Undersökning av bensenförorening i grundvatten, Norra Djurgårdsstaden, Stockholm : JB- sondering, installation av grundvattenrör samt provtagning med passiv diffusionsprovtagare

Sammanfattning: Norra Djurgårdsstaden is an urban area in northeastern Stockholm and has been soil remediated down to the water table. The contamination in the area includes polycyclic aromatic hydrocarbons (PAH), cyanide, heavy metals and BTEX. In 2003 an extensive environmental assessment initiated after which they found high levels of benzene in one of the groundwater monitoring wells. The benzene contamination in groundwater was followed up with an in-situ attempt to remove it, but the method had low efficiency. The aim of this study was to try to investigate a possible contamination source of benzene and determine the contamination plume in groundwater. The thesis would also contribute with new knowledge of a new sampling methodology. The methodology of the thesis work was one part literature study and theory, one part of field work and another part of evaluation the results. After a sampling plan based on the area's geology was established the soil-rock penetration test was performed and then two new groundwater monitoring wells were installed. During the soil-rock penetration test, samples were taken out in the steel probe of the groundwater water. Sampling was carried out as an initial screening in the area in order to get a picture of the extent of benzene contaminated groundwater. After the installation of groundwater monitoring wells, they were sampled for benzene analysis with traditional groundwater sampling and passive diffusion sampling. The sampling methods were then compared statistically and methods were also evaluated in a literature study. Generally, the analyzed samples gave high benzene concentrations in the monitoring wells that also have had high concentrations before. Traditional sampling gave the highest levels, while the passive sampler was more efficient to detect low benzene concentrations. The passive sampling detectable benzene levels in more monitoring wells than at the traditional sampling. The results showed that the groundwater is contaminated with benzene at levels above SPIMFABs general guidelines for the protection of surface water and protection against vapor intrusion. The benzene concentrations in the area were diffuse and no clear source of contamination could be identified. Statistically, the sampling techniques were different, but the passive samplers still seems to follow the same pattern as sampling with traditional sampling. More data are needed to do reliably statistically evaluations of the method. The passive sampler has many advantages over the traditional sampler regarding volatile organic contaminants, such as benzene. Measurements of benzene in the gas phase were performed with PID in all the field work. It generally showed low levels of benzene. Based on the topography, bedrock levels and groundwater flow in the area, it is believed that the encountered contamination is relatively local around the points where it was originally found. The groundwater flow shows no clear direction and the superficial groundwater reservoir is connected with Husarviken and Saltsjön/Värtan.