Richard Theodule Amos

Carleton University · Department of Earth Sciences

Agricultural drainage ditches are necessary for regulating moisture contents in fields for crop production, and moreover, they can provide and regulate important ecosystem services. Drainage ditches and their associated riparian zones can be significant sources of enhanced N2O, CH4 and CO2 emissions, since they receive nutrient laden runoff and dra...

Vegetation management and dredging of agricultural drainage ditches are practices often necessary to improve field drainage. However, these practices can influence soil greenhouse gas (GHG) emissions in and around the drainage ditches by influencing, for instance, soil/sediment profiles, water/air temperatures, plant nutrient uptake, and hydrology...

The prediction of water quality from waste-rock stockpiles is an important aspect of mine planning and closure. These predictions are complex, and a well-documented mechanistic approach can provide greater confidence in the results. In this study, humidity-cell experiments (1-kg sample) conducted at 5° and 22°C were used to estimate the effluent wa...

Agricultural soils contribute significantly to global CO2 emissions. Soils can be both a CO2 sink and source depending on vegetation cover and the physical‐chemical characteristics of the soil environment. This study uses a new ¹⁴C dating approach to elucidate soil physical and geochemical properties that drive the production and transport of CO2 i...

One of the large-scale field waste rock experiments (test piles) conducted as part of the Diavik Waste Rock Project was deconstructed, providing a spatially located set of geochemical, mineralogical, and particle-size distribution samples. Geostatistical analyses were conducted for sulfur and carbon content and saturated hydraulic conductivity, whi...

The Diavik Waste Rock Project (DWRP) project included four principal components focused on the development of techniques for assessing the environmental impacts of waste rock at mine sites. These components were small-volume laboratory experiments, intermediate- and large-volume field experiments, and assessment of the operational-scale waste-rock...

Field experiments previously conducted to assess organic carbon (OC) amendments for in situ biological treatment of tailings porewater at the Greens Creek Mine (Alaska, USA) showed SO4 reduction, metal-sulfide precipitation, and decreased fluxes of SO4 and dissolved metals. Here, we develop two reactive transport models using the reactive transport...

In situ thermal recovery is utilized extensively for unconventional bitumen extraction in the Cold Lake-Beaver River (CLBR) basin in Alberta, Canada. Public health concerns have been raised over potable groundwater contamination and arsenic release adjacent to these operations within the CLBR basin, which have been linked to subsurface heating of a...

Mine waste-rock piles can release low quality drainage that is harmful to the surrounding environment. Many studies have investigated recently placed waste rock, but fewer have examined geochemical processes within, and downgradient of, old waste rock, even though these processes may be expected to persist for many decades. The Ore Chimney property...

Steam assisted gravity drainage is a form of thermal recovery technology used for unconventional oil. It can result in the heating of surrounding sediments and associated porewater and has the potential to mobilize otherwise immobile groundwater contaminants, such as arsenic. The current study was conducted to continue with the analysis of geochemi...

A historic waste-rock stockpile (WRS) at the Detour Lake Mine (DLM), covered with a thin layer (<1 m) of local overburden, was studied to determine the potential for microbially-mediated generation of acid rock drainage (ARD). The sulfur content of the waste rock ranged from 0 to 2.2 wt %, with pyrite and pyrrhotite identified as the principal sulf...

Supplementary Material

Formation of acid rock drainage is a temporal balance of acid-generating and alkalinity-generating reactions during mineral weathering. Accessory calcite and apatite are commonly present in granitoid rocks, and their weathering can be a source of net alkalinity. To evaluate the acid-consuming capability of the calcite and apatite group minerals in...

The Diavik Waste Rock Project, located in a region of continuous permafrost in northern Canada, includes complementary field and laboratory experiments with the purpose of investigating scale-up techniques for the assessment of the geochemical evolution of mine waste rock at a large scale. As part of the Diavik project, medium-scale field experimen...

The Diavik Waste Rock Project consists of laboratory and field experiments developed for the investigation and scale-up of the geochemical evolution of sulfidic mine wastes. As part of this project, humidity cell experiments were conducted to assess the long-term geochemical evolution of a low-sulfide waste rock. Reactive transport modelling was us...

Chemical weathering of sedimentary rocks is of great importance in determining seepage water chemistry, carbon, iron, calcium and sulfur turnover, as well as mineral transformation. In this study, we used the numerical code MIN3P to investigate controls on seepage water chemistry during chemical weathering of marine mudrocks. In particular, we focu...

Temperature changes can drive cycling of semi-volatile pollutants between different environmental compartments (e.g. atmosphere, soil, plants). To evaluate the impact of daily temperature changes on atmospheric concentration fluctuations we employed a physically based model coupling soil, plants and the atmosphere, which accounts for heat transport...

Drill cuttings were collected at 1 m depths from an instrumented, low sulfur, experimental waste rock pile containing a 4C-pyrrhotite that had been exposed to the extreme freeze-thaw cycle of a tundra climate. Boreholes were drilled from the top to base in the center of the pile and near the core-batter transition. Waste rock samples were analyzed...

