Environmental Risk Assessment and Leachate Evolution at the Ekebyboda Landfill Site, Uppland, Sweden.

Examensarbete vid Institutionen för geovetenskaper

Degree Project at the Department of Earth Sciences

ISSN 1650-6553 Nr 334

Environmental Risk Assessment and Leachate Evolution at the Ekebyboda Landfill Site, Uppland, Sweden

Miljöriskbedömning och lakvattenutveckling vid Ekebyboda deponi, Uppland, Sverige

Jonas Fors

INSTITUTIONEN FÖR GEOVETENSKAPER

D E P A R T M E N T O F E A R T H S C I E N C E S

Examensarbete vid Institutionen för geovetenskaper

Degree Project at the Department of Earth Sciences

ISSN 1650-6553 Nr 334

Environmental Risk Assessment and Leachate Evolution at the Ekebyboda Landfill Site, Uppland, Sweden

Miljöriskbedömning och lakvattenutveckling vid Ekebyboda deponi, Uppland, Sverige

Jonas Fors

ISSN 1650-6553

Copyright © Jonas Fors and the Department of Earth Sciences, Uppsala University

Published at Department of Earth Sciences, Uppsala University (www.geo.uu.se), Uppsala, 2015

Abstract

Environmental Risk Assessment and Leachate Evolution at the Ekebyboda Landfill Site, Uppland, Sweden

Jonas Fors

Ekebyboda is a closed landfill north west of Uppsala where the leachate water was studied to evaluate the status of the landfill for, the Uppsala environmental office. Leachate water has been measured continually for different parameters, during the period 1959-2007. The landfill differs from other landfills because of its mixed content of domestic and industrial waste. Close to the investigated area is a small number of residents with private water wells which enhances the importance of the investigation of the landfill. In this thesis, the period 1990 -2007 is the investigated with an additional measurement during 2014. Precipitation data is compared with leachate water composition, to evaluate correlations between leachate water and precipitation. Correlation between leachate water, and precipitation also gave an indication of the status of the cover on the landfill during, 2014. Due to the problematic history of Ekebyboda the aim of the thesis is to evaluate the status of the landfill and do a risk classification according to MIFO, which is a classification system for polluted sites from the Swedish Environmental Protection Agency. Measurements were made in four wells in the spring of 2014. These results showed a decline in eight analysed parameters and increase or stagnant trend for pH, NO3- + NO2 and SO42-. Most of the parameters have large fluctuations during the period. A field investigation is also show a non-functional culvert system with stagnant water and indications of water running in the direction of the residential area due to malfunctioning pumps. The stagnant water and problematic culvert system raised concerns for the quality of the datasets. The data analysis shows that the correlation between precipitation and leachate water was non-existent and the second covering of the landfill has reduced the amount of infiltrating water. Analysis of the leachate water and problematic management of leachate water were two major causes for a high risk classification. The MIFO classification of this landfill was set as one which is the highest possible which mainly was due to a possible risk for contamination for private water wells.

Keywords:

Supervisor: Christian Zdanowicz

Departmentof EarthSciences,UppsalaUniversity,Villavägen16, SE-75236 Uppsala (www.geo.uu.se) ISSN 1650-6553, Examensarbete vid Institutionen för geovetenskaper, No. 334, 2015

The whole document is available at www.diva-portal.org

Populärvetenskaplig sammanfattning

Miljöriskbedömning och lakvattenutveckling vid Ekebyboda deponi, Uppland, Sverige Jonas Fors

Ekebyboda är en nedlagd deponi nordväst om Uppsala vars lakvatten studeras för att utvärdera deponins tillstånd på uppdrag av Miljökontoret i Uppsala. Lakvattenkvalitén från deponin har kontinuerligt blivit mätt under perioden, 1959-2007. Deponin skiljer sig från andra deponier främst på grund av sitt blandade innehåll av både hushållsavfall och industriavfall. Deponin stängdes 1970 och täcktes över i två omgångar först 1970 och senare även 1994. Ekebyboda har under den aktiva fasen orsakat en rad olika problem så som förorenade brunnar och vattendrag samt åkrar inom närliggande område. I när- heten av det undersökta området finns ett mindre antal privata hushåll med egna dricksvattenbrunnar vilket är en förhöjande faktor till att deponin undersöks. Uppsatsen fokuserar på åren 1990-2007 med en ytterligare mätning under 2014 som ligger till grund för utvärderingen av deponins rådande tillstånd.

Lakvattensammansättningsmätningar under denna tidsperiod jämförs med nederbörden för att utvärdera hur stor inverkan nederbörden har på lakvatten sammansättning och uppmätta ämnen i det. Korrelationer mellan lakvattensammansättning och nederbörd gav även en indikation om deponins tillstånd idag. På grund av deponins problematiska historia ska detta området studerats men även riskklassificera enligt Naturvårdsverkets MIFO modell. MIFO står för Metod för Inventering av Förorenade Områden och är en mall för att riskklassificera förorenade områden. Fältprovtagning visade även ett ickefungerande kulvertsystem för transport av lakvatten. Stillastående vatten och problematiska lakvatten kulvertar ledde till att datasetets kvalité ifrågasätts. Korrelationen mellan nederbörden och lakvattenkvalitén var låg och en andra täckning av deponin minskade mängd infiltrerat vatten. Analysen av lakvattnet sammansättning och problematisk hantering av lakvatten var ytterligare två anledning för en hög risk- klassificering av deponin. För den fyrskaliga klassificeringen som metoden består av fick Ekebyboda den högsta riskklassificeringen som mestadels beror på en viss risk för spridning av lakvatten till när- liggande privata brunnar. Mätserien är en generell nedåtgående trend där ett flertal näringsämnen m.m.

har minskat i koncentration samt att mängden infiltrerat vatten i deponin har minskat i mängd.

