Browsing by Subject "Groundwater"

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Data for Evolving Mineralogy and Reactivity of Hematite-Coated Sands During Reduction by Fe(II) of 4-Chloronitrobenzene in Column Reactors
(2024-10-14) Harris, Celina M; Soroush, Adel; Hildebrandt, Alanna M; Amen, Kamilah Y; Corcoran, Louis G; Feinberg, Joshua M; Arnold, William A; Penn, R Lee; arnol032@umn.edu; Arnold, William; Arnold, Penn and Feinberg labs at the University of Minnesota
This study explores the reaction of contaminants mediated by iron oxide minerals in a column reactor that simulated iron reducing groundwater conditions. Reaction of the model nitroaromatic pollutant with hematite-coated sand in column reactors leads to growth of goethite and evolving reactivity due to changes in accessible surface area. Data collected include concentrations of the model pollutant (4-chloronitrobenzene) and its reaction product, the amount of new iron oxide mineral formed, and chloride concentrations in tracer studies.
Development of Alternative Onsite Treatment Systems [On-site treatment systems for domestic wastewater: A field comparison of alternative technologies] (1995-1997)
(University of Minnesota Duluth, 1999) Axler, Richard P
Approximately 500,000 Minnesota residences depend on individual or small community on-site wastewater treatment systems and 55-70% of them are either not in compliance with State Rules or are failing hydraulically to the surface. This is a direct human health threat from diseases, causes groundwater, stream and lake water quality degradation, and is a major impediment to the environmental and economic sustainability of the State’s water resources. The MTI projects over the period 1995-1999 keyed the development of an extremely successful state-wide partnership between the University (NRRI, UMD and UM-St. Paul), government resource & regulatory agencies (county, region, state and federal), and the private sector (engineering and consulting firms, contractors, vendors) to establish year-round, long-term performance, design criteria, cost-effectiveness and sustainability of alternative technologies for removing pathogens & nutrients from domestic wastewater. The program incorporates existing and newly created technology transfer and outreach/extension programs to efficiently transfer our findings to the private sector, to private citizens, to public planners and to policy makers to expedite potential changes in state or local rules. New business opportunities for new or existing companies have already occurred as a result of this project (>50 industry partners) and the total Match from 1995- 1999 was estimated to be $1,335,280 compared to MTI funding of $189,581 over the same period. Besides the business opportunities related to this project, effective alternative wastewater treatment systems will contribute to resolving some of our rural wastewater problems (e.g. affordable sewage systems for resorts and other commercial establishments throughout rural Minnesota) including the environmentally and politically sensitive northshore of Lake Superior, in addition to numerous other smaller, but sensitive lakes, and in geologically sensitive areas.
Effects of perennial and annual vegetation on a soil water balance and groundwater recharge.
(2010-06) Trost, Jared Jeffrey
The movement of land applied fertilizers, pesticides, and other agricultural chemicals from land surface to groundwater is a major environmental concern, especially in regions of coarse textured soils with shallow unconfined aquifers. A replicated field experiment was conducted on the Anoka Sand Plain, Minnesota, to examine the effects of perennial and annual vegetative cover on the movement of water through the unsaturated zone to groundwater. A Darcian analysis of soil water flow, water table hydrograph analysis, and chemical analysis of a bromide tracer in pore water in the unsaturated and saturated zones were utilized to estimate recharge rates and amounts to a shallow unconfined aquifer beneath four land cover types: corn (Zea mays), well-established prairie, newly-established hay, and bare ground. Soil water storage and precipitation were measured directly. Evapotranspiration estimates were determined by difference in the other water balance terms. Prairie soils to 125 cm were maximally drier than corn by mid-July each season due to greater early season ET demands by prairie than corn, with the maximum difference in soil water storage being 6.3 cm. Hay, prairie, corn, and bare ground recharge estimates from 6/3/2008 through 12/31/2009 were 31.6 +/- 4.5 cm, 37.9 +/- 3.3 cm, 40.2 +/- 3.4 cm, and 43.7 +/- 6.8 cm representing 28 %, 33%, 35%, and 39% of precipitation, respectively. Piston flow model estimates of residence time in the upper 225 cm of the soil profile were 312, 410, 352, and 318 days for hay, prairie, corn, and bare ground respectively. Bromide mass loss as determined for soil pore water 160 cm below land surface in one continuously monitored plot of each treatment resulted in 0.7%, 34%, 34%, and 100% of applied bromide leaching in prairie, hay, corn, and bare ground plots respectively. Peak bromide concentrations in prairie soil water were marginally significantly lower than all other treatments. Bromide was detected in the groundwater of all five replicate plots for hay, bare ground, and corn treatments, but only detected in two of five prairie replicate plots. Results indicate that on coarse soils, well established annually harvested perennial prairies have the potential for reducing inputs of land applied chemicals to groundwater relative to corn through slight reductions in recharge and reductions in solute transport.
