Effect of Redox Processes on Soil and Water Quality
Investigators (most current known information)
The long-term goal of this research is to characterize more fully the consequences of sustained irrigation of agricultural soils with reclaimed sewage effluent on the surface and colloidal properties of soil and clay minerals, which, in turn, affect the quality of the soil and the water percolating through it. The specific objectives of the current proposal, and the next steps toward achieving this long-term goal, are to continue the field-scale measurements and controlled-conditions experimentation involving measurements of redox and related chemical changes of agricultural/plant-growing systems irrigated with reclaimed sewage effluents and to examine the potential risks and benefits of such changes with respect to nutrient and pesticide fate. Where risks have been or are identified, possible remediation strategies will be investigated. The central hypothesis to be tested is that long-term exposure to reclaimed effluent waters causes large variations in redox potential of the soil, which in turn causes a transformation in the constituent Fe and Mn minerals and alters the fate of metals and pesticides in the soil. We plan to test our central hypothesis and accomplish the overall objective of this proposed study by pursuing the following five specific aims:
- Determine the long-term patterns of in situ variations in redox potential and soil solution chemistry caused by effluent irrigation . We postulate that the variations in redox potential will continue to be much greater in soils receiving effluent irrigation than in soils receiving freshwater irrigation, and that the redox potential will continue to cycle, giving the suggestion of reversibility; but soil-solution pH, moisture tension, and/or composition will fail to be fully restored upon reoxidation, suggesting that transformations in mineralogy due to reduction are not completely reversible.
- Determine the impact of growing plants on long-term redox patterns. We hypothesize that the presence of plants in the soil opens channels to the atmosphere which supply some oxygen to the subsoil, thereby, partially mitigating the amplitude of in situ redox cycles. On the other hand, under restricted gas-exchange conditions, such as in partly flooded irrigation, the enhanced activity of roots will cause more intensive reduction of the soil in the root zone resulting in lower redox potential over longer periods of time.
- Identify key indicators of differences among various soils subjected to effluent irrigation. We propose that, at lower reduction potentials, structural Fe in phyllosilicates is reduced to Fe(II), Mn is reduced to Mn(II), and manganese oxides, goethite, and ferrihydrite are partially removed. These indicators will differ depending on the original composition of the soil and the amplitude or extent of redox cycles.
- Devise a method to overcome the adverse impact of Fe reduction in soil clays on nutrient cation availability . We hypothesize that natural amino sugars and amino acids can be utilized as additives to K fertilizers to prevent clay-layer collapse and thereby inhibit K fixation during redox cycling.
- Determine the effect of redox cycles on pesticide fate and toxicity. We postulate that the surfaces of soil clay minerals are much more reactive with pesticides if structural Fe in the clay is in the reduced Fe(II) state than if it is in the oxidized Fe(III) state, and that such reactions alter the mammalian toxicity of the pesticide.
Articles in Journals
Stucki, J.W. and J.E. Kostka. 2006. “Microbial reduction of iron in smectite.” Compte Rendu Geosciences.(in press)
Lee, Kangwon, Joel E. Kostka, and Joseph W. Stucki. 2006. “Comparisons of structural iron reduction in smectites by bacteria and dithionite: an infrared spectroscopic study.” Clays and Clay Minerals. (in press)
Sorensen, K.C., J.W. Stucki, R.E. Warner, E.D. Wagner, and M.J. Plewa. 2005. “Modulation of the genotoxicity of pesticides reacted with redox-modified smectite clay.” Environmental and Molecular Mutagenesis 46:174-181.
Sorensen, K.C., J.W. Stucki, R.E. Warner, and M.J. Plewa. 2004. “Alternation of mammalian-cell toxicity of pesticides by structural iron(II) in ferruginous smectite.” Environmental Science Technology 38:4383-4389.
Sorensen, K.C., C. Kara, J. Michael, M. J. Plewa, and J.W. Stucki. 2003. “Comparative quantitative analysis of agricultural chemicals using a microplate mammalian cell cytotoxicity assay.” Bulletin of Environmental Contamination and Toxicology 70: 1083-1088.
Ribeiro, F.R., K. Lee, J.W. Stucki, and J.D. Fabris. 2004. Effects of redox reactions on the structure of Garfield nontronite: A Mössbauer spectroscopic study. Pp. 467-470. In Applied Mineralogy, Developments in Science and Technology, volume 1. eds, M. Pecchio, et al. ICAM 2004 Sao Paulo, Brazil.
Ribeiro, F.R., J.W. Stucki, R.A. Larson, K.A. Marley, P. Komadel, and J.D. Fabris. 2004. Degradation of oxamyl by redox-modified smectites: Effects of pH, layer charge, and extent of reduction. In Applied Mineralogy, Developments in Science and Technology, volume 1 pp. 471-474. eds. M. Pecchio, et al. ICAM 2004 Sao Paulo, Brazil.
Stucki, J. W. 2006. Iron redox processes in smectites. In Chapter 8, Handbook of Clay Science, eds. F. Bergaya, B.K.G. Theng, and G. Lagaly. Elsevier, Amsterdam. (in press)
Paul, T. and J.W. Stucki. 2004. “Inhibition of potassium fixation in reduced clay by a new additive.” In Environmental Horizons, 2004.University of Illinois. (poster presentation)