Nyckelord

Handledare: Christian Zdanowicz

Institutionen för geovetenskaper, Uppsala universitet, Villavägen 16, 752 36 Uppsala (www.geo.uu.se) ISSN 1650-6553, Examensarbete vid Institutionen för geovetenskaper, Nr 334, 2015

Hela publikationen finns tillgänglig på www.diva-portal.org

Abbreviations frequently used in the text

BOD Biochemical Oxygen Demand COD Chemical Oxygen Demand

IVL Svenska Miljöinstitutet, Swedish Enviromental Research Institute KEMI Kemikalieinspektionen, Swedish Chemicals Agency

MIFO Methodology for Surveying of Contaminated Land

MKB Miljökonsekvensbeskrivning, Environmental impact assessment PAH Polycyclic Aromatic Hydrocarbons

S-EPA Swedish Environmental Protection Agency

SFS Svensk författningssamling, Swedish Code of Statutes

SGU Sveriges Geologiska Undersökning, Swedish Geological Survey

Table of Contents

1. Introduction and aims ... 1

2. Specific work objectives ... 3

3. Background ... 4

3.1. History of Ekebyboda ... 4

3.2. Geography of the area ... 7

3.3. Swedish environmental politics ... 8

3.4. Leachate from landfills ... 10

3.4.1. Ageing process of landfill ... 10

3.4.2. Effect of precipitation on leachate ... 12

3.4.3. Leachate containment and treatment measures ... 13

3.5. Important physical and chemical properties of landfill leachates ... 15

3.5.1 Chemical properties ... 15

3.5.2 Major ions... 16

3.5.3 Ions commonly associated with organic matter ... 16

4. Data and methods ... 18

4.1. MIFO environmental risk classification ... 18

4.2. Measurements of leachate quality ... 19

4.2.1. Leachate monitoring data ... 19

4.2.2. Leachate sampling and measurements, April 2014 ... 20

Figure 8. Filtration equipment used prior to leachate analysis (Picture taken by the author). ... 22

5. Results ... 23

5.1. MIFO risk level classification ... 23

5.2. Evolution of Ekebyboda leachate quality, 1990-2014 ... 25

5.2.1 Temporal trends ... 25

5.2.3 Influence of precipitation on leachate quality ... 29

Table of Contents (continued)

6. Discussion ... 33

6.1 Limitations and uncertainties in the leachate quality data ... 33

6.2. Temporal evolution of the landfill leachate ... 35

6.3. Effect of precipitation variations on leachate quality ... 36

7. Conclusions ... 38

8. Acknowledgements ... 40

9. References ... 41

Appendices 1 ... 45

Appendices 2 ... 47

Appendices 3 ... 48

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1. Introduction and aims

Landfill sites are a necessary infrastructure in modern societies to store and/or- treat waste materials and substances. Environmental contamination from landfill sites is also one of the world’s most common environmental problems. Leaching water (leachate) from a landfill site can adversely impact the water and soil quality in the surrounding area. The environmental politics of a country/region plays a major role in dealing with these issues, as they determine the legislation that regulates waste handling and treatment. The environmental laws in Sweden have become significantly stricter over the last 40 years as a result of continued development of environmental politics. This has resulted in tighter regulations regarding landfill location and design. Older landfills usually constitute higher environmental threats than newer landfills. In this thesis, an old (>50 years) landfill site situated northwest of Uppsala was investigated. The Ekebyboda landfill site was originally created in 1953. It closed for operation in the 1970s, and was completely covered in 1994.

The Aim of this thesis to evaluate Ekebybodas leachate evolution from 1990-2007 and investigate how the precipitation is influencing the leachate. Additional measurementsis taken 2014 to compare with precious measurements. Along with the leachate evaluation will the landfill be evaluated and risk classified according to the MIFO methodology.

As a part of this thesis, an evaluation of the environmental risk level presented by the old Ekebyboda landfill site was conducted following a protocol developed by the Swedish Environmental Protection Agency (Naturvårdsverket) to classify contaminated lands. MIFO is a Swedish abbreviation for “Method for Inventories of Contaminated Land” (Metodik för Inventering av Förorenad Områden).

This protocol is used both to make recommendations for waste management plans in a given area, and also determine the environmental risk level for potentially contaminated land (Naturvårdsverket 2002).

This thesis also evaluated a long (1990-2007) series of measurements of leachate quality in order to support the MIFO environmental risk level classification of the Ekebyboda landfill, but also to obtain some insights on the biogeochemical evolution of the landfill. The leachate monitoring data were provided by the Uppsala county environmental office, which is the authority responsible for Ekebyboda. Various physical and chemical parameters measured in the leachate were compared with local precipitation data provided by the meteorology group at the University of Uppsala. This was done on order to assess the possible role of inter-seasonal /inter-annual changes in precipitation on the leachate quality.

Conditions inside many domestic waste landfills sites follow characteristic “development curves” over time. These curves are determined by the waste content of the landfill and the biochemical evolution that accompanies the ageing of the waste heap. Documented development curves are mainly based on landfills containing household waste products, which are mostly organic.

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Ekebyboda is a special case since it started as a household landfill, but changed into an industrial waste landfill. Due to the relativity weak environmental legislations that were in place during the main period of operation of the site (1950-1970s), there are few existing records to indicate exactly what was dumped in the waste heap in these years. Only a rough estimation can be made. A lack of historical information makes it difficult to compare the landfill development curve with the majority of landfills documented in literature, which were typically used for domestic waste disposal. However this subject is an important one to address, because old (closed) landfills are very common around Sweden, and elsewhere in the world. New landfills will undoubtedly continue to be established in the future. Information presented in this thesis therefore contributes to improve knowledge of the biogeochemical evolution of landfills with mixed (domestic /industrial) composition. It also clarifies the current environmental risk level of the Ekebyboda landfill site, which is information required by the Uppsala county administrative board. This thesis could serve as a template for future investigations of other old landfills in this or other regions.

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2. Specific work objectives

Part of the work presented in this thesis was conducted for the Uppsala county environmental office. This part consists of an evaluation of the current environmental risk level Ekebyboda landfill site. The evaluation was partly done by integrating data from previous landfill leachate monitoring reports, and from other archived documentation material about the Ekebyboda landfill. In addition, on April 23, 2014. new measurements of current leachate quality were taken at Ekebyboda, which were compared with the older data. Previous reports and published studies were used for interpreting the leachate data. Based on these compiled results, a risk classification was performed for the Ekebyboda site on a standard scale from 4 (lowest risk factor) to 1 (highest risk factor). Results were communicated to the Uppsala county environmental office in a separate technical report and are only summarized in the present thesis.

In the second part of the thesis, presented here, the leachate monitoring data provided by the Uppsala county environmental office, as well as the new (2014) leachate measurements, were used to investigate how the composition of the water leaching from the landfill changed over the period 1990- 2014. Previous case studies of landfill leachate indicate that there often is a gradual decline in the concentrations of substances such as major ions, nutrients and trace metals in leachate, in years that follow a landfill closure (e.g. Statom et al., 2004). These declines reflect changes in the bio- geochemical conditions (e.g., redox state) inside the landfill over time. Redox conditions, however, can follow different patterns over time, depending on the initial content of the waste heap (percentage of organic matter). Redox states whether elements tend to be in in their higher (oxidized) or lower (reduced) oxidation states, In the thesis, temporal trends observed in the leachate quality of the Ekebyboda landfill site were evaluated, and interpreted in terms of bio-geochemical evolution of the waste heap. Since the Ekebyboda landfill contains mixed domestic and industrial waste, the temporal trends in selected physical and chemical properties of the leachate could differ from those observed in landfills with domestic waste only.