Evaluating the Eco-Hydrochemical Response of Tropical Glacierized Mountainous Watersheds to Climate Change: A Case Study of the Volcán Chimborazo, Ecuador
(2021-05) Saberi, Leila
With global climate change, some of the highest rates of warming are occurring at high elevations in low latitudes, making tropical glacierized mountains some of the most vulnerable hydrological systems in the world. In the Andes, which hold 99% of all tropical glaciers, observations reveal that streamflow in many watersheds is already decreasing due to the retreat of glaciers. With the water security threat this presents to populations who rely on stream discharge from these glacierized mountains, understanding the hydrological impacts of climate change in these systems is critical. Recent studies have begun to investigate the response of streamflow to fast-retreating glaciers. However, many important knowledge gaps remain. For example, the contribution of meltwater to streamflow through subsurface flow has been largely overlooked, and this may be biasing estimates of how much groundwater may buffer glacier retreat. Further, in addition to causing glacier retreat, warming temperatures are also driving upslope vegetation migration, yet little is known about how this will further affect stream discharge in tropical glacierized watersheds. Finally, climate-driven changes in hydrology can alter solute weathering and transport on glacierized mountain slopes, but the effect on solute export from these watersheds has not been investigated, even though this could have implications for geochemical cycling and ecological function downstream in the Amazon Basin. Data sparsity in these remote, tropical glacierized mountainous watersheds, as well as unique characteristics such as their year-round glacier ablation and endemic páramo ecosystem, present major uncertainties associated with predicting hydrogeological, hydrochemical, and ecohydrological responses to climate change. We address these challenges by implementing a recently developed watershed model with reactive transport, BioRT-Flux-PIHM, for a sub-humid glacierized watershed on Volcán Chimborazo in the Ecuadorian Andes. BioRT-Flux-PIHM integrates multicomponent reactive transport with hydrological processes and land surface interactions, and thus has the potential to capture spatiotemporally distributed watershed surface and subsurface flows and pathways as well as hydrochemical processes. Implementing BioRT-Flux-PIHM with available field observations makes it possible extend sparse measurements over space and time, and to uncover unobserved processes. Our model results indicate that glacier melt contributes a broad range of 10-90\% of weekly discharge (~50% on average) over the course of one study year, mostly through fast surface runoff, but also through infiltration that increases groundwater flow by nearly 37%. Combined removal of glacier melt, upslope migration of vegetation, and a 4.5 °C increase in temperature results in substantial reduction of streamflow by 74% from current conditions, primarily due to an increase in evapotranspiration. Under this scenario, the model shows that near no-flow conditions can occur in the stream, which has crucial implications for local communities who rely on this water for irrigation. The model further predicted a unique relationship between the concentration (C) of weathering solutes in the stream and discharge (Q) that was mostly chemostatic (constant C with varying Q) because of large melt-supported groundwater inputs, but superimposed by melt event-driven dilution episodes. In a model scenario with no glacier melt, major ion concentrations, including Na+, Ca2+, and Mg2+, became higher and much more stable, but weathering rates decreased, which ultimately attenuated solute export by 23% compared to current-day estimates. We expect this reduction to be exacerbated by higher evapotranspiration and drier conditions with expanded vegetation. This work brings to light the importance of understanding interactions among warming temperatures, mineral weathering, subsurface meltwater flow, and vegetation changes to predict hydrological and hydrochemical processes in tropical watersheds with rapidly retreating glaciers.
