Oskarshamn site investigation. Monitoring of shallow groundwater chemistry 2009

In 2009 sampling of shallow ground water in water wells in soil has been performed in a regular programme at eight sites within the site investigation area at Oskarshamn. The purpose of the activity is to monitor (long term observation) and characterise the shallow ground water in the site investigation area. Some physical and chemical parameters were measured directly in the field but most parameters were analysed at different laboratories. The ground water sampling activity consisted of one programme, chemical programme class 5 (reduced). The large number of sites and parameters analysed have generated a large amount of data, which will later be used for advanced analysis and modelling. In this report the evaluation aims to give a simple overview of the results and to describe the quality of the data sampled 2009. As an addition radon activity was measured at fourteen sites in the area. Seven of these sites were the same as in the regular programme. The results showed a large variation between the wells. The concentrations of major ions and conductivity ranged from low to high or very high values. The concentration of HCO3 also varied extensively throughout the investigation area, but since the concentrations were above 60 mg/l in most wells the results indicate a good ground water quality with respect to acidification. The concentration of heavy metals and trace elements also varied. High concentration of Pb in some of the wells indicated pollution. Since Pb had a similar relation to Al as most other elements it was argued that high concentrations of lead probably can be explained by the natural composition of minerals within the site investigation area. The ratio of δ18O showed a good relationship with the conductivity. The activity of tritium (3H) was markedly lower in two of the wells. This might be an indication of older groundwater in these wells. The average hydrogen isotope ratio of deuterium (δ2H) varied with similar values in most wells. The δ2H ratio correlates reasonably well with the δ18O ratio but the linear relation differ markedly from the 'Global Meteoric Line' (δ2H = 8xδ18O+10) which is based on precipitation data. The concentration of NO3-N varied to some extent between the wells but according to the Swedish Environmental Quality Criteria the concentration was very low. The concentration of NH4-N and PO4-P varied with markedly higher values in some of the ground water wells. The site SSM000241 differed even more with extremely high values of NH4-N and PO4-P. The concentration of carbon (TOC and DOC) varied with low to moderately high concentrations in most wells. Again the well SSM000241 differed with very high concentrations.