Finally, the possible influence of inter-annual variations of precipitation in winter, spring, or total annual precipitation on the concentration (by dilution) of various measured substances in the leachate was investigated (e.g., Arora et al., 2013). This was done by comparing the time series of leachate water quality data with precipitation records for the Uppsala region.

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3. Background

3.1. History of Ekebyboda

Ekebyboda is an old disused landfill site situated northwest of Uppsala, with a total area of more than 50 000 m² se figure 1. Ekebyboda is situated in an area which was bought by the municipality in 1944 for the specific purpose of establishing a landfill. The location was favorable from a logistics point of view, being only 9 km distant from the city center. Despite its closeness to Uppsala, Ekebyboda was considered remote and isolated enough to host a landfill. Ekebyboda and the surroundings were investigated some years later to gain better knowledge about the local geology in order to assess if it was suitable for a landfill. Investigations by the Public Health office (Later called Environmental office) revealed that ditching was required to drain the land, and accordingly the area was ditched, and the drainage redirected towards Librobäck creek (Hälsovårdsnämnden VI:3). The Ekebyboda landfill site opened in 1953 and at first was planned to receive domestic waste only.

Figure 1.Location map of the Ekebyboda landfill site. Uppsala Municipality 2014, used with permission.

But this changed in 1963 when the Uppsala waste incinerator was built. Aerial photograph of the landfill could be seen in Figure 2. After the construction of the waste incinerator a large amount of waste produced in Uppsala was used in the incinerator rather than being dumped directly in the landfill. Ashes from the incinerator were then buried in the landfill instead of the waste. The incinerator was used for a large variety of waste, and records state that at least once radioactive waste was burned in it, and also as medical waste residues from the Pharmacia pharmaceutical company.

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Ashes from the incinerator were dumped at Ekebyboda through the 1960s and beginning of the 1970s (Hälsovårdsnämnden VI:4). Along with these ashes, industrial process waste, oil residues as well as medical waste products such as needles were also disposed of at Ekeyboda. Unfortunately due to the relatively weak environmental laws that were in place during the 1950-s 70s in Sweden, only a rough estimation of the landfill waste content can be made, since no detailed records were kept of the dumped materials (Hälsovårdsnämnden VI:3).

Under the active operation phase at Ekeyboda, a common waste disposal technique called the

“Bradford method” was used, which involved compacting and covering the waste heap continually with clay as long as the waste accumulation continued. Two years after the opening of the Ekebyboda

Figure 2. Aerial photographs of Ekebyboda in 1963 (left) and in 2009 (right). Air photos from Lantmäteriet 2014, used with permission.

landfill site, the first complaint was registered regarding pollution of a nearby water well owned by a local farmer. Hänbogård was the farm that raised these first complaints, which were soon followed by two more from other farms. Complaints continued to come in to the health authorities through the early 1960s, with reports of polluted wells for private households. A long series of investigations was started to evaluate the source of the pollution. At the most affected farm, it was concluded that landfill leachate had polluted the drinking water well, and a new well was drilled as compensation. This farm was eventually bought by the Uppsala municipality and demolished following many problems during which the landfill leachate resulted in poisoned farmland, pens, and a drinking water well (Hälsovårdsnämnden VI:4).

Already by 1957, the Ekebyboda site was considered as "very unsuitable" for landfill usage by the Swedish Geological Survey (SGU), and contamination levels of various substances in the leachate were estimated to be 10-30 times higher than in ordinary household sewers. Therefore in the late 1950s drainage wells were installed to collect the leachate water and improve the situation around the landfill site. These wells were drained through a culvert system and open ditch towards the south- west. Of the total length of the landfill drainage system (2200 m), 300 m were through culverts, and the remaining part was in an open ditch that drained into Librobäck creek (Hälsovårdsnämnden VI:4).

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The leachate drainage system was soon proven to be inadequate, especially during times of high precipitation, when the flow rate could reach 30-40 m³/hin the culverts^. The culverts were found to be leaking, which was thought to be one cause of the pollution of wells at nearby farms. Complaints were also reported along Librobäck, as the water in the creek started to have a bad odor and taste. Farmers could no longer use the creek for watering their fields or as drinking water for the animals. Further complaints were also reported regarding the smell emanating from the drainage ditches and from the landfill itself along with reports of problems with rats in nearby villages that came from the landfill.

Complaints were even registered from a church some kilometers away where there were problems to perform the regular service due to the stench from the landfill (Hälsovårdsnämnden VI:3).

Leachate eventually started to accumulate north of the Ekebyboda landfill where marshes had developed, and a drainage project was started along with new damming infrastructure to prevent the contaminated water to cause further damage to the private wells north of the landfill. The houses there have private water wells at depths of 14-112 m (SGU 2014). An electrical pump was installed north of the Ekebyboda landfill to improve the pressure in the culvert system. This pump was ineffective, however, had many breakdowns, and was eventually removed in 1990 (Hälsovårdsnämnden VI:4).

In the 1960s the Ekebyboda landfill had become a highly debated issue and was considered a serious threat for the health of people living in the surroundings. Therefore, continued measurements of leachate began to be performed in the early 1960s and continued thereafter over varying intervals.

The archived leachate quality data used in this thesis came from yearly monitoring measurements over the period 1990-2007.

The covering of the Ekeyboda landfill was completed during two phases, with the first phase taking place immediately after the landfill closure in the early 1970s. A later, improved covering operation started in 1993 and was completed in 1994, when trees were planted on top of the landfill, although with poor results. Today the Ekebyboda site landfill is partly overgrown by trees, and partly an open field. The area around Ekebyboda has since the start of the landfill operations also hosted a firearm shooting range. Since the closure of the landfill site, the shooting range has expanded into Sweden’s biggest shooting range, and today overlays a small part of the former landfill area (Hälsovårdsnämnden VI:3).

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3.2. Geography of the area

Uppland province is a relatively flat region, and the highest point is only 113 meters above sea level (m asl). Surficial sediments in Uppland are mainly glacial sediments, such as glacial till, glaciolacustrine and/glaciomarine clays, and postglacial outwash sediments which have made the region particularly fertile for agriculture. The predominantly clay-rich soil is impermeable compared to other sediments such as glaciofluvial sand or moraine (SNA 1996).

The local landscape in much of Uppland consists in a “mosaic” of fields, forest and lakes. The area is mostly used for crops, cattle farming or forestry. This region is one of Sweden’s most densely populated areas, especially around Lake Mälaren, and it hosts almost half of Sweden’s population.

Ekebyboda is situated 9 km north-west of Uppsala, within the drainage area of the Fyris river (Fig. 2).

The river, which drains a large part of Uppland, discharges into Lake Mälaren just south of Uppsala and the lake itself drains into the Baltic Sea (SNA 1996).

The bedrock in the area consists of granite and, further north, of leptite gneiss. North of the former Ekebyboda landfill site, the surficial geology is dominated by moraine deposits, flat or low- relief bedrock exposures, while in low areas marshy ground and clay cover is common. South to southwest of the landfill the subsoil is dominated by clay and moraine deposits, >5 m thick in places.

