Heavy Metal Accumulation in Bioswales Over Time

In an effort to better understand the long term function of bioswales as toxicological sinks & a filtration point for aquatic road pollutions while working as a green stormwater structure. Bioswales are channels filled with sediment, drought/flood tolerant vegetation & organic matter that mitigates flooding, sequesters carbon, and cycles nutrients - preventing eutrophication downstream while reducing pressure on sewage & other stormwater systems.

Because bioswales are used to slow stormwater infiltration and filter out pollutants from roadside water run off, they are a potential point of concern regarding the accumulation of heavy metals in sediment and possible leaching of toxic heavy metals into water over time.

By assessing the levels of heavy metals found in bioswale sediments and comparing it to the age of that bioswale the results would provide context for how effective these stormwater systems are for the remediation of non-point source road pollution into streams. This project focuses on Zinc, Copper and Iron contamination in soil and the proportion of nitrification levels as an indication of plant function in those sediments to determine the long term survival of those ecosystems. In this project, a series of samples from Portland, OR were assessed using portable x-ray fluorescence spectroscopy to determine the concentrations of Zinc, Copper and Iron. These concentrations were compared to legacy sampling by Dr. Erin Looper Rivers during her ongoing research at Portland State University from 5 other cities: Baltimore, Charlotte, New York City, Phoenix and Syracuse.

Proposal

Results