This project was a part of a study to evaluate natural attenuation (NA) as a viable remedial option for petroleum hydrocarbon (PHC) contamination at upstream oil- and gas-contaminated sites in Alberta, Canada. Laboratory mesocosms were set up using groundwater and sediment materials collected from two PHC contaminated sites (Site 1 and Site 3) in Alberta to investigate the enhancement of anaerobic PHC biodegradation by amendment of terminal electraon acceptors (TEAs, nitrate or sulfate) and/or nutrients (ammonium and phosphate). Multiple lines of evidence, including the removal of benzene, toluene, ethylbenzene and xylenes (BTEX) and CCME F1 fraction hydrocarbons (C6 to C10), rapid depletion of TEAs, the production of biogenic gases, and detection of the metabolites verified that anaerobic PHC biodegradation was occurring in both laboratory mesocosm studies. Selective biodegradation of PHCs under different reducing conditions was observed. However, there was no conclusive evidence that one reducing condition will universally favor the biodegradation of specific PHCs. In both studies, nutrient amendment showed no enhancement effects. The calculated first-order biodegradation rates in Site 1 mesocosm study ranged from 0.0032 to 0.033 d-1 for benzene, 0 to 0.028 d-1 for ethylbenzene, 0.0021 to 0.036 d-1 for m-, p-xylenes, and 0.0006 to 0.0045 d-1 for F1-BEX (F1 hydrocarbons exclduding BEX) under the tested conditions. The laboratory first-order biodegradation rates of BEX were higher than the estimated field rates, indicating the potential of enhanced anaerobic biodegradation in situ. However, when comparing the TEA amended mesocosms with the unamended controls (in which iron reduction might be the predominant process), the enhancement effects were less apparent and inconsistent. The calculated first-order biodegradation rates in Site 3 mesocosm study ranged from 0 to 0.0009 d-1 for benzene, 0 to 0.011 d-1 for ethylbenzene, 0 to 0.0016 d-1 for m- and p-xylenes, and 0 to 0.15 d-1 for o-xylene. Sulfate amendment significantly stimulated biodegradation of all xylenes and CCME F1 hydrocarbons. However, there was no definitive evidence that nitrate or sulfate amendment could enhance benzene or ethylbenzene biodegradation. / Environmental Engineering

Research is presented that evaluates a semi-passive treatment system for remediation of contaminated groundwater with elevated dissolved metal concentrations, including selenium and sulphate, at the Wolverine Mine, Yukon. Laboratory up-flow columns were used to treat simulated mine impacted waters. Five columns were filled with varying compositions of gravel and creek substrate organics, and were un-amended or amended with manure, sewage sludge, zero-valent iron, or wood chips and alfalfa. Selenium, sulphate and other parameters of concern were lowered in column effluents, most effectively by the control column and by the columns amended with sewage sludge. Column effluent metal and sulphate concentrations provided evidence that co-precipitation, adsorption and microbially mediated redox reactions were the predominant biogeochemical mechanisms operating within the columns. Based on this research, recommendations are made to further the design of a semi-passive treatment system that may be installed at the mine site upon closure.

No description available.

Deponering är globalt sett det vanligaste sättet att hantera avfall, men i Sverige får sedan 2001 enbart avfall som inte kan återanvändas deponeras. Innan deponiförordningen trädde i kraft 2001 deponerades många olika typer av avfall. En deponi används idag som ett slutförvar för avfall och för att minimera infiltration av regnvatten och eventuell föroreningsspridning sluttäcks gamla deponier. Sluttäckningen består av flera skikt som tillsammans ska täta deponin och leda bort vatten. Att förvara avfall i en sluttäckt deponi är miljöfarlig verksamhet och det är därför av intresse att kontrollera omgivningarna under och efter sluttäckning för att säkerställa att eventuell föroreningsspridning minskar. På Hovgårdens avfallsanläggning i Uppsala kommun har en deponi som använts sedan 1971 sluttäckts under hösten 2018. I två provtagningsrör vid deponin, i vilka provtagning och analys skett regelbundet sedan 1991, har förhöjda halter av vissa ämnen kunnat uppmätas efter att arbetet med sluttäckningen påbörjades. Syftet med detta examensarbete var att få ökad förståelse för trender i ämneshalter samt att utreda hur sluttäckning påverkar grundvattennivåer och ämneskoncentrationer runt deponin. Uppmätta halter i provtagningsrören sammanställdes och trender analyserades med statistiska verktyg i mjukvaran R. Dessutom konstruerades en grundvattenmodell över avfallsanläggningen i MODFLOW och MT3DMS. Stationära flödessimuleringar och transportsimuleringar med klorid utfördes. Tolv av 33 analyserade ämnen och parametrar uppvisar statistiskt signifikanta ökningar i antingen ett av provtagningsrören, båda eller båda analyserade tillsammans. Dessa är alkalinitet, elektrisk konduktivitet, sulfat, klorid, kalcium, natrium, svavel, kalium, magnesium, strontium, barium, och nitratkväve. Sex av dem minskar statistiskt signifikant och dessa är pH-värdet, kadmium, zink, kvicksilver, bly och arsenik. Grundvattenmodellen visar att grundvattnet under etapp 1 flödar mot resten av anläggningen men att flöden ut från deponin finns i de sydvästra och sydöstra hörnen. Sluttäckningen leder till lägre nivåer och en förändrad grundvattendelare vilket kommer minska läckaget, främst i den sydvästra delen. Modellsimuleringar med olika grundvattenbildningsmängder och kloridkoncentrationer visade att ökningar av kloridhalter inte kan förklaras med minskad grundvattenbildning i kombination med förhöjda koncentrationer. Förklaringen bör därmed vara andra fysikaliska och eventuellt kemiska processer som skett samtidigt som sluttäckningen. De parametrar som påverkade simulerade ämneshalter mest var konduktansen i diken och dränering samt moränens hydrauliska konduktivitet. / Landfills are globally the most common waste treatment method but in Sweden the method is since 2001 used only for waste that cannot be reused in any way. Before 2001, almost any type of waste could be landfilled. Today a landfill is used as a final storage and old landfills are capped to minimize infiltration and contaminant transport. A capping consists of several layers which together seal and drain the landfill surface. Storing waste in a capped landfill is considered an environmentally hazardous activity, therefore it is of great interest to monitor the surrounding groundwater during and after capping to make sure that any contaminant concentrations decreases. At Hovgården waste treatment plant in Uppsala, Sweden, a landfill used since 1971 was capped during 2018. Elevated contaminant concentrations have been measured in two monitoring wells close to the landfill after the capping procedure started. The aim of this master thesis was to increase the understanding of trends in contaminant concentrations and to investigate how capping affects groundwater levels and concentrations. Concentration data were compiled and statistical tools in R were used to analyze trends. Additionally, a groundwater model of the area was created in MODFLOW and MT3DMS. The model was used to simulate different steady state scenarios with and without chloride transport. Twelve of 33 analyzed substances and parameters show a statistically significant increase. These are alkalinity, electrical conductance, sulphate, chloride, calcium, sodium, sulfur, potassium, magnesium, strontium, barium and nitrate. Six show a decrease, these are pH, cadmium, zinc, mercury, lead and arsenic. The groundwater model indicates that the groundwater flow in the landfill is directed towards the rest of the waste treatment plant except for two places where leakage occurs: the southwest and southeast corners of the landfill. The capping results in lower groundwater levels and an altered groundwater divide, which will reduce the contaminant leakage, particularly in the southwest part. Model simulations with varying recharge and chloride concentrations showed that the increase in chloride levels cannot be explained with only decreased infiltration combined with increased concentrations. Therefore, the explanation is assumed to be other physical processes and possibly chemical reactions due to or at the same time as the capping. The model parameters that effected the simulated concentrations to the greatest extent are the conductances in drains, and the hydraulic conductivity of the till soil.

