The report, PBT Trends in Lake Sediment Cores, 2016 Results, is available at https://fortress.wa.gov/ecy/publications/SummaryPages/1803029.html.

 The Department of Ecology’s Persistent, Bioaccumulative, and Toxic (PBT) Monitoring Program conducts long-term monitoring of freshwater sediment cores to help characterize the occurrence and temporal trends of PBTs in Washington State.  A single sediment core is collected each year from three waterbodies and age-dated in order to reconstruct contaminant deposition profiles. 

 In 2016, sediment cores collected from Deep Lake, Spanaway Lake, and Lake Spokane were analyzed for up to 209 polychlorinated biphenyl (PCB) congeners.  Age-dated sediment core profiles indicated the following trends:

·         Total (T-) PCB concentrations in Deep Lake and Spanaway Lake sediments have declined since peak levels, and recent concentrations appear to have stabilized.

·         T-PCBs were fairly stable in Lake Spokane sediments between the early 2000s and early 2016, but increased in the most recently deposited sediment layer.  Current T-PCB levels were much lower than historical peaks observed in the 1960s.

·         PCB congener profiles revealed no consistent temporal patterns in individual congeners across sites.  PCBs associated with Aroclor sources and resistant to degradation were dominant in all three cores.

 The report recommends that the PBT Monitoring Program continue to evaluate how levels of PCBs in the environment are changing.  The next sampling for PCBs is scheduled for 2022.  Additional investigation into sediment-bound PCBs in Lake Spokane is also recommended.

 If you have questions, contact Callie Mathieu at 360-407-6965 or callie.mathieu@ecy.wa.gov.