Grundvattenmodellering av föroreningstransport   – Ett uppdragsanpassat beräkningsverktyg Emil Friberg Målet för detta arbeta var att bygga upp en modell i modelleringsprogrammet MODFLOW för spridning av förorenande ämnen i grundvattnet. Syftet med modellen var att finna en balans mellan den mycket enkla modellen som Naturvårdsverket har satt upp för förorenad mark och en fullskalig platsspecifik modell. Utgångspunkten var att studera litteraturen för att finna lämpliga generella parametrar som beskriver föroreningstransport i grundvattnet. Tre genomförda uppdrag med förorenad mark användes som referenskälla, men även för att evaluera den framtagna modellen. Föroreningarna som förekom i dessa uppdrag och som studerades i detta arbete är bensen, PCE och arsenik. Att finna lämpliga parametrar för beskrivning av transporten visade sig vara ganska enkelt, det finns en god förståelse för vilka faktorer som har betydelse. Däremot var det svårare att finna generella värden till dessa parametrar. Sammanställningar gjorda av Naturvårdsverket var en god källa. Den uppbyggda modellen döptes till ESM. Alla valda parametrar analyserades och modellen känslighetsanalyserades. Resultatet visade att vissa parametrar ger större känslighet än andra. Samtidigt visade analyserna att känsligheten varierar beroende på vilket intervall en viss parameter studeras samt att modellens känslighet även är beroende på värdena på de andra parametrarna. Bland annat visade det sig att dispersion alltid är en känslig parameter inom vissa intervall. Sorption och grundvattenflödets gradient visade sig enbart vara känsliga i vissa fall. ESM jämfördes med analytiska lösningsmetoder, Naturvårdsverkets riktlinjesmodell samt de tre utvalda uppdragen. Resultatet var blandat. I jämförelsen med den enklaste analytiska lösningsmetoden med enbart advektion och dispersion överensstämde inte resultaten . Då även sorption användes blev resultatet mycket bra med en hög överensstämmelse. Det gick inte att jämföra Naturvårdsverkets modell rakt av med ESM då förutsättningarna var ganska skilda. Däremot visade jämförelsen i ett större perspektiv att ESM ger en bättre bild av föroreningsspridningen än vad Naturvårdsverkets riktlinjesmodell ger.  Även jämförelsen mellan ESM och de utvalda uppdragen gav blandat resultat, vissa fall blev resultatet mycket bra medan andra mindre. Generellt gav ESM en bra bild av föroreningssituationen och dess karaktär men den har svårigheter att återspegla verkligheten beträffande uppmätta halter och andra mer specifika parametrar. Slutsatsen blev att ESM kan användas initialt för att få en bild av situationen och att modellen är enkel att förändra men kan inte återspegla alla aspekter på föroreningstransporten. Nyckelord: MODFLOW, MT3DMS, föroreningstransport, PCE, bensen, arsenik, riktvärde för förorenad mark Institutionen för geovetenskaper; luft-, vatten- och landskapslära. Uppsala universitet Villavägen 16, Se-752 36 UPPSALA

Geothermal energy can be extracted from an aquifer, where the groundwater is used as heat exchange medium while heat and cold are stored in the surrounding material in the aquifer and to some extent in the groundwater. Application of aquifer storage for the use of geothermal energy is mainly used in large scale facilities and is limited to sites with suitable aquifers in the form of ridges, sandstone and limestone aquifers. Löwenströmska hospital in the municipality of Upplands Väsby, north of Stockholm, is located nearby the northern part of the Stockholm esker. This means that it can be profitable and environmentally beneficial for the hospital to examine the possibilities of aquifer storage in the esker material next to its property. The purpose of this master thesis has been to investigate if geothermal energy storage with a seasonal storage of heat and cold can be applied within Löwenströmska hospital’s property area using groundwater modeling. A hydraulic groundwater model was constructed in MODFLOW based on a simplified conceptual model of the groundwater system. The hydraulic groundwater model was calibrated and validated against observed groundwater levels before and after a pumping test. The hydraulic groundwater model was then used to implement a fictitious geothermal energy storage with MT3DMS. MT3DMS is a modular function used with MODFLOW, which can be modified to simulate heat transport. The result shows that the geothermal energy storage can store seasonal heating and cooling of about 4 GWh, which covers 85 % of the hospital’s heating demand with an assumed SP-factor of 4, and the entire cooling demand. To cover 50 % of the peak heating power it was calculated that a flow of 63 l/s was needed, and according to the model this is possible. The geothermal energy storage does not need to be completely in energy balance, since the aquifer is recharged with its natural groundwater. The location of the wells influences which flows that are needed to create energy balance. A too close placement of the wells leads to a thermal breakthrough. The hydraulic conductivity of the esker material affects the amount of energy that can be stored. A higher hydraulic conductivity provides greater energy losses and a lower hydraulic conductivity favors the energy storage but gives a greater influence area. A number of assumptions have been made in the model construction of the hydrogeological model and further investigation of the geological and hydrogeological conditions are desirable to improve the model.