Le potentiel de biodégradation des éthènes chlorés (ECs) et du dichlorométhane (DCM) dans les eaux souterraines de l’ancien site industriel de Themeroil (Varennes-le-Grand, France) a été évalué par des études en microcosmes, à travers l’utilisation de biomarqueurs moléculaires, et par analyse isotopique spécifique au composé (compound specific isotope analysis, CSIA). L’objectif de ce travail a été d’évaluer i) la biodégradation de ces polluants et la diversité bactérienne associée dans les eaux du site, et ii) l’impact de mélanges de contaminants et des conditions rédox dans ce processus. L’implication majeure d’un taxon bactérien affilié à Dehalococcoides dans la dégradation du PCE dans les eaux du site, et son lien potentiel aux gènes de déshalogénase pceA et vcrA associés au processus de déchloration, ont été mises en évidence. La dégradation du DCM en présence d’ECs dans les eaux du site a ensuite été démontrée, et des souches bactériennes dégradant le DCM ont été isolées à partir d’eaux du site et caractérisées. La CSIA a révélé une forte biodégradation du DCM in situ. Des analyses des eaux du site, par qPCR ciblant les gènes dcmA et dhlA de la biodégradation bactérienne du DCM, et par séquençage haut-débit du gène de l’ARNr 16S, ont permis d’évaluer le rôle potentiel de différents taxa bactériens associés à la dégradation du DCM. Il a ainsi été montré que la répartition spatiale de ces taxa sur site dépend dans une large mesure des conditions rédox et du niveau de contamination. L’influence de ces paramètres sur la biodégradation, étudiée ensuite en microcosmes, a été confirmée par l’observation de différents profils de dégradation dans des conditions rédox et de co-contamination distinctes. Ceci suggère la participation de différents types de métabolisme à la biodégradation des éthènes et alcanes chlorés sur site. Les résultats obtenus confirment la pertinence d’études en microcosme pour évaluer le potentiel de biodégradation des polluants halogénés dans les sites contaminés, et pour orienter les traitements de dépollution à privilégier. / The biodegradation potential of chlorinated ethenes (CEs) and dichloromethane (DCM) in groundwater from the former industrial site of Themeroil (Varennes-le-Grand, France) was evaluated in microcosm studies, using molecular biomarkers and compound-specific isotope analysis (CSIA). The objective of this work was to evaluate i) the biodegradation of these pollutants and the associated bacterial diversity in site groundwater, and ii) the impact of contaminant mixtures and redox conditions on biodegradation. The major role of a taxon affiliated to Dehalococcoides in PCE degradation in site groundwater, and its potential link to dehalogenase genes pceA and vcrA associated with the process, were highlighted. Degradation of DCM in the presence of CEs in site groundwater was then demonstrated, and DCM-degrading strains were isolated from site groundwater and characterised. CSIA revealed a large extent of DCM biodegradation in situ. Analyses of groundwater from the site, targeting dcmA and dhlA genes for DCM biodegradation by qPCR, as well as by high-throughput sequencing of the 16S rRNA gene, allowed to evaluate the potential role of different bacterial taxa associated with DCM dehalogenation in DCM degradation on site. It was shown that the spatial distribution of these taxa on site depends significantly from redox conditions and contamination level. The influence of these parameters on biodegradation was also investigated in microcosms, and distinct degradation profiles were observed under different redox and co-contamination conditions. This suggests that different types of metabolism participate in biodegradation of chlorinated ethenes and alkanes on site. Obtained results confirm the relevance of microcosm studies in evaluating halogenated pollutants biodegradation potential on contaminated sites, and in guiding the choice of remediation approaches to be favoured.