ANALYSIS OF URBAN RUNOFF SEDIMENT ALONG STORM DRAINS AND IMPERMEABLE SURFACES THROUGHOUT THE MERCYHURST UNIVERSITY

In order to help understand the effects of urban runoff on the Lake Erie watershed, we conducted an experiment at Mercyhurst University aimed at characterizing the sediment contained within the runoff. Sandbags were emplaced as sediment barriers along six storm drains across campus where the most urban runoff was most likely to accumulate. Sediment from each storm drain was collected on a regular basis from each drain and analyzed for sediment size distribution and chemistry. Grain sizes of the collected samples varied from 0.25-4.00 mm in diameter. After determining grain size distribution, each sample was analyzed using a Bruker handheld XRF to determine their chemical make-up. Initial XRF results show that the sediments contain high concentrations of iron and calcium. Secondary elements consist of chlorine, copper, and nickel, while trace elements include strontium, manganese, and aluminum. Storm drains located near parking lots with gradual, flat slopes accumulated the most sediment on campus while those located along areas with steeper slopes held the least sediment. Overall chemistry showed only negligible variation; all major and secondary elements were the same but in slightly different ratios. Although the given results are useful, they do not offer complete insight into the chemical composition of urban runoff on Mercyhurst campus due to the inability of XRF to monitor the presence of organic elements within samples. Also, the sandbag technique is only a simplified means of collecting sediment and provides only a minimal constraint as to the amount of sediment contributed from Mercyhurst; sediment catches that can be installed into storm drains would be more ideal for future research. Continued monitoring of these drains over the course of one year will provide a greater degree of accuracy as far as observing runoff and sediment variation on our campus. Understanding runoff distribution and chemistry is crucial within urban settings, especially those near bodies of water. Failure to responsibly monitor runoff transport and deposition may result in environmental complications such as toxin exposure, pH changes, and salinity increase. Future experiments will be conducted to test these possible complications.