To the east and west are mostly thin layers of moraine deposits, till or flat bedrock. The soil layer in the immediate surroundings of the former landfill site is <5 m in low laying areas, and 1 m on higher grounds (SGU 1995).

The former Ekebyboda landfill site itself is located well outside both the outer and the inner Uppsala water protection area and away from any local nature reserves. In the near surroundings of Ekebyboda, the Jumkils creek runs within a small trench 300 m north of the landfill. Jumkils creek discharges into the Fyris river which supplies water to around 200 000 people.

North of the former landfill are a few houses that have private drinking water wells. The water in these wells was affected by the landfill leachate during the 1960s, but there is no currently reported contamination problem (SNA 1996). According to SGU, the hydraulic conductivity of the local bedrock is high, with an estimated volumetric flow rate between 600 and 2000 L hr^-1 (SGU 1995).

Groundwater flow in the landfill area is primarily determined by the local topography, and the dominant groundwater movement is from north to south. Under the landfill, however, the general groundwater movement is diverted in to the west due to the groundwater extraction north of the landfill, which maintains an artificial groundwater flow divide as long as pumping is active. The ground water level varies depending on the season. High values of conductivity, chloride (Cl^-) and total nitrogen (N) concentration were measured in the small wetland north of Ekebyboda landfill in 1995, which indicate a slight leachate leakage from the landfill to this wetland (SGU 1995). These high values gradually decrease northwards. Some leakage of leachate therefore appears to occur even with a functioning groundwater pumping system, but this is diverted away by a trench and is therefore

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not affecting the private drinking water wells nearby (SGU 1995). The leachate pumps in Ekebyboda were removed in the 1990s due to high maintenance costs. The last sampling taken at Ekebyboda by Uppsala environmental office were taken 2007 and 2014 was one additional sampling taken for this thesis.

3.3. Swedish environmental politics

The environmental question in Swedish politics has not always been on the political agenda.

Environmentally related questions were regulated by law in various forms since the end of 1800s. In early times, environmental considerations were only subject to regulations if these had an obvious, direct impact on the economy or on human health. An example is the law that regulated the hunting of small birds, as these birds controlled populations of insects and of vermins in farmers’ fields. Other examples are laws on the exploitation of natural resources which have existed for hundreds of years.

In contrast, there were no laws or regulations designed to benefit the natural environment for its own sake. Historically, environmental laws were regulated following specific codes for different categories of human activities such as farming, mining or forestry (Mahmoudi and Rubenson, 2004).

An early example of a law that was promulgated for the benefit of nature itself was the one that led to the establishment of Swedish national parks and other protected nature reserves in 1909. Later in the 1950s, the growing conflict between natural resources exploitation activities and outdoor leisure activities led to the Nature Conservation Act. This act regulated outdoor life, forestry and mining. This new act created conflicts and confusion when different sets of laws contradicted each other. To resolve these conflicts a new code of environmental laws came in effect in 1964. This code has continued to evolve and develop since the 1960s.

As in most western countries, the start of modern environmental awareness movement coincided with the release of the book “Silent Spring” by Rachel Carson. As a result of the public debate that followed the publication of Carson´s book, a succession of changes were introduced to regulate more strictly the release of man-made chemicals into the environment (Mahmoudi and Rubenson 2004). Several chemicals of environmental concern became subject to regulations under the new environmental protection law, which took effect in 1969. This law was continually updated with new regulations which eventually resulted in the Environmental Code of 1999. A major reason for this update was that environmental laws had become too numerous. This was changed and the Swedish government collected all environmental laws under a unified environmental code. This is the most complete environmental legislative code in Sweden so far, and it covers everything from toxic chemicals to radiation and landfills (Mahmoudi and Rubenson, 2004).

Another important step for environmental politics in Sweden was the creation of Miljöpartiet (the Environmental Party) in 1981, and their first entrance in the parliament in 1988 (Mp 2014). This

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was an important step because environmental questions then became subject of parliamentary debates on the same public level as other prominent political subjects such as jobs, housing and health care. In 1995, Sweden joined the European Union, which also introduced new obligations and laws in many areas, including the environment (Mahmoudi and Rubenson, 2004).

The main consequence of the evolution of Swedish environmental politics described above for the management of public landfills is that regulations for maintaining and setting up landfills have become much stricter than they used to be. Before the 1970s, landfills could be created almost anywhere that seemed appropriate or convenient. The content of the landfills was not regulated either, which is now done very strictly in modern landfills. Non-sorted, old landfills (containing both domestic and industrial waste) were particularly problematic as the mixing of different types of waste could lead to a toxic cocktail effect. The toxicity of the leachate could also remain elevated longer than if different waste types were not mixed.

Nowadays, the operators of a waste disposal landfill site, regardless of its size, are obligated to secure a permission by the County Administrative Board before the site can be established. There are different requirements from the legislations to be satisfied depending on whether the landfill is closed or open. Dumping on a landfill site is forbidden after its closure, and legislations state that covering of the waste heap and treatment of the landfill leachate after closure must be performed (Avfall Sverige 2012). Once closed, a landfill does not have to be reported to authorities with a few exceptions, for example if the landfill could be affiliated to a specific industry or similar. Also, if the closed landfill is identified as a polluted site, it becomes subject to specific rules that apply to polluted sites.

Provisions by the Swedish environmental protection agency state that all municipalities should have plans for waste management in the future, but also plans for the management of closed landfills.

These landfills should have leachate reducing measures, and information must be kept about where old landfills are situated. Municipalities must evaluate the status of their landfills sites. Those who have created the landfill and caused the environmental impact are responsible for the treatment and management of it after closure (Naturvårdsverket 2008). Environmental law considers leachate water as a byproduct of the landfill, which should be treated in a way such that it could be released without interfering with current regulations (Miljöbalken 1998). If the landfill was closed before 30 June 1969 when the current environmental laws came into force, the individual responsibility for the site cannot be established. Responsibility for the landfill then becomes the municipality’s. The environmental law states that those who conduct environmentally harmful activities are obligated to take action to prevent harmful substances from being dispersed into the environment (Naturvårdsverket 2008).

Treatments of leachate have the goal of reducing the levels of harmful substances entering the environment from a landfill, at a ''reasonable cost''. This implies that there are a limits to the cost and scope of the prescribed treatment. Environmental legislation exists that are specific for landfills, but are also embraced under the general Swedish environmental law. Before a new landfill can be stablished, an environmental impact assessment (“Miljökonsekvensbeskrivning” or MKB), must be

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performed. This assessment must consider all potential effects of the project for environment and health in the affected area. This MKB is then used in the decision making-process to determine if a project like a landfill development will take place or not (Hedlund and Kjellander 2007).

