Abstract Title

Using sequential extractions to measure potentially bioavailable phosphate in soil systems with poorly crystalline iron oxides

Abstract

Rising global temperatures are affecting Earth’s hydrologic cycle, which will in turn influence biogeochemical cycles. In some areas where soil systems are flooded due to melting of ice or increased precipitation, fluctuating water tables can create variable redox conditions. Poorly crystalline iron-oxides formed in these fluctuating conditions may have more potential to adsorb phosphate ions compared to more crystalline iron oxides that exist in drier soils. When phosphate, an essential nutrient for plants, bonds to iron oxides, it is no longer bioavailable. This theoretical decrease in bioavailable phosphate due to the presence of poorly crystalline iron oxides could affect vegetation growth in areas with fluctuating redox conditions. To test the impacts of iron oxide crystallinity on phosphate bioavailability, mesh bags containing peat, sand, and iron-oxides (poorly crystalline or crystalline), with or without added phosphorus, were buried in vernal pond soils experiencing fluctuating redox conditions over four months. To measure changes in bioavailable phosphate during incubation, we extracted water-soluble (potentially bioavailable) and dithionite-extractable (iron oxide bound) phosphate from initial and incubated oxides. Colorimetric assays and UV-Visible Light Spectroscopy were used to measure the concentrations of extractable phosphate in the soil. Results will show the degree to which different iron-oxides influence phosphorus bioavailability. This same extraction procedure will be used on soils from similar redox environments in the Alaskan arctic for comparison. This research will allow us to describe the effects of rising global temperature on soil and biological systems, and their interactions.

Modified Abstract

Rising global temperatures are affecting Earth’s hydrologic cycle, which will in turn influence biogeochemical cycles. In some areas where soil systems are flooded due to melting of ice or increased precipitation, fluctuating water tables can create variable redox conditions. Iron-oxides formed in these fluctuating conditions may have potential to adsorb phosphate than in more stable conditions. When phosphate, an essential nutrient for plants, bonds to iron oxides, it is no longer bioavailable. Decrease in bioavailable phosphate in environments effected by global warming could affect vegetation growth in areas with fluctuating redox conditions. These conditions were studied through sample incubation in a vernal pond followed by sequential extractions of phosphate.

Research Category

Geology/Geography

Author Information

Nicolle Di DomenicoFollow

Primary Author's Major

Geology

Mentor #1 Information

Dr. Elizabeth

Herndon

Presentation Format

Poster

Start Date

April 2019

Research Area

Biogeochemistry | Geochemistry | Geology

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Apr 9th, 1:00 PM

Using sequential extractions to measure potentially bioavailable phosphate in soil systems with poorly crystalline iron oxides

Rising global temperatures are affecting Earth’s hydrologic cycle, which will in turn influence biogeochemical cycles. In some areas where soil systems are flooded due to melting of ice or increased precipitation, fluctuating water tables can create variable redox conditions. Poorly crystalline iron-oxides formed in these fluctuating conditions may have more potential to adsorb phosphate ions compared to more crystalline iron oxides that exist in drier soils. When phosphate, an essential nutrient for plants, bonds to iron oxides, it is no longer bioavailable. This theoretical decrease in bioavailable phosphate due to the presence of poorly crystalline iron oxides could affect vegetation growth in areas with fluctuating redox conditions. To test the impacts of iron oxide crystallinity on phosphate bioavailability, mesh bags containing peat, sand, and iron-oxides (poorly crystalline or crystalline), with or without added phosphorus, were buried in vernal pond soils experiencing fluctuating redox conditions over four months. To measure changes in bioavailable phosphate during incubation, we extracted water-soluble (potentially bioavailable) and dithionite-extractable (iron oxide bound) phosphate from initial and incubated oxides. Colorimetric assays and UV-Visible Light Spectroscopy were used to measure the concentrations of extractable phosphate in the soil. Results will show the degree to which different iron-oxides influence phosphorus bioavailability. This same extraction procedure will be used on soils from similar redox environments in the Alaskan arctic for comparison. This research will allow us to describe the effects of rising global temperature on soil and biological systems, and their interactions.