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: Behavior of Organic Contaminants in Soils, and Consequences for Ecotoxicity Tests
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
   

 

ERDC TN-DOER-R3
September 2004
The use of this grass species is limited to the southern part of North America as far north as
Kentucky. Earthworms did not exhibit metal toxicity in the range studied, and a correlation was
found between bioaccumulation and substrate Zn levels. Thus, earthworm bioaccumulation was
considered as a valid Tier III assay for Zn (Best et al. 2003).
Behavior of Organic Contaminants in Soils, and Consequences for Ecotoxicity
Tests: Organic compounds differ from metals with respect to their behavior in the soil (e.g.
organic contaminants are biodegradable, while metals are not) and toxic action. Their interaction
with plants differs from that of metals. Moreover, ecotoxicological research on organic contami-
nants is far scarcer than on metals. The bioavailability of organic contaminants can change sig-
nificantly over time due to complexation, degradation, or loss by volatilization, runoff, or
leaching.
Hydrophobic organic contaminants (HOC) in sediments/soils and dredged material can exist in
any of the following four states: solids (soil and organic matter particles), fluid (water), gas
(within the sediment/soil), and biota (Brusseau 1997). Partitioning of the contaminant over these
phases depends on the contaminant characteristics and the processes affecting the transitions
from one phase to the other. The most important phase transition processes are the solubilization
(transition of pure contaminant into the water phase), volatilization (transition from the water to
the gas phase), and sorption (binding to the solid phase; Beck et al. 1993). The most immobile
HOCs are hydrophobic (low solubility in water) and lipophilic. These contaminants are usually
strongly bound to organic material and sediment/soil particles (Tenner et al. 1997). These char-
acteristics decrease bioavailability and toxicity for plants (Shimp et al. 1993), soil macrofauna
(Belfroid et al. 1995), surface fauna, and microorganisms. Bioavailability of HOC decreases with
aging (Alexander 1995). Therefore, short-term laboratory experiments in which spiked substrates
are tested may lead to overestimates of the ecotoxicological risks of aged contaminants. The
aging process results in adsorption of HOC in micro- or nanopores and/or the soil matrix. This
means that strongly bound, non-extractable, or difficult to extract HOC residues can be present in
the soil long after HOC pollution took place. Although the concentrations of aged HOCs may be
high, ranging from 100 to 1000 mg/kg organic soil matter, desorption processes are extremely
slow, and, therefore, the relationship between total HOC concentration and ecological processes
in the same soil is difficult to establish (De Jonge 1996).
The organic carbon fraction of DM can play an important role in the bioavailability of HOCs
(Fredrickson et al. 2003). A large fraction of the HOC that is extractable from sediments with
organic solvents can be non-available to biota, and the proportion of the non-biologically avail-
able fraction to total extractable HOC levels can vary greatly from sediment to sediment. For
instance, Talley et al. (2002) showed that Soxhlet-extractable PAH concentrations in DM from a
CDF in Milwaukee Harbor averaged 115 mg kg-1, but only 46 mg kg-1, i.e. less than half, was
bioavailable. These results and others have led to questioning the validity of the equilibrium par-
titioning theory developed by DiToro et al. (1991), that describes bioaccumulation of HOCs
from sediments by a simple constant partitioning process between sediment and organic carbon
and biomass (Kraaij et al. 2002). The quality of organic carbon may also have a large effect on
the bioavailability of HOCs. For instance, in several studies the non-bioavailable fraction of
solvent-extractable HOCs was associated with pitch and coke-derived particles (Paine et al.
1996; Talley et al. 2002).
2

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

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