There are today thousands of active and disused landfills around Sweden. New landfills have to meet high standards to prevent spreading of contaminants from the landfill, and the more hazardous the waste is, the higher the requirements. This study investigates how contaminants from the landfill Ullnatippen can spread around the area. Ullnatippen is a landfill that today only is used for inert waste, which is waste that does not release hazardous contaminants. The landfill has been used since the 1950s and there is some information that suggests that more hazardous waste has been left on the landfill in the past. Ullnatippen has a control program, consisting of 6 groundwater pipes where samples have been taken every year for many years. The purpose with the control program is to discover contaminants spreading from the landfill. This study also investigates whether the control program is designed in such a way that contaminants measured in the pipes actually derive from the landfill.  To be able to investigate this a groundwater model was built with the program Modflow. From this model, a particle tracking to see the possible routes for contaminants to spread was performed. The result showed that the groundwater from the landfill is moving towards the lake Ullnasjön. The model also confirmed that possible contaminants from the landfill are measured by the control program, but that there is room for improvement since the pipes are located with such long distances. The study also discusses general uncertainties with groundwater modeling and which improvements that have to be done to establish the result from this study.

Per- and polyfluoroalkyl substances (PFASs) are a group of man-made organic chemicals that have been commercially used since the 1950s in many consumer products, including impregnated textiles, impregnated paper, nonstick products (e.g., Teflon), cleaning agents, and in firefighting foams. However, PFASs have in recent years received increasing public attention due to their persistence, bioaccumulative potential, and potentially toxic effects on humans and animals. Firefighting training sites have been identified as one of the most important sources for the spread of PFASs in the environment, due to the use of PFAS-containing firefighting foam of type AFFFs (aqueous film forming foams). This has resulted in contamination of both drinking water and groundwater in several municipalities in Sweden. At the former fire station in Åkersberga, AFFFs were handled and used during the fire-training exercises. WSP Environmental Sweden has performed a preliminary investigation on site and elevated levels of PFASs in both soil and groundwater were observed. Since the property is located next to a railroad track, there is a concern that PFASs will spread through the railroad track towards the nearby Åkers canal. The aim of this master’s thesis has therefore been to map the transport of PFASs in groundwater from this former fire station. A groundwater flow model was first constructed in the software program Visual MODFLOW. The groundwater model was then used as a basis for the construction of a transport model with MODPATH and MT3DMS. The transport of four PFAS homologues was modeled; perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), 6:2 Fluorotelomer sulfonate (6:2 FTS), and perfluoropentanoic acid (PFPeA). The result of the groundwater modelling showed that groundwater from the property flows towards the southwest and then further towards Åkers canal. The approximated velocity of a water molecule varied between 270 m/year and 400 m/year. The transport modelling showed that all four PFAS homologues traveled towards Åkers canal via the railroad track and that the short-chain PFAS homologues (6:2 FTS and PFPeA) traveled longer and faster than the long-chain PFAS homologues (PFOS and PFOA). The approximated velocity of the contaminant plume for the concentration 4.5 ·10−5 mg/L was 0.6 m/year for PFOS, 3 m/year for PFOA, 8 m/year for 6:2 FTS, and 16 m/year for PFPeA. / Per- och polyfluorerade alkylsubstanser (PFAS) är en grupp av konstgjorda organiska kemikalier som sedan 1950-talet har kommersiellt använts i många konsumentprodukter, inklusive impregnerade textilier, impregnerat papper, nonstick-produkter (t.ex. Teflon), rengöringsmedel och brandsläckningsskum. PFAS har dock under senare år fått ökad allmän uppmärksamhet på grund av deras persistens, bioackumuleringspotential och potentiella toxiska effekter på människor och djur. Brandövningsplatser har identifierats som en av de största källorna för spridningen av PFAS i miljön, på grund av användningen av PFAS-innehållande brandsläckningsskum av typen AFFF (aqueous film forming foams). Detta har resulterat i förorening av både dricksvatten och grundvatten i flera kommuner i Sverige. På den tidigare brandstationen i Åkersberga har hantering och användning av AFFF ägt rum under släckningsövningarna. WSP Environmental Sverige har utfört förundersökning på plats och förhöjda halter PFAS i både jord och grundvatten observerades. Då fastigheten gränsar mot en banvall, finns det en oro att PFAS ska sprida via banvallen mot den närliggande Åkers kanalen. Syftet med detta examensarbete har därför varit att kartlägga transporten av PFAS i grundvatten från denna tidigare brandstation. En grundvattenflödesmodell konstruerades först i programvaran Visual MODFLOW. Grundvattenmodellen användes sedan som grund för konstruktionen av en transportmodell med MODPATH och MT3DMS. Transporten av fyra PFAS-homologer modellerades; perfluoroktansulfonat (PFOS), perfluorooktansyra (PFOA), 6:2 fluortelomersulfonat (6: 2 FTS) och perfluorpentansyra (PFPeA). Resultatet av grundvattenmodelleringen visade att grundvatten från fastigheten strömmar mot sydväst och sedan vidare mot Åkers kanal. Den approximerade hastigheten hos en vattenmolekyl varierade mellan 270 m/år och 400 m/år. Transportmodelleringen visade att alla fyra PFAS-homologerna spred mot Åkers kanal via banvallen och att de kortkedjiga PFAS-homologerna (6:2 FTS och PFPeA) spred längre och snabbare än de långkedjiga PFAS-homologerna (PFOS och PFOA). Ungefärlig hastighet av föroreningsplymen för koncentration 4.5 ·10−5 mg/L var 0,6 m/år för PFOS, 3 m/år för PFOA, 8 m/år för 6: 2 FTS och 16 m/år för PFPeA.

