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17. Cross-borehole DCIP monitoring of ZVI in-situ distribution. Hvedemarken 3-5, Farum

Author

Lévy, Léa, Thalund-Hansen, Rasmus, Bording, Thue, Vest Christiansen, Anders, and Bjerg, Poul L.

Abstract

This report assesses the application of cross-borehole ERT at a pilot scale test site undergoing remediation by injection of reactive reagents to remove chlorinated ethenes. The pilot scale test site, the design, result and recommendation with respect to the remediation are reported in Region Hovedstaden (2023).This report describes the use of cross-borehole DCIP (direct current – induced polarization) for monitoring the injection pilot scale remediation at Hvedemarken. The report describes three aspects:• Monitoring the injection by use of DCIP data• Determination of hydraulic conductivity (K) from DCIP data• Quantification of Contaminant Mass Discharge (CMD)The main focus will be on the monitoring of the remediation reagents which was the original focus of the project.A scientific paper describing in more details the methods and results is published in Water Resources Research [Lévy et al.20022]. A second paper focusing on hydraulic conductivity and contaminant mass discharge is currently under revision [Thalund-Hansen et al., 2023]. A note describing the application of the contaminant mass discharge at the site is included as an appendix in Region Hovedstaden (2023). Finally, a paper describing the biogeochemical processes and potential relationship to DCIP is under preparation [Thalund-Hansen et al., in prep].

Published
2023

21. High‐Resolution Geological Information from Crosshole Ground Penetrating Radar in Clayey Tills.

Author

Jensen, Bolette B., Rosenberg, Louise, Tsitonaki, Aikaterini, Tuxen, Nina, Bjerg, Poul L., Nielsen, Lars, Hansen, Thomas M., and Looms, Majken C.

Subjects
GROUND penetrating radar, HAZARDOUS waste sites, INDUSTRIAL sites, WATER distribution, ELECTRIC conductivity, RADIO interference
Abstract

Heterogeneous glacial deposits dominate large parts of the Northern Hemisphere. In these landscapes, high‐resolution characterization of the geology is crucial for understanding contaminant transport. Geological information is mostly obtained from multiple boreholes drilled during a site investigation, but such point‐based data alone do not always provide the required resolution to map small‐scale heterogeneity between boreholes. Crosshole ground penetrating radar (GPR) is suggested as a tool for adding credible geological information between boreholes at contaminated site investigations in industrial sites where infrastructure, such as electrical installations, can pose a challenge to other geophysical methods. GPR data are sensitive to the dielectric permittivity and the bulk electrical conductivity, which can be related to the distribution of water content and sand/clay occurrences. Here we present a detailed crosshole GPR dataset collected at an industrial contaminated site in a clay till setting. The data are processed using a novel inversion approach where information on changes in the velocity and attenuation of the radar signal are obtained independently. The GPR results are compared to borehole logs, grain size analyses, and relative permeability data from the site. The GPR data analysis provided valuable information on the understanding of the lateral geological variability. A silt layer with a thickness of a few decimeters, likely important for flow characterization, was confirmed and resolved by GPR data. Our findings suggest that crosshole GPR has the potential for contributing with high‐resolution geological information by filling the data gap between boreholes, thereby becoming a relevant tool in contaminated site investigations. [ABSTRACT FROM AUTHOR]

Published
2023
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22. Assessing Contaminant Mass Discharge Uncertainty With Application of Hydraulic Conductivities Derived From Geoelectrical Cross‐Borehole Induced Polarization and Other Methods.

Author

Thalund‐Hansen, Rasmus, Troldborg, Mads, Levy, Léa, Christiansen, Anders Vest, Bording, Thue S., and Bjerg, Poul L.

Subjects
HYDRAULIC conductivity, PARTICLE size distribution, INDUCED polarization, IN situ remediation, HAZARDOUS waste sites, MODEL airplanes
Abstract

