Decadal Differences in Emerging Halogenated Contaminant Profiles in Great Lakes Top Predator Fish

Legacy
halogenated contaminants have been monitored in the Great
Lakes for decades, but there are many additional unknown halogenated
contaminants potentially affecting the Great Lakes ecosystem. To address
this concern, lake trout (Salvelinus namaycush) were collected in 2005/2006 and 2015/2016 from each lake and screened
for previously unidentified compounds. The isotopic profile deconvoluted
chromatogram algorithm was used to isolate unknown halogenated components
using high-resolution mass spectrometry data files generated by an
atmospheric pressure gas chromatography-quadrupole time-of-flight
mass spectrometer operated in positive and negative modes. The temporal
and spatial differences in the newly detected features were used to
isolate new potential contaminants. Decadal differences in the unknown
halogenated compounds (or features) were compared with the total polychlorinated
biphenyl concentration trends. Greater than 2000 unknown halogenated
features were detected. As expected, Lake Superior contained the lowest
number of unknown halogenated features, whereas Lake Ontario contained
the highest. Unknown features tended to have fewer Cl and/or Br atoms
compared to traditional legacy contaminant features typically monitored.
Diverse patterns of unknown halogenated compounds between lakes suggested
that there continues to be unidentified sources of halogenated contaminants
in the Great Lakes missed by current monitoring programs.