Swedish Geotechnical Institute

Sea level rise is a key effect of modern climate change. The ~500 km-long Scania coastline is uniquely sensitive within Sweden to sea level rise (SLR) because it is mostly formed of sediments and its low-lying topography hosts extensive built environments. Swedish municipalities are legally obliged to include climate- and erosion-related risks in their spatial planning. However, it is a challenge for coastal municipalities to fully comply with the legal requirements because the scientific basis is currently difficult to interpret for coastal adaptation to sea level rise and there is still limited research describing the effects of sea-level rise on erosion along Swedish coasts. Our research is addressing these shortcomings through: (i) developing physical process-based predictions of erosion driven by sea level rise for the Scania coastline; and (ii) alongside end-users, co-creating an understanding of how erosion predictions are best communicated to make them accessible, actionable and relevant from the end-user’s perspective. Key challenges to predicting coastal response to sea level rise in southern Sweden include complex topography, varying wave and sediment conditions, and limited material supply. Because of shortcomings in the scientific understanding of SLR-driven coastal erosion, we take an ensemble approach that combines deterministic and probabilistic methods. Our preliminary modelling has focused on translation of equilibrium profiles of different shapes to estimate erosion. We find that a gradual increase in sea level, where the translated profile at the previous time step is used as input to the next step, induces more erosion than an instantaneous shift over the total sea level rise, because more material is deposited in the offshore during this iterative procedure. Our modelling of shoreline responses is being further developed and predictions of coastal response to sea level rise, including analyses of probabilities, will be communicated to our end-users using a GIS platform.

Groundwater contamination by per- and polyfluoroalkyl substances (PFAS) is an emerging threat to drinking water quality, highlighting the need for effective treatment solutions. This study investigated subsurface flow constructed wetlands for treating groundwater contaminated with PFAS. The wetlands used a peat, biochar, and lightweight expanded clay aggregate (LECA) filter substrate, planted with either tufted sedge (Carex elata), fiber hemp (Cannabis sativa Futura 75), or an intercropping of the two Salix clones S. Wilhelm and S. Loden. The experiment was conducted under field conditions in Sweden, during one growing season, using PFAS-contaminated groundwater impacted by landfill leachate. The study showed accumulation of PFAS in all plant species and the peat and biochar part of the filter substrate, with short-chain PFAS and perfluoroalkyl carboxylates (PFCAs) dominating when considering the whole plants (57% and 77% of ƩPFAS, respectively) and long-chain PFAS and perfluoroalkyl sulfonates (PFSAs) dominating in the peat and biochar filter substrate (77% and 54% of ƩPFAS, respectively). Sorption to the filter substrate was shown to be the primary mechanism for PFAS removal. The highest plant PFAS concentrations were found in leaves, followed by roots, for all species. There was a difference in the PFAS composition profile when comparing different plant tissues, with PFCAs dominating in leaves (84% of ƩPFAS) and PFSAs dominating in roots (66% of ƩPFAS). All plant species were determined to have an above-ground tissue/water phase concentrations >10/1 for C3-PFCA (PFBA). This was also observed for C. sativa with C4- and C7-PFCAs (PFPeA, PFOA), and C4- and C5-PFSAs (PFBS, PFPeS), for C. elata with C8-PFSA (L-PFOS), and for S. Loden with PFPeA. ∑PFAS phytoextraction potential from landfill leachate-impacted groundwater (mg/ha yr) was estimated to be 940±670 for C. sativa, 390±310 for S. Loden, 330±160 for S. Wilhelm, and 160±56 for C. elata.

ABSTRACT Achieving climate-neutral building construction requires a comprehensive understanding of the climate impact of all relevant building elements, including geotechnical works. However, research on life cycle assessment (LCA) of geotechnical works in building construction remains limited. This study conducted a ‘cradle-to-handover’ LCA of geotechnical works for a 36-storey office building situated on soft clay in Sweden. Using project-specific data and the European Product Environmental Footprint (PEF) method v3.1 in SimaPro v9.6.0.1, the geotechnical works (modules A1–A5) contributed a climate impact of 121.1 kg CO2 equivalent (CO2eq) per square metre (m2) of gross floor area (GFA). This accounts for approximately 23.9% of the total climate impact during the construction stage, assuming the superstructure meets the proposed national-level limit value of 385 kg CO2eq/m2 GFA in Sweden. The three main contributors to the total climate impact of the geotechnical works were steel piles (64.9%), concrete piles (22.3%) and sheet pile walls (9.9%). The results highlight the need to incorporate geotechnical works into decarbonization strategies for building construction, particularly in challenging soil conditions. Furthermore, the study underscores the importance of fostering more effective communication among stakeholders to drive sustainability efforts throughout the building construction stage.

