Risk assessment of Pursiala groundwater area in poor chemical state

Abstract

The population in Finland relies heavily on the aquifers as a source of potable water. The aim of the project was to understand if the industrial activities have caused a deterioration of the groundwater quality of the Pursiala aquifer and to study if the use of groundwater at Pursiala may cause significant health risks to the local people. The literature review focused on some methods used to manage a contaminated site/groundwater and on the characteristics of the chemicals of interest. The Master's Thesis dealt with two areas around a sawmill and a wood impregnation plant, which, respectively, have caused a discharge of chlorophenols (CPs) and polycyclic aromatic hydrocarbons (PAHs) in the groundwater. The study of the aquifer vulnerability was conducted with the DRASTIC method, which gives as result the DRASTIC vulnerability index (DVI). As a result, the higher is the index, the higher is the vulnerability. The maximum DVI values of 175.9 (CPs) and 180.2 (PAHs) indicate that the aquifer is very vulnerable. The dispersion of the contaminants in the aquifer was analyzed using a Danish preliminary risk assessment tool named GrundRisk. Monitoring data collected from years 2004-2013, for each chemical detected in the source area in the aquifer, were considered for the simulations in GrundRisk. In the case of PAHs, the simulations showed an excess of the groundwater guidelines (for drinking-water) at the point of compliance for only benzo(a)pyrene. The assessment of risks caused by CPs was based on the concentrations detected in the groundwater monitoring wells located in the sawmill area. All the concentrations were above the groundwater guidelines. Based on these results, a human health risk assessment was executed on the two groups of chemicals. The sum of the Hazard Quotients HQs gave a maximum Hazard Index HI of 460.1 and 54.3 for, respectively, CPs and PAHs. To summarize, the DRASTIC method and the GrundRisk tool showed the high vulnerability of the Pursiala aquifer and the negative impact of the industrial activities on the groundwater quality. Because the acceptable level for non-carcinogenic risks is HI=1, the industrial activities cause a threat to human health. It is therefore recommended to execute further investigations and remedial actions. Lastly, the simulations gave almost similar concentrations than those documented in the POVET database, which shows that GrundRisk is applicable to the preliminary risk assessment of groundwater contamination.