To Örebro University

Hillringsberg, a former sawmill site in Sweden, is severely contaminated with polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study collected site-specific data to assess the human health risks associated with locally produced food. To evaluate potential exposure, samples of salmon, perch, cow's milk, cattle, and sheep were collected near the site and analyzed for PCDD/Fs. The findings reveal that the most frequently detected congeners in the food samples corresponded with the most abundant congeners in the soil, underscoring the impact of contaminated sites on PCDD/F concentrations in locally produced food. Particularly concerning is the level of PCDD/Fs in sheep meat, which was found to be 11 times higher than the Tolerable Weekly Intake (TWI) for adults and 26 times higher for children. Comparing food samples from the sawmill site to those from the National Swedish Control Programme revealed that all food samples from Hillringsberg exhibited some level of contamination, even though the concentrations of PCDD/Fs remained below the European Maximum Limits (MLs) and Action Limits (ALs). The concentrations and patterns of contaminants in nearly all samples, particularly those from sheep, cattle and perch, were influenced by local contamination from the historical use of pentachlorophenol (PCP) at the old sawmill site. PCA showed that sheep and soil samples from the storage area exhibited strong covariance. Perch and sediment samples from the sawmill pond were also grouped together. These findings highlight the necessity of evaluating food production activities near contaminated sites during the initial stages of site-specific risk assessments. Ensuring food safety in these areas is crucial, and if necessary, relocating grazing lands, fish farms, and similar operations can help mitigate health risks associated with contaminated food.

Green liquor dreg (GLD) is a calcite dominated alkaline byproduct from the pulp and paper industry with high buffering capacity and thixotropic properties, making it suitable for treatment of acidic mining waste. In a comprehensive four-year study, GLD from 16 Swedish mills was characterised through multiple sampling campaigns, analysing elemental composition, buffering capacity, sequential leaching, and interactions with acid rock drainage. This dataset is now a robust foundation for understanding the variability of GLD between mills, offering key insights into which parameters are most critical for different mining waste applications.

Several small and medium sized tests have been performed, with good results, to determine the suitability and possible drawbacks when mixing GLD and acid mining waste. As a final confirmation of the technique approximately 4,500 tonnes of acid mining waste at Gladhammar, Sweden (pH 3.8, 96 mg/L copper and 21 mg/L cobalt) was slurry injected with 100 tonnes of GLD in 2017.

During injection, pH in the drainage from the area increased from 3.5 to around 10 due to excess GLD being washed out. One to two months after injection, pH was around 7.5 and concentrations of copper and cobalt was 38 and 4.9 mg/L, respectively. During 2024, pH was 8 and concentrations of copper and cobalt were 1.1 and 0.95 mg/l, respectively.

The challenge at Gladhammar was to reduce metal loads while allowing the waste rock piles to be accessible for mineral hunters and geoscientific studies in the future. With alkaline injections, areas with cultural, historical and geological values can be treated with low visual impact.

The full-scale reclamation at Gladhammar confirms that GLD can be used for reclamation of historical mining waste as pH increases and trace element concentrations decrease. 

Green liquor dregs (GLD) is an alkaline by-product from the pulp and paper industry with a pH between 10 and 14. Today most of the produced GLD in Sweden is landfilled. As a fine-grained alkaline material, it might be possible to use it for acid-generating mining waste remediation. To increase the utilization, quality characteristics and environmental performance need to be determined. In this study samples were collected 5 times from 16 mills during a period of 2.5 years, and were characterized by analyzing dry matter content, loss on ignition (LOI) 550 °C and LOI 950 °C, elemental analysis, pH, electrical conductivity, and calorific value. The results were then evaluated using multivariate statistics (PCA) as well as being compared to other studies and Swedish till. The results show that even if GLD is heterogenous (both within a mill and between different mills) trends can be seen for samples from most mills. When samples do stand out, it is predominately related to the same four mills. Most of the studied parameters showed characteristics favorable for use as a remediant; however, TOC, sulfur, and some of the elements require further study. In general, this study concludes that GLD can be a viable option for the remediation of small orphaned sulfidic mining sites and thus worthy of further studies on the interaction between GLD and acidic mining waste.Overall, GLD can be a good alternative for cost-effective remediation of smaller orphaned mining sites. It is readily available in large quantities, has the qualities needed for remediation of many orphaned acidic mining sites, and can often be locally sourced near the mining site. The use of GLD for mining site remediation is likely also a more sustainable method compared to traditional remediation methods.

