An isotopic assessment of oil sands mine site waters to improve water management practices

Current oil sands mining technology requires approximately 2 m3 in the production of 1 m3 of crude oil. This water demand has resulted in massive volumes of process-affected waters being stored on-site – a volume that is currently not well quantified, though estimated to be in in the order of billions of m3. A site wide water balance must be closed at each mine in order to effectively manage the on-site storage and reuse of process-affected waters, in addition to planning for future remediation and release of this water following site closure. Oil sands mining operators have identified the constantly evolving nature of both operational water demands and the tailings management infrastructure as key challenges preventing accurate closure of a site wide water balance. Stable isotopes of oxygen and hydrogen (18O and 2H) have been widely used as tracers to close water balances of natural reservoirs. To date, their application to mine water containment systems, such as tailings management facilities, has not yet been implemented. This study demonstrates the use of 18O and 2H as tools to track key components of the water balance associated with the Mildred Lake mine, operated by Syncrude Canada Ltd in Northern Alberta. There, process affected waters are stored in interconnected tailings ponds referred to as the recycle water (RCW) circuit, with approximately 200 million m3 of water accessible for reuse in the extraction and transport of bitumen. This thesis characterizes the primary mechanisms of each water balance component contributing to the seasonal and inter-annual evolution of isotopic signatures of the RCW circuit and an end pit lake located at Mildred Lake mine. The thesis uses isotopic “finger-printing” of contributing water sources to characterize each part of the system. Isotope mass balance techniques were implemented to estimate evaporative loss from these systems and are compared to traditional methods of estimating evaporation (e.g., Penman combination equation and eddy covariance towers). This study found that isotopic seasonality of both the RCW circuit and the end pit lake were muted compared to natural systems within the region due to the contribution of large volumes of highly enriched pore water to tailings pond water stores as a result of tailings settlement. Samples collected from tailings ponds showed a systematic shift towards greater isotopic depletion during the ice-on period. I hypothesized that this shift occurred as a result of fractionation during ice formation in addition to mixing with process water released from tailings. Such mechanisms appeared to contribute to the observable spring depletion of the RCW circuit in addition to depleted snowmelt during the spring freshet. The seasonal variations in the isotopic signatures of individual tailings ponds were consistent with differences in water management between ponds. I then used an integrated isotopic signature as a proxy for the entire RCW circuit in isotope mass balance modelling scenarios. The proportion of inflow lost to evaporation from the RCW circuit was calculated as a decimal ratio using isotope mass balance modelling. The evaporation/inflow ranged from 0.11 to 0.22 over a five-year period, consistent with a high through-flow system with low residence time. These ratios correspond to 67–133 mm yr-1 of inflow water lost to evaporation from the RCW circuit based on estimated volumes of the water balance inputs. A simplified isotope mass balance model of the RCW circuit was used to estimate evaporative losses based on observable temporal isotopic enrichment during the open water period and assuming all other outflows of the water balance were zero. Using this model evaporation rates were found to range from 418 to 931 mm yr-1, while evaporation rates measured on-site using eddy covariance ranged from 350-520 mm yr-1. The difference between the isotope mass balance and eddy covariance results suggest a contribution of highly enriched tailings pore water to the overall enrichment of the RCW circuit in addition to open water evaporation. The isotope mass balance model was also used to simulate the evolution of the daily isotopic signature of a highly monitored demonstration end pit lake. The simulated pattern of isotope evolution was used to obtain an optimized estimate of lake evaporation. This estimate was then compared to a measured water balance over a four-year period. The model showed good agreement when 18O was used as the tracer; however, when 2H was used as the tracer the model consistently under predicted open water enrichment - likely due to evaporative fractionation effects. This thesis represents the first study that we are aware of that applies isotope mass balance techniques to an engineered system within the Alberta oil sands region. Our results highlight the potential value of using stable isotope tracers to aid in on-site water management of tailings ponds as well as helping to improve our understanding of the transport and distribution of water moving through mine closure landscapes

Cross Correlation of IceCube Neutrinos with Tracers of Large Scale Structure

The origin of most astrophysical neutrinos is unknown, but extragalactic neutrino sources may follow the spatial distribution of the large-scale structure of the universe. Galaxies also follow the same large scale distribution, so establishing a correlation between galaxies and IceCube neutrinos could help identify the origins of the diffuse neutrinos observed by IceCube. Following a preliminary study based on the WISE and 2MASS catalogs, we will investigate an updated galaxy catalog with improved redshift measurements and reduced stellar contamination. Our IceCube data sample consists of track-like muon neutrinos selected from the Northern sky. The excellent angular resolution of track-like events and low contamination with atmospheric muons is necessary for the sensitivity of the analysis. Unlike a point source stacking analysis, the calculation of the cross correlation does not scale with the number of entries in the catalog, making the work tractable for catalogs with millions of objects. We present the development and performance of a two-point cross correlation of IceCube neutrinos with a tracer of the large scale structure

Mechanical design of the optical modules intended for IceCube-Gen2

IceCube-Gen2 is an expansion of the IceCube neutrino observatory at the South Pole that aims to increase the sensitivity to high-energy neutrinos by an order of magnitude. To this end, about 10,000 new optical modules will be installed, instrumenting a fiducial volume of about 8 km3. Two newly developed optical module types increase IceCube’s current sensitivity per module by a factor of three by integrating 16 and 18 newly developed four-inch PMTs in specially designed 12.5-inch diameter pressure vessels. Both designs use conical silicone gel pads to optically couple the PMTs to the pressure vessel to increase photon collection efficiency. The outside portion of gel pads are pre-cast onto each PMT prior to integration, while the interiors are filled and cast after the PMT assemblies are installed in the pressure vessel via a pushing mechanism. This paper presents both the mechanical design, as well as the performance of prototype modules at high pressure (70 MPa) and low temperature (−40∘C), characteristic of the environment inside the South Pole ice

