PHOSPHORUS RELEASE IN LITTLE SEBAGO LAKE IN RELATION TO CONCENTRATIONS OF ALUMINUM AND IRON IN SEDIMENTS

Phosphorus release from lake sediments is a threat to lake water quality and can cause algal blooms. Internal loading of phosphorus is thought to be driven by reducing conditions that dissolve iron within sediments. Some research suggests that there are certain thresholds that either promote or discourage the release of phosphorus. Molar ratios of aluminum/iron that are less than 3:1 are correlated to greater phosphorus release, while ratios of aluminum/iron that are greater than 3:1 are correlated to lower phosphorus release.

The Little Sebago Lake Association, located in Raymond, Maine, is interested in determining if algal blooms are occurring because of phosphate release from sediments and if so, what can they do to prevent and minimize the release of phosphorus. Little Sebago Lake is separated into three smaller basins (Lower, Middle, and Upper), each connected by shallow, narrow straits. A total of five sediment cores were collected , including at the deepest spots of the three basins and at two shallow inlets where algal blooms have caused noticeable problems in the past.

Both alum-amended and unamended dried sediment samples were put through the sequential Psenner extraction procedure to better understand phosphorus speciation. The extracts were then analyzed for concentrations of phosphorus, aluminum and iron by ICP-OES and converted into element ratios to determine whether or not phosphorus release from the sediment of Little Sebago Lake is threatening the water quality.