Availability of Clay Surfaces in Soils for Sorption of Organic Contaminants. (S02-charles335312-poster)
Authors:
S. Charles* - M.S.U.
B.J. Teppen - M.S.U.
H. Li - M.S.U.
C. Johnston - Purdue S.A. Boyd - M.S.U.
Abstract:
The assertion that, in soil, clay and organic matter (OM) are intimately associated with each other as well as with other soil components, particularly iron oxides, has been dogmatized by soil scientists.
Accordingly, OM and iron oxides may reduce the efficacy of the clay mineral fraction for the sorption of nonionic organic compounds (NOCs) in soil via obscuration of the clay surfaces. This dogma would predict that the sorption of an NOC by soil may differ (i.e. be less than) from the summation of its sorption by the soil’s isolated individual components (particularly clay and OM). Two methods were used to assess the fractional availability of clay surfaces in soils (fa) for sorption of nitrocyanobenzene.
One is the Karickhoff equation which involves the summation of sorption of an NOC to soil clays and to soil OM. An alternative approach we developed for determining fa utilizes two systems exchanged with cations of different hydration energies which manifest maximum and minimum nitrocyanobenzene sorption by the clay mineral fraction. This equation alleviates methodological limitations encountered using the Karickhoff equation. Preliminary results reveal excellent agreement between fa values obtained from the two disparate approaches. Furthermore, both approaches indicate very high availability of clay surfaces in soils.
Speaker Information: Simone Charles, M.S.U., PO Box 6774, East Lansing, MI 48826; Phone: (517) 355 9284; E-mail: [email protected]
Session Information: Wednesday, November 5, 2003, 4:00 PM-6:00 PM Presentation Start: 4:00 PM (Poster Board Number: 1227)
Keywords: Pesticides; Clays; Sorption; Availability
