Geochemical and Microbiological Methods for Evaluating Anaerobic Processes in an Aquifer Contaminated by Landfill Leachate

Abstract

A combined geochemical and microbiological approach was needed to delineate the biogeochemical processes occurring in an aquifer contaminated by landfill leachate in Norman, OK, where the important microbially mediated reactions in an anoxic plume were iron reduction, sulfate reduction, and methanogenesis. The highest rates of sulfate reduction (13.2 μM/day) were detected near the water table where sulfate levels were maximal (up to 4.6 mM). The enrichment of 34S in the sulfate pools (δ34S of SO4 2- was 67−69‰), and dissolved hydrogen measurements provided additional support for the importance of sulfate reduction near the water table. Methane was detected in the center of the plume where sulfate was depleted. Microbial incubations demonstrated concomitant sulfate reduction and methanogenesis in the anoxic portion of the plume. Although high concentrations of soluble reduced iron were detected throughout the aquifer and H2 levels were indicative of iron reduction under steady-state conditions, microbiological experiments showed that iron reduction was active only at the edges of the sulfate-depleted portion of the plume. This study demonstrates the benefits of using a combined geochemical and microbiological approach to elucidate the spatial distribution of biogeochemical processes in contaminated aquifers.

Impacts of anthropogenically influenced groundwater seepage on water chemistry and phytoplankton dynamics within a coastal marine system

“…The infiltration of rainfall through older, unlined landfill waste can create leachate plumes, which traverse through groundwater aquifers along prevailing hydraulic gradients (Freeze & Cherry 1979, Fetter 1994. Since landfill leachate plumes are typically enriched in nitrogen and phosphorus (Bjerg et al 1995, Cozzarelli et al 2000, Christensen et al 2001, they may contribute to eutrophication of aquatic systems. Moreover, the short distance between coastal landfills and nearshore discharge of groundwater may prevent substantial hydrodynamic dispersion, microbial degradation, and/or retention of such plumes (Fetter 1994, Christensen et al 2001).…”

The Effect of the Ammonium Concentration in the Groundwater

“…KB 33 also worrying when the increasing pattern in the year (Refer Anthropogenic activities such as urbanization are one of the major components that are causing the hight NH 4 in the ground water. NH 4 in aquifer is contaminated by the landfills and the waste disposal method (Baedecker& Back, 1979;LeBlanc, 1984;Cozzarelli et al, 2000;Heaton et al, 2005). …”

Anaerobic Degradation of Polycyclic Aromatic Hydrocarbons at a Creosote-Contaminated Superfund Site and the Significance of Increased Methane Production in an Organophilic Clay Sediment Cap

“…Although difficult to determine whether the deep porewater samples were in fact taken within the native sediment, based on the in situ parameters and geochemistry, it is likely both the upper and lower porewater samples at Site 1 were taken from within the sand cap (Tables 2.2 Site 3 porewater, with elevated CO 2 levels and increased alkalinity, indicates the mineralization of organic compounds to inorganic species. In the absence of oxygen, the accumulation of reduced species, such as Fe (II), H 2 S and NH 4 + results from microorganisms readily consuming electron-accepting compounds in the biodegradation of organic compounds [33]. Again, the porewater at Site 3 displays these characteristics, with the exception of the accumulation of H 2 S. Sulfide is a reactive compound and thus its concentration can be affected by its precipitation with metals such as iron.…”

“…Since weak acid extraction measures bioavailable iron, the higher porewater concentrations and lower sediment values suggest that microbial iron reduction was occurring in Site 3 sediments. However, the dominant terminal electron accepting process is difficult to define, as these processes can co-occur over very short distances [33,49].…”