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Downers Grove South High School ESRP 2014

Presence of Metals and Metalloids in Wild Salmon Compared to Farmed Salmon Studied with Hard X-ray Fluorescence Microscopy

Authors:

  • Students:
    • Sam Boroumand
    • Abigail Kargol
    • Julian Martinez
    • Thomas Matysik
    • Andrew Molina
    • Rachel Smith
    • Apoorva Sooranahalli
    • Amanda Thate
    • Eric Wynne
  • Teachers:
    • Theresa Quain
  • Mentors:
    • Sophie Gleber (Argonne National Laboratory, X-ray Science Division)
    • Qiaoling Jin (Northwestern University, Department of Physics and Astronomy)

Advanced Photon Source Sector 2: Microscopy

The presence of metals in fish is an issue of food safety due to persistence in the body as well as their tendency to bioaccumulate.   Consumers rely increasingly on farmed fish due to pressure on fisheries.  The quality of farmed fish compared to wild fish is therefore of public health interest.  The purpose of this research study is to determine if there is a difference in the amount of inorganic contaminants in wild versus farmed salmon.   Previous studies have found that in multiple species the concentrations of metals present in wild-caught fish differ from the metal concentrations in farmed fish. Concentrations vary from species to species as well as between tissues in individual fish.  Whether the concentrations reach harmful levels varies with the species.   Previous comparisons of wild and farmed salmon have found that the farmed salmon had significantly higher levels of arsenic while wild salmon had significantly higher concentrations of cobalt, copper, and cadmium, though none of the metals were present in high enough quantities to harm a person.  In this study, samples of wild salmon and farmed salmon were purchased from the same grocery store, which claims that both products meet the highest quality standards; thus this study compares the best-case farmed salmon with the best -case wild salmon.  Both samples were chemically fixed followed by sucrose embedding and sectioning at -80°C. Hard x-ray fluorescence microprobe at 2-ID-E was used to map the metal concentrations and distributions with high spatial resolution on these thin sections. Methods of sample preparation and results of the x-ray fluorescence microscopy will be presented. Results showed that Ni and Cr were significantly higher in farmed salmon than in wild salmon. No significant differences in concentrations of other metals were found.

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