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 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

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

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

Study Lakes Highland Lake Pennesseewassee Lake Salmon Pond China Lake Webber Pond Cobbosseecontee Lake

Hydrologic Characteristics

Sequential Extraction Sediment Residue Residue Residue Ca-PLabile NaOH-TPNaOH-rPNaOH-nrP -= 1 M NH 4 pH 7 1 M NaOH 0.1 M Na 2 S 2 O 4 /NaHCO M HCl 1 M NaOH Fe-P Residue ResidueRefractory-P Al-POrg./Bact.-P Digestion

Extraction Results

Prerequisite 1

Prerequisite 2

Calculated P-Flux

Al:Fe vs. P Flux

Conclusions Prerequisites for low P release  NaOH-Al:[NH 4 Cl-Fe+BD-Fe] > 3*  NaOH-Al:[NH 4 Cl-P+BD-P] > 25*  [NH 4 Cl-P+BD-P]:TP < 0.1 Other possible factors   Alkalinity during summer  Fe-flux during summer †  Quality of organic matter * Kopačék et al. (2005) † Amirbahman et al. (2003)

 Alkalinity * Pearce (1999)

Fe-flux

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?

Acknowledgements Kyle CoolidgeKyle Coolidge Advisory CommitteeAdvisory Committee Maine DEPMaine DEP Environmental Chemistry LaboratoryEnvironmental Chemistry Laboratory National Science FoundationNational Science Foundation NEAEBNEAEB