3.4. Leachate from landfills

When speaking of waste disposal sites, “leaching water” (leachate) refers to the water which has percolated through the waste heap and has neither evaporated nor been permanently absorbed in the heap. The substances that are leached from the waste are the components (or degradation products) of the dumped waste material which are dissolved totally or partly in the percolating water. This leachate can then enter into the groundwater or exit into nearby streams (IVL 2000). The quality (physical and chemical properties) of leachate can vary depending on the content of waste heap. A leachate could for example contain varying amounts of inorganic ions, like ammonium (NH4+), nitrate (NO3-), carbonate (CO32-) as well as some heavy metals (Pb, Cd, Zn) if conditions are favorable to dissolve and mobilize these substances. Oil and other insoluble organic liquids can also be transported by the leachate if the heap contains these types of waste products. Municipal waste disposal sites typically contain a high percentage of organic waste products, which take a long time to decompose.

3.4.1. Ageing process of landfill

Studies of landfills conducted in different regions of the world have shown that leaching water plumes can affect the groundwater for decades or even centuries after closure of a landfill (e.g., Flyhammer, 1997; Statom et al. 2004; Cozzarelli et al. 2011). This is partly due to biochemical processes that take place in the waste heap, and depends on the sustainability of these processes over time. Landfills that contain waste with a high organic content undergo an ageing process through a series of steps which have an impact on leachate composition. These steps are mainly determined by bacterial degradation of the waste. The duration of this ageing process is difficult to predict due to the number of variables that can affect the efficiency of different bacterial degradation stages. Factors such as the water percolation rate, heat supply, and oxygen availability can all contribute to modify the composition and toxicity of the leachate over time. The degradation of organic waste in landfills typically goes through the following phases (Naturvårdsverket 2008):

• Phase 1: Aerobic phase (a few days to a few weeks)

• Phase 2: Acidic anaerobic phase (a few weeks to a decade)

• Phase 3: Methanogeic phase (a few months to a few hundred years)

• Phase 4: Humus generation phase (>100 years, uncertain)

In the early stages of the landfill evolution (Fig. 3), waste degradation occurs under aerobic conditions, which generates heat and may enhance leachate production (Flyhammar, 1997). Heat

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supplied to the landfill can increase the fermentation rate, which in turn will affect the efficiency of aerobic/anaerobic processes in the waste. This heat supply is controlled by natural conditions such as weather. The next stage of landfill waste degradation is anaerobic, which also tends to develop acidic conditions inside the landfill. This evolution is usually reflected by changes in the Chemical Oxygen Demand (COD) in the leachate which in a newly-closed landfill is above 10 000 mg L^-1, but 10 years later is typically in the order of 3000 mg L^-1. This decline reflects the microbial degradation of the organic waste which gradually consumes most of the available oxygen (Kulikowska and Klimiuk 2007). As a consequence, younger landfills tend to contain larger amounts of volatile organic acids produced by fermentation than older landfills.

Figure 3. Degradation phases in household waste, modified from Flyhammar (1997).

Under Phase 2, the leachate typically has a low pH, high Biological Oxygen Demand (BOD) and low COD. It contains high levels of dissolved N and hydrogen sulfide (H2S), and may also contain high levels of dissolved metals such as Zn, Fe and Mn. Phase 3 is characterized by increasing values of pH and BOD, high dissolved N and Cl^-, but lesser metal concentrations, except for Pb. During this phase, particularly in landfills containing much organic and biodegradable material, large amounts of carbon dioxide (CO2) and especially methane (CH4) gas can be produced. The gas can be burned, or, as in some modern landfills, it can be collected and be re-used as biofuel for transportation. A requirement for this is the installation of a pipe system in the landfill. In some cases, a simpler flaring

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system is installed to burn the CH4 and convert it to the less potent greenhouse gas CO2. Phase 4 of the ageing process is characterized by very low biological activity, when most of the organic material has already been degraded and what remain is non-biodegradable material. Addition of oxygen in the landfill during this phase could however trigger a renewed increase of bacterial activity and therefore restart the landfill ageing process. This would lower the pH, and increase the risk for metal leaching and renewed gas production.

The waste degradation process should eventually return conditions in the waste heap to neutral to near alkaline, at which point the landfill is no longer a threat to the surrounding environment (Salem et al. 2008). Different waste degradation phases can also occur simultaneously at several places in a landfill since the ageing and conditions in the heap may differ locally (Naturvårdsverket 2008). To control the rate of the degradation process, and also reduce the production rate of contaminated leachate, a soilcover is usually placed over landfills.

3.4.2. Effect of precipitation on leachate

The amount of precipitation that falls in different seasons / years can affect both the quality and the quantity of leachate from a landfill site. According to Statom et al. (2004), who conducted research on a site in Florida (USA), there is a strong relationship between leachate concentration and rainfall. However, the effects of rainfall on leachate could take up to 30 days or more to manifest themselves, i.e. before any resulting differences in leachate can be measured. Statom et al. (2004) observed, for example, a positive correlation between rainfall and Cl^- concentration in the leachate while the landfill still was in use. An opposite correlation was found after the closure of the landfill, with lower Cl^- levels following rainfall. The rainwater then had a dilutive effect: once addition of new waste in the landfill was stopped, the amount of highly soluble Cl^- quickly decreased in the leachate by dilution. However, a separate study by Huan-Jung et al. (2006) at a landfill site in Taiwan showed that the seasonal effects of precipitation can vary for different leachate properties. In Taiwan, the spring and summer are the rainy seasons and winter and fall the dry seasons. The authors found a clear seasonal effect of rainfall on pH and COD in the leachate, with higher values measured in the winter, but for other parameters like conductivity, the seasonal effect was opposite, or sometimes not noticeable. Studying a landfill site in Slovenia, Kalčíková et al. (2011) also found that during winter, below-freezing temperatures in the ground greatly reduced biological activity in the waste heap and limited water percolation and leachate production.

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3.4.3. Leachate containment and treatment measures

To reduce leaching from a closed landfill waste heap, a coating of clay can be placed over it.

In modern landfills this method is applied continuously during landfill operations to limit the exposure of the waste to open air. Nowadays when landfill sites are being planned, consideration is given to the local geography and hydrology. This is particularly necessary in order to meet the strict regulations concerning the closure of landfills. One of the requirements is that the waste deposit should be located or designed in such a way that dispersion of leachate produced during and after the operational phase is slowed down or preferably stopped by geological barrier. The nature of this barrier can differ but usually consists of mud or of an equally low-permeability material.