At the Diavik Waste Rock Project's mine-research site, the microbial colonization and oxidation of waste rock sulfide minerals is attenuated by the extreme freeze-thaw cycle of a permafrost environment. The closure design for the waste rock stockpile consists of a low sulfide waste rock and low permeability till covering a relatively higher sulfide...

Soil-atmosphere exchange is important for the environmental fate and atmospheric transport of many semi-volatile organic compounds (SVOCs). This study focuses on modeling the vapor phase exchange of semi-volatile hydrophobic organic pollutants between soil and the atmosphere using the multicomponent reactive transport code MIN3P. MIN3P is typically...

A benchmark problem set consisting of four problem levels was developed for the simulation of Cr isotope fractionation in 1D and 2D domains. The benchmark is based on a recent field study where Cr(VI) reduction and accompanying Cr isotope fractionation occurs abiotically by an aqueous reaction with dissolved Fe2+ (Wanner et al., 2012., Appl. Geoche...

Leachate from a humidity cell experiment provided a geochemical framework to evaluate the early evolution of weathering of the same waste rock in an Arctic environment. Comparison of laboratory and field results indicates the hydrogeochemical system within the higher sulfide (0.01–0.27 wt.% S) waste rock pile has attained a peak weathering state, i...

Continuous monitoring of a 15 m high heavily instrumented experimental waste rock pile (0.053 wt.%S) since 2006 at the Diavik diamond mine in northern Canada provided a unique opportunity to study the evolution of fresh run-of-mine waste rock as it evolved over annual freeze-thaw cycles. Samples were collected from soil water solution samplers to m...

Chromium isotope analysis is rapidly becoming a valuable complementary tool for tracking Cr(VI) treatment in groundwater. Evaluation of various treatment materials has demonstrated that the degree of isotope fractionation is a function of the reaction mechanism, where reduction of Cr(VI) to Cr(III) induces the largest fractionation. However, it has...

Anaerobic biodegradation of organic amendments and contaminants in aquifers can trigger secondary water quality impacts that impair groundwater resources. Reactive transport models help elucidate how diverse geochemical reactions control the spatiotemporal evolution of these impacts. Using extensive monitoring data from a crude oil spill site near...

A series of replicate flow-through cell experiments was conducted to characterize Cr isotope fractionation during Cr(VI) treatment by granular zero-valent iron (ZVI). Synthetic groundwater containing 50 mg L−1 Cr(VI) was pumped upward through a custom-made cell packed with ZVI under anaerobic conditions. The geochemical evolution of the system was...

Secondary water quality impacts can result from a broad range of coupled reactions triggered by primary groundwater contaminants. Data from a crude-oil spill research site near Bemidji, MN provide an ideal test case for investigating the complex interactions controlling secondary impacts, including depleted dissolved oxygen and elevated organic car...

The oxidation of sulfide minerals in waste rock has the potential to generate low-quality drainage that can present a significant challenge to mine owners, regulators, and other stakeholders. Challenges involved in managing waste rock include the large volume of waste rock produced and the difficulty in predicting the quality and quantity of leach...

Wind-induced gas transport in a test-scale unsaturated waste rock pile was investigated at the Diavik diamond mine, Northwest Territories, Canada. Differential gas pressures were measured in 2008 at 49 locations within a field-scale experimental waste rock pile (test pile) and at 14 locations on the surface of the test pile at 1-min intervals. Wind...

The interior thermal regime of a field-scale experimental waste rock pile in the Northwest Territories, Canada, was studied. Test pile construction was completed in the summer 2006, and temperature data was collected continuously since that time to February 2009. The temperature data indicates the test pile cooled over the study period, with an ave...

The reactive and hydraulic efficacy of zero valent iron permeable reactive barriers (ZVI PRBs) is strongly affected by geochemical composition of the groundwater treated. An enhanced version of the geochemical simulation code MIN3P was applied to simulate dominating processes in chlorinated hydrocarbons (CHCs) treating ZVI PRBs including geochemica...

MIN3P, a multicomponent reactive transport model for variably saturated porous media, is used to simulate the outputs of column tests carried out using zero valent iron (ZVI) for nickel contaminated groundwater remediation. The objective of this study is to investigate the main chemical reactions involved in contaminant removal and the main causes...

Chromium isotope fractionation is indicative of mass-transfer processes, such as reduction of Cr(VI) to Cr(III) during groundwater remediation. Laboratory experiments comparing batch and column treatment of Cr(VI) using organic carbon suggest that the associated isotope fractionation may be influenced by solute-transport mechanisms. These batch and...

In a methanogenic crude oil contaminated aquifer near Bemidji, Minnesota, the decrease in dissolved CH(4) concentrations along the groundwater flow path, along with the positive shift in δ(13) C(CH) (4) and negative shift in δ(13) C(DIC) , is indicative of microbially mediated CH(4) oxidation. Calculations of electron acceptor transport across the...

