PHOSPHORUS TRANSPORT THROUGH DIFFERENT HYDROLOGIC UNITS IN A SMALL SUBURBAN WATERSHED

In general prairie (range: 366 -56 µg/g, average 151.8 µg/g) soils had the highest TP values followed by agricultural (range: 10-412 µg/g, average 74.92 µg/g), urban (range: 0-285.4 µg/g, average 56.4 µg/g), wetland (range: 0-290.5 µg/g, average: 32.6 µg/g) and stream bank (range:0-42 µg/g, average 8.3 µg/g) soils. In all hydrologic units, there was a sharp decrease in soil TP concentration after May. TP concentration decreased mostly in surface soil profiles. This can be correlated with the agricultural activities and the rainfall pattern in the area. There were no spatial variations in TP within the agricultural soils. In urban soil, TP values showed a gradual increase toward the central portion of the urban areas. For stream water, sites located in agricultural areas and those that received flows from both agricultural and urban areas showed relatively high P concentrations. On the other hand, sites located in downstream areas or the areas that received water from urban runoff had P concentration below detection level.

Both the agricultural and the urban areas showed fluctuations in TP values throughout the study period. Thus, both of these areas seem to have delivered P to the stream channels. Wetland sediments had high TP values, probably due to the accumulation of suspended sediments during flood events. Temporal and spatial fluctuations of TP showed that all hydrologic units were very active and were interacting with one another during the study period.