Temporal dynamics of biogeochemical processes at the Norman Landfill site

Abstract

[1] The temporal variability observed in redox sensitive species in groundwater can be attributed to coupled hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate biogeochemical data sets from a municipal landfill site to identify the dominant modes of variation and determine the physical controls that become significant at different time scales. Data on hydraulic head, specific conductance, 2 H, chloride, sulfate, nitrate, and nonvolatile dissolved organic carbon were collected between 1998 and 2000 at three wells at the Norman Landfill site in Norman, OK. Wavelet analysis on this geochemical data set indicates that variations in concentrations of reactive and conservative solutes are strongly coupled to hydrologic variability (water table elevation and precipitation) at 8 month scales, and to individual eco-hydrogeologic framework (such as seasonality of vegetation, surface-groundwater dynamics) at 16 month scales. Apart from hydrologic variations, temporal variability in sulfate concentrations can be associated with different sources (FeS cycling, recharge events) and sinks (uptake by vegetation) depending on the well location and proximity to the leachate plume. Results suggest that nitrate concentrations show multiscale behavior across temporal scales for different well locations, and dominant variability in dissolved organic carbon for a closed municipal landfill can be larger than 2 years due to its decomposition and changing content. A conceptual framework that explains the variability in chemical concentrations at different time scales as a function of hydrologic processes, site-specific interactions, and/or coupled biogeochemical effects is also presented.

Hot Spots and Persistence of Nitrate in Aquifers Across Scales

“…Several studies have demonstrated that precipitation patterns impact the extent of agricultural nitrate-N leaching [16][17][18][19][20]. The thickness, composition of the vadose zone and aquifer heterogeneity [9] that vary across space in aquifers are significant factors that can affect nitrate-N delivery to groundwater because of active biogeochemical processes in this zone [21,22]. Furthermore, types of aquifers (confined or unconfined) affect the level of contamination, as unconfined shallow aquifers are more prone to nitrate-N contamination [23].…”

Identification of priority organic compounds in groundwater recharge of China

“…Also, in this study only degradation was considered in the soil, but time was not taken into account. Arora et al (2013) have studied that biogeochemical process and redox reactions are often characterized by high temporal variability. In the future, the relationship between degradation and time will be studied to get a generalize method which would represent the influence of time to the biogeochemical process.…”

Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

“…Data from this same study were used to develop a method for organizing microbial data into groupings reflecting the degree of leachate contamination [ Pearce et al ., ]. The fate of leachate has been studied at long‐term research sites in Norman, Oklahoma, USA [ Arora et al ., ] and in Grindsted, Denmark [ Albrechtsen et al ., ; Rügge et al ., ]. At the Grindsted Landfill site, the fate of 18 xenobiotic leachate compounds with a range of degradation rates was investigated with an experimental injection lasting 195 days.…”

“…Results from monitoring the injection cloud for 924 days showed slow degradation rates with long lag times under predominantly iron‐reducing conditions [ Rügge et al ., ]. Research carried out at the Norman Landfill site has shown that temporal variations in dissolved organic carbon leaching from the landfill can occur on time scales longer than 2 years [ Arora et al ., ]. Organic contaminant mixtures have also been studied at wastewater disposal sites such as a sewage plume located on Cape Cod, Massachusetts, USA, where Abrams and Loague [] found that representation of the degradable dissolved organic carbon in the plume as CH 2 O was adequate to simulate the observed redox zonation.…”

“…Arora et al . [] documented temporal fluctuations in sulfate concentrations at a landfill site in Norman Oklahoma, USA. Using wavelet analyses, they related recharge events to increased dissolution of sulfate‐bearing minerals and reoxidation of sulfide minerals.…”