Organic Phosphorus in Marine Sediments: Chemical Structure, Diagenetic Alteration, and Mechanisms of Preservation
Abstract
Phosphorus, an essential nutrient, is removed from the oceans only through burial with marine sediments. Organic phosphorus P(org) constitutes an important fraction (Ca. 25%) of total-P in marine sediments. However, given the inherent lability of primary P(org) biochemicals, it is a puzzle that any P(org) is preserved in marine sediments. The goal of this thesis was to address this apparent paradox by linking bulk and molecular-level P(org) information. A newly-developed sequential extraction method, which isolates sedimentary P(org) reservoirs based on solubility, was 31 used in concert with P31 nuclear magnetic resonance spectroscopy (P31-NMR) to quantify P(org) functional group concentrations. The coupled extraction/P31-NMR method was applied to three sediment cores from the Santa Barbara Basin, and the first-ever high-resolution depth profiles of molecular-level P(org) distribution during diagenesis were generated. These depth profiles were used to consider regulation of P(org) distribution by biomass abundance, chemical structure, and physical protection mechanisms. Biomass cannot account for more than a few percent of sedimentary P(org), No evidence for direct structural control on remineralization of P(org) was found. Instead, sorptive protection appears to be an important mechanism for P(org) preservation, and structure may act as a secondary control due to preferential sorption of specific P(org) compound classes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA384552
Entities
People
- Kirsten L. Laarkamp
Organizations
- Massachusetts Institute of Technology