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant (POP) and emergent contaminant that are widespread in the environment. Understanding the mechanisms controlling the distribution of PFOS and its isomers between hydrargillite and the water phase is important in order to study their redistribution and mobility in the environment. This study investigated the effects of pH, humic acid, fulvic acid and Na₂SO₄ on sorption of PFOS isomers to hydrargillite. A mixture of PFOS isomers was spiked into water and hydrargillite was added to the system and shaken for one day; the system was tested with different aqueous composition. Concentrations of PFOS isomers in the aqueous phase were quantified using an ultra-performance liquid chromatograph coupled to a triple quadrupole mass spectrometer. Our results showed that the distribution coefficients of PFOS isomers were found to be 0.76, 0.71, 0.93 and 0.90 at pH 6.5, for 3-/4-/5- PFOS, 6-/2-PFOS, L-PFOS and total PFOS respectively. The distribution coefficients increased at lower pH and decreased at alkaline conditions. The presence of humic substances (HS) increased the sorption slightly at the environmental pH of 6.5, although a competition effect was observed during acidic conditions. A tendency of PFOS distribution to hydrargillite in the presence of Na₂SO₄ was like its behavior in the presence of HS although the mechanisms behind the sorption were interpreted differently. This study revealed that L-PFOS was readily sorbed when no other chemicals were added or in 20 mg/L FA or 100 mg/L Na₂SO₄. We suggest that an increase in PFOS sorption in the presence of HS may be due to hydrophobic mechanisms while Na₂SO₄ contributed to increased sorption through ionic strength effects.

Perfluorooctane sulfonic acid (PFOS) has been produced in large quantities for the use in various applications. As a consequence, PFOS is ubiquitous in the environment. Managing transportation of PFOS requires a clear understanding of PFOS mobilization in soils and their interactions with different soil components. The current study investigated a pH-dependent sorption of PFOS isomers onto soil and the effect of dissolved humic substances and Na2 SO 4 . Sorption experiments of PFOS isomers was conducted on top and subsoils to assess their capacity to retain PFOS. Topsoil and subsoil samples were sampled from two areas in Kvarntorp, Kumla, Sweden. Sorption experiments were performed by shaking a mixture of soil and soil solutions spiked with PFOS isomers. One way ANOVA showed that linear PFOS (L-PFOS) and branched PFOS (Br-PFOS) isomers showed different sorption behavior onto soils. Calculated logarithmic partition coefficients revealed that L-PFOS is readily sorbed onto soils sampled at area 1) at very low pH (<4.5) whereas it was the least sorbed onto soils collected at area 2) under the studied pH range. Electrostatic interactions governed the sorption of PFOS isomers during acidic conditions whereas other mechanism controlled the sorption during neutral to alkaline conditions. The presence of humic acid enhanced the sorption of all PFOS isomers whereas fulvic acid inhibited their sorption onto soil. Sorption results revealed that the topsoil had a high capacity to sorb all PFOS isomers compared to the subsoil from the same area. For soils collected from an area covered by young oak trees, a high sorption on the topsoil was attributed to a high organic content [measured as loss on ignition (LOI)] and cation exchange capacity (CEC). However, there was no correlation between sorption capacity and LOI or CEC content for soil collected from another area covered by spruce forest. This suggested that the sorption on latter soils was controlled by other physicochemical properties.

Oil production (1942-1966) and uranium extraction (1953-1961) from the Alum Shale Formation in Kvarntorp, Sweden has had a great environmental impact on the area. Other industrial activities have also contributed to pollution. This study combines archive research with monitoring data and new sampling in order to assess the extent of the impact. During the production period, process water containing oil, phenols, sulfur compounds and high concentrations of iron reached the stream resulting in low water quality downstream. Also the landscape was reshaped, resulting in water filled pit lakes and a 100-meter-high shale waste deposit. Today, past alum shale activities still have an impact on the environment. Sulfate concentrations in the pit lakes are significantly higher than background values and downstream water also shows higher concentrations of elements such as nickel and uranium. The waste deposit still has a hot interior and an important question is the cooling rate and possible future leaching scenarios. Remaining hydrocarbons show today only a local impact while trace elements are transported downstream and affect a larger area.