Håbo municipality is looking for alternative drinking water sources for its residence city of Bålsta. One possible source is the Vreta-Bålsta esker located northeast of Bålsta, which could be used for artificial infiltration and extraction of groundwater. Located on this esker is an area called Dragets industrial area, in which several objects of potential contamination have been identified. One of these is a Landfill located in the northern part of the industrial area in which the local fire fighting forces has used this area for training exercises. During these exercises they have used aqueous film forming foams (AFFFs) containing Per- and polyfluoroalkyl substances (PFAS). Some PFASs have demonstrated adverse health effects already at low concentrations and no more than 90ng l-1 is recommended in Swedish drinking water. In order to assess the suitability of the esker as a source for drinking water a model of the esker was created inside the program GMS (Groundwater modeling system). In GMS the package MODFLOW was used to create a groundwater flow model, and the package MT3DMS was used for contamination transport of PFAS from the landfill. The finished model showed a groundwater divide located in the central parts of Dragets industrial area, with the water either running south toward Lake Mälaren or north towards Lilla Ullfjärden. In total three different PFAS species were used in the transport model with the abbreviations PFOS, PFPeA and PFBA. The transport model was created as a point source to see the transport behavior of PFAS from the landfill. This showed that all the contamination transport that occurred would transport the PFAS north towards Lilla Ullfjärden. Based on this result this would mean that a use for artificial infiltration and extraction of groundwater in the southern part of the esker would not pose a contamination risk from the landfill.

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.

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.

No description available.

Gotland suffers from a shortage of drinking water at infrequent intervals which is onlypredicted to get worse with time. The problem is not a shortage of precipitation, the shortagelies in the combined problem of runoff and high water usage during the summer months.From September to March there is an abundance of water which mostly goes to runoff intothe sea surrounding Gotland. Due to the fact that Gotland is an island, a concave boundryis formed between the deeper saline groundwater and the fresh groundwater closer to thesurface. In an effort to possibly help in solving the water shortage, an idea was introducedto pump out the saline groundwater from the deep and thus creating an increase in storageof fresh groundwater.Firstly an investigation into suitable locations for modeling was conducted where two siteswere chosen. To test this concept and see if the idea was feasable a 2D-model was establishedusing GMS, MODFLOW, MT3DMS and SEAWAT with the aim of simulating the groundwaterat the well chosen sites on Sudret, Gotland. Two wells were implemented in the model,one for extracting fresh groundwater and one for extracting saline groundwater. The hopeswere to be able to simulate an increase of the storage of fresh water during the rechargeperiod and thus helping to solve the problem with insufficient water during the strenuoussummer months. Hopefully the results of the simultations can make up the foundations foran implementation of the concept at a location at Gotland.Results for site 1 indicate that the volume of fresh water in the akvifer can be increasedby 13of the extraction volume when only saline groundwater is removed. The maximumflow of only saline extraction at site 1 has been determined to 35m3år per meter. For example,with only an extraction of saline water of 35m3år at site 1 the fresh water in the aquifer willincrease by 340m3 per metre after 10 years.The model indicates that the volume of fresh water in the akvifer can be increased bya minimum of 15 of the saline extraction volume when only saline water is removed. Themaximum flow of only saline groundwater at site 2 was decided to be 65m3år per meter. Forexample, with only an extraction of saline water of 65m3år at site 1 the fresh water in theakvifer will increase by 940m3 per metre after 10 years. / Gotland lider till och från av vattenbrist under sommaren, problemen förväntas även ökai samband med klimatförändringar och expanderande antropogen påverkan. Under vinterhalvåretfår Gotland mer än tillräckligt med sötvatten för att täcka efterfrågan, problemetuppkommer från att majoriteten av vattnet evapotranspireras samt går till ytavrinning tillÖstersjön. Ytterligare en orsak till vattenbristen beror på att Gotlands grundvatten omgesav saltvatten. Saltvattnet kring Gotland bildar en konkav gräns mellan sött och salt vatten igrundvattenmagasinet vilket väsentligt begränsar den möjliga lagringen av sött grundvatten.För att hjälpa till att lösa problemen med vattenbrist på Gotland introducerades en idé attutöka andelen sött vatten i grundvattenmgasinen genom att pumpa salt grundvatten fråndjupet under återhämtningsperioden.Arbetet påbörjades genom att undersöka en lämplig plats på Gotland, både ur en modelleringssynpunktsamt inför ett eventuellt fortsatt arbete. Två platser valdes slutligen dären 2D-grundvattenmodell skapades vid båda platserna med hjälp av GMS, MODFLOW,MT3DMS och SEAWAT. I modellen implementerades två uttagsbrunnar, en för salt grundvattenfrån djupet och en för sött grundvatten närmare ytan. Eftersom modellen skapats i 2Dinnebär det det en förenkling av geometrin och modellresultat motsvarar då en horisontelltborrad brunn, därför anges resultaten som flöde per meter horisontell brunn. Förhoppningenvar att genom simulering kunna påvisa en ökning av sötvatten i grundvattenmagasinet genomatt extrahera salt grundvatten under återhämtningsperioden. målet är att undersökningarnaska leda till en implementering av metoden i verkligheten i ett försök att minska vattenbristen.Modellresultat för plats 1 indikerar att volymen sött vatten i akviferen ökar med 13 avuttaget när endast salt vatten extraheras. Det maximala uttagsflödet vid plats 1 för endastsalt vatten bestämdes till 35m3år per meter. Vid ett saltvattenuttag på 35m3år vid plats 1 ökarsötvattenvolyem i akviferen t.ex. med 340m3 per meter efter 10 år.Modellresultat för plats 2 indikerar att volymen sött vatten i akviferen ökar med 15 avuttaget när endast salt vatten extraheras. Det maximala uttagsflödet vid plats 2 för endastsalt vatten bestämdes till 65m3år per meter. Vid ett saltvattenuttag på 65m3år vid plats 2 ökarsötvattenvolyem i akviferen t.ex. med 940m3 per meter efter 10 år. / diva2:1345440