(Nanako Ogi and Steven Cruickshank)

Abstract

The relative difference of phosphorus concentration in Lake Oswego and Tualatin River waterways was determined to observe the effect of Lake Oswego on the phosphorus content. Samples taken from five different spots around the area were applied to the EPA method 4500-P. The absorbance was measured by Agilent 8453 UV-visible Spectroscopy system at 888 nm with a path length of 5 cm. The phosphorus concentration was calculated for each sample using calibration curve made from 0.01, 0.05, 0.1, 0.3 and 0.4 µg/mL standards. The average concentration of samples 1 and 2 from Tualatin River area and samples 3-5 from Lake Oswego area were 0.13 and 0.043 µg/mL respectively. Although the accuracy is not trustworthy due to the experimental errors, it can be concluded that phosphorus concentration level is much lower in Lake Oswego area compared to Tualatin River area. This could be due the slower water flow and the cleaning effort that has been made over the past few years.