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January 26, 2024 <br />Don Peterson <br />Page 9 of 21 <br />Reference: Water Quality Assessment of Silver View Pond, Mounds View, MN <br />proportion of organic matter in the sediments (28-55%). There was quite a bit of variability in rates between <br />cores at each station. For each rate shown in Figure 3, two sediment cores were collected to achieve an <br />average rate with a measure of variability (± 1 standard deviation of the mean). No phosphorus <br />accumulated in one of the sediment cores for station 1, so that measure represents one single core instead <br />of an average rate. All replicates for Stations 2 and 3 showed high variability in rates as well, which is <br />common in lake and pond sediments. <br />d <br />r <br />�a <br />5 <br />yr <br />�a <br />dN 4 <br />O� E <br />yr <br />o E 3 <br />t <br />a <br />yr 2 <br />0 <br />t <br />a <br />1 <br />0 <br />Silver View Pond <br />■ Anoxic Conditions ■ Oxic Conditions <br />Sampling Station <br />Figure 3. Phosphorus release rates under oxic and anoxic conditions in Silver View Pond. <br />Sediments were also analyzed for phosphorus fractionation to quantify the mobile and non -mobile pools of <br />phosphorus (Figure 4). This data provides us with an understanding of the potential for continued flux of <br />phosphorus from the sediments. The pool of phosphorus that is considered most likely to diffuse from the <br />sediments based on its reactivity and capacity to mobilize is redox-sensitive phosphorus (redox-P). This <br />includes the iron -bound phosphorus fraction and the pool that is considered loosely bound (meaning it has <br />simple bonds that can be easily broken). The horizontal lines in Figure 4 represent the 25t", 50t" (median), <br />and 75t" percentiles for redox-P in our Minnesota lake sediment chemistry database. Redox-P <br />concentrations in Silver View Pond sediments were in the lower range of concentrations observed in our <br />database of lake sediments. <br />Design with community in mind <br />