Browsing by Subject "Bioproducts/biosystems science engineering and management"

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    Quantifying solids and nutrient recovered through street sweeping in a suburban watershed
    (2015-04) Kalinosky, Paula Marie
    Solids that collect on street surfaces are comprised of varying proportions of inorganic particles ranging in size from silt and clays to gravels, vegetative and other organic material, trash, and a host of pollutants deposited from surface runoff and atmospheric sources (ex. car exhaust). This material has alternatively been called `street dust' `street dirt', `street dirt', `road sediments', `street particulate matter' or `SPaM', `urban particulate matter', or simply referred to as `gross solids'. Whatever name it goes by, it is a significant source of pollution to urban stormwater and one mean of limiting this source is street sweeping. The coarse organic component of street particulate matter (leaves, grass clippings, and other vegetative matter) is not well characterized in existing street sweeping literature. Coarse organic debris that enters storm sewers can accumulate in catch basins and pipes, or be transported into streams, lakes, and rivers, releasing nutrients along the way as it decomposes. The primary objectives of the study were to quantify the influence of tree canopy (a source of organic debris), season, and street sweeping frequency on the quantity of solids and nutrients recovered from streets through street sweeping. We measured the total solids and nutrient loads (TP, TN, TOC) recovered in 392 street sweeping operations over a 2-year period in residential areas of Prior Lake, MN. Coarse organic material was separated from finer, soil-like material through dry sieving followed by density separation (floating the material retained on the sieve in a water bath). Chemical analysis (total phosphorus, TP, total nitrogen, TN, total organic carbon, TOC, % moisture, and % organic matter, %OM) was carried out on each fraction. Coarse organic material made up 15% of the total dry weight of swept material collected during the study, but 36% of the TP and 71% of the TN. Percent overhead tree canopy cover was a significant predictor of average recoverable loads of coarse organic material and associated nutrients in all months of the year. Sweeping frequency was a significant predictor of total recoverable loads in several months of the year. Seasonal influences were apparent in both fractions of sweepings. The loading intensity (kg/curb-meter) of fines was greatest in the early spring immediately following snow melt and the loading intensity of coarse organic matter was greatest in October during fall leaf litter drop. Fresh coarse organics recovered during May had a significantly higher leaching potential than coarse organics collected at other times of the year.Regression analysis was used to develop predictive metrics for planning sweeping operations. The regressions predict the average expected solids and nutrient recovery by month, sweeping frequency, and tree canopy cover. Metrics for tracking total phosphorus (TP) and total nitrogen (TN) recovery based on the mass of sweepings collected were also developed based on study findings.
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    Through lignin biodegradation to lignin-based plastics
    (2015-01) Wang, Yun-Yan
    The consequences of strong noncovalent intermolecular interactions between oligomeric and/or polymeric lignin components are encountered during enzyme-catalyzed lignin degradation and in the properties of lignin-based plastics. A new chapter in the 30-year quest for functional lignin-depolymerizing enzymes has been opened. The lignin-degrading capacity of the flavin-dependent monooxygenase, salicylate hydroxylase acting as a putative lignin depolymerase, has been characterized using a water-soluble native softwood lignin substrate under mildly acidic aqueous conditions. When macromolecular lignins undergo lignin-depolymerase catalyzed degradation, the cleaved components tend to associate with one another, or with nearby associated lignin complexes, through processes mediated by the enzyme acting in a non-catalytic capacity. As a result, the radius of gyration (Rg) falls rapidly to approximately constant values, while the weight-average molecular weight (Mw) of the substrate rises more slowly to an extent dependent on enzyme concentration. Xylanase, when employed in an auxiliary capacity, is able to facilitate dissociation of the foregoing complexes through its interactions with the lignin depolymerase. The flavin-dependent lignin depolymerase must be reduced before reaction with oxygen can occur to form the hydroperoxy intermediate that hydroxylates the lignin substrate prior to cleavage. In the absence of the cofactor, NADH, the necessary reducing power can be provided (albeit more slowly) by the lignin substrate itself. Under such conditions, a simultaneous decrease in Rg and Mw is initially observed during the enzymatic process through which the lignin is cleaved.The partially degraded product-lignins arising from lignin depolymerase activity can be readily converted into polymeric materials with mechanical properties that supersede those of polystyrene. Methylation and blending of ball-milled softwood lignins with miscible low-Tg polymers, or simple low-molecular-weight compounds, readily produce plastics with 80-100% lignin contents that exhibit >60 MPa tensile strengths and >10% elongations at break. X-ray powder diffraction analyses reveal that these materials are largely composed of associated lignin complexes. During casting, continuity between the macromolecular species is established through conformational changes in the peripheral components of the associated complexes that make up the plastics. Such a working hypothesis is supported by atomic force microscopy of surfaces created by ultramicrotomy of these new lignin-based polymeric materials.