River-Induced Flow Dynamics in Long-Screen Wells and Impact on Aqueous Samples

Vermeul, Vincent R.; McKinley, James P.; Newcomer, Darrell R.; Mackley, Rob D.; Zachara, John M.

doi:10.1111/j.1745-6584.2010.00769.x

Cited by 20 publications

(32 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An extensive characterization of all environmental variables potentially relevant to bacterial physiology is not yet available for our system. However, it is known that sediment texture varies vertically (Bjornstad et al, 2009) Vermeul et al, 2011). Sampled groundwater (4 l) was passed through a 0.2-mm polyethersulfone filter (Supor200, Pall Corporation, Port Washington, NY, USA).…”

Section: Data Collectionmentioning

confidence: 99%

Stochastic and deterministic assembly processes in subsurface microbial communities

et al. 2012

View full text Add to dashboard Cite

A major goal of microbial community ecology is to understand the forces that structure community composition. Deterministic selection by specific environmental factors is sometimes important, but in other cases stochastic or ecologically neutral processes dominate. Lacking is a unified conceptual framework aiming to understand why deterministic processes dominate in some contexts but not others. Here we work toward such a framework. By testing predictions derived from general ecological theory we aim to uncover factors that govern the relative influences of deterministic and stochastic processes. We couple spatiotemporal data on subsurface microbial communities and environmental parameters with metrics and null models of within and between community phylogenetic composition. Testing for phylogenetic signal in organismal niches showed that more closely related taxa have more similar habitat associations. Community phylogenetic analyses further showed that ecologically similar taxa coexist to a greater degree than expected by chance. Environmental filtering thus deterministically governs subsurface microbial community composition. More importantly, the influence of deterministic environmental filtering relative to stochastic factors was maximized at both ends of an environmental variation gradient. A stronger role of stochastic factors was, however, supported through analyses of phylogenetic temporal turnover. Although phylogenetic turnover was on average faster than expected, most pairwise comparisons were not themselves significantly non-random. The relative influence of deterministic environmental filtering over community dynamics was elevated, however, in the most temporally and spatially variable environments. Our results point to general rules governing the relative influences of stochastic and deterministic processes across micro-and macro-organisms.

show abstract

Section: Data Collectionmentioning

confidence: 99%

Stochastic and deterministic assembly processes in subsurface microbial communities

et al. 2012

View full text Add to dashboard Cite

show abstract

“…The former could be a consequence of habitat heterogeneities imposed by local physicochemical regimes (Dechesne et al, 2007;Lehman, 2007;Vermeul et al, 2011), such as partially filled or unfilled voids between gravelly cobble within the Hanford formation (Lindberg and Bond, 1979), that would disperse nutrients and microbes. Groundwater samples were collected at depths where sediments were coarsegrained with silty sands filling voids between rounded river cobbles (Bjornstad et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Groundwater samples were collected at depths where sediments were coarsegrained with silty sands filling voids between rounded river cobbles (Bjornstad et al, 2009). Within those sediments, differential measurements of hydraulic conductivity detected a zone of lower permeability within the central portion of the aquifer (Vermeul et al, 2011), where the intermediate-depth wells in each cluster were screened. Preferential groundwater flowpaths and regions of low sediment permeability could drive significant vertical variations in community composition.…”

Section: Discussionmentioning

confidence: 99%

Spatial and temporal dynamics of the microbial community in the Hanford unconfined aquifer

et al. 2012

View full text Add to dashboard Cite

Pyrosequencing analysis of 16S rRNA genes was used to study temporal dynamics of groundwater bacteria and archaea over 10 months within three well clusters separated by ∼30 m and located 250 m from the Columbia River on the Hanford Site, WA. Each cluster contained three wells screened at different depths ranging from 10 to 17 m that differed in hydraulic conductivities. Representative samples were selected for analyses of prokaryotic 16S and eukaryotic 18S rRNA gene copy numbers. Temporal changes in community composition occurred in all nine wells over the 10-month sampling period. However, there were particularly strong effects near the top of the water table when the seasonal rise in the Columbia River caused river water intrusion at the top of the aquifer. The occurrence and disappearance of some microbial assemblages (such as Actinobacteria ACK-M1) were correlated with river water intrusion. This seasonal impact on microbial community structure was greater in the shallow saturated zone than deeper zone in the aquifer. Spatial and temporal patterns for several 16S rRNA gene operational taxonomic units associated with particular physiological functions (for example, methane oxidizers and metal reducers) suggests dynamic changes in fluxes of electron donors and acceptors over an annual cycle. In addition, temporal dynamics in eukaryotic 18S rRNA gene copies and the dominance of protozoa in 18S clone libraries suggest that bacterial community dynamics could be affected not only by the physical and chemical environment but also by top-down biological control.