Nature-based solutions (NBSs) offer an opportunity to address environmental and societal challenges worldwide while simultaneously providing benefits for human well-being as well as biodiversity. Despite a growing demand and evidence base for NBSs in coastal systems, the scaling of their implementation and mainstreaming of their principles in policy and practice are constrained by multiple barriers, such as misinterpretations of concepts, effectiveness, or locked-in preferences or conventions of traditional solutions. To address these constraints, an international consortium of coastal authorities and experts in the North Sea Region collaborates to validate, document, and share learnings of NBSs to establish a framework for mainstreaming NBSs for flood and coastal erosion risk management around the North Sea. Co-creation processes of workshops, field visits, and expert knowledge sessions contributed to a theoretical framework and baseline assessments of exemplary sandy and muddy case study sites in the region, amongst others, iteratively providing and showcasing building blocks for the mainstreaming framework. This article takes stock halfway of the project’s activities, learnings, and status of the called-for common language.

In this paper, some results from an on-going project regarding long-term properties of in situ lime-cement stabilized columns of clay, are presented. In the field, core sampling and pillar sounding were performed on 30 years old columns at the test site Håby in Sweden. In the laboratory, strength tests and accelerated leaching tests on the core samples were conducted. For the leaching tests and the strength tests respectively, newly developed equipment was used. The results show a possible strength increase with time and the new equipment seem to work well.

Scenario analysis is a widely employed method for addressing uncertainties when assessing the physical and socio-economic impacts if climate change. Global scenarios have been extensively used in this context. However, these scenarios are in most cases not suitable for supporting local analyses. On the other hand, locally developed scenarios may lack the global context, thus having limited comparability with or transferability to other locations. The Shared Socioeconomic Pathways, which have been primarily developed for climate impact research, provide the possibility to extend the existing global narratives and adapt them to local characteristics in order to develop locally relevant scenarios. Here, we propose a methodological framework for producing harmonized scenarios across different case studies. This framework was developed in the EVOKED project and combines elements of top-down and bottom-up approaches to develop local scenarios for five regions in northern Europe. We employ the SSP as boundary conditions and, in cooperation with stakeholders from these five regions, develop local scenarios for a range of SSP. The developed sets of scenarios are consistently informed by global developments and are therefore comparable with other downscaled scenarios developed in different regions. At the same time, they have been based on local participatory processes, thus being locally credible and relevant to the needs of stakeholders. The local scenarios constitute a climate service per se as they can raise stakeholder awareness of the processes that will drive risk, exposure, and adaptive capacity in the future and inform discussions on mitigation strategies and adaptation pathways.

Arsenic (As) is carcinogenic and of major concern in groundwater. We collected sediment material from a contaminated anoxic aquifer in Sweden and investigated the immobilization of As by four commercial zero-valent iron (ZVI) particles. Solid-phase As and Fe speciation was assessed using X-ray absorption spectroscopy (XAS) and solution-phase As speciation using chromatographic separation. Without ZVI addition, arsenite dominated in solution and As(V) species in the solid phase. Adding ZVI caused a sharp increase in solution pH (9.3–9.8), favoring As oxidation despite a lowered redox potential. ZVI greatly improved As retention by complex binding of arsenate to the Fe(III) (hydr)oxides formed by ZVI corrosion. Uncoated ZVI, both in nano- and microscale, performed better than their sulfidated counterparts, partly due to occlusion of As by the Fe(III) (hydr)oxides formed. The effect of particle size (micro vs. nano ZVI) on As immobilization was small, likely because immobilization was related to the corrosion products formed, rather than the initial size of the particles. Our results provide a strong geochemical background for the application of ZVI particles to remove As in contaminated aquifers under anoxic conditions and illustrate that immobilization mechanisms can differ between ZVI in As spiked solutions and sediment suspensions. Environmental implicationArsenic ranks first on the list by the US ATSDR of substances posing a threat to human health and the WHO considers groundwater the riskiest source for human intake of As. However, dealing with As contamination remains a scientific challenge. We studied the immobilization of groundwater As by commercially available ZVI particles at field-realistic conditions. Arsenic immobilization was highly efficient in most cases, and the results suggest this is a promising in situ strategy with long-term performance. Our results provide a strong geochemical background for using ZVI to remove As in contaminated anoxic aquifers.

Soil improvement using cementitious binders is used throughout the world to improve the strength and stiffness characteristics of soft soils. Strength verification is typically performed using unconfined compression tests; however, these are destructive and do not give detailed information on strength development over time. This note presents a laboratory investigation using the non-destructive resonant column free-free (RC-ff) technique to assess the primary wave velocity. This velocity is correlated to strength, and hence strength development over time can be investigated in detail using this simple and effective technique. Two soft clays, one inorganic and one organic, were improved with the industrial by-products cement kiln dust and ground-granulated blast-furnace slag in combination with cement. A semi-theoretical correlation between primary wave velocity and strength is proposed, and it is seen that this correlation is independent of these soil and binder types. This also applied to the seismic small-strain compressive modulus. The strength development up to 91 days of curing was investigated and it was seen that this highly depends on binder type, but to a lesser degree soil type. It is demonstrated that the RC-ff technique can be of great value both in engineering practice and research.