Frequently-used leachate treatment methods in modern landfills include leachate ponds, treatments plants, and specially-created wetlands. The type of method adopted varies partly depending on the chemical characteristics of the leachate and on geographical factors. Other considerations are local legislation and the sustainability of the method(s). Treatments at the landfill site should be as simple and efficient as possible to avoid buildup of high volumes of leachates in case of a temporary failure in the process. In Sweden, there are currently ten different methods to treat landfill leachates Naturvårdsverket 2008), which are, in decreasing order of usage frequency:

• Aerated lagoon

• Treatment plant

• Irrigated ground plant system

• Repumping to landfill

• Infiltration

• Prematurity

• Soil filter

• Chemical precipitation

• Sequencing batch reactor

• Mechanical treatment

The majority of these treatment methods demand large land surface areas to be applied, which is a very important factor to take into consideration when modern landfills are planned. Consideration also has to be given to the technical requirements and cost of the treatment. The aforementioned methods all have different costs for establishment and maintenance. The selection of the right leachate treatment method for a landfill is therefore a choice that must take many parameters into consideration (Naturvårdsverket 2008). The environmental law also takes into account economic risks. By law, a

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landfill-operating company should have a certain amount of money available to fulfill its environmental obligations after landfill closure.

Older landfills often lacked most of the precautionary measures used today, and therefore present a bigger environmental risk than the more recently created landfills. An old landfill site that had no leachate reduction or containment measures can result in more contaminants being released from the waste heap and transported in to the surrounding environment. In older landfills, a trench was sometimes dug around the waste heap. However such a system is usually insufficient to contain the leachate. Unfortunately, in such old landfill sites, little or no consideration was given to the local hydrology, which often led to contamination issues.

In the case of the Ekeyboda landfill site, as described earlier, a system of wells had been created around the landfill. These wells and the associated culvert system enabled the leaching water to be pumped, prevent it from flowing in an undesired direction or seeping into the groundwater (Fig.

4). In more recently-created landfills, the leachate can be directed through a culvert system to a treatment pond, wetland or some other, more suitable outlet system. Some undesired consequences of this type of system are changes to the local hydrology around the landfill site, for example an inflow of groundwater to the pumps, or the drainage of streams. These consequences can however be avoided with some careful planning and by installing double trenches. Modern landfills have stricter criteria for discharge of leachate then older landfills. To achieve these criteria several treatment methods have been elaborated. Older landfills have been covered with clay to reduce the amount of water that percolates through the waste, but this is usually the only leachate-reduction measure that has been taken (IVL 2000).

Figure 4. Map showing the position of the Ekebyboda landfill leachate wells (red dots) and drainage culverts (black lines) in relation to the local hydrology (From information provided in Hälsovårdsnämnden VI:4).

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3.5. Important physical and chemical properties of landfill leachates

Under the Swedish environmental law, there are strict permissible limits for different physical and chemical properties of landfill leachates. The toxicity of chemicals in leachate can be determined by tests on algae or other small aquatic living organisms.

3.5.1 Chemical properties

pH is a measure of the ionic strength of an acidic or basic substance expressed on a logarithmic scale, which measures the activity of hydrogen ions (H⁺). This is an important parameter to measure to determine in what phase of waste degradation the landfill is. The pH strongly affects the solubility and mobility of metals in the landfill leachate (EPA 2014, 1).

Alkalinity is a measure of the capacity of an aqueous solution to receive an addition of hydrogen ions without increasing the pH. Hydrogen ions are created when an acid is dissolved in water. Alkalinity therefore expresses the capacity of solutions to neutralize acidity (Naturvårdsverket 1999).

Conductivity is a measure of how well a material will lead an electrical current. In water, the amounts of dissolved substances such as metals, nutrients and other ions largely determine how well the water carries electricity. Major ions with a negative charge are nitrate (NO3-), sulphate (SO42-), and Cl^-. Major ions with a positive charge are sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), other metal ions (e.g., Cu²⁺, Fe³⁺). Substances such alcohols, sugars and phenols have weak or no charge and therefore have a limited impact on conductivity. Leachate temperature will also impact its conductivity (EPA 2014,2).

Redox is an abbreviation of reduction and oxidation that states whether elements tend to be in their higher (oxidized) or lower (reduced) oxidation states. Oxidation reactions lead to a gain of one or more electrons and an increase in oxidation state, while reactions that lead to a loss of free electrons lower the oxidation state (reduced state). Redox state is dependent on pH, availability of oxygen, etc.

in water, soils and sediments, and strongly affects the mobility of contaminants in landfills. In landfills, oxidation is commonly associated with bacterial consumption of organic matter, common oxidizers being H2O, O2 and Cl2. Reducers are very diverse and consist of positively charged ions such as Fe³⁺, Zn²⁺ and Na⁺. Under anaerobic conditions, metals can undergo a reduction from oxidation states (III) to (II), the latter form being more mobile than the first. Reduction of SO42- is used in a series of biogeochemical processes, for example by anaerobic bacteria which convert metal sulphates to sulphides. Oxidation of scrap metal inside the landfill results in an easy recognizable orange rusty coloring of leachate water (Sterner 2010).

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COD is a measurement of the amount of oxygen in complete chemical degradation of organic substance in water. This measurements is used to determine the biological activity in a landfill (Natuvårdsverket 2008).

3.5.2 Major ions

Magnesium (Mg²⁺) is a metal ion that is very abundant in the natural environment, as well as in water due to its high solubility. Mg²⁺ is also one of several biologically essential metals for functions in the human body and other organisms in nature (Jordbruksverket 2013).

Chloride (Cl^-)in solution is highly oxidizing and is often used as a bleaching agent and disinfectant.

In landfills, Cl^- could be derived from materials such as textiles, solvents, paint, petroleum, plastics, medicines, etc. Due to its reactivity, Cl^- typically occurs in nature in the form of compounds such as salts (e.g., NaCl). Also because of its reactivity, it does not tend to accumulate readily in the human body (Kemi 2010).

Potassium (K⁺) is an ionic salt often associated with name saltpeter. It is also one of the bio-essential nutrients for humans, and can be found in most consumable organic products and is moderately soluble in water which in increase with temperature (Jordbruksverket 2013).

Sodium (Na⁺) is another essential nutrient for humans. In high doses, Na⁺ can cause several heart- related problems with humans. In landfills, Na⁺ exists in large amounts and is derived from materials such as, soap, textiles, oils, chemicals and paper (Landskapsgrundammen 2014).

Sulphate (SO42-) is highly soluble in water. H2SO4 is one of the most utilized acids in industry today for numerous purposes, including in electrolytic batteries. It is also commonly produced by combustion of organic fuels such as coal, oil and gas. SO42- could have a harmful impact on humans and nature especially in combination with other chemical compounds. Consequences for humans and nature are therefore diverse (Naturvårdsverket 2006).

