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Full-Text Articles in Physical Sciences and Mathematics
A Novel Method For Determination Of Ammonium Isotope Ratios With Electrospray Ionization Mass Spectrometry, Rebecca J. Chmiel
A Novel Method For Determination Of Ammonium Isotope Ratios With Electrospray Ionization Mass Spectrometry, Rebecca J. Chmiel
Honors Theses
Nitrogen (15N) isotope tracer studies are an invaluable tool for understanding the rate of N transformations in the environment. A mechanistic understanding of N cycling is critical to management of excess N availability in freshwater and marine ecosystems. Conventional methods for measuring 15N:14N of dissolved inorganic nitrogen species are time consuming and require large sample volumes. Here, we present a technique for measuring 15N:14N in ammonium (NH4+) using electrospray ionization mass spectrometry (ESI-MS). NH4+ present in small volumes of sample (3 ml) is complexed with phenol via …
The Impact Of Dams On Nitrogen Cycling In The Messalonskee Stream, Rebecca K. Forgrave
The Impact Of Dams On Nitrogen Cycling In The Messalonskee Stream, Rebecca K. Forgrave
Honors Theses
The Messalonskee Stream in central Maine has five hydroelectric dams on 16.6km. Each dam drastically changes the flow regime of the stream, dividing it into segments with different patterns of sediment settling and organic matter retention. I investigated how these disruptions impact nitrogen cycling, specifically nitrification rates above and below each dam. I expected higher nitrification rates above the dams, where levels of organic matter are higher, and lower rates below the dam where scouring removes organic matter and fine sediment from the streambed. I measured sediment nitrification rates with a nitrapyrin-inhibition assay and potential drivers of nitrification including sediment …