I Sverige förekommer det sura sulfatjordar som är resultatet av när sulfidrika sediment, som avsattes för 4000 – 7000 år sedan, introduceras i en oxisk miljö. Sedimenten avsattes i botten av Litorinahavet främst längs östkusten samt Mälardalen i anaeroba förhållanden där sulfider kunde bildas. När dessa sulfider kommer i kontakt med syret i atmosfären vittar sulfiderna och medför en pH sänkning. Detta påskyndas av en antropogen påverkan samt en pågående landhöjning som förekommer i Sverige. Ett lågt pH medför att toxiska metaller kan bli mobila och utlakas till miljöer där de kan medföra stora konsekvenser. I anläggningsprojekt deponeras stora volymer sulfidjordsmassor varje år, som ett resultat att de är försurande samt har en hög sättningsbenägenhet. Detta medför flera kostnader i byggprojekt för deponi, transport och nytt utfyllnadsmaterial. Som en följd motverkar detta ett cirkulärt samhälle när jordens resurser deponeras istället för att återvinnas och återanvändas. Skanska har beslutat om ett mål, att samtliga verksamhetsgrenar ska uppnå s.k. klimatneutralitet vid år 2045. Att framtida kunna återvinna och återanvända sulfidjord kan vara ett bidrag för Skanska att uppnå detta mål genom minskade transporter och återanvändande istället för att deponera sulfidjord och vid anläggningsarbeten tillföra jungfruligt material. För att neutralisera sulfidjord kan olika material användas som förhöjer jordens alkalinitet och motverkar försurningen från oxidationen. Två sådana material är bränd kalk och bioaska som är de två material som jämförs i detta arbete, för att se hur kvalitén på porvattnet samt växtetableringen påverkas av respektive tillsats. För att kontrollera sammansättningen av provattnet samt växtetableringen utfördes flera laborationer, kontroll av torrsubstans, glödförlust, lakförsök, bestämning av mängd buffert, kontroll av vattenhållningskapacitet, återväxtförsök, ämnes analys av porvatten och en beräkning för att uppskatta hur länge den behandlade sulfidjorden bör kunna buffra systemet mot syror.   Vanlig planteringsjord tillät bäst växtetablering och den obehandlade sulfidjorden var den jord som medförde sämst växtetablering. Porvattnet hade högre pH, kring neutralt, än initialt pH för den obehandlade sulfidjorden som var kring pH 4,5. Flera ämnen återfanns i lägre halter i porvattnet för sulfidjorden som har behandlats jämfört med den obehandlade, med vissa variationer. Porvattnet i sulfidjorden som behandlats med bioaska hade högre halter av flera ämnen jämfört med sulfidjorden som behandlats med bränd kalk, framförallt höga nivåer av arsenik samt svavel. Slutsatsen är att båda sulfidjordsblandningarna uppskattas kunna buffra systemet i mer än 10 000 år. Tillsammans med halterna i porvattnet förespråkar resultatet att det finns goda förutsättningar till att behandla sulfidjord och återanvända i olika projekt. Vidare forskning krävs till att optimera ett förhållande mellan mängd tillsatser samt mängd sulfidjord. Skanska bedöms ha goda förutsättningar till att arbeta vidare och kunna etablera en eller flera återvinningsanläggningar i landet för sulfidjord. / In Sweden there are acid sulphate soils that are the result of when sulphide rich sediments, deposited 4000 – 7000 years ago, enters an oxic environment. The sediments deposited at the bottom of the Littorina sea mainly along the east coast as well as Mälardalen in anaerobic conditions where the sulphide could precipitate. When these sulphides get in contact with the oxygen in the atmosphere weathering occurs where the reaction lowers the pH. The rate is increased due to anthropogenic actions along with land rise which occurs in Sweden. Low pH contributes the toxic metals can become mobile and leach to other environments where they could do significant damage. In construction projects, large volumes of sulphide soils are deposited at landfills annually, due to the soil being acidifying as well as the soil often have a high tendency to settle. This entails several costs in constructions projects for landfill, transport and new filling material. As a result, this offsets a circular society when natural resources are landfilled rather than reused. Skanska has decided on a goal, that all branches in their network should achieve climate neutrality by 2045. Recycling and reusage of the sulphide soil would help Skanska to achieve this goal by reduced transport and reusage of the soil instead of outsourcing for virgin material. To neutralize sulphide soils, various materials can be used as buffers that increases the alkalinity of the soil and counteract the acidification from the oxidation. Two possible materials that could achieve this is quicklime and bio-ash, which are the two materials that are compared in this work to see how the porewater quality and