3.5.3 Ions commonly associated with organic matter

Nitrate (NO3-) and nitrite (NO2-) these substances are essential nutrients for aquatic life and biological production. The main consequence of NO2-and NO3- pollution is the eutrophication effect in aquatic systems, which lead to algal blooms and oxygen deficiency (hypoxia). Sources of NO2-and NO3- in landfills are many and diverse and may include fertilizers, untreated sewage explosives, toothpaste, pesticides and laundry detergents (Naturvårdsverket 2014).

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Ammonium (NH₄⁺) is the ion formed when NH³ is dissolved in water and is a weak acid. NH3 is produced by degrading organic matter. It was long used as a fertilizer and can also be found in explosives and many other products (KEMI 2011).

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4. Data and methods

4.1. MIFO environmental risk classification

The classification of a landfill in terms of environmental risk level is a decision that must take into account both the physical and human geography of the landfill area, and the potential for contaminants to spread into nature and to inhabited sites. Specifically, the risk being investigated is that of contaminants from the landfill infiltrating buildings, drinking water wells, soils used for food production etc., such that they could constitute a threat to human health. The types of substances leaching from the landfill and their chemical properties are therefore parameters which are essential to take into consideration in the risk classification. Phase 1 of the MIFO protocol lays the foundation for a possible phase 2, in which more comprehensive environmental sampling and measurements are performed. The MIFO phase 1 mainly evaluates information about previous landfill history and related processes. This information can be obtained through interviews with persons having insight on the actual site history, or from reports, protocols, maps, etc. (Naturvårdsverket, 2002).

In the case of Ekebyboda, there is limited information on the history of the landfill (see previous sections). The existing documentation is limited to few reports from SGU and the Uppsala county environmental office. However, leachate quality measurements from the landfill were documented from approximately the time of closing of the landfill in the 1970s, until 2007, when the last measurements were performed (Naturvårdsverket, 2002). The MIFO risk assessment for Ekebyboda which was performed as part of this thesis was based largely on archived data from the leachate quality monitoring program over the period 1990-2007, supplement by new field sampling and measurements performed in April 2014. These compiled measurements, together with background information, formed the basis for the risk level classification. Published scientific case studies on the evolution of landfill leachates, as well as literature from the Swedish Environmental Protection Agency (Naturvårdsverket) provided an additional scientific foundation.

The MIFO system classifies levels of environmental risk on a scale of one to four (one being the highest) using a two-axis grid, were the risk of spreading (migration) of pollutants is one of the axes, and other factors such as the toxicity of substances, the present contamination level, and the sensitivity and protection value of the investigated site define the other axis (Fig. 5). The estimated values of these different criteria for an investigated site are then positioned in this space. The assignment of an environmental risk level class is based on where the different factors are concentrated with respect to the main criteria defining the axes of evaluation (Naturvårdsverket 2002).

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Figure 5. MIFO risk classification diagram (Naturvårdsverket 2002).

4.2. Measurements of leachate quality

4.2.1. Leachate monitoring data

Over the period 1990-2007, the Uppsala county environmental office regularly monitored the quality of leachate from the Ekebyboda landfill, and 33 physical and chemical parameters were measured in samples, including selected metals, major ions, and nutrients. This was done to monitor the chemical evolution of the landfill leachate. Samples were collected from four wells situated around the landfill, once a year, typically in May, but somewhat later duringa few years (four times in June, and once in August). The analyses were performed by different laboratories under contract with the environmental office, because no adequate analytical facilities existed within the services of the Uppsala municipality. Unfortunately, few or no details on how the various laboratories performed their analyses were recorded or saved. For the field sampling conducted in 2014 (see below), the samples were sent to ALS Scandinavia for analysis, and this laboratory provided all details on procedures. In this thesis, 11 parameters in leachate were considered. For the MIFO categorization of the landfill has additional measurements been considered for Pb, Cu, Zn and Cd for year 2014. These parameters is used to determine the right MIFO risk classification. Archived printed reports obtained from the Uppsala county environmental office were digitized, and the data compiled into a single computer spreadsheet program for analysis. Because water quality analysis has been typically performed by the same standard methods over the past decade, it was assumed, in this work, that the analysis methods specified by ALS Scandinavia for the 2014 samples (Table 1) were comparable, in terms of precision, to those used in the earlier period of monitoring (1990-2007). Correlation between analysed parameters and precipitation is displayed in a diagram. Pairwise correlation has been

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calculated using the Pearson’s product-movement correlation. This method is a way of calculating the linear correlation between two variables and display the correlation in percentage were -1 is a negative correlation and 0 is no correlation and 1 is a good positive correlation (Alm and Britton 2008).

Table 1. Methods and precision of leachate quality analyses performed by ALS Scandinavia. ICP-AES = Inductively Coupled Plasma Atomic Emission Spectrometry; ICP-SFMS = Inductively Coupled Plasma Sector Field Mass Spectrometry; AFS = Atomic Fluorescence Spectrometry; CDM = Conductivity meter; ABU93 = Radiometer. 2σ = Uncertainty of the analysis.

4.2.2. Leachate sampling and measurements, April 2014

Water samples were collected at Ekebyboda during the spring of 2014 and analyzed to reveal the current quality of the landfill leachate and to complement the monitoring data from 1990-2007 provided by the Uppsala County environmental office. Field sampling at Ekebyboda was performed on April 23, 2014, between 09:00 to 10:30, under sunny weather conditions with air temperature around 10 °C. The four wells were visited in the following order: A3, A2, A1 and A1-4 (Fig. 4). Well A3 was the first to be sampled. The lid of the well showed no signs of previous (recent) opening.

Organic debris such as twigs, leafs and several dead rats were found floating in the well. The water seemed to be stagnant and no motion or mixing could be seen or heard. On top of the well is a small ventilation pipe which could be a possible entrance for the rats. In Fig. 6a, a black hole can been seen at the bottom of well. This hole is covered with a metal lid which protects the lower well chamber where pumps were situated before. The metal lid was lifted and water samples were taken at approximately 150 cm depth in this lower chamber. The water did not smell nor had any remarkable coloration. Well number A1 (Fig. 6b) has a similar design to well A3 but is slightly larger. The water in well A1 was also clear with no distinctive smell. There was very little organic debris in this well

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compared to other wells. The metal lid in the bottom did not cover the lower chamber, and the water sample was taken in the deeper part of the well at an approximate depth of 0.5 m. Well A2 contained running water with a few twigs and leafs in it, and the water had a slightly dark color, but no distinctive smell.

Figure 6: Pictures showing Ekebyboda leachate well A3 (left) and A1 (right). Pictures taken by the author.

In contrast to A1, A2 and A3, the water in well A1-4 (Fig. 7) had a pronounced yellow/orange color, and a strong and distinctive smell of oil or diesel fuel. The smell of oil and diesel was so strong that it could be detected a couple of meters from the well. A sediment deposit in the well was approximately 5-8 cm deep, and the water samples were taken close to the outlet of the well were the three pipes join into one. The depth of the moving water was barely 0.1 m.

