Modeling solute transport and sulfate reduction in marsh sediments |
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| Institution: | 1. All-Russian Research Geological Oil Institute, shosse Entuziastov 36, Moscow, 105118, Russia;2. Nord-WestLTD, Business center “Rumyantsevo”, bld. 1, korpus “A”, office 412, der. Rumyantsevo, Leninskii raion, Moskovskaya oblast, 142784, Russia;1. Leibniz Institute for Baltic Sea Research Warnemünde, IOW, 18119 Rostock, Germany;2. Institute for Chemistry and Biology of the Marine Environment, ICBM, University of Oldenburg, 26111 Oldenburg, Germany;1. Department of Geological Science, Indiana University, Bloomington, IN 47405, USA;2. School of Earth Sciences, Zhejiang University, Hangzhou 300027, People''s Republic of China;3. Doctoral Program in Environmental Science, Indiana University, Bloomington, IN 47405, USA;4. Water Research Center, Trent University, Peterborough, ON, Canada;5. Northwest University, Department of Geology, State Key Laboratory Continental Dynamic, Xi''an 710069, People''s Republic of China;6. Department of Geological Sciences, Virginia Tech, Blacksburg, VA 24061, USA |
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| Abstract: | The seasonal oscillation in sulfate and chloride concentration profiles in some salt marsh sediments is due to exchange of solutes with water on the surface of the marsh, and to the desiccation of the sediment in summer. Desiccation is manifested by disappearance of surface waters, fluctuations in the location of the water table, and by removal of water from the sediment above the water table. The loss of water from the pore space is commonly accompanied by entry of air into the soil, which oxidizes sulfide. The oxidation causes titratable alkalinity to decrease and results in CO2 degassing.Diffusion models of salinity can account for the observed profiles but only as long as the marsh is maintained inundated. The complexities introduced to the solute transport equations by sediment desiccation invalidate steady-state modeling of solute transport and diagenesis. The concentration profiles of dissolved products of sulfate reduction, such as bicarbonate, require months to reestablish a steady state after being disrupted. If the profiles of dissolved products of sulfate reduction are disrupted seasonally, such as by a seasonal fluctuation in the water table, they may remain transient throughout the year. |
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