Environmental Engineering Reference
In-Depth Information
4
Natural Colloids and Nanoparticles
in Aquatic and Terrestrial
Environments
Mohamed Baalousha 1 , Jamie R. Lead 1 , Frank von der Kammer 2
and Thilo Hofmann 2
1 School of Geography, Earth and Environmental Sciences, University of Birmingham,
United Kingdom
2 Department of Environmental Geosciences, Vienna University, Austria
4.1
Introduction
Environmental colloids have important environmental functions in aquatic and
terrestrial systems. For instance, they dominate the physico-chemical speciation of
trace elements and organic pollutants. A large proportion of these trace compounds
(typically 40-90% or more) are adsorbed to colloids (Stumm, 1992; Stumm and
Morgan, 1996). The binding of trace pollutants by colloids can be interpreted as a
function of colloidal size (Lead et al. , 1999), chemistry of the colloidal phases
(Lienemann et al. , 1997) or both (Baalousha et al. , 2006a ; Lyven et al. , 2003 ). The
importance of colloids in metal binding stems from the inverse relationship between
size and specifi c surface area, although other phenomena such as quantum related
effects may be important in the smallest fraction (
100 nm) of colloids (Wigginton
et al. , 2007). It has been found that small colloids of about 50 nm (Lead et al. , 1999 )
or
<
25 nm (Lyven et al. , 2003) are capable of binding the largest fraction of total
trace metals. Further, Lyven et al. (2003), assumed that iron oxides and organic
carbon were the main binding phases and that elements were distributed between
dissolved (e.g. molybdenum), organic (e.g. copper and zinc) and iron oxides (e.g.
<
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