As an effort to gain a better understanding of the processes that enable and sustain coal bed methanogenesis in the western Powder River Basin, a steady-state groundwater flow model using MODFLOW 2005 was constructed. The model covers the middle Tongue River Watershed of north-central Wyoming and southeastern Montana and is comprised of five heterogeneous layers. The model is designed to determine the location of recharge and quantify the volume and velocity of groundwater fluxes to, from and within methanogenic coal beds. Analysis of the model's results indicate a groundwater regime dominated by horizontal flow, with little hydrologic connection between the methanogenic coal beds and the near-surface aquifers and streams. The model predicts only 3.88 cubic feet per seconds (cfs) or 2.17 percent of the total steady state flux within the modeled domain percolates downward to potentially reach the methanogenic coal beds. Most of this downward flux is predicted to occur at the base of the Bighorn Mountains. Additionally, the model predicts that the transit time to and resultant groundwater age within the methanogenic coal beds in the study area is on the order of thousands of years (predicted minimum age of 8,967 years).

Groundwater is an important natural resource in Sweden due to almost 50 % of the produced drinking water origins from groundwater, 50 % of the groundwater is artificially made. Artificial recharge is necessary in some areas in Sweden to enable enough groundwater extraction for the drinking water supply. Artificial recharge will affect the groundwater levels in the system. The infiltration of water can also affect the spread of pollution in the area. The effect of pollution spreading is due to the change in available oxygen in the system. When infiltrating water, the soil can go from anaerobic- to aerobic conditions, which in turn can cause mobilization of pollutants. This master project was carried out in collaboration with the consultancy company WSP. In this thesis, an esker assessed as suitable for artificial recharge from a hydrogeological point of view, is investigated regarding the contamination spread. Stockholm vatten och avlopp (SVOA) is investigating the possibilities for producing drinking water by artificial recharge in the esker. The area has been identified as a potential hazardous area by the Swedish environmental protection agency and increased levels of zinc, lead and copper have been found in the soil. The aim with this project is to investigate how zinc, lead and copper could spread in the groundwater for the current situation. This project also aims to investigate how the artificial recharge would affect the groundwater levels in the system as well as the effect of the spread of zinc, lead and copper regarding the mass transport, transportation time and the contaminant plume. A hydrogeological model was created in MODFLOW where the effect of infiltration was simulated. Models for groundwater transport as well as mass transport was created in MODPATH respectively in MT3DMS. The hydrogeological model´s Normalized root mean square (nRMS) was 7,4 % and the maximal residual between observed and simulated groundwater levels was 0, 16 meters. Two different scenarios for artificial recharge were investigated, one called pilotförsöket and the other called fullskaleanläggningen. For the pilotförsöket was 100 L/s infiltrated and for fullskaleanläggningen was 280 L/s infiltrated, the amount of extracted groundwater was assumed to be equal as the amount of infiltrated surface water. The simulations were indicating that the groundwater levels could rise up to 7 meters locally around the infiltration area. The groundwater levels closer to the extraction wells could decrease by 4 meters in pilotförsöket and decrease by 10-15 meters in fullskaleanläggningen. The simulations of zinc, copper and lead in the infiltration area, are indicating an increase in maximal concentration as well as an increase for the plume of contaminants as a result of infiltration. The maximal concentrations in the simulations of pilotförsöket were found to be in the following ranges 4x10-5 to 2,8x10-8 mg/L for lead; 8 x10-4 to 2,5x10-6 mg/L for copper and 0,012 to 9x10-4 mg/L for zinc. Fullskaleanläggningen resulted in the highest concentrations of the simulated scenarios. The following ranges were observed in the simulations of fullskaleanläggningen 4,5x10-5 to 4x10-8 mg/L for lead; 0,014 till 2,5x10-6 mg/L for copper, and 0,035 till 3x10-3 mg/L for zinc. The plume of contaminants was observed to increase with an increasing amount of infiltrated water. During the simulation period of 10 years, the simulation implies that zinc, copper and lead mainly will be transported close to the infiltration area. The results for simulations in all scenarios indicate that the plume of contaminant will not reach the extraction wells. These results can be due to longer transportation times than 10 years, as well as that the increase volume of water in the system will dilute the levels of metals. This master project indicates that the artificial recharge in the area will affect the groundwater levels in the system. Due to the change in groundwater levels can also the spread of zinc, copper and lead increase in magnitude and in size. This master project also indicates that zinc, copper and lead would not reach the extraction wells in high levels within a 10 years period. The simulations indicate that the area could be appropriate to use for artificial recharge, when considering zinc, copper and lead. This assessment is only based on the simulations of the mass transport of zinc, copper and lead and with the assumption that the contaminated soil would be excavated if an infiltration area is built. Even though the simulations indicate that the area could be appropriate. Other pollutants that was found, but not simulated, at increased levels could have a different transportation time as well as mass transport from the infiltration area. Regarding the age of the landfill it is likely in the methanogenic phase and leaching of contaminants could already have happened decades ago. With these two aspects in mind, my recommendation is that more investigations are made regarding the spread of other pollutants as well as the level of zinc, lead and copper in the groundwater closer to the extraction wells.

