Photometric Analysis of Phosphates in Lake Macatawa Watershed Sediment

Student Author(s)

Rachel Kreb

Faculty Mentor(s)

Dr. Graham Peaslee

Document Type


Event Date



High levels of phosphorous in the Lake Macatawa watershed contribute to its hypereutrophic state resulting in harmful algal blooms, which decrease the overall water quality. Phosphates are transported in the watershed after heavy rainfall by adhering to clay particles suspended in water. Determining concentrations of these phosphates is critical for monitoring sediment erosion and runoff contributing to the eutrophic state of the watershed. After heavy precipitation, sediment samples were collected from 46 sediment samplers distributed throughout the watershed. From the dried sediment samples, water-soluble, iron-bound, and calcium-bound phosphates were extracted separately and measured using an AutoAnalyzer IIITM continuous flow colorimetric analysis. The AutoAnalyzer IIITM uses a molybdo-phosphate complexation reaction and a colorimeter to quantitatively determine the concentration of phosphates. Concentrations from the three different extractions were recorded and summed to get a total bioavailable inorganic phosphate value at each site. These results will be used to help pinpoint the origins of the non-point-source pollution and to characterize the baseline phosphate load entering Lake Macatawa before remediation efforts are performed.

This document is currently not available here.