Malin Norin

SCORE: A novel multi-criteria decision analysis approach to assessing the sustainability of contaminated land remediation

The multi-criteria decision analysis (MCDA) method provides for a comprehensive and transparent basis for performing sustainability assessments. Development of a relevant MCDA-method requires consideration of a number of key issues, e.g. (a) definition of assessment boundaries, (b) definition of performance scales, both temporal and spatial, (c) selection of relevant criteria (indicators) that facilitate a comprehensive sustainability assessment while avoiding double-counting of effects, and (d) handling of uncertainties. Adding to the complexity is the typically wide variety of inputs, including quantifications based on existing data, expert judgements, and opinions expressed in interviews. The SCORE (Sustainable Choice Of REmediation) MCDA-method was developed to provide a transparent assessment of the sustainability of possible remediation alternatives for contaminated sites relative to a reference alternative, considering key criteria in the economic, environmental, and social sustainability domains. The criteria were identified based on literature studies, interviews and focus-group meetings. SCORE combines a linear additive model to rank the alternatives with a non-compensatory approach to identify alternatives regarded as non-sustainable. The key strengths of the SCORE method are as follows: a framework that at its core is designed to be flexible and transparent; the possibility to integrate both quantitative and qualitative estimations on criteria; its ability, unlike other sustainability assessment tools used in industry and academia, to allow for the alteration of boundary conditions where necessary; the inclusion of a full uncertainty analysis of the results, using Monte Carlo simulation; and a structure that allows preferences and opinions of involved stakeholders to be openly integrated into the analysis. A major insight from practical application of SCORE is that its most important contribution may be that it initiates a process where criteria otherwise likely ignored are addressed and openly discussed between stakeholders.

Leaching of organic contaminants from storage of reclaimed asphalt pavement

Abstract Recycling of asphalt has been promoted by rapid increases in both the use and price of petroleum‐based bitumen. Semi‐volatile organic compounds in leachates from reclaimed asphalt pavement, measured in field samples and in laboratory column test, were analysed through a GC/MS screen‐test methodology. Sixteen PAH (polyaromatic hydrocarbons) were also analysed in leachates from the column study. The highest concentrations of semi‐volatile compounds, ‐ 400 μg 1‐1, were measured in field samples from the scarified stockpile. Naphthalene, butylated hydroxytoluene (BHT) and dibutyl phthalate (DBP) were the most dominant of the identified semi‐volatiles. The occurrence of these compounds in urban groundwater, also indicate high emission rates and persistent structures of the compounds, making them potentially hazardous. Car exhausts, rubber tires and the asphalt material itself are all probable emission sources, determined from the organic contaminants released from the stockpiles. The major leaching mechanism indicated was dissolution of organic contaminants from the surface of the asphalt gravels. In the laboratory column test, the release of high‐molecular weight and more toxic PAH was higher in the leachates after two years than at the commencement of storage. The concentrations of semi‐volatiles in leachates, were also several times lower than those from the field stockpile. These results demonstrate the need to follow up laboratory column test with real field measurements.

Organic contaminants in urban sediments and vertical leaching in road ditches

This is a study of the environmental impact of organic contaminants emitted from urban traffic and road infrastructure in Goteborg, Sweden. The vertical leaching of organic contaminants in road ditches, and the occurrence of organic contaminants in stormwater sediment, urban soil and shallow groundwater, have also been investigated. A total of 80 specific organic contaminants were analysed in the stormwater sediment sample, and of these as many as 40 specific organic contaminants were identified. The concentration of total semi-volatiles, alkylbenzenes, aliphatics, 4-nonylphenols, total of mono- and di-nonylphenol ethoxylates, carcinogenic US EPA polycyclic aromatic hydrocarbons PAH–16, diethyl hexylphthalate DEHP and several brominated flame retardants, were all analysed in high concentration. Depth profiles, in clay, clay/sand and sand road ditches, at four places along highway E20, were analysed for a total of 40 specific organic compounds. In the soil profiles, total semi-volatiles (< 2,300 mg∙kg-1dw) and carcinogenic PAH-16 (< 1.0 mg∙kg-1 dw) were identified in high concentrations. In one of the clay/sand profiles, total semi-volatiles were identified in decreasing concentrations but until a depth of 1 m, and the carcinogenic PAH-16 until 1.5 m. In reference surface soil samples, taken in the centre of Goteborg, total semi-volatiles and carcinogenic PAH-16 were also analysed in high concentrations. Even in the Goteborg urban shallow groundwater, total semi-volatiles (< 1400 μg∙l-1), and carcinogenic PAH-16 (< 0.4 μg∙l-1) were identified in remarkably high concentrations. The occurrence of total semi-volatiles and carcinogenic PAH-16 deep in road ditches, and the high levels in urban groundwater, show the need for efficient construction of road ditches or efficient treatment of road runoff water in urban and traffic-related areas to prevent contamination. The high levels of total semi-volatiles in all samples show that most of the contaminants occurring in urban environments are still unidentified compounds with unknown environmental effects. The relative composition of the specific PAH-16 indicates rubber tyres, vehicle exhausts and asphalt materials to be the main sources of PAH contamination.

