New article on Great Lakes PCDD/PCDF Inputs/accumulation rates

[asagady@sojourn.com]

  The current (October 1997) issue of Environmental Science and Technology
  has an interesting article by Pearson, Swackhamer, Eisenreich and Long 
  concerning chlorinated dibenzo-dioxin/furan 
  (PCDD/F) concentrations, accumulations and 
  inventories in Great Lakes sediments.  ES&T 1997, 31, 2903-2909
  
  The article indicates that PCDD/PCDF accumulation rates in sediments
  peaked in 1970 ( plus or minus 10 years) and declined to present day
  rates which are 30-70% of the maximum rates.
  
  Highest accumulation rates are in Lake Ontario.
  
  The article discusses accumulation rates as to sources by percentage...
  
  .... regional air deposition 
  
  .... subregional air deposition  (air parcels having higher concentrations
       of PCDD/F than "remote air" due to local sources)
  
  ....  non-atmospheric inputs
  
  For subregional air deposition and non-atmospheric inputs,
  the article indicates that  Lake Superior receives of the 
  order of 0% from these two sources, southern Lake 
  Michigan receives 20%, northern Lake Michigan
  receives 60%,  and Lake Ontario receives 90%.....
  
  The authors conclude:
  
  "Atmospheric deposition from suburban air can support
  the accumulation of PCDD/F in southern Lake Michigan
  but some non-atmospheric sources to northern 
  Lake Michigan are implicated.  Lake Ontario may be
  receiving greater than 70% of its current 
  inputs of PCDD/F from non-atmospheric sources."
  
  
  Looks like there is still more work to do on 
  both PCDD/F air discharges and the
  potential  PCDD/F waste-water discharges, in-place river sediment
  contributions and waste-site runoff issues as well.
  
  One criticism of the Pearson article is that no sediment cores
  were taken from northeastern Lake Superior, which
  would be a location closer to some poorly controlled
  bleached kraft pulp mills in that region, and that failure
  would understate the non-atmospheric contributions
  in that part of Lake Superior..
  
  The same issue of ES&T also has a brief article
  about joint US/Canada plans to study PCDD/F
  emissions from iron and steel plants; as well as
  a technical article on PCDD/F deposition rates
  to vegetation.
  
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