Ground Water/Surface Water Interaction in Nearshore Areas of Three Lakes on the Grand Portage Reservation, Northeastern Minnesota, 2003–04
(2006) Jones, Perry M
This is a geologic and hydrological study of three lakes on the Grand Portage Reservation and is largely technical in scope. These three lakes have higher conductivity levels than other lakes in the Reservation. Public water comes from surficial water supplies, while ground water is used for private water sources such as wells, mainly within two miles from Lake Superior. Ground water is too saline to use for public water use. Results of the study show that water movement and quality in this geologically-fractured area are complex, and that lake sediment temperature monitoring may be the most reliable method for natural resources managers. Key findings from the report are extracted and reproduced below. “The availability of good quality water from lakes and wetlands on the Grand Portage Reservation in northeastern Minnesota is an important concern of the Grand Portage Band of Chippewa Indians. Development and changing land-use practices may affect the quality and quantity of water resources on the reservation. To effectively protect the water quality and quantity of the lakes and wetlands, an understand¬ing of exchanges between ground water and surface water on local and regional scales is needed. Numerous hydrologic studies have been done on the reservation, but none of these studies has focused on determining ground-water/surface-water interactions of lakes and wetlands. The U.S. Geological Survey (USGS), in cooperation with the Grand Portage Band of Chippewa Indians, conducted a study to assess ground-water/surface-water interactions in nearshore areas of three lakes, North, Teal, and Taylor Lakes on the Grand Portage Reservation in 2003 and 2004. These three lakes were selected on the basis of the rela¬tively high specific conductance values of water from these lakes compared to other lakes on the reservation. The high specific conductance values of the lake water may indicate that ground-water inflow is an important component of the water balance of the lakes. The objective of the study was to identify areas of ground-water inflow to the three lakes and surface-water outseepage to local aquifers through the assess¬ment of existing aerial photographs and water-quality data. Results from this study indicate that ground-water and surface-water interactions at the study lakes are complex, and the ability of the applied techniques to identify ground-water inflow and surface-water outseepage locations varied among the lakes. Measurement of lake-sediment temperatures proved to be a reliable and relatively inexpensive reconnaissance technique that lake managers may apply in complex settings to identify general areas of ground-water inflow and surface-water outseepage.”
Groundwater Fluctuations in Certain Open and Forested Bogs of Northern Minnesota
(Minnesota Agricultural Experiment Station, 1954-12) Manson, Philip W.; Miller, Dalton G.
Groundwater Management: Capacity Assessment at the Local Level, A survey of Minnesota Association of Soil and Water Conservation Districts
(2015-12-04) Pradhananga, Amit Ph.D.; Davenport, Mae A. Ph.D.; Perry, Vanessa M.S.
This report describes a capacity assessment of Minnesota Soil and Water Conservation District (SWCD) staff to engage in groundwater protection. The study was conducted by the Department of Forest Resources, University of Minnesota in partnership with the Minnesota Department of Natural Resources (MNDNR) and Minnesota Association of Soil and Water Conservation Districts (MASWCD). The overarching goal of the study was to examine local capacity and capacity building programs for groundwater management.
Guide to groundwater sensitivity rating techniques.
(University of Minnesota, Water Resources Research Center, 1992-09) Geier, Theodore W.; Perry, James A.