plant establishment are affected by the additive. In order to analyse the difference in porewater quality and plant establishment between the two additives, several laboratory works were conducted. Control of dry matter, loss of ignition, batch leaching test, determination of the amount of buffer needed to buffer the soil mixture, control of water holding capacity, growth rate test, analysis of porewater and estimation of buffer capacity. Ordinary topsoil allowed the best plant establishment and the untreated sulphide soil had the worst plant establishment. The porewater from the treated sulphide soil mixtures had a higher pH, around neutral, than the initial pH of the untreated sulphide soil, which was around pH 4,5. Several substances in the porewater had lower concentrations in the treated sulphide soil compared to the untreated, with some variation. The porewater from the soil mixture with the additive bio-ash had higher concentrations for several substances than the sulphide soil that have been treated with quicklime, especially high levels of arsenic and sulphur. The conclusions are that both sulphide soil mixtures have been estimated to be able to buffer the system for over 10 000 years. Together with the porewater properties it suggests that there are great prerequisites to treat and reuse sulphide soil. Although, a more optimum recipe for the ratio of sulphide soil, buffer and stabilizer is required. Skanska is considered to have excellent prerequisites to establish recycling facilities for sulphide soil.

This thesis project was carried out by two students on behalf of SMA Mineral AB, which owns the lime plant in Rättvik, where there was need to establish a sampling method for the local quick lime product. The aim was to ensure a maximum concentration of impurities in the product—primarily carbon and sulphur. The mean value of sulphur found in the input material varied over time. Consequently, a suitable statistical method was needed to ensure product quality for the prospective customer as they required that the sulphur content of the proposed product never exceed 500 ppm.The aim was, on the one hand, to process and compile the sampling results in accordance with a suitable statistical method which enabled reasonable conclusions about the product quality and, on the other hand, to answer three key queries that SMA Mineral AB posed:• to investigate whether the product’s sulphur content was affected during conveyance through the lime plant;• to investigate whether sampling at various time intervals may have been a factor which affected the product’s sulphur content;• to investigate whether there was, or were, any particular times of day at which the sulphur content always maintained the correct level.A number of phases were required to find answers to these questions. The planning phase was initiated by a visit to Rättvik, with the purpose of gaining an overall picture of how work at the plant was conducted as well as which guidelines and regulations were in effect. After this visit, a project plan was drawn up in order to serve as support for further work.The sampling campaign took place during the period of 13–16 April 2015 and analysis of the collected material was carried out the following week at the company’s laboratory in Persberg, Sweden. However, the results from the sampling campaign did not provide sufficient basis for answering the company’s questions, which is why data from SMA Mineral AB’s own data collection was used. Data collected during the sampling campaign proved to follow normal distribution. Subsequently, the statistical analysis of variance method, ANOVA, was applied in order to investigate whether the sulphur content changed with respect to the time interval and the sampling site. The test results demonstrated p-values under 0.005, which meant that neither the sampling site nor the sampling time intervals had an effect on the product’s sulphur content. The company’s question, whether there were daily time intervals of acceptable sulphur content in the product, was answered with the assistance of the company’s own data collection, which demonstrated that it did not follow normal distribution. For that reason, the bootstrap method was used to create confidence intervals for the different points in time. The result showed that there were no points in time during which acceptable material was produced. One reason for this is the occurrence of a set of deviating values that were observed to have a sulphur content that exceeded 1,000 ppm. This report presents recommendations for various measures independently of any opinions SMA Mineral AB may have concerning the source of these values and whether they can possibly be avoided. / <p>Validerat; 20160612 (global_studentproject_submitter)</p>