Figure 7. Picture showing Ekebyboda leachate well A1-4. Pictures taken by the author.

In each of the sampled drainage wells, three separate water samples were taken, and the water in one of the bottles was later filtered and analyzed for a suite of metals. The filtration was done in a laboratory at the Department for Earth Sciences. Fig. 8 shows the filtration apparatus that was employed. The filters used had a diameter of 0.45 µm and were made of polyethersulfone.The filtered

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water was stored in acid-cleaned bottles, which were then sent to the ALS Analytica laboratory in Täby for analysis.

Figure 8. Filtration equipment used prior to leachate analysis (Picture taken by the author).

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5. Results

Results of the work conducted in this thesis consist in two parts. The first part was the actual risk level characterization of the Ekebyboda landfill, conducted site in accordance with the MIFO protocol. This evaluation was presented in a separate report to the Uppsala County environmental office, and is only summarized below (section 5.1). The second part of the results, which occupy the remainder of this chapter, concerns trends in landfill leachate quality obtained by monitoring over the period 1990-2007, which were interpreted in terms of biogeochemical evolution of the landfill, and possible correlations with precipitation (section 5.2).

5.1. MIFO risk level classification

The MIFO evaluation protocol consists in several parts, which together provide the foundations for the environmental risk level classification, as summarized in Fig. 10.

Figure 10. MIFO classification of the Ekebyboda landfill site (Naturvådsverket 2014)

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The leachate itself, which was sampled in wells, is regarded as contaminated groundwater. In the case of Ekebyboda, the category “risk of contamination to buildings” is not represented because there are no affected buildings in the immediate vicinity of the landfill site.

Different landscape elements (ground, surface water, sediments, etc.) are considered during the evaluation, which are represented by horizontal lines with letters on the figure. The point where these lines intersect the vertical axis reflects the estimated risk of contaminant dispersion (slight to very great) for each particular landscape element. Many different landscape elements can play a role in an assessment, but they will only appear on the MIFO classification diagram if they are represented, and considered relevant, at the contaminated site being evaluated site. The diamond symbols with letters (H, C, S, P) on the horizontal lines represent different parameters (e.g., toxicity, contamination level) which should be taken into consideration in each landscape element. These symbols are positioned along the lines according to the perceived risk level (slight to very great) associated with each parameter and landscape element. When each relevant landscape element and parameter has been assessed and plotted on the MIFO diagram, the field that holds the most diamond symbols indicates the suggested comprehensive risk classification level, from 4 (lowest) to 1 (highest). A landfill is considered in the MIFO protocol to be ''land'', as opposed to a construction, and is evaluated as such.

Determination of the toxicity (H; ''hazard assessment'') and contamination level (C) of the landfill leachate should be based on the identification and measurement of as many of the contaminants present as possible. Types of pollutants that are, according to the MIFO protocol, classified as ''high risk'' for toxicity are metals such as Cu, Ni and Al, and various types of oil, oil residues and other petroleum-derived products. Pollutants regarded as presenting ''very high risk'' in terms of toxicity are As, Pb, Cd, Hg, Cr, Na (metal form), and persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), chlorinated solvents, and chlorophenols. Identification and measurement of these pollutants are an important part of the MIFO process for the risk classification of the landfill. In the most recent Ekebyboda leachate sample analyzed, taken on April 23, 2014, concentrations of several trace metals were measured that correspond to the following MIFO risk categories for ground water: slight (Pb), moderate (Cu), great (Zn) and very great (Cd). However, the comprehensive MIFO classification also took into consideration the strong likelihood that other, unmeasured chemical substances, such as oil residues and solvents, may be present at high levels in the leachate as well, as suggested by the strong smell of petrol/oil detected in well A1-4. Accordingly, the estimated risk classes for toxicity and for contamination level in groundwater were considered to be 2 (great) and 1 (very great), respectively.

The risk level for protective value (P; the level of environmental protection required) that applies to ground and groundwater at Ekebyboda was rated as 4 (low), because the land and water in the landfill area and its surroundings do not have any special status (e.g., a natural reserve) and are not protected by any special environmental law(s). Water-courses near Ekeyboda such as Jumkilsån is more than 1 km away from the landfill leachate water is therefore considered to have minor affect on

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it. However, the risk level for ''human sensitivity to exposure'' (S) around Ekebyboda was rated as 1 (very great) because there are several persons in the area who use drinking water from local wells.

Leachate from the landfill could also affect nearby farmland and cultivated fields. Previous reports documenting polluted wells, the displacement of farms, contamination of streams, as well as estimates of leachate volumes produced when the landfill was in operation, also contributed to assigning a sensitivity risk level classification 1 to Ekebyboda. Although the landfill has been closed for almost 40 years, these documents contribute to a picture of a landfill with a long history of severe environmental impacts which must be taken into account when evaluating the present-day risk level. The shooting range near Ekebyboda is not, by itself, a sensitive area, but it attracts many people to the areas affected (or potentially affected) by the landfill.

With regards to the migration potential of contaminants from the landfill (vertical axis on the MIFO diagram), this was rated as a ''very great'' risk for groundwater. The culvert system around Ekebyboda was set up to transport leachate from the landfill away from the groundwater table and from nearby wells and towards the south of the landfill, and also, by dilution, to reduce the threat of leachate contamination in surface waters and soils. However, as discussed earlier, the wells experienced frequent problems with groundwater pumps for a long time, which resulted in their removal. There has been no active pumping in these wells since the beginning of the 1990s, and consequently risks of leachate spreading away from the landfill have increased. Interruption of pumping at the northern part of the landfill led to the diversion of the leachate flow towards the north, rather than the south, which resulted, by 1995, in the formation of a small wetland with anomalously elevated water conductivity (total solutes), and high levels of chloride (Cl^-) and total nitrogen (N).

Measurements of Cl^- and nutrients done by SGU in 1995 revealed continued minor leaching from the landfill towards the north and into the wetland. The leachate sampling performed on April 23 2014 also established that wells A1 and A3 contained large amounts of stagnant water. The efficiency of leachate transport in the culverts near these wells is therefore questionable. Wells A2 and A1-4, however, showed that a certain amount of active flow exists in the nearby part of the culvert system.

The risk for leachate spreading to nearby water wells north of the landfill is a realistic threat which should be taken seriously. The MIFO risk classification level of 1 for the Ekebyboda could possibly be reduced to 2 if the current state of the culvert system and the volume of leachate flowing northward of the site could be clarified.

5.2. Evolution of Ekebyboda leachate quality, 1990-2014

5.2.1 Temporal trends

As described earlier, most of the landfill leachate quality data used in the thesis are based on sampling conducted by the Uppsala County environmental office as part of a monitoring program of the Ekebyboda landfill which ended in 2007. Additional measurements of leachate were performed in