Biogeochemical cycling of phosphorus in the Chesapeake Bay and its watershed: insights from phosphate oxygen isotope ratios
| Author(s) | Joshi, Sunendra | |
| Date Accessioned | 2017-02-08T12:17:20Z | |
| Date Available | 2017-02-08T12:17:20Z | |
| Publication Date | 2016 | |
| Abstract | The Chesapeake Bay and its watershed suffer from varying degrees of water quality issues fueled by both point and non–point nutrient sources. Methodological limitations on source tracking and identification of the specific phosphorus (P) pools that can be biologically cycled (or remain recalcitrant) in both the short and long terms are the major obstacles preventing accurate assessment of the nutrient loads that could impact water quality. This research utilized phosphate oxygen isotope ratios, mineralogical (XRD and micro-XRD), microscopic (SEM), elemental, and spectroscopic (31P NMR and 57Fe Mössbauer) methods to characterize P speciation and investigate mechanisms and pathways of P transformations in the Chesapeake Bay and its watershed. In an agricultural soil, short-term transformation of externally applied P to a less or non-bioavailable P pool was tracked by using 18O labeled phosphate. This enabled identification of sources and precipitation pathways of acid extractable P pools. In East Creek, a tidal tributary of the Chesapeake Bay, impact of P loading primarily from agricultural runoff was reflected on the pathways and intensity of P cycling: both input flux higher than microbial cycling and remineralization (degradation of organic P) contributed to higher pore water Pi in the headwater region. In the wetland region, on the other hand, porewater Pi was completed cycled. In the Chesapeake Bay sediments, ferric Fe-bound and authigenic P pools were the two major P sinks, regardless of bottom water hypoxia. Regeneration of Pi from organic matter degradation was found to be the predominant, if not sole, pathway for authigenic P precipitation. Overall, this work generated new insights into the sources, stability, and transformations of various P pools in soils, waters, and sediments under different biogeochemical conditions. These findings are expected to be useful to watershed nutrient management plans as well as to widen source- and pathway- based research in the Chesapeake Bay and other watersheds. | en_US |
| Advisor | Jaisi, Deb | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Plant and Soil Sciences | |
| DOI | https://doi.org/10.58088/210f-g394 | |
| Unique Identifier | 971612585 | |
| URL | http://udspace.udel.edu/handle/19716/20455 | |
| Publisher | University of Delaware | en_US |
| URI | https://search.proquest.com/docview/1840889276?accountid=10457 | |
| Title | Biogeochemical cycling of phosphorus in the Chesapeake Bay and its watershed: insights from phosphate oxygen isotope ratios | en_US |
| Type | Thesis | en_US |