Measuring in situ reaction rate constants in wetland sediments
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Wetlands are ecologically important and play a key role in many environmentally significant chemical reactions. However, an accurate way of measuring in situ reaction rates in wetland sediments has yet to be established. This study evaluates the feasibility of adapting the push–pull test often used to measure in situ kinetics in subsurface environments, to wetlands. Experiments comparing the rates obtained with two methods, the push–pull test and a steady-state flow-through reactor, were conducted in a constructed wetland microcosm. First-order kinetic rate constants were determined for both sulfate and chromate reduction using both methods. Chromate reduction rates showed good agreement between the two methods, while sulfate reduction rates determined by the two methods differed significantly. Since the analysis for the push–pull test is based on a first-order kinetic, this discrepancy is likely due to the non-first-order behavior of sulfate reduction under the given environmental conditions. The largest obstacle identified prohibiting the use of this method is the availability of a tracer that is conservative in the presence of plants.
KeywordsWetlands Push–pull test Reaction rates Sulfate Chromium
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- Addy, K., Kellogg, D. Q., Gold, A. J., Groffman, P. M., Ferendo, G., & Sawyer, C. (2002). In situ push–pull method to determine ground water denitrification in riparian zones. Journal of Environmental Quality, 31(3), 1017–1024.Google Scholar
- Baptista, J. D. C., Donnelly, T., Rayne, D., & Davenport, R. J. (2003). Microbial mechanisms of carbon removal in subsurface flow wetlands. Water Science and Technology, 48(5), 127–134.Google Scholar
- Hangen, E., Gerke, H. H., Schaaf, W., & Huttl, R. F. (2005). Assessment of preferential flow processes in a forest-reclaimed lignitic mine soil by multicell sampling of drainage water and three tracers. Journal of Hydrology (Amsterdam), 303(1–4), 16–37. doi:10.1016/j.jhydrol.2004.07.009.CrossRefGoogle Scholar
- Kaspar, H. F. (1982). Denitrification in marine sediment—measurement of capacity and estimate of in situ rate. Applied and Environmental Microbiology, 43(3), 522–527.Google Scholar
- Maher, K., Steefel, C. I., DePaolo, D. J., & Viani, B. E. (2006). The mineral dissolution rate conundrum: Insights from reactive transport modeling of U isotopes and pore fluid chemistry in marine sediments. Geochimica et Cosmochimica Acta, 70(2), 337–363. doi:10.1016/j.gca.2005.09.001.CrossRefGoogle Scholar
- Oremland, R. S., Umberger, C., Culbertson, C. W., & Smith, R. L. (1984). Denitrification in San-Francisco Bay intertidal sediments. Applied and Environmental Microbiology, 47(5), 1106–1112.Google Scholar
- Paramasivam, S., Alva, A. K., Fares, A., & Sajwan, K. S. (2002). Fate of nitrate and bromide in an unsaturated zone of a sandy soil under citrus production. Journal of Environmental Quality, 31(2), 671–681.Google Scholar
- Roden, E. E., & Wetzel, R. G. (2002). Kinetics of microbial Fe(III) oxide reduction in freshwater wetland sediments. Limnology and Oceanography, 47(1), 198–211.Google Scholar
- Schnabel, R. R., Stout, W. L., & Shaffer, J. A. (1995). Uptake of a hydrologic tracer (bromide) by Ryegrass from well and poorly-drained soils. Journal of Environmental Quality, 24(5), 888–892.Google Scholar
- Whitmer, S., Baker, L., & Wass, R. (2000). Loss of bromide in a wetland tracer experiment. Journal of Environmental Quality, 29(6), 2043–2045.Google Scholar