Hydrochemical Signatures of Glacial Meltwater on Volcán Chimborazo, Ecuador
(2017-11) McLaughlin, Rachel
Glacier recession in the tropical Andes is generating significant concern over future water availability for domestic use, irrigation, and hydropower. Sparse data sets, extreme heterogeneity in climate patterns, and the limited understanding of groundwater and ecohydrological processes in these catchments make predicting the hydrologic response to glacier retreat difficult. Here I examine a glaciated watershed on Volcán Chimborazo, Ecuador. I use geospatial analysis and recent geologic studies to evaluate the vegetation and geologic factors that influence the hydrologic response of the watershed. Additionally, I utilize hydrochemical and stable isotope signatures to investigate how melt and groundwater contributions to streamflow have changed over time along with possible meltwater-groundwater connections. A new landcover map of Volcán Chimborazo, generated using object based image analysis, reveals a significant increase in the upper limit of vegetation on the mountain and expansion of crop and pasture land since 1978. Geologic cross-sections, based on recent studies, show that near surface geology is dominated by glacial deposits and underlain by relatively young volcanic bedrock. Results from a hydrochemical mixing model (HBCM) combined with discharge measurements reveal spatial variability in groundwater discharge and suggest that groundwater discharge during the dry season has decreased from 2012-2017. Short time scale variability is clearly influenced by precipitation, but long-term discharge trends remain uncertain. Lastly, stable isotope and solute concentrations in samples suggest groundwater in the study watershed is recharged by precipitation falling at high elevations where ice and snow may dominate the hydrologic system.
Hydrology and Water Quality of the Grand Portage Reservation, Northeastern Minnesota, 1991-2000
(2002) Winterstein, Thomas A
This is a technical geo-hydrologic study of water resources on the Grand Portage Reservation. There are few references to human uses of water resources, or to anthropogenic factors. The abstract with key points are extracted and reproduced below. Abstract: “The Grand Portage Reservation is located in northeastern Cook County, Minnesota at the boundary between Minnesota, USA, and Ontario, Canada. Between 1991 and 2000 the U.S. Geological Survey conducted a series of studies, with the cooperation with Grand Portage Band of Chippewa, to describe the water resources of the Grand Portage Reservation. Ground water moves primarily through fractures in the bedrock, probably in three ground-water systems: local, regional, and deep. Lake Superior is thought to be the discharge point for brines in the deep ground-water flow system. The watersheds in the Grand Portage Reservation are small and steep; consequently streams in the Grand Portage Reservation tend to be flashy. Lake stages rise and fall with rainfall. The pH of water in the Reservation is generally alkaline (pH greater than 7.0). The alkalinity of water in the Reservation is low. Concentrations of major ions are much greater in ground water than in spring water and surface water. The ionic composition of water in the Reservation differs depending upon the source of the water. Water from 11 of the 20 wells sampled are a calcium-sodium-chloride type. Water from wells GW-2, GW-7, and GW-11 had much greater specific conductance concentrations of major ions compared to the other wells. Some spring water (SP-1, SP-3, SP-4, SP-6, and SP-8) is calcium-bicarbonate type like surface water, whereas other spring water (SP-5 and SP-7) is similar to the calcium-sodium-chloride type occurring in samples from about one-half the wells. The major chemical constituents in surface water are bicarbonate, calcium, and magnesium. Measured tritium and sulfur hexafluoride (SF6) concentrations in water samples from springs and wells were used to determine the recharge age of the sampled water. The recharge ages of two of the wells sampled for tritium are before 1953. The recharge ages of the remaining 10 samples for tritium are probably after 1970. The recharge ages of seven SF6 samples were between 1973 and 1998.”
Integrating urban recharge uncertainty into standard groundwater modeling practice: A case study on water main break predictions for the Barton Springs segment of the Edwards Aquifer, Austin, Texas
(2017-05) Sinner, Kate
Groundwater models serve as integral tools for understanding flow processes and informing stakeholders and policy makers in management decisions. Historically, these models tended toward a deterministic nature, relying on historical data to predict and inform future decisions based on model outputs. This research works toward developing a stochastic method of modeling recharge inputs from pipe main break predictions in an existing groundwater model, which subsequently generates desired outputs incorporating future uncertainty rather than deterministic data. The case study for this research is the Barton Springs segment of the Edwards Aquifer near Austin, Texas. Researchers and water resource professionals have modeled the Edwards Aquifer for decades due to its high water quality, fragile ecosystem, and stakeholder interest. The original case study and model that this research builds upon was developed as a co-design problem with regional stakeholders; the model outcomes are generated specifically for communication with policy makers and managers. Recently, research in the Barton Springs segment demonstrated a significant contribution of urban, or anthropogenic, recharge to the aquifer, particularly during dry periods, using deterministic data sets. Due to social and ecological importance of urban water loss to recharge, this study develops an evaluation method to help predicted pipe breaks and their related recharge contribution within the Barton Springs segment of the Edwards Aquifer. To benefit groundwater management decision processes, the performance measures captured in the model results, such as springflow, head levels, storage, and others, were determined by previous work in elicitation of problem framing to determine stakeholder interests and concerns. Through additional modeling processes, this study compares the results of the previous deterministic model and the stochastic model to determine gains to stakeholder knowledge.
