Analysis of Phosphates in Macatawa Watershed Sediment

Student Author(s)

Adam Maley, Hope CollegeFollow

Faculty Mentor(s)

Dr. Graham Peaslee, Hope College

Document Type


Event Date



Analysis of phosphates, a non-point source pollutant, in sediment is important for understanding the eutrophic nature of the Macatawa Watershed. These phosphates, which enter Lake Macatawa, are transported throughout the watershed by adhering to clay particles suspended in water, typically after heavy precipitation. Phosphorous is the limiting reagent in eutrophication, therefore, high amounts result in potentially harmful algae blooms that decrease the overall quality of the water. Accurate analysis of phosphate levels help pinpoint the most important areas to manage sediment erosion and phosphate runoff in the watershed. After heavy precipitation, sediment samples are collected and water-soluble, iron-bound, and calcium-bound phosphates are extracted for continuous flow analysis by the AutoAnalyzer IIITM. Results are recorded in concentrations of phosphates where the sum of the three extractions gives the total amount of bioavailable inorganic phosphates. Preliminary results have shown the areas of most concern are the Noordeloos Creek subwatershed and the North and South branches of the Macatawa River. Comparison of iron-bound and calcium-bound phosphate level ratios shows a strong correlation between rain events for each sample site. Additionally, comparison with Particle Induced X-Ray Emission (PIXE) data shows a strong correlation between Fe:Ca elemental ratios and the iron-bound and calcium-bound phosphate levels.


This material is based upon work supported by The National Science Foundation, The Macatawa Area Coordinating Council, The Outdoor Discovery Center, and the Michigan Department of Environmental Quality.

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