Worldwide, black shales and shale waste are known to be a potential source of metals to the environment. This project demonstrates ongoing weathering and evaluates leaching processes at a 100-m-high shale waste deposit closed in the 1960s. Some deep parts of the deposit are still burning with temperatures exceeding 500 °C. To demonstrate ongoing weathering and leaching, analyses of groundwater and solid samples of shale and shale waste have been undertaken. Largest impact on groundwater quality was observed downstream the deposit, where elevated temperatures also indicate a direct impact from the burning waste deposit. Groundwater quality is largely controlled by pH and redox conditions (e.g., for arsenic, nickel, molybdenum, uranium and vanadium), and the mixture of different waste materials, including pyrite (acidic leachates) and carbonates (neutralizing and buffering pH). Analyses of shale waste from the deposit confirm the expected pyrite weathering with high concentrations of iron, nickel and uranium in the leachates. No general time trends could be distinguished for the groundwater quality from the monitoring in 2004-2019. This study has shown that black shale waste deposits can have a complex long-term impact on the surrounding environment.

Several large pits were left after alum shale was mined from 1942 to 1966 in the Kvarntorp area of Sweden. Of these, the pit lakes Polen and Norrtorpssjon are the focus of this study. They have elevated levels of Na, K, Mg, Ca, Al, Mn, Fe, and sulphate, as well as trace elements, from weathering of the exposed shale. Both lakes had a stable pH below 4 until 1996 when the pH in Norrtorpssjon started to increase, exceeding 8 in 2010, due to inflow of leachates from alkaline waste dumped in an adjacent waste deposit, similar to a large scale anoxic limestone drain (ALD). Iron and Al concentrations decreased as the pH increased, indicating formation of particulate species which accumulate as sediments. The Co, Ni, and Zn concentrations also decreased, probably due to association with the solid phases, while Cu was less affected by the increase in pH, possibly due to formation of complexes with dissolved organic matter. Vanadium concentrations show limited solubility, while Mo concentrations increased at higher pH. Uranium concentrations decreased from above 80 mu g/L to below 10 mu g/L before rising to 30-35 mu g/L due to the formation of soluble carbonate complexes at higher pH levels. The elevated levels of Li, Sr, and U indicate that weathering has continued despite the pH change. Both pit lakes are stratified, but no seasonal overturn has been observed. Long-term behaviour of this large-scale ALD and its implications are also discussed.

Alum shale was mined for oil and uranium production in Kvarntorp, Sweden, 1942-1966. Remnants such as pit lakes, exposed shale and a 100-meter-high waste deposit with a hot interior affect the surrounding environment, with elevated concentrations of, e.g., Mo, Ni and U in the recipient. Today most pit lakes are circumneutral while one of the lakes is still acidic. All pit lakes show signs of sulfide weathering with elevated sulfate concentrations. Mass transport calculations show that for elements such as uranium and molybdenum the western lake system (lake Soderhavet in particular) contributes the largest part. For sulfate, the two western lakes contribute with a quarter each, the eastern lake Norrtorpssjon about a third and a serpentine pond system receiving water from the waste deposit contributes around 17%. Except for a few elements (e.g., nickel 35%), the Serpentine system (including the waste deposit area) is not a very pronounced point source for metal release compared to the pit lakes. Estimates about future water runoff when the deposit has cooled down suggest only a slight increase in downstream water flow. There could possibly be first flush effects when previous hot areas have been reached by water.

It is difficult to evaluate the potential for reprocessing and extraction of minerals from waste rock with valuable and/or harmful elements.

We suggest a new sampling strategy/protocol for waste rock, specifically developed for historic mining sites, in combination with XRF-XRT scanning with a GeoCore X10 instrument.

Håkansboda historical mine site in Sweden was used as a case study to look at the potential for the combination of techniques.

The combination of the suggested randomized sampling strategy/protocol and the dataset from the GX10 scanning enables prediction of amenability for pre-processing with the use of mechanical sorting or if the extraction of valuable minerals only can be achieved through fine grinding, flotation or leaching.