Characterizing Groundwater Flow in Monitoring Wells by Altering Dissolved Oxygen

ABSTRACTNear-surface groundwaters are prone to receive (in)organic matter input from their recharge areas and are known to harbor autotrophic microbial communities linked to nitrogen and sulfur metabolism. Here, we use multi-omic profiling to gain holistic insights into the turnover of inorganic nitrogen compounds, carbon fixation processes, and organic matter processing in groundwater. We sampled microbial biomass from two superimposed aquifers via monitoring wells that follow groundwater flow from its recharge area through differences in hydrogeochemical settings and land use. Functional profiling revealed that groundwater microbiomes are mainly driven by nitrogen (nitrification, denitrification, and ammonium oxidation [anammox]) and to a lesser extent sulfur cycling (sulfur oxidation and sulfate reduction), depending on local hydrochemical differences. Surprisingly, the differentiation potential of the groundwater microbiome surpasses that of hydrochemistry for individual monitoring wells. Being dominated by a few phyla (Bacteroidetes,Proteobacteria,Planctomycetes, andThaumarchaeota), the taxonomic profiling of groundwater metagenomes and metatranscriptomes revealed pronounced differences between merely present microbiome members and those actively participating in community gene expression and biogeochemical cycling. Unexpectedly, we observed a constitutive expression of carbohydrate-active enzymes encoded by different microbiome members, along with the groundwater flow path. The turnover of organic carbon apparently complements for lithoautotrophic carbon assimilation pathways mainly used by the groundwater microbiome depending on the availability of oxygen and inorganic electron donors, like ammonium.IMPORTANCEGroundwater is a key resource for drinking water production and irrigation. The interplay between geological setting, hydrochemistry, carbon storage, and groundwater microbiome ecosystem functioning is crucial for our understanding of these important ecosystem services. We targeted the encoded and expressed metabolic potential of groundwater microbiomes along an aquifer transect that diversifies in terms of hydrochemistry and land use. Our results showed that the groundwater microbiome has a higher spatial differentiation potential than does hydrochemistry.

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Degradation of permafrost beneath a road embankment enhanced by heat advected in groundwater1This article is one of a series of papers published in this CJES Special Issue on the theme of Fundamental and applied research on permafrost in Canada.

Canadian Journal of Earth Sciences ◽

10.1139/e2012-018 ◽

2012 ◽

Vol 49 (8) ◽

pp. 953-962 ◽

Cited By ~ 43

Author(s):

Isabelle de Grandpré ◽

Daniel Fortier ◽

Eva Stephani

Keyword(s):

Groundwater Flow ◽

Soil Layer ◽

Permafrost Degradation ◽

Soil Consolidation ◽

Monitoring Wells ◽

The Road ◽

Road Pavement ◽

Advective Heat Transfer ◽

Road Data ◽

Northwestern North America

For the past few decades, northwestern North America has been affected by climate warming, leading to permafrost degradation and instability of the ground. This is problematic for all infrastructure built on permafrost, especially roads and runways. Thaw settlement and soil consolidation promote embankment subsidence and the development of cracks, potholes, and depressions in road pavement. In this study, we investigate highway stability in permafrost terrain at an experimentally built road embankment near Beaver Creek, Yukon. A network of 25 groundwater monitoring wells was installed along the sides of the road to estimate groundwater flow and its thermal impact on the permafrost beneath the road. Data on topography, water-table elevation, ground temperature, and stratigraphy of the soil were collected at the site. The geotechnical properties of each soil layer were determined by laboratory analysis and used to calibrate a two-dimensional groundwater flow model. Field observations showed that water was progressively losing heat as it flowed under the road embankment. Our results suggest that advective heat transfer related to groundwater flow accelerated permafrost degradation under the road embankment.

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Lateral groundwater flow and pond interactions during dry and wet years

SURG Journal ◽

10.21083/surg.v9i1.3821 ◽

2017 ◽

Vol 9 (1) ◽

pp. 27-39

Author(s):

Andrew Wicke ◽

Thair Patros ◽

Gary Parkin

Keyword(s):

