In Boden, northern part of Sweden, there is a site called Solgårdarna which has been used for wood impregnation. The activities on the site have led to soil contamination with chrome (Cr), copper (Cu) and arsenic (As), where the arsenic contamination is the most problematic. This master’s thesis has studied the possibility to stabilise As in-situ with iron (Fe). The aim of the thesis was to investigate how well the distribution of Fe in the soil with the help of electrokinetics occurs. The work was divided into 3 parts, where part 1 and part 2 were performed in the laboratory and part 3 was performed in field. Part 1 investigated how Fe can distribute depending on how the electrodes were connected. This was done using quartz sand so visual assessment of the distribution could be done. Part 2 used the results from part 1 for a similar experiment performed on soil from Solgårdarna to see how stabilisation of As in the soil will work. Part 3 was a field test at Solgårdarna where it was tested on a pilot scale. Part 1 of was performed in two sets, 7 days each. It showed that it is possible to spread iron in the sand with the help of this method. The sand experiments achieved a covering area of 27 % respectively 28 % of rust over the entire profile during one week. Measurement with the XRF showed that where the electrode had been located the concentration of Fe increased up to 0.21-0.29 % and the concentration of Fe between the electrodes were 0.04-0.06 %. Part 2 of the experiment was performed in one setup over a 51-day period, after day 35 the experimental setup was changed due to highly fluctuating pH. The results from the experiment with soil showed that the pH is highly affected by how long the electrodes close to the sampling points were anodes or cathodes. During the experiment, a general trend for increasing As concentration in the different locations in the cell were seen. After the experiment the leachable amounts of As decreased down to 0.8-1.7 mg/kg TS compared to the untreated soil, 2.9 mg/kg TS. Part 3 of the experiment represent a 2-month field pilot test period during the autumn. Towards the end of the sampling period there was a general decrease in dissolved As and Fe in the groundwater, during the same time the groundwater level decreased, the redox potential increased and the electrical conductivity decreased. The laboratory experiments with the sand showed a removal rate around 90 % or higher, which is a good result. Those experiments were however performed using a clean inert material which is not comparable with real conditions. The field experiment was done over a short period of time due to time limitations of this thesis, while follow up of the pilot test was done within the scope of a continued research project at LTU. The given results showed a decrease in dissolved arsenic in groundwater which is a positive result. To determine whether the decrease is due to the natural adsorption of As to soil or due to the impact of provided Fe oxides requires longer monitoring of the experiment.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-88206 |
| Date | January 2021 |
| Creators | Engström, Kajsa |
| Publisher | Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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