Limnological Assessment of Mine Pit Lakes for Aquaculture Use
(University of Minnesota Duluth, 1992) Axler, Richard P; Larsen, Christen; Tikkanen, Craig A; McDonald, Michael E; Host, George E
This study addresses water quality issues associated with current and future uses of mine pit lakes for intensive aquaculture. In current net pen aquaculture operations (Minnesota Aquafarms, Inc.), metabolic wastes and uneaten food are dispersed into the lakewater. Intensive aquaculture at Twin City-South and Sherman increased levels of phosphorus (P) and nitrogen (N) and reduced dissolved oxygen (DO) in the water column, and increased the deposition of organic matter to the bottom relative to their previous conditions and to unused mine pit lakes. Numerous trophic status indices suggest that TC-S and Sherman have shifted (or are shifting) from an oligotrophic state to a more eutrophic one. However, due to MAPs intensive aeration, and circulation, conditions necessary for algal blooms (typical of eutrophication) have been infrequent, due to light limitation from vertical mixing. Blooms of scum-forming bluegreen algae have never been observed.
Modeling hydrothermal inputs to cold-water streams in urban watersheds.
(2011-05) Janke, Benjamin David
This research investigated the impact of urban development on the temperature of cold-water streams, which are crucial to maintaining viable populations of biota that are unable to survive in warmer waters. Since the temperature of these streams is typically maintained by significant amounts of groundwater inflow and riparian shading, the land cover conversion associated with urban development - replacement of crops or natural land with buildings, roads, lawns, and parking lots - has a negative impact, as these land-use changes tend to increase the amount of impervious surface area and reduce the amount of natural shading provided by vegetation. As a result, surface runoff rates and temperatures from rainfall events are amplified, watershed infiltration is reduced, and stream temperature increases. A primary goal of the project was to produce a tool to assess the impact of proposed urban development on stream temperatures in a particular watershed. The research procedure focused primarily on understanding and developing models for the hydrologic and heat transfer processes within a watershed, with particular focus on rainfall-runoff. Specifically, two process-based models were developed: one for estimation of runoff flow and temperature from urban surfaces, and a second for estimation of groundwater input to a stream from observations of water quality. The runoff temperature model demonstrated that heat export by rainfall-runoff from a paved surface is determined by antecedent pavement temperature and rainfall intensity/duration, and that stream-wise gradients in runoff temperature are negligible. The model contributed to the development of a more comprehensive stormwater modeling tool (MINUHET) by justifying the simpler solution technique used by MINUHET's runoff model. MINUHET was shown to accurately simulate runoff flow rate and temperature at the outlet of a small urban watershed, particularly when hydrologic data is available for calibration. The roof surface temperature analysis provided evidence that the contribution of heat from rooftops is negligible relative to that of paved surfaces. Lastly, the use of temperature as a groundwater tracer was shown to be an effective and inexpensive method for determining groundwater input to a stream, provided that the limitations of the approach are borne in mind when applying the method.
Neonicotinoid and Fipronil Insecticides in Minnesota: A Statewide Survey into the Occurrence, Detection, and Removal of Neonicotinoids and Fiproles in Minnesota Surface Waters ,Groundwater, and Engineered Treatment Systems.
