Graduate Thesis Or Dissertation

 

Sea-Salt Impacts On Nutrient Cycling In Oregon Coastal Soils Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/00000511j

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  • Sea-salt aerosols (SSA) impact the cycling of nutrients within coastal soils, including the mobility of dissolved organic carbon (DOC) and ammonium, denitrification, and litter decomposition. These aerosols are formed during tumultuous weather in the open ocean and are transported and deposited inland by wind. Soils closer to the ocean are exposed to greater amounts of SSA while soils farther inland have less exposure. If the current trend of increasing wind speeds continues the production and reach of these SSA may increase with it, exposing soils to greater amounts of marine salt. The objective of our research was to quantify how coastal soils that have historically experienced varying amounts of SSA deposition will respond to a simulated increase in deposition. We performed this research using coastal forest soils formed on upper to late Eocene basalt flows in the Cascade Head Experimental Forest given the forest’s astounding ability to sequester carbon. Soils within Cascade Head have been found to store up to 36 kg C/m² compared to the <20 kg C/m² found in more inland forests. Surface soils (0-30 cm) were extracted along an inland gradient spanning 1-3 km, 3-5 km, and 5-7 km to account for differences in SSA deposition. The soils from each range band were homogenized and then packed to field bulk density in Nalgene Sterile Filter Analytical Units (0.45 µm pore size) using 100 g of soil. Soils were then treated over a month with a complex sea-salt mixture of comparable composition to precipitation in the 1-3 km range band. Their extracts were analyzed for DOC, ammonium, nitrate, phosphate, base cations, chloride, and sulfur. Our results indicated a significant decrease in DOC mobility in the 3-5 km and 5-7km soils after the second treatment while the 1-3 km soil displayed no change. This decrease in DOC was strongly correlated with the concentration of base cations in the extract, more so with polyvalent cations, signifying their importance in immobilizing DOC through cation bridging and flocculation. There was no significant impact to nitrogen or phosphorus cycling found, however both ammonium and phosphate were seen to be mobilized to a degree by the salt treatments. Our results highlight the role that SSA play in nutrient cycling in coastal soils and more so that the role is magnified in soils undergoing an increase in deposition.
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  • Ongoing Research
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  • 2018-12-06 to 2021-01-07

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