A new methodology was developed to support contaminant mass discharge (CMD)‐based risk assessment of groundwater contamination downgradient of point source zones. Geoelectrical cross‐borehole induced polarization (IP) data were collected at a site undergoing in situ remediation of chlorinated solvents for determining 2D hydraulic conductivity (K) distributions with an inversion model resolution of 0.15 m (vertically) x 0.50 m (horizontally) in three control planes from 10 to 20 m depth. Additionally, 18 slug tests and 31 grain size distribution analyses (GSA) from the control planes, were used for K‐estimation. The geometric means and variance of the IP, slug test, and GSA derived K‐estimates were consistent with previously studied sandy aquifers. Furthermore, the vertical variation in K between two geological settings, a sandy till and a meltwater sand formation, was clearly identified by the IP K‐estimates. The vertical variation was backed up by hydraulic profiling tool (HPT) measurements. Random realizations of CMD were simulated based on the cross‐borehole IP derived K‐values. For comparison, the CMD was also estimated with a geostatistical conditional simulation approach, using the data from slug tests and GSAs. The high IP resolution captured the small scale variations in K across the transects and led to CMD predictions with a narrow uncertainty interval, whereas slug test and GSA either under‐ or overestimated the magnitude of the areas with the highest CMD. Applying the geophysical cross‐borehole method for estimating K‐distributions in addition to traditional methods would improve CMD‐based risk assessment and evaluation of remediation performance at contaminated sites. Key Points: Cross‐borehole induced polarization (IP) data have successfully been used to infer a high resolution hydraulic conductivity fieldHydraulic conductivity estimates from cross‐borehole IP, slug test, grain size distribution and hydraulic profiling tool compared wellCompared to other hydraulic conductivity estimation methods, application of cross‐borehole IP data enables an improved estimation of contaminant mass discharge [ABSTRACT FROM AUTHOR]

Published
2023
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36. Skelnen mellem pesticidkilder:Fund i grundvand – fladekilde eller punktkilde?

Author

Roost, Sandra, Tsitonaki, Katerina, Nielsen, Anna Krog, Bjerg, Poul L., Mosthaf, Klaus, Fjordbøge, Annika Sidelmann, Johnsen, Anders Risbjerg, and Thorling, Lærke

Abstract

Baggrund Fund af pesticider i grundvandet udgør et problem for grundvandsressourcen og er en hyppig årsag til lukning af vandforsyningsboringer. Pesticider i grundvandet kan enten stamme fra fladekilder eller punktkilder, hvilket har stor betydning for relevante handlemuligheder og hvilke myndigheder, der skal handle. Regionernes indsats er rettet mod punktkilder, og derfor er det vigtigt at kunne skelne mellem en punktkilde eller en fladebelastning fra f.eks. regelret anvendelse på de omkringliggende marker.I 2013 blev der udviklet en metoder med 11 indikatorer, som gjorde det muligt at skelne mellem pesticidkilder (Miljøprojekt 1502). Anvendelsen af indikatorerne er blevet et vigtigt redskab i regionernes planlægning af deres pesticidindsats. Derudover er der en række andre aktører, som har anvendt indikatorerne, herunder vandforsyninger og kommuner. Der har været væsentlige ændringer i omfanget af analysepakkerne i forbindelse med regionernes forureningsundersøgelser, boringskontrollen og grundvandsovervågningen. Der konstateres nu en række pesticider, som ikke indgik i projektet fra 2013. En del af disse pesticider konstateres nu hyppigere end nogen pesticider tidligere har gjort. Indikatorerne fra 2013 kan således ikke længere anvendes på det grundlag, de blev identificeret på. Der er derfor behov for indikatorer, der bygger på den nye situation. Projektet er udført som et samarbejde mellem Miljøstyrelsen, de fem regioner, Regionernes Videncenter for Miljø og Ressourcer, DTU Miljø, GEUS og WSP under Miljøstyrelsens teknologiudviklingsprogram. Herudover har der været input fra InSa Drikkevand. Dette hæfte beskriver udvalgte resultater fra projektet, som bygger på en hovedrapport og tilhørende appendiks, der er udgivet som Miljøprojekt nr. 2200. Formål Projekts formål var at opdatere og videreudvikle metoden til skelnen mellem pesticidkilder, som er beskrevet i Miljøprojekt 1502 fra 2013. Projektet har justeret nogle af de tidligere indikatorer samt suppleret med nye indikatorer og input. Derudover har formålet været, at metoden skal kunne anvendes fremadrettet på de pesticider, som er dominerende i grundvandet i dag. Målgruppe Målgruppen er som udgangspunkt regionerne, som har brugt og fortsat vil bruge indikatorerne i forbindelse med deres indsats overfor potentielle pesticidpunktkilder, der kan være årsag til fund i indvindingsboringer. Derudover vil målgruppen også omfatte forsyninger, vandværker og kommuner og andre der kan have interesse i at opspore et pesticidfund.

Published
2022

46. Oxygen-enhanced biodegradation of phenoxy acids in ground water at contaminated sites

Author

Tuxen, Nina, Reitzel, Lotte A., Albrechtsen, Hans-Jorgen, and Bjerg, Poul L.

Subjects
Aquifers -- Research, Biodegradation -- Analysis, Water, Underground -- Research, Herbicides -- Chemical properties, Earth sciences
Abstract

The effects of adding oxygen to anaerobic aquifer materials on biodegradation of phenoxy acid herbicides are studied by laboratory experiments with aquifer material from contaminated sites. The results suggest that stimulated biodegradation by addition of oxygen might be a feasible remediation technology at herbicide-contaminated sites, although oxygen consumption by the sediment could limit the applicability.

Published
2006

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