(2023-10) Goedjen, Grant
Neonicotinoids and fiproles have been used extensively in Minnesota agriculture for the last three decades. Their high mobility in water and longevity in aquatic systems makes them key candidates for transport in surface runoff and groundwater to contaminate Minnesota surface and groundwater systems. Four large field studies of (1) Minnesota groundwater and natural springs, (2) Minnesota surface waters, (3) stormwater and precipitation at stormwater-impacted Saint Paul Lake, and (4) wastewater, drinking water, and compost treatment systems were conducted over three years (2019-2022) to evaluate the state of neonicotinoids and insecticides in Minnesota’s natural waters and the current capacity for removal by existing treatment processes. Shallow unconfined groundwater and natural springs were more susceptible to contamination than deeper groundwater. Clothianidin (41% of springs, 14% of wells) was the most common insecticide detected followed by thiamethoxam (31% of springs, 12% of wells), imidacloprid (22% of springs, 10% of wells), thiacloprid (19% of springs, 2% of wells), acetamiprid (12% of springs, 14% of wells), and fipronil (19% of spring, 1% of wells). Groundwater depth also appeared to limit groundwater contamination to shallow systems with detections increasing with increasing urban land use and watershed imperviousness. Tritium/groundwater age, dissolved oxygen (DO), and total nitrite plus nitrate (total oxidized nitrogen), all correlated to noenicitinoid occurrence. Clothianidin (31% lakes, 60% rivers), thiamethoxam (19% lakes, 44% rivers), imidacloprid (65% lakes, 85% rivers), acetamiprid (29% lakes, 35% rivers), thiacloprid (15% lakes, 13% rivers), and fipronil (32% lakes, 30% rivers) were all detected in surface water lakes and rivers. Thiamethoxam and clothianidin has an association with agricultural watersheds while acetamiprid, thiacloprid, and fipronil were associated with urban watersheds. Increasing watershed catchment size and imperviousness increased the likelihood of contamination but the previous year’s application rates were the largest determining factor in the risk of insecticide contamination. All five neonicotinoid and fipronil were detected in stormwater (6% - 49%) and snow melt (13% - 29%). Stormwater and snow melt concentrations spiked with the “spring flush” during the early spring and summer months. Imidacloprid (17% rain, 47% snow), acetamiprid (6% rain, 33% snow), and clothianidin (44% rain, 39% snow), were all detected in direct rainfall and snowfall samples. Most of the contamination in stormwater (>76% stormwater, >67% snowmelt) was picked up as water moves through the watershed with correlated strongly correlations to application rates and soil and lipophilicity. Neonicotinoids and fipronil were present in drinking water, wastewater, and compost material provided by a commercial composting center. Current wastewater biological treatment technologies did not result in a significant reduction in concentrations. Biologically-activated carbon filtration with and without pre-oxidation provided a substantial reduction in concentrations (86% - 100% removal). Pre-oxidation did generate oxidized transformation products (<3.5% yield) but all transformation products were removed by downstream filtration. Compost was capable of degrading fipronil in both residential and commercial composting operations while clothianidin and acetamiprid were degradable in commercial composting systems and acetamiprid, clothianidin, imidacloprid, fipronil were partially degradable in residential composters. Runoff produced from rainfall at the composting facility with substantial neonicotinoid and fipronil concentrations.
OFR14-02, Geologic controls on groundwater and surface water flow in southeastern Minnesota and its impact on nitrate concentrations in streams
(Minnesota Geological Survey, 2014) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Retzler, Andrew J.
This report summarizes the results of a Minnesota Geological Survey (MGS) investigation conducted for the Minnesota Pollution Control Agency (MPCA) designed to support watershed planning efforts in southeast Minnesota. Specifically it provides better understanding of the geologic controls on nitrate transport in the region, including nitrate in groundwater that is the source of baseflow to streams. Nitrate contamination of surface water and groundwater is a long- standing issue in southeastern Minnesota. We focused much of our investigation on an evaluation of nitrate (NO3 ion) transport in the Root River watershed because of the relatively advanced understanding of the karstic conditions in that area. However, the overall scope of the project includes the entire bedrock-dominated landscape of southeast Minnesota. Our results therefore support a broader MPCA watershed planning effort that directly pertains to the Root River, as well as to other watersheds within the Lower Mississippi River Basin in Minnesota.