The next generation neutrino telescope: IceCube-Gen2

The IceCube Neutrino Observatory, a cubic-kilometer-scale neutrino detector at the geographic South Pole, has reached a number of milestones in the field of neutrino astrophysics: the discovery of a high-energy astrophysical neutrino flux, the temporal and directional correlation of neutrinos with a flaring blazar, and a steady emission of neutrinos from the direction of an active galaxy of a Seyfert II type and the Milky Way. The next generation neutrino telescope, IceCube-Gen2, currently under development, will consist of three essential components: an array of about 10,000 optical sensors, embedded within approximately 8 cubic kilometers of ice, for detecting neutrinos with energies of TeV and above, with a sensitivity five times greater than that of IceCube; a surface array with scintillation panels and radio antennas targeting air showers; and buried radio antennas distributed over an area of more than 400 square kilometers to significantly enhance the sensitivity of detecting neutrino sources beyond EeV. This contribution describes the design and status of IceCube-Gen2 and discusses the expected sensitivity from the simulations of the optical, surface, and radio components

Sensitivity of IceCube-Gen2 to measure flavor composition of Astrophysical neutrinos

The observation of an astrophysical neutrino flux in IceCube and its detection capability to separate between the different neutrino flavors has led IceCube to constraint the flavor content of this flux. IceCube-Gen2 is the planned extension of the current IceCube detector, which will be about 8 times larger than the current instrumented volume. In this work, we study the sensitivity of IceCube-Gen2 to the astrophysical neutrino flavor composition and investigate its tau neutrino identification capabilities. We apply the IceCube analysis on a simulated IceCube-Gen2 dataset that mimics the High Energy Starting Event (HESE) classification. Reconstructions are performed using sensors that have 3 times higher quantum efficiency and isotropic angular acceptance compared to the current IceCube optical modules. We present the projected sensitivity for 10 years of data on constraining the flavor ratio of the astrophysical neutrino flux at Earth by IceCube-Gen2

Estimating the coincidence rate between the optical and radio array of IceCube-Gen2

The IceCube-Gen2 Neutrino Observatory is proposed to extend the all-flavour energy range of IceCube beyond PeV energies. It will comprise two key components: I) An enlarged 8km3 in-ice optical Cherenkov array to measure the continuation of the IceCube astrophysical neutrino flux and improve IceCube\u27s point source sensitivity above ∼100TeV; and II) A very large in-ice radio array with a surface area of about 500km2. Radio waves propagate through ice with a kilometer-long attenuation length, hence a sparse radio array allows us to instrument a huge volume of ice to achieve a sufficient sensitivity to detect neutrinos with energies above tens of PeV. The different signal topologies for neutrino-induced events measured by the optical and in-ice radio detector - the radio detector is mostly sensitive to the cascades produced in the neutrino interaction, while the optical detector can detect long-ranging muon and tau leptons with high accuracy - yield highly complementary information. When detected in coincidence, these signals will allow us to reconstruct the neutrino energy and arrival direction with high fidelity. Furthermore, if events are detected in coincidence with a sufficient rate, they resemble the unique opportunity to study systematic uncertainties and to cross-calibrate both detector components

Direction reconstruction performance for IceCube-Gen2 Radio

The IceCube-Gen2 facility will extend the energy range of IceCube to ultra-high energies. The key component to detect neutrinos with energies above 10 PeV is a large array of in-ice radio detectors. In previous work, direction reconstruction algorithms using the forward-folding technique have been developed for both shallow (≲20 m) and deep in-ice detectors, and have also been successfully used to reconstruct cosmic rays with ARIANNA. Here, we focus on the reconstruction algorithm for the deep in-ice detector, which was recently introduced in the context of the Radio Neutrino Observatory in Greenland (RNO-G)

Deep Learning Based Event Reconstruction for the IceCube-Gen2 Radio Detector

The planned in-ice radio array of IceCube-Gen2 at the South Pole will provide unprecedented sensitivity to ultra-high-energy (UHE) neutrinos in the EeV range. The ability of the detector to measure the neutrino’s energy and direction is of crucial importance. This contribution presents an end-to-end reconstruction of both of these quantities for both detector components of the hybrid radio array (\u27shallow\u27 and \u27deep\u27) using deep neural networks (DNNs). We are able to predict the neutrino\u27s direction and energy precisely for all event topologies, including the electron neutrino charged-current (νe-CC) interactions, which are more complex due to the LPM effect. This highlights the advantages of DNNs for modeling the complex correlations in radio detector data, thereby enabling a measurement of the neutrino energy and direction. We discuss how we can use normalizing flows to predict the PDF for each individual event which allows modeling the complex non-Gaussian uncertainty contours of the reconstructed neutrino direction. Finally, we discuss how this work can be used to further optimize the detector layout to improve its reconstruction performance

Sensitivity of the IceCube-Gen2 Surface Array for Cosmic-Ray Anisotropy Studies

The energy of the transition from Galactic to extra-galactic origin of cosmic rays is one of the major unresolved issues of cosmic-ray physics. However, strong constraints can be obtained from studying the anisotropy in the arrival directions of cosmic rays. The sensitivity to cosmic-ray anisotropy is, in particular, a matter of statistics. Recently, the cosmic ray anisotropy measurements in the TeV to PeV energy range were updated from IceCube using 11 years of data. The IceCube-Gen2 surface array will cover an area about 8 times larger than the existing IceTop surface array with a corresponding increase in statistics and capability to investigate cosmic-ray anisotropy with higher sensitivity. In this contribution, we present details on the performed simulation studies and sensitivity to the cosmic-ray anisotropy signal for the IceCube-Gen2 surface array