Texas-Louisiana Shelf(2014-08-06) Zuck, Nicole AThe Mississippi-Atchafalaya river system discharges into the northern Gulf of Mexico and peaks during the spring freshet bringing high levels of nutrients that spur eutrophication in surface waters, often resulting in hypoxic (dissolved oxygen concentrations less than 1.4 mL/L) sub-pycnocline conditions. Hypoxia is generally manifest seasonally along the Louisiana coast over the shelf. In summer 2011, high rainfall in the Mississippi-Atchafalaya watershed caused high discharge into the northern Gulf of Mexico. In summer 2012 drought conditions in the watershed significantly reduced the discharge. Summer 2013 conditions returned to the climatologic average river discharge. Discrete samples were collected and continuous measurements were made via an onboard surface-water flow-through system, CTD casts, and by an undulating towed vehicle. Total particulate matter and particulate organic carbon samples were obtained from Niskin bottles on CTD casts. Samples were also taken to measure dissolved oxygen concentration and nutrients along with other hydrographic parameters. Water-column particulate matter and particulate organic carbon were analyzed to investigate the relationship between hypoxia and the composition of the particulate matter along the Texas-Louisiana shelf during different discharge rates in summer 2011 (for C:N of particulate matter), 2012 and 2013 for a larger suite of particle composition and relationship to hydrographic conditions of the Mississippi-Atchafalaya river system. The goal of this research is to determine if a statistically significant relationship is manifest, between shelf hypoxia and total particulate matter, as well as between particulate organic carbon and hypoxia, during periods of different river discharge (i.e. average, flood, or drought conditions). Correlations were identified between some variables, but no direct relationship between particulate matter and hypoxia was observed. There were however, some statistically significant changes in several parameters between summer 2013 and summer 2013.