PCBs are transported through the atmosphere in both gas and particulate phases. In Great Lakes and Baltic Sea, the majority of aquatic PCBs come from atmospheric transport. Transport from Asia to BC takes 2-10 days. One sampling site at Ucluelet as reference for Saturna Island samples (gas (86% of PCBs, 63% PBDEs), particulate (porportionally more heavy congeners), and rain phases). PCB heavy congeners dominated by tri and tetra; PBDEs by tetra, penta and deca.
PBDE deposition was higher than PCBs overall. PCBs about same between sites, suggesting global sources. ~50% of PBDEs are coming from local sources, and the increase above reference is mostly due to heavier PBDEs (tetra, penta, deca). The point of origin is 20% from Asia; no north American sources can account for the coastal deposition in BC.
2004 deposition mass: 3.5 kg PCB, 20 kg PBDE (BDE 209 makes of 56%)
Mapping C flow through the food web can help us understand trophic strucure and species interactions and ass feeding guilds and which species may be most at risk from bioaccumulation. Our model is a steady state partitioning (Arnot and Gobas, 2004; Condon, 2007) that uses Tim Essingtons trophic structure data, diet data from John Ruem (2006 UW thesis), and other parameters from many others. Essington’s data show that biomass and diet change dramatically with depth strata.
Our simplified model for the central basin of Puget Sound yields 9 out of 10 estimates for species or feeding guilds that are within factor of 2 of field measurements. We have almost no data for plankton and spiny dog fish in the central basin.
- For every unit you reduce water concentrations of PCBs, you get a 0.7 unit reduction in tissues; this is a linear response for all species; for 50% reduction in loading you get about 55 picograms/l in tissues.
- The ratio for sediment conentrations of PCBs is 0.3; taking out all PS hot spots will reduce tissue concentrations by only about 15%.
- These ratios vary by species (benthic, pelagic); eg English sole is most affected by sediment concentrations. (Scott thot: SRKWs are known to eat Dover Sole in non-summer seasons…)
- Even in most optimistic scenario, tissue reductions are only likely to be 15-25%.
Simplified food web structure seems to do well in approximating carbon flows, so we believe we are accurately modeling transfer of PCBs, generally. You can add complexity to understand specific species’ situations. We also believe you’ll need different simplified model for each basin in the Salish Sea. That means we’ll need data from each basin! And it means that we’ll need more complicated (trans-basin) models for species with complex foraging behaviors, like killer whales.
long-term fate and bioaccumulation of PCBs in Puget Sound,
Models of contaminant kinetics:
- Davis 2004 includes an active 10cm layer in Puget Sound
- Field data: In Puget Sound 1400kg PCBs (estimates range from 600-3500) are in active layer compared with ~7kg in water and ~40kg in biota (estimated from Sandy’s measurments)
- [PCB] in water: measured mean ~60-100 ng/gD.
- Model says PCB mass in sediment will plateau in ~50yrs at 1000-8000kg and depend mostly on on-going external loading ( from 25 to 500 kg/yr) not historical because it is getting buried by new sedimentation)
- Atmospheric deposition is l~50kg/yr and ocean exchange may be 100s kg/yr… these numbers are uncertain but may mean PCB mass is actually increasing in Puget Sound now.
- Long-term means of 20-200kg/year is about what must have been loaded to get to current measured masses.
Since 1990s, English sole PCBs have been increasing (but not in other species). This may be caused by on-going external loading. Our model predictions match measured biota within a factor of 2.
External loading in Puget Sound is probably non-point source from watersheds. Policies that control general toxics loading and runoff should help reduce PCB loading.
Scott: External loading is still a problem?! The orca community should be lobbying HARD for global PCB bans!
Persistent organic pollutants as chemical tracers for Puget Sound marine biota, Gina Ylitalo
Chemical tracers can be used to determine geographic ranges. Persistent organic pollutants (POPs) like PCBs and PDBEs in Salish Sea herring (3 yr old males collected ’99 and ’04) showed elevated levels in Puget Sound relative to Georgia Strait, though difference was small in DDT. West et al, 2008, Science of the Total Environment showed herring could be differentiated by these differences in contaminant concentrations.
Regional differences are shown by whole-body analysis of Chinook salmon from CA, Columbia River, and the Salish Sea. PS resident Chinook (blackmouth) have [PCB]~90 ng/g ww — twice non-resident PS Chinook. CA Chinook were highest in [DDT] where it was used much more extensively than in the Northwest.
In NE Pacific killer whales, west coast transients have highest [DDT, PCB, PDBE]. SRKWs are most contaminated of residents (relative to Gulf of Alaska and Aleutian residents). West Coast transients (feeding off CA coast) have highest DDT:PCB. Breaking down SRKWs, L pod has highest DDT:PCB of all pods (not sure if K pod was assessed). For PBDE:PCB, WC transients still highest and no significant difference between SRKW pods (L slightly higher ~0.7 vs 0.6).
Six gill sharks: [DDT]sum~40k ng/g lipid in mom and unborn pups that washed ashore in 2008, comparable to L pod concentration; local PS juveniles’ [DDT]sum is more similar to (~0.5x) J pod values. This implies not only that the six gill mother was a Californian, but also that J pod really isn’t going too far south during any wintertime foraging excursions…