Hydrochemical impact of construction of the western section of the Hallandsås rail tunnel in Sweden

This paper presents a study of the hydrochemical changes that took place during construction of a section of the Hallandsås rail tunnel in southwest Sweden based on monitoring from spring 2011 to summer 2012. Leakage into the tunnel during construction caused lowering of the groundwater levels, which in turn resulted in a decrease in or absence of base flow in the streams. The water in the streams became dominated by meteoric water during the drawdown periods. Meanwhile, wetlands were aerated, and oxygen could penetrate to oxidise reduced S, releasing acids and SO4. The results for the groundwater in the bedrock differed spatially depending on local geological conditions. In each of the three monitored boreholes, higher redox potentials, higher concentrations of organic matter and lower concentrations of dissolved Mn and Fe were observed. In two of the boreholes, oxidation of pyrite, FeS2, present as a fracture mineral, caused the formation of SO4 and acids with subsequent falls in pH and alkalinity. Leakage into underground constructions generally shortens the residence time of the groundwater significantly. Silicate weathering would thus become less important for the hydrochemistry compared to processes that occur during shorter time frames. As regards the durability of the tunnel, the hydrochemical changes observed in two of the three boreholes indicate a more aggressive environment for several parameters known to increase corrosivity of steel. The recovery of the groundwater levels occurred rapidly following completion of the waterproofing systems in the Tunnel. However, hydrochemical recovery with regard to major ions and pH occurred gradually and with an expected duration of several years.

Arsenic Contamination After Wood Impregnation: Speciation, Sorption and Leaching

In this project a site with arsenic (As) contamination from a former wood impregnation facility was investigated for total concentrations of As and As species, as well as other elements in soil, leachates and groundwater samples. Leaching of the As species from the soil and the effects of different environmental conditions on leaching were investigated. Extremely high As concentrations, up to 3,000 mg/kg in soil and 42 mg/L in groundwater, were identified in the close vicinity of the former impregnation barrel. Arsenate/As(V) was the dominant species in all soil, leachates and groundwater samples, but the concentrations of arsenite/As(III) were relatively high in the groundwater. The leaching tests revealed that vigorous mixing of soil in water as well as a reducing environment significantly enhances the leaching of all As species. The partitioning coefficients determined both in leaching tests and in the real-life groundwater environment showed that the As leachability is greatly underestimated in the standardizes laboratory test, especially for leaching of As(III).

Environmental emission impact from transport during soil remediation

The Swedish Environmental Protection Agency has identified more than 80 000 potentially contaminated sites in Sweden. One of these is the “former Hexion site” in Molndal, south of Gothenburg. The property was bought by the construction company NCC in order to build a new housing area. On the site industrial production has been performed for almost 200 years. The products have been chemicals, e g binders for the coatings industry and plastics additives like phthalates. Measured concentrations of pollutants exceed the EPA’s general guidelines on “sensitive land use” and a remediation is necessary.

Reactive soil barriers for removal of chromium(VI) from contaminated soil

The aim of this project was to find effective reactive materials as use in soil-bed barriers, for remediation of soil contaminated with chromium at Stallbacka industrial area in Sweden. Materials with different reduction/ adsorption capacities of Cr(VI)/Cr(III) were tested in laboratory and in a field pilot-scale experiment. Concentrations of total Cr and Cr(VI) in the soil, highly contaminated with ferrochrome slag, were exceeding the guideline values for contaminated sites in Sweden. Zero-valent iron (Fe0) filling, FeSO4 o7H2O, Na2SO3, field pine bark, modified pine bark, pine sawdust, and sphagnum peat were tested in batch or columns in mixture with the contaminated soil. All the materials, except peat, showed a good ability to reduce Cr(VI) in the batch experiments, and were chosen for further dynamic studies in columns. Iron sulphate and sodium sulphite were both shown to have a good ability to quickly reduce Cr(VI) in the columns, but the use might result in leaching of Fe and SO2- 4 to surface and groundwater. For field bark it took a longer time to reduce/ adsorb the same amounts of chromium, but it was functional for a longer time. Reactive soil-bed barriers were constructed in field: soil with embedded layers of FeSO4, pine bark underlying the soil, and soil without any reactive material layer. The iron sulphate was determined not to be suitable for the soil treatment, due to the high percentage of coarse materials in the soil texture, and thereby a quick washout of FeSO4 during the water infiltration. The field reactive soil barrier with pine bark was proven to be effective in reducing Cr(VI), and also had the capacity to adsorb both total and dissolved chromium leaching from the contaminated soil.