SREL Reprint #3199
Soil Colloidal Behavior
Sabine Goldberg1, Inmaculada Lebron2, John C. Seaman3, and Donald L. Suarez1
States Department of Agriculture
The importance of colloids in soil science has been appreciated
for many years. However, recent understanding that organic and inorganic
contaminants are often transported via colloidal particles has increased
interest in colloid science. Essentially, all chemicals and individual
species are to some extent reactive with soils, including species such
as chloride ions, which undergo repulsion from negatively charged surfaces.
With few exceptions, soil chemistry is primarily the chemistry of colloids
and surfaces. The primary importance of colloids in soil science stems
from their surface reactivity and charge characteristics. The overwhelming
majority of surface area and electrostatic charge in a soil resides
in the less than 1 µm size fraction with particles with radii
between 20 and 1000 nm constituting the major part of the soil surface
area (Borkovec et al., 1993). A significant fraction of reactive soil
colloidal material falls within the <100 nm size range and thus is
relevant to the growing interest in the properties and behavior of nanoparticles.
Furthermore, soil is often the ultimate repository for anthropogenic
nanomaterials of environmental concern (Hochella, 2008; Theng and Yuan,
2008; Waychunas and Zhang, 2008). The unique aspects of nanoscience
as a discipline separate from colloid science reflect deviations in
material properties in the nanoparticle size range, especially for materials
<10 nm, and in many cases the lack of a natural bulk analog in the
larger size fractions, for example, ferrihydrite (Hochella, 2008; Waychunas
and Zhang, 2008).
SREL Reprint #3199
Goldberg, S., I. Lebron, J. C. Seaman, and D. L. Suarez. 2011. Soil Colloidal Behavior. pp. 15·1-15·39 In: P. M. Huang, Y. Li, and M. E. Sumner (Eds.). Handbook of Soil Sciences: Properties and Processes, Second Edition. CRC Press. 1,442pp.