Perfluorerade alkylsyror (PFAS) är en grupp ämnen som de senaste åren har uppmärksammats för dess persistenta, bioackumulerande och toxiska egenskaper för människor och djur. Det är känt att brandövningsplatser där det filmbildande skummet AFFF har använts utgör betydande punktkällor för PFAS. Förutom att förorena marken vid brandövningsplatserna kan PFAS spridas med grundvattnet, vilket har orsakat förorenade dricksvattentäkter på ett flertal platser i Sverige. Hydrogeologiska modeller kan användas för att modellera grundvattnets flöden och medföljande föroreningar. Syftet med examensarbetet är att med en hydrogeologisk modell undersöka föroreningsspridning och transporttider av PFAS-ämnet perfluoroktansulfonat (PFOS) från en brandövningsplats till ytvatten och grundvattentäkter i Bredåkradeltat, väster om Kallinge i Blekinge. Den hydrogeologiska modellen skapades i Visual MODFLOW och transportmodelleringen gjordes med MT3D99 och MODPATH. Modellen kunde reproducera uppmätta grundvattennivåer, med en korrelationskoefficient (R) på 0,98 mellan modellerade och uppmätta nivåer. Med antagandet försumbar adsorption visade modellresultaten att en föroreningsplym med hög PFOS-koncentration (~90.000 ng/l) spreds från brandövningsplatsen till ett våtmarksområde väster om Klintabäcken, och vidare till dalen längs Klintabäcken med lägre koncentrationen (0–4.000 ng/l). Enligt modellen spreds dock inte föroreningen lika långt som uppmätta värden visar. När PFOS väl har nått Klintabäcken bedöms den kunna spridas snabbt med ytvattnet mot grundvattentäkterna, för att sedan infiltrera ned i isälvsmaterialet nära aktiva grundvattentäkter. Transporttiden av PFOS från brandövningsplatsen till Klintabäcken beräknades till sex år för den bäst kalibrerade modellen, vilket betyder att grundvattentäkterna kan ha varit förorenade sedan slutet av 1980-talet eller början av 1990-talet. Beräkningar av masstransport indikerar att runt 3,5 kg PFOS flödar genom Klintabäcken varje år, och att det mesta av den mängden kommer från området vid brandövningsplatsen. Trots förenklingar av Bredåkradeltats komplexa geologi och svårigheter att nå konvergens i modellen bedöms den kunna reproducera hydrogeologiska egenskaper inom deltat, samt föroreningsplymens spridning från brandövningsplatsen till Klintabäcken.

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