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Bjorn Lake Doctoral Student Civil and Environmental Engineering The University of Maine

FACTORS CONTRIBUTING TO THE INTERNAL LOADING OF PHOSPHORUS FROM ANOXIC SEDIMENTS IN SIX MAINE (USA) LAKES. Bjorn Lake Doctoral Student Civil and Environmental Engineering The University of Maine. Research Goals.

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Bjorn Lake Doctoral Student Civil and Environmental Engineering The University of Maine

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  1. FACTORS CONTRIBUTING TO THE INTERNAL LOADING OF PHOSPHORUS FROM ANOXIC SEDIMENTS IN SIX MAINE (USA) LAKES Bjorn Lake Doctoral Student Civil and Environmental Engineering The University of Maine

  2. Research Goals • Perform a sedimentary analysis on six lakes with varying trophic status using a common sequential extraction procedure. • Delineate P, Al, and Fe speciation in the sediments • Decipher any temporal trends in sediment P, Al, and Fe speciation • Determine any correlations/predictors that are characteristic of lakes with internal P load • Calculate sedimentary P-flux using publicly available water column data and bathymetric data from Maine DEP

  3. Background • How do lakes become anoxic? • Why is phosphorus important? • What controls phosphorus availability? Al(OH)X

  4. SRP Fe 3+ Ferric ion Fe(OH)X Iron Hydroxide Oxic Anoxic Fe 2+ Ferrous ion SRP Classic Model of P Sorption

  5. Study Lakes • Highland Lake • Pennesseewassee Lake • Salmon Pond • China Lake • Webber Pond • Cobbosseecontee Lake

  6. Hydrologic Characteristics

  7. Sediment 1 M NH4Cl @ pH 7 Residue 0.1 M Na2S2O4/NaHCO3 Residue 1 M NaOH Digestion Residue 0.5 M HCl NaOH-TP - NaOH-rP = NaOH-nrP Al-P Org./Bact.-P Residue Labile Fe-P Ca-P 1 M NaOH Residue Refractory-P Sequential Extraction

  8. Extraction Results

  9. Prerequisite 1

  10. Prerequisite 2

  11. Calculated P-Flux

  12. Al:Fe vs. P Flux

  13. Conclusions • Prerequisites for low P release • NaOH-Al:[NH4Cl-Fe+BD-Fe] > 3* • NaOH-Al:[NH4Cl-P+BD-P] > 25* • [NH4Cl-P+BD-P]:TP < 0.1 • Other possible factors • D Alkalinity during summer • Fe-flux during summer † • Quality of organic matter * Kopačék et al. (2005) † Amirbahman et al. (2003)

  14. Alkalinity * Pearce (1999)

  15. Fe-flux

  16. Future Research • What’s going on in Cobbosseecontee? • What role does Org-P have in anoxic sedimentary P-flux? • How accurate is water column data for calculating P-flux?

  17. Acknowledgements • Kyle Coolidge • Advisory Committee • Maine DEP • Environmental Chemistry Laboratory • National Science Foundation • NEAEB

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