Order this information in Print

Order this information on CD-ROM

Download in PDF Format

     

Click here to make tpub.com your Home Page

Page Title: Benthic impact-Theoretical bioaccumulation potential for nonpolar organic compounds
Back | Up | Next

Click here for a printable version

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Combat
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
USMC
   
Products
  Educational CD-ROM's
Printed Manuals
Downloadable Books
   

 

b. Contaminants that are released in the water can become associated with
dissolved organic matter in the water column and become less
bioavailable for accumulation by biota.
If the results of the screening level calculation exceed applicable WQS, the
mixing model can be rerun using the results from a standard elutriate test.
Professional judgment can be used to provide estimates of the range of
possible values for the mixing area. Uncertainty in the mixing model approach
can be evaluated by changing specific parameters in the model and evaluating the
impact on the results. Therefore, uncertainty in the ability of this screening-level
approach to make conservative predictions of concentrations of COCs in water is
assumed to be "easy" to quantify. The magnitude of uncertainty is ranked
"moderate" because such simple mixing zone modeling techniques yield order-
of-magnitude estimates (USEPA/USACE 1998). The accuracy of WQS values
was not assessed in these rankings.
Benthic impact-Theoretical bioaccumulation potential for nonpolar
organic compounds
The TBP is an approximation of the equilibrium concentration of nonpolar
organic contaminants in tissues of benthic invertebrates if the dredged material
were the only source of contaminant to the organism. In this tier, a comparison is
made between TBP calculated for the nonpolar organic contaminant of concern
in the dredged material and for the same contaminants in the reference sediment.
If the TBP for the dredged material exceeds that of the reference sediment,
further evaluation of bioaccumulation in Tiers III or IV is appropriate.
At present, the TBP can be calculated only for nonpolar organics, such as
polychlorinated biphenyls (PCBs). At equilibrium, a nonpolar organic chemical
would be expected to associate with organic matter in sediment and with lipids in
tissue. Therefore, the potential bioaccumulation of nonpolar organic chemicals
from dredged material can be estimated from the organic carbon content of the
material, the lipid content of the organism, and the relative affinities of the
chemical for each of these phases. Biota-sediment accumulation factors (BSAFs)
are ratios that describe the relationship between the concentration of a nonpolar
organic chemical in the lipid phase in tissue of a sediment-dwelling organism and
the concentration in the sediment organic carbon phase to which the organism is
exposed. BSAFs are defined as:
BSAF = ( CB / fL )/( CS / fOC)
(1)
where
CB = concentration of contaminant in biota, mg/kg wet weight
fL  = the fraction lipid of the biota, kg lipid/kg wet weight
19
Chapter 4 Uncertainty in Tiered Evaluation of Dredged Material

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business