Surface Water ◽

Groundwater Flow ◽

Flow Direction ◽

Unconfined Aquifer ◽

Hydrologic Cycle ◽

Future Climate Change ◽

Visual Modflow ◽

Evaporative Demand ◽

Monitoring Wells ◽

Tightly Coupled

Groundwater and surface water are tightly coupled elements of the hydrologic cycle that have often been treated as separate entities. Future climate change modelling has predicted that hydrologic cycle changes, namely increasing drought frequency and flood-type events, are likely to occur. These events may directly impact the quality and quantity of both groundwater and surface water. Future water management policies must therefore be based on an understanding of how interactions between groundwater and surface water will change with a warming climate. The aim of this study was to model and analyze the lateral flow of groundwater and its interactions with a nearby pond in a shallow, unconsolidated, unconfined aquifer. Data were collected as part of a larger and ongoing study during the year 2012, a comparatively dry year, and 2013, a comparatively wet year. We first used ArcGIS and Visual MODFLOW Flex to create a conceptual model of the system, its soil layers, monitoring wells, and potential flow patterns. We then analyzed hydraulic head data, and calculated groundwater flow volumes using the Dupuit equation. We found that the groundwater flow direction reversed in the summer of 2012 and continued until the spring of 2013. Additonally, flow rate was greater in 2013 than 2012. The flow reversal was likely caused by higher evaporative demand during the summer months of 2012, drawing substantially more water from the pond than from the soil. The two-year timeframe was not long enough to determine whether this was a typical, yearly pattern, or was primarily due to the fact that 2012 was a particularly dry year.

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Groundwater Flow Field Distortion by Monitoring Wells and Passive Flux Meters

Ground Water ◽

10.1111/gwat.12290 ◽

2015 ◽

Vol 53 (6) ◽

pp. 933-942 ◽

Cited By ~ 3

Author(s):

G. Verreydt ◽

J. Bronders ◽

I. Van Keer ◽

L. Diels ◽

P. Vanderauwera

Keyword(s):

Flow Field ◽

Groundwater Flow ◽

Monitoring Wells ◽

Field Distortion ◽

Groundwater Flow Field

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Testing the relation between pre-sample purge extent, parameter stabilization and dissolved contaminant concentration at a DNAPL site

10.5194/egusphere-egu2020-948 ◽

2020 ◽

Author(s):

Agnes Reka Mathe ◽

Artur Kohler ◽

Jozsef Kovacs

Keyword(s):

Dissolved Oxygen ◽

Sampling Procedure ◽

Low Flow ◽

Contaminated Site ◽

Actual State ◽

Volatile Components ◽

Stagnant Water ◽

Monitoring Wells ◽

Sampling Procedures ◽

Sandy Aquifers

Groundwater contamination resulted from anthropogenic activity often proves to be a persistent feature of the affected groundwater regime. The contaminated groundwater body is a complex and dynamic entity commonly called the &#8220;contaminant plume&#8221;, it is characterized by spatially dependent concentration pattern that exhibits temporal changes. In order to assess the actual state of the plume contemporaneous sampling of all assigned monitoring wells is necessary. These contemporaneous samplings should provide compatible results, just like subsequent sampling campaigns. Differences between consecutive concentration patterns help to understand the temporal behavior of the plume.A monitoring well provides direct contact between the water originating from of the screened aquifer and the atmosphere. The water within the well may undergo physicochemical changes, between sampling events, mainly when aquifer water movement at the screened section of the well is slow. Among diverse alterations the stagnant water within the well may be depleted in volatile components, enriched in dissolved oxygen therefore the chemistry of the stagnant water within the well is typically not representative of the aquifer water. These alterations would not confine to the water contained inside of the well casing, they will diffuse into the aquifer at the screened section. The extent of this altered zone is hard to calculate, as it depends on a number of factors. The sampling procedure should ensure that representative formation water is sampled instead of altered water.It is well known for long that sampling procedure can affect sample integrity. Most standardized sampling procedures consist a pre-sampling purge phase to avoid the sampling of stagnant water instead of aquifer water. Most procedures aim to define the necessary extent of the purging in well volumes (from three-five to twenty volumes). The other approach is to purge the well until all or some of certain field parameters (such as pH, specific electric conductivity, temperature, dissolved oxygen, oxidation-reduction potential, turbidity) stabilize, however definitions for parameter stabilization criteria are not uniform. Parameter stabilization approach is used mostly, when low-flow sampling technique is applied. In addition to the stabilization of field parameters low-flow technique requires water level stabilization as well.The test site is a chlorinated hydrocarbon contaminated site, the affected subsurface consists of layered sandy aquifers and silt-clay aquicludes. Three monitoring wells were repeatedly tested quarterly on five sampling occasions. Field parameters were measured in a flow through cell and recorded regulary. Three samples were taken during purging: at the beginning of the purging; after extraction of three well volumes; and when field parameters are stabilized. The samples were analysed for organic and inorganic components.Results indicate that at wells with lower contaminant concentrations insufficient purging may result in overestimating the proportion of contaminant degradation products over primer contaminant components.

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