IMPACT STATEMENT Mineralogical controls on colloidal dispersion and solid-phase speciation of soil contaminants
REGIONAL PROJECT S-280
ISSUE: A major portion of relatively insoluble nutrients (e.g., P) and pesticides are transported to
surface and subsurface waters associated with mobile colloids comprised of clay minerals and
humic substances. Likewise, a range of metal and organic contaminants associated with
industrial processes and with land disposal of wastes can be mobilized via a colloid facilitated
transport. The objectives of this project were to identify major soil types of the Southern U.S.
containing a high water dispersible clay fraction and to evaluate the physicochemical and
mineralogical properties of soils leading to a high propensity for colloid dispersion.
WHAT HAS BEEN DONE: Major soil types from throughout the Southern region having
variable compositional and mineralogical properties have been fully characterized and been
investigated for their propensity to generate colloids. Based on the data generated in this project,
a model has been developed to relate clay mineral composition, organic matter content, and
solution chemical parameters to dispersibility.
IMPACT: The project has identified those physicochemical and mineralogical factors critical to
the generation and potential transport of colloids from major soil types of the Southern region.
This project has provided information critical to identifying those soils that are of concern for
colloid facilitated transport of P, pesticides, and other inorganic and organic contaminants to
surface and groundwater systems. The information can also be useful in developing strategies for
managing these soils to minimize the deleterious impacts of the facilitated transport mechanism.
Future studies will focus on validating and refining the predictive model and on examining the
interaction of nutrients and contaminants with the important easily dispersible colloidal phases
found in major soil types from the Southern Region.
FUNDING SOURCES: Regional project No. S-280 "Mineralogical controls on colloidal dispersion and solid-phase speciation of soil contaminants"