LATERAL AND VERTICAL DISTRIBUTION OF PHOSPHORUS IN A NORTHEAST IOWA WETLAND SYSTEM

This study was conducted north of Cedar Falls, Iowa. The purpose of this study was to determine the Phosphorus (P) inflow from the surrounding land. This Northeast Iowa wetland system contains homogenized P concentrations in the top 15 cm of sediment. West Lake's top 15 cm sediment average is 500µg/g while Railroad Lake's average is 691µg/g. The cause of P homogeneity in this range is most likely due to the suspension and mixing of fine-grained soil particles sorbed with P. Vertical distribution in West Lake shows high P concentrations at 20-30 cm with concentrations 29-48µg higher than the 15-20 cm range. These concentrations are most likely from the historical drainage of a nearby livestock pasture. In conjunction with this, it is hypothesized that a flood event deposited increased quantities of sediment into West Lake. This may have caused P at depth to rapidly become unavailable for uptake. The responsible flood event is most likely from the large Midwestern United States flood in 1993. Unlike West Lake, the average vertical gradient of Railroad Lake shows a downward trend of P concentration. This trend was noticed in previous research done on Silver Lake and Casey Lake (both in Iowa). This was thought to be a land use factor; however, chemical change of P to an inorganic form not detectable by the ascorbic acid method of P testing may also cause this trend. Mineral Phosphate levels need testing to determine their relationship to this trend. The observed P levels were comparable between Railroad Lake (499µg/g) and West Lake (449µg/g). The lateral P distribution was studied around West Lake. This distribution shows high P concentrations in the livestock area as well as high P concentrations near T5S1 and T1S1. These data are preliminary and more investigations will be required in the future.