Humic matter and contaminants. General aspects and modeling metal
Luuk K. Koopal1,**, Willem H. van Riemsdijk2, and David G. Kinniburgh3
1Laboratory of Physical Chemistry and Colloid Science,
Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands;
2Sub-department of Soil Science and Plant Nutrition, Wageningen University,
Dreijenplein 10, 6703 HB Wageningen, The Netherlands; 3British Geological
Survey, Wallingford, Oxon OX10 8BB, UK
Abstract: Humic substances are soil and fresh-water components
that play an important role in the binding and transport of both organic
and inorganic contaminants. Transport of the contaminants due to ground-
and fresh-water dynamics is directly related to the risks associated
with contaminations. The mobility of soluble humic substances is related
to their interaction with soil mineral particles. Some key references
for the binding of organic and inorganic contaminants and for the binding
of humics to mineral particles are presented. Humic substances also
play a role in the analysis of the contaminants in natural waters and
with remediation of water or soil polluted with pesticides, heavy metal
ions, and radionuclides. These aspects are illustrated with some examples.
The problems that are encountered with the modeling of the binding of
contaminants to humics and of heavy metal ions in particular are illustrated
by considering the nonideal competitive adsorption model (NICA) extended
with electrostatic interactions. The NICA-Donnan model gives quite good
results for the description of metal ion binding, as is illustrated
for metal ion binding to purified peat humic acid (PPHA). Finally, some
remarks are made with respect to the use of the NICA-Donnan model in
general purpose speciation programs and of simplified versions of the
model for predictions under restricted environmental conditions.
* An issue of reviews and research papers based on
presentations made at the IUPAC/ICSU Workshop on
Electrochemistry and Interfacial Chemistry in Environmental Clean-up
and Green Chemical Processes, Coimbra, Portugal, 6-7 April, 2001.
** Corresponding author.
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