Using total organic carbon for the assessment of groundwater vulnerability in karst regions at regional scales

Groundwater vulnerability is the likelihood of contaminants reaching the groundwater system after introduction at some location above the aquifer. The objective of this work was to investigate the relationship between total organic carbon concentration in groundwater and the intrinsic vulnerability of groundwater in karst areas at the regional scale. For this purpose hydrochemical data from 17 springs draining a Dinantian pure bedded Limestone rock unit were analysed to investigate their relationship with known parameters of groundwater vulnerability (e.g. degree of karstification, type of recharge). Statistical methods that could be useful to investigate such relationships are suggested. Principal components analysis showed the potential to visualise the relationships among hydrochemical data based on estimates of the median value. Multiple correspondence analysis was applied to visualise the relationship between total organic carbon and potential sources of organic carbon on the surface, a novel approach which has not been used in similar studies. Moreover, multiple regression analysis was used to determine the significance of these relationships. The results showed that, taking into consideration differences in background concentration, total organic carbon was significantly related to groundwater vulnerability.