Browsing by Subject "organic carbon"

Now showing 1 - 3 of 3
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    Geomorphic controls on mineral weathering, elemental transport, carbon cycling, and production of mineral surface area in a schist bedrock weathering profile, Piedmont Pennsylvania
    (2016-10) Fisher, Beth
    Association of organic carbon (OC) with mineral surface area is a key mechanism for protecting OC from microbial consumption, yet the development of mineral surface area by biogeochemical weathering processes and its role in controlling the organic carbon cycle and distribution within hillslopes have rarely been explicitly delineated. Addressing this significant knowledge gap is the goal of this study. The measurement of deep mineral surface area profiles in the Laurels Schist within the Christina River Basin Critical Zone Observatory, revealed abrupt transitions in mineral specific surface area at 3 meters. This depth did not coincide with the soil-weathered rock boundary or the water table, which is contrary to the present paradigm in delineating depth progression of weathering. This finding instead highlights the potential role of oxygen penetration as a critical process defining the vertical distribution of biogeochemical weathering process. The site’s schist bedrock is highly variable. Such heterogeneity has challenged earth scientists attempting to mark and determine the extent of chemical weathering in terrain underlain by sedimentary and meta-sedimentary bedrocks. To overcome this limitation, a new statistical model was developed to delineate the subsurface boundaries in heterogeneous rock types and to clearly assess and display weathering trends buried in elemental data. This comprehensive understanding of weathering trends and the genesis of mineral surface area facilitated the assessment of changes in OC and mineral surface area (OC/SA) in the hillslope soil transect. Minerals are found to hold more organic matter on their surface in response to soil mixing and soil erosion and deposition. Organic matter properties such as C/N, del15N, and del13C also respond to soil mixing as a function of soil profile depth and landscape position. A strong correlation between C/N and OC/SA indicates that both properties may provide a proxy for organic matter stability.
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    Minnesota Pollution Control Agency Wild Rice Sulfate Standard Mesocosm Study: Water, Sediment, and Porewater "Synoptic" Sampling 2013 and 2015
    (2017-05-30) Myrbo, Amy; amyrbo@umn.edu; Myrbo, Amy
    This dataset represents opportunistic, "synoptic" sampling of 30 experimental mesocosms for chemical parameters. The mesocosm experiments were undertaken by Dr. John Pastor (UMN-Duluth) and the Minnesota Pollution Control Agency (MPCA) to improve the understanding of why wild rice (Zizania palustris, manoomin, psin) is observed to thrive only in waters with low sulfate (SO4), and to contribute to evaluation of Minnesota Rules 7050.0224, promulgated in 1973, which seeks to limit the exposure of wild rice to sulfate concentrations exceeding 10 mg/L.The dataset is now released as manuscripts using it are being published.
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    Sampling of St. Louis Estuary and Lake Superior surface water after the Superior Refinery Fire in 2018
    (2018-11-20) Minor, Elizabeth C; Shreiner, Kathryn; Sheik, Cody; eminor@d.umn.edu; Minor, Elizabeth C
    On April 26, 2018, there were multiple explosions and a fire at the Husky Refinery in Superior, WI. Safety measures worked well, with no loss of life and few injuries; however, significant smoke and soot emissions from the fire itself did impact the local airways and may also have impacted local watersheds, the Twin Ports harbor and far western Lake Superior. Thus, we measured water quality in the St. Louis estuary and far-western Lake Superior in an attempt to determine if residual petroleum products and/or black carbon (soot) associated with the refinery fire entered Lake Superior or the Saint Louis estuary in measurable amounts. There were indications of very localized impact in total organic carbon and dissolved organic carbon data and aerial deposition of soot in some black carbon samples from surface waters. We did not find measurable petroleum hydrocarbon in our samples.