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Geochemical Controls over Phosphorus Bioavailability as a Function of Redox Sensitive Iron Oxides

Maximilian, Barczok R
http://orcid.org/0000-0002-0496-921X
http://rave.ohiolink.edu/etdc/view?acc_num=kent1657801116459316

Abstract Details

2022, PHD, Kent State University, College of Arts and Sciences / Department of Earth Sciences.
BARCZOK, MAXIMILIAN R., Ph.D. AUGUST 2022 APPLIED GEOLOGY GEOCHEMICAL CONTROLS OVER PHOSPHORUS BIOAVAILABILITY AS A FUNCTION OF REDOX SENSITIVE IRON OXIDES (180 PP.) Dissertation Advisor: David Singer Understanding the geochemical controls on how phosphorus (P), a limiting or co-limiting nutrient for plants and microorganisms in many ecosystems, adsorbs to iron (oxyhydr)oxides minerals (henceforth called Fe oxides) is vital to predict the bioavailability of P in a system. Orthophosphate (henceforth called phosphate), the major ion of P utilized by biota, binds strongly to Fe oxides and is removed from solution, decreasing its bioavailability. The ability of Fe oxides to adsorb phosphate and act as a geochemical control on phosphate bioavailability depends on the crystallinity and mineralogy of the Fe oxides. Changes in hydrology and resulting shifts in redox conditions, represented by field measurements of redox potential (Eh), can directly impact phosphate bioavailability by either dissolving Fe oxides and releasing phosphate or precipitating low crystallinity Fe oxides adsorbing phosphate. Additional importance of the interaction of Fe oxides and P is their impact on the stability of soil organic carbon (OC) in Arctic permafrost soils. Permafrost ecosystems store a significant amount (~60%) of the worlds soil OC that are vulnerable to emissions to the atmosphere with increasing permafrost thaw. As such I hypothesize that shifts in soil EH caused by climatic variations such as progressing permafrost thaw and will shift Fe speciation in soil towards low crystallinity Fe oxides, such as ferrihydrite, and increase the capacity of phosphate adsorption and over a longer time period decrease bioavailability of phosphate to microorganism stabilizing soil OC. In this dissertation, I investigate 1) how EH responds to hydrological change, 2) the impact of EH and Fe oxide mineralogy on Fe oxide dissolution and transformation, as well as 3) the resulting impact of changing Fe oxide mineralogy on phosphorus bioavailability to the system, and 4) the impact of thawing permafrost on soil EH and Fe crystallinity and speciation, and the resulting impact on phosphorus sorption to Fe oxides . Methods employed to address the above mentioned research goals included 1) continuous, high resolution measurements of EH with platinum electrodes, 2) sequential extractions to quantify extractable Fe and P in soils and in field-incubated minerals, and 3) x-ray absorption fine structure (XAFS) spectroscopy to evaluate changes in Fe speciation. In Chapter 2, I present research on how soil EH responds to hydrological change in and around a vernal pond . I show how Eh can vary within a small pond temporally and spatially, and how Fe reducing conditions can persist without surface water ponding. In Chapter 3 I describe how Fe oxide speciation evolves over time towards lower crystallinity in contrasting redox conditions at the same vernal pond as in Chapter 2. I also show how Fe oxides can retain phosphate and how freshly precipitated Fe oxides adsorb phosphate potentially reducing bioavailability of P. In Chapter 4 I show how Eh differs along a permafrost gradient in Sweden. I also show how Fe speciation shifts towards the poorly crystalline Fe oxide ferrihydrite as permafrost thaw progresses. Additionally, I show the strong association of P to Fe oxides along the permafrost gradient.
Elizabeth Herndon (Committee Co-Chair)
Lauren Kinsman-Costello (Committee Member)
Kuldeep Singh (Committee Member)
David Singer (Committee Co-Chair)
181 p.
Geochemistry; Geology
Phosphorus; redox; iron oxides; arctic; permafrost thaw

Recommended Citations

Citations

  • Maximilian, B. R. (2022). Geochemical Controls over Phosphorus Bioavailability as a Function of Redox Sensitive Iron Oxides [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1657801116459316

    APA Style (7th edition)

  • Maximilian, Barczok. Geochemical Controls over Phosphorus Bioavailability as a Function of Redox Sensitive Iron Oxides. 2022. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1657801116459316.

    MLA Style (8th edition)

  • Maximilian, Barczok. "Geochemical Controls over Phosphorus Bioavailability as a Function of Redox Sensitive Iron Oxides." Doctoral dissertation, Kent State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=kent1657801116459316

    Chicago Manual of Style (17th edition)

kent1657801116459316
139
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