OFR14-03, Geologic Controls on Groundwater and Surface Water Flow in Southeastern Minnesota and its Impact on Nitrate Concentrations in Streams: Local Project Area Report
(Minnesota Geological Survey, 2014) Steenberg, Julia R.; Tipping, Robert G.; Runkel, Anthony C.
This report summarizes the results of part of a Minnesota Geological Survey (MGS) investigation conducted for the Minnesota Pollution Control Agency (MPCA) designed to support watershed planning efforts in southeast Minnesota. The broader project provides better understanding of the geologic controls on nitrate transport in the region, including nitrate in groundwater that is the source of baseflow to streams. This report describes a local scale subproject focused on a relatively small part of the Root River watershed in Fillmore County. We conducted new mapping that provides a more detailed depiction of the geologic conditions in a three dimensional electronic format suitable for groundwater-surface water modeling. In addition, we used existing maps and reports along with new field data collected during the course of this project to improve the hydrostratigraphic characterization of the bedrock. This led to a more comprehensive understanding of the hydrostratigraphic attributes of bedrock that forms the Upper Carbonate Plateau, which dominates the landscape in the local project area. Cross sections within the local project area are used to illustrate how nitrate is transported in the ground and surface water system.
Potential for slumps, sediment volcanoes, and excess turbidity in the Nemadji River Basin.
(2010-06) Mossberger, Irvin Gerald
Beginning in the early 1990‘s, a portion of Deer Creek, a tributary of the Nemadji River in the Lake Superior basin, experienced the formation of sediment volcanoes in its creek bed, along with related slumping, enhanced erosion rates, and turbidity in excess of state total maximum daily load (TMDL) limits. Slumping near the stream has increased erosion rates and may eventually threaten the stability of nearby structures. The resulting excess turbidity negatively impacts aquatic wildlife, and increases sedimentation rates and dredging costs in downstream navigable waters. Slumping and formation of sediment volcanoes at Deer Creek were likely caused when dynamite was used to destroy a nearby beaver dam on the creek. Some combination of rapid pond drainage and/or disturbance from the explosives may have led to fracturing of a glacio-lacustrine clay confining layer over a locally extensive aquifer. A sediment volcano and associated slumping are also present along nearby Mud Creek. The sediment volcano areas at Deer and Mud Creeks both occur at the toe of 10-meter high slumps. The failure planes of these slumps may facilitate formation of sediment volcanoes by providing pathways for groundwater to reach the surface. Predicting slump locations should then also help predict the location of potential sediment volcanoes. The stratigraphic and hydrologic conditions in Deer and Mud Creeks are similar to those throughout nearby areas in the Nemadji River basin. This project examines the relationship between the slumps and sediment volcanoes, and develops a predictive model of the potential for slope failure in the lacustrine clay portions of the basin. A 3-D model of stratigraphy and hydraulic potential from more than 300 wells is used, along with slope stability analysis with the stress-slope and Mohr-Coulomb equations in a GIS. Results of the modeling found higher susceptibility for slumping in areas of high slope and high potentiometric surface. The model correlated well at a 92% rate with a data set of 322 inventoried slumps, and included both volcano areas, without overpredicting high-risk slump areas. Another model, SINMAP 2.0, was run to test the veracity of the original model‘s results. Both models were in good agreement with each other. This project provides a reasonable approximation of slope stability and can be used to assist in land use planning to help reduce erosion and its consequences.
