347-2 Reactions of Nitrite with Goethite and Surface Iron(II)-Goethite Complexes.



Wednesday, October 19, 2011: 1:15 PM
Henry Gonzalez Convention Center, Room 213A, Concourse Level

Prakash Dhakal, Plant and Soil Sciences, University of Kentucky, Lexington, KY and Christopher Matocha, Plant and Soil Science, Univ. of Kentucky, Lexington, KY
Nitrite (NO2) is often observed in water and soil-water systems as a toxic anion that occurs as an intermediate in nitrification and denitrification processes.  In the presence of NO2-, microbial production of Fe (II) is halted.  One potential pathway explaining this is the reoxidation of surface-bound Fe(II) by NO2-.  In the past, there have been a few studies which have used iron oxides and iron oxy(hydr) oxide minerals as sorbents for microbially-generated Fe(II) to study NO2- reactivity.  These studies have shown that Fe(II) bound on iron minerals is capable of reducing NO2-.   Yet, spectroscopic measurements and kinetic data on reactivity of NO2- with goethite and goethite-bound Fe(II) are not found in the literature.  In this study, the sorption behavior of NO2- onto 300m2L-1 goethite-water slurry was investigated under anoxic conditions as a function of pH and ionic strength for time periods up to 72 hours.  Nitrite sorption ranged from 11 to 15% of the initial NO2- added (100 µM NO2-) at pH 5, and it decreases with increasing pH (at 7 and 8).  The sorption was not affected by ionic strength.  Further experiments will follow sorption of Fe(II) onto goethite as a function of pH and ionic strength.  Additional experiments will be carried out using XRD, SEM, and ATR-FTIR to investigate mineralogical changes in goethite, and coordination chemistry of Fe(II) at the Fe(II)-goethite water interface in the presence of NO2-. It is expected that NO2- sorption in Fe(II)-goethite ternary system would be greatly enhanced, perhaps due to reduction processes.  This research has important implications in biogeochemical cycling of nutrients, global warming, and contaminant transport.
See more from this Division: S02 Soil Chemistry
See more from this Session: Redox and Surficial Reactions In Soils: I