In granular iron permeable reactive barriers (PRBs), hydrogen gas formation, entrapment and release of gas bubbles, and secondary mineral precipitation have been known to affect the permeability and reactivity. The multicomponent reactive transport model MIN3P was enhanced to couple gas formation and release, secondary mineral precipitation, and th...

MIN3P was developed as a general purpose multicomponent reactive transport code for variably saturated media. The basic version of the code includes Richard's equation for the solution of variably-saturated flow, and solves mass balance equations for advective-diffusive solute transport and diffusive gas transport. Biogeochemical reactions are desc...

Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of ura...

Isotope ratio measurements provide a tool for indicating the relative significance of biogeochemical reactions and for constraining estimates of the extent and rate of reactions in passive treatment systems. In this paper, the reactive transport model MIN3P is used to evaluate sulfur isotope fractionation in column experiments designed to simulate...

Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates whether it will reside in the aqueous or solid phase and thus plays an integral role in the mobility of uranium within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO2(2+) and associated species) ma...

At a crude-oil spill site near the town of Bemidji, MN, entrapped oil is present at residual saturations exceeding 10% in the vadose zone and floating at the water table at saturations of 30-60%. The degradable fraction of the light crude oil includes n-alkanes, aromatics, and alkyl-cyclohexanes. Together these compounds constitute a reduced carbon...

An automated data logging system designed to measure gas pressures within a 15-m-high waste rock test pile was installed at a diamond mine site In the Northwest Territories, Canada. Data collected from 12 Aug. 2007 to 15 Oct. 2 007 shows distinct gas pressure gradients within the waste rock pile. The magnitude of the gradients within the pile shows...

Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation co...

Although anaerobic methane oxidation (AMO) under iron reducing conditions is energetically feasible, its existence is still an open question. At a crude oil spill site near the town of Bemidji, MN, methanogenic degradation of entrapped oil floating at the water table has been occurring for more than 20 years. In the anaerobic portion of the hydroca...

1] The collection of representative samples of dissolved volatile compounds requires particular care to ensure that degassing does not occur during sampling, particularly for sites where the water table is deep. Furthermore, the investigation of physical and chemical processes involving volatile components can be enhanced by collecting vadose zone...

The strongly reducing nature of permeable reactive barrier (PRB) treatment materials can lead to gas production, potentially resulting in the formation of gas bubbles and ebullition. Degassing in organic C based PRB systems due to the production of gases (primarily CO2 and CH4) is investigated using the depletion of naturally occurring non-reactive...

Ebullition of gas bubbles through saturated sediments can enhance the migration of gases through the subsurface, affect the rate of biogeochemical processes, and potentially enhance the emission of important greenhouse gases to the atmosphere. To better understand the parameters controlling ebullition, methanogenic conditions were produced in a col...

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water...

At many sites contaminated with petroleum hydrocarbons, methanogenesis is a significant degradation pathway. Techniques to estimate CH4 production, consumption, and transport processes are needed to understand the geochemical system, provide a complete carbon mass balance, and quantify the hydrocarbon degradation rate. Dissolved and vapor-phase gas...

Reactive transport modeling was used to evaluate the performance of two similar column experiments. The experiments were designed to simulate the treatment of acid mine drainage through microbially mediated sulfate reduction and subsequent sulfide mineral precipitation by means of an organic carbon permeable reactive barrier. Principal reactions co...

A quantitative density model for alkali germanate and alkali germano-phosphate glasses has been developed based on Raman spectra and density data. The model demonstrates that for lighter/smaller cations such as lithium and sodium, the transition from 4- to 3-membered GeO4 rings is the prominent structural change responsible for changes in the densi...

Dissolved and vapour phase gas data, including Ar, N2, O2, CH4 and CO2, were collected at a crude oil spill site near Bemidji, MN. The dataset includes sampling points in the saturated and unsaturated zones from upgradient of the source zone, within the source zone, and down-gradient extending beyond the anoxic vapour and dissolved phase plumes. In...

A series of alkali germanophosphate glasses ((R2O)x(GeO2:P2O5)1−x where R=Na, K and Rb) with variable GeO2:P2O5 ratios (8:1, 6:1, 4:1 and 2:1) have been investigated using Raman spectroscopy. The glass network may be treated as being made up of separate germanate and phosphate components. Addition of alkali cations indicates that the alkalis prefer...

Knowledge of the behaviour of internal pile temperatures is of significance in reaching and maintaining freezing temperatures within potentially acid generating waste rock materials. Convective heat transfer in porous media is a complex process involving free and forced movement of air, which affects the heat transfer in the waste pile. The pressur...

A field study is on-going at the Diavik Diamond Mine, NT, Canada, to examine at several spatial scales the hydrologic, geochemical, microbiologic, gas transport, and heat transport mechanisms that control drainage water quality. Data sets on volumetric moisture content within a 15 m high waste rock pile (test pile), estimated using time domain refl...