Solid-phase arsenic speciation in glacial aquifer sediments of west-central Minnesota, USA: a micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation
(2017-06) Nicholas, Sarah
Abstract Arsenic (As) is a geogenic contaminant affecting groundwater in geologically diverse systems. The footprint of the Des Moines Lobe glacial advance in west-central Minnesota, is a regional nexus of drinking-water wells that exceed the US EPA maximum contaminant level for arsenic (As>10µgL-1). Arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions in aquifers fluctuate. The specific objective of this research was to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching hypothesis is that gradients in hydrologic conductivity and redox conditions found at aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (µXAS) approach was developed and applied to rotosonic drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addressed the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The solid-phase Fe and As speciation was interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results are consistent with three different As release mechanisms: (1) desorption from Fe oxyhydroxides, (2) reductive dissolution of Fe oxyhydroxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity observed in the distribution of elevated-As wells. Supplementary file “Nicholas dissertation supplementary files 1 to 5.xlsx” was submitted to the UMN digital conservancy with this thesis. It is an excel workbook with five tables. Tables 1 and 2 are the complete provenance and citation information for all As and Fe reference spectra used. Tables 3, 4, and 5 are the reference spectra fits, fractions, and scores for the sampled spectra from cores OTT3, TG3, and UMRB2.
A Source to Tap Investigation of Minnesota's Groundwater Supplies Used for Drinking Water
(2018-11) Galt, John
Groundwater is often a desirable drinking water source because it is generally free of suspended solids and microbial pathogens and thus requires minimal, if any, treatment prior to distribution. Epidemiological studies have shown, however, that consumption of untreated groundwater increases risk of gastrointestinal illness. Previous work in Wisconsin, USA reported the occurrence of pathogenic viruses in groundwater supplies and resulting health impacts but bacterial pathogens were not investigated. In this study, a high-volume (300 – 1500 L) dead-end ultrafiltration sampling method was used to capture and recover microbes from 16 public groundwater systems throughout the State of Minnesota. The systems were sampled at the wellhead or source, after treatment if any (i.e., two systems did not treat or disinfect before distribution), and from one location in the distribution system. DNA was extracted from the microbes recovered in these samples and used as template for quantitative PCR analyses targeting 14 genes corresponding to pathogenic bacteria, one gene for a DNA virus, and the 16S rRNA gene as a marker for total bacteria. All samples were negative for the targeted genes from Campylobacter jejuni, Shigella spp., and Adenovirus; Escherichia coli-specific genes were only detected in water from a non-potable well with a documented history of contamination. Genes markers for two genera, Legionella and Mycobacteria, that include species that are opportunistic pathogens, were detected in four of the 16 public groundwater supplies, with Legionella levels decreasing in disinfected systems while Mycobacteria levels tended to increase. Raw water 16S rRNA gene concentrations ranged from 10^5 – 10^8 gene copies/L, decreased to background levels after disinfection, then rebounded at the tap in the majority of cities. There was no significant difference in 16S rRNA gene concentrations from source-to-tap in the two non-disinfecting cities. Raw water samples contained diverse and previously uncharacterized organisms as revealed by DNA sequencing analyses, and beta diversity analyses suggest that community composition is driven by source water and/or disinfection. The results from this study suggest that groundwaters supplying public water systems in Minnesota are largely free of enteric pathogens but may contain opportunistic pathogens.
Study of De-icing Salt Accumulation and Transport Through a Watershed
(Minnesota Department of Transportation, 2017-12) Herb, William; Janke, Ben; Stefan, Heinz
The accumulation of chloride in surface waters and groundwater from road deicing and other sources is a growing problem in northern cities of the U.S., including the Minneapolis-St. Paul metro area. To inform mitigation efforts, the transport of chloride in surface waters of a metro-area watershed (Lake McCarrons) was studied in this project to characterize chloride transport by surface runoff, the residence time of chloride in surface water, and how variations in weather influence chloride transport and accumulation processes. Monitoring work over three winters showed that the residence time of chloride in small, sewered watersheds varied from 14 to 26 days, depending on winter weather conditions, with 37 to 63% of chloride applied as de-icers exported in snowmelt and rainfall surface runoff. In contrast, a monitored highway ditch exported less than 5% of chloride applied to the adjacent road. Stormwater detention ponds were found to act as temporary storage for chloride, with persistent layers of high chloride content at the bottom. Chloride monitoring data and runoff simulations were used to explore the possibility of snowmelt capture as a chloride pollution mitigation strategy. We found that capturing snowmelt runoff close to source areas (roads and parking lots) yields the highest chloride concentrations and removal potential.

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