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Geomorphologic Controls On The Age Of Particulate Organic Carbon From Small Mountainous And Upland Rivers, El Leithold, Ne Blair, Dw Perkey
Geomorphologic Controls On The Age Of Particulate Organic Carbon From Small Mountainous And Upland Rivers, El Leithold, Ne Blair, Dw Perkey
VIMS Articles
To assess the role that erosion processes play in governing the character of particulate organic carbon (POC) discharged from small mountainous and upland rivers, a suite of watersheds from Oregon, California, and New Zealand was investigated. The rivers share similar geology, tectonic setting, and climate, but have sediment yields that range over 3 orders of magnitude. The (14)C age of the POC loads is highly correlated with sediment yield. Carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern-plant-and ancient-rock-derived OC. At lower yields, modern plant OC dominates the material delivered to the river by sheetwash and …
Dissolved And Particulate Organic Matter Source-Age Characterization In The Upper And Lower Chesapeake Bay: A Combined Isotope And Biochemical Approach, An Loh, Je Bauer, Ea Canuel
Dissolved And Particulate Organic Matter Source-Age Characterization In The Upper And Lower Chesapeake Bay: A Combined Isotope And Biochemical Approach, An Loh, Je Bauer, Ea Canuel
VIMS Articles
In order to characterize the sources and ages of organic matter contributing to river and estuarine outflow waters, the present study investigated Delta C-14 and delta C-13 signatures of the major operationally defined biochemical classes of ultrafiltered dissolved organic matter (UDOM) in conjunction with lipid biomarker and elemental compositions of UDOM and suspended particulate organic matter (POM) in the Chesapeake Bay. Freshwater (Susquehanna River) UDOM was dominated by a molecularly uncharacterized (MUC) fraction, followed by total carbohydrate (TCHO), total hydrolysable amino acid (THAA) and total lipid (TLE) components. In contrast, UDOM at the bay mouth (salinity similar to 22-24) was …
Dam Impacts On The Changjiang (Yangtze) River Sediment Discharge To The Sea: The Past 55 Years And After The Three Gorges Dam, Z Yang, H Wang, Y Saito, Jd Milliman, K Xu, S Qiao, G Shi
Dam Impacts On The Changjiang (Yangtze) River Sediment Discharge To The Sea: The Past 55 Years And After The Three Gorges Dam, Z Yang, H Wang, Y Saito, Jd Milliman, K Xu, S Qiao, G Shi
VIMS Articles
In 5 recent years ( 2000 - 2004), the Changjiang ( Yangtze) River has discharged past Datong (600 km from the river mouth) an average of similar to 250 million tons (mt) of sediment per year, a decrease of more than 40% since the 1950s and 1960s, whereas water discharge at Datong has increased slightly. Water and sediment discharge data from the upper, middle, and lower reaches of the river suggest that the reduction of the Changjiang sediment load has occurred in two phases between 1950 and 2002: following the closure of the Danjiangkou Reservoir on the Hanjiang tributary in1968 …
Physical Processes Behind Delta Propagation And Flood Layer Dynamics, Po River, Italy, Aaron J. Bever
Physical Processes Behind Delta Propagation And Flood Layer Dynamics, Po River, Italy, Aaron J. Bever
Dissertations, Theses, and Masters Projects
Rivers discharge around 20 billion tonnes of sediment to the coastal ocean each year (Milliman and Syvitski, 1992). Many supply dominated rivers possess large subareal and subaqueous deltas, whose growth depends on the physical processes controlling sediment deposition or removal. There has yet to be a complete understanding of how short term processes such as settling from buoyant plumes, wave/current resuspension, and transport by currents and gravity flows, interact to produce the depositional products that develop over varying timescales. The Po River in Northern Italy forms a substantial delta in the Adriatic Sea. It has five distributary mouths, and is …
Linking Land To Ocean: Flux And Fate Of Water And Sediment From The Yangtze River To The East China Sea, Kehui Xu
Dissertations, Theses, and Masters Projects
Although precipitation and runoff for the entire Yangtze River watershed have changed little since 1950, the increase of runoff in Yangtze southern sub-basin has been much larger than that of precipitation, reflecting decreased temperatures and evapotranspiration, In contrast, the marked decreases in runoff in northern Yangtze have been due mainly to increased water consumption. Since the 1980s, the Yangtze sediment load has declined dramatically, and 2004 loads at Yichang (just below the Three Gorges Dam - TGD) and Datong (lower stream) were only 12% and 33% of those in the 1950s and 60s, reflecting precipitation decline, landuse change, and most …
Disposition Of Wastewater-Associated Polybrominated Diphenyl Ethers In A Freshwater Receiving Stream, Mark Joseph La Guardia
Disposition Of Wastewater-Associated Polybrominated Diphenyl Ethers In A Freshwater Receiving Stream, Mark Joseph La Guardia
Dissertations, Theses, and Masters Projects
No abstract provided.
Bioreactivity Of Estuarine Dissolved Organic Matter: A Combined Geochemical And Microbiological Approach, Sl Mccallister, Je Bauer, Elizabeth A. Canuel
Bioreactivity Of Estuarine Dissolved Organic Matter: A Combined Geochemical And Microbiological Approach, Sl Mccallister, Je Bauer, Elizabeth A. Canuel
VIMS Articles
An integrated multidisciplinary study utilizing geochemical and microbial ecological approaches was conducted to characterize the origins, chemical nature, and quantities of dissolved and particulate organic matter (OM) utilized by heterotrophic bacteria in a temperate estuary. C: N, stable isotope (delta C-13), and lipid biomarker analyses revealed differences in the inferred reactivity of autochthonous versus allochthonous OM sources. Isotopic comparison of OM size fractions and bacterial nucleic acids suggests that high-molecular-weight dissolved OM (DOM) is consistently linked to bacterial biomass synthesis along the estuarine salinity gradient. Polyunsaturated fatty acids (as percent of total fatty acids, FA) were a reliable predictor of …
Sediment Biogeochemistry Of Northern Cascadia Margin Shallow Gas Hydrate Systems, John W. Pohlman
Sediment Biogeochemistry Of Northern Cascadia Margin Shallow Gas Hydrate Systems, John W. Pohlman
Dissertations, Theses, and Masters Projects
Methane contained in gas hydrate is a significant component of the global organic carbon inventory. Describing the methane sources supporting these systems and the mechanisms that control the distribution of methane in marine sediments are critical elements in evaluating the resource potential, climate change implications and geologic hazards associated with gas hydrate. The northern Cascadia margin (offshore Vancouver Island, Canada) is a convergent margin with gas hydrate-bearing cold seeps composed of both thermogenic (Barkley Canyon) and microbial (Bullseye vent) gas sources. Gas hydrate and sediment cores were collected from each of these settings to examine the sources that sustain the …