show abstract

“…Differing degrees of connectivity between the upper and lower high hydraulic conductivity zones and an overall complex hydraulic conductivity structure resulted in head differences that drove wellbore flows both upward and downward. Head differences between the shallow and deep zones were well correlated with wellbore flow (Vermeul et al 2011). Because of the high hydraulic conductivities in the well field, only a small amount of head difference was required to induce vertical flow.…”

Section: Johnson Et Al (In Pressmentioning

confidence: 77%

“…Further interpretation and validation of these results in the saturated zone are enabled by comparison to core measurements and EBF profiles. The high electrical conductivity, low-permeability zone revealed in the saturated Hanford formation was noted by Vermeul et al (2011) as a primary contributor to vertical borehole flow within wells that fully penetrate the saturated zone. This work shows that unit to be continuous throughout the well field.…”

Section: Johnson Et Al (In Pressmentioning

confidence: 99%

Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

Zachara¹,

Freshley²,

Last³

et al. 2012

View full text Add to dashboard Cite

SummaryThe 300 Area uranium groundwater plume in the 300-FF-5 Operable Unit is residual from past discharge of nuclear fuel fabrication wastes to a number of liquid (and solid) disposal sites. The source zones in the disposal sites were remediated by excavation and backfilled to grade, but sorbed uranium remains in deeper, unexcavated vadose zone sediments. Despite source term removal, the groundwater plume has shown remarkable persistence, with concentrations exceeding the drinking water standard over an area of approximately 1 km 2 . The plume resides within a coupled vadose zone, groundwater, river zone system of immense complexity and scale. Interactions between geologic structure, the hydrologic system driven by the Columbia River, groundwater-river exchange points, and the geochemistry of uranium contribute to persistence of the plume.The U.S. Department of Energy (DOE) recently completed a Remedial Investigation/Feasibility Study (RI/FS) to document characterization of the 300 Area uranium plume and plan for beginning to implement proposed remedial actions. As part of the RI/FS document, a conceptual model was developed that integrates knowledge of the hydrogeologic and geochemical properties of the 300 Area and controlling processes to yield an understanding of how the system behaves and the variables that control it. Recent results from the Hanford Integrated Field Research Challenge (IFRC) site and the Subsurface Biogeochemistry Scientific Focus Area Project funded by the DOE Office of Science were used to update the conceptual model and provide an assessment of key factors controlling plume persistence.Hanford IFRC research identified several refinements to the conceptual model that can be extended to the 300 Area. Studies at the IFRC site with geophysics, hydraulic testing, and tracers confirm the presence of a lower permeability intermediate zone within the Hanford formation that has a large impact on the hydrologic system. Resulting vertical borehole flows have implications for monitoring, persistence of the uranium plume, and remediation approach. Research at the IFRC site has shown that uranium is mobilized in a heterogeneous way from the lower vadose zone in concentrations exceeding the drinking water standard during the spring high water table event, showing large fluctuations in concentrations over the approximate 3-month period of spring snowmelt. The observed behaviors of uranium strongly impact monitoring results, and should be considered in their interpretation. Improved persistence calculations should address more accurate adsorption-desorption parameters (e.g., surface complexation) for the saturated zone derived from fitting of new IFRC field experiment data.

show abstract

River-Induced Flow Dynamics in Long-Screen Wells and Impact on Aqueous Samples

Cited by 20 publications

References 21 publications

Stochastic and deterministic assembly processes in subsurface microbial communities

Stochastic and deterministic assembly processes in subsurface microbial communities

Spatial and temporal dynamics of the microbial community in the Hanford unconfined aquifer

Updated Conceptual Model for the 300 Area Uranium Groundwater Plume

Contact Info

Product

Resources

About