Pollution source delineation of emerging organic contaminants in groundwater using cumulative distribution functions

A statistical approach that utilises cumulative distribution functions (CDFs) has proven effective for establishing threshold values that can be used to identify and delineate potential contamination sources in groundwater studies. Although this approach has been widely applied in the hydrogeology field, its application to understand sources of emerging organic contaminants (EOCs) in groundwater research has not yet been explored. This study used CDF approach to establish local EOC threshold values. As a novel approach, established local EOC thresholds were compared against conventional tracers such as Cl, NO3, and Cl/Br ratio to delineate contamination sources. The estimated threshold values for atrazine, bisphenol A, carbamazepine, and caffeine were 0.0032 µg/L, 0.033 µg/L, 0.0054 µg/L, and 0.01 µg/L respectively, and were linked to sites with anthropogenic influence. Most groundwater samples collected near residential areas were characterised by Cl/Br mass ratio < 88, placing them under a type 1 water based on Cl vs NO3 relationships, indicating less contamination. These samples, however, displayed atrazine, bisphenol A, and carbamazepine concentrations above the estimated threshold suggesting influence by runoff from domestic and agricultural emissions. Groundwater samples from areas near mine tailings, mineral processing, and paper manufacturing plants were classified as type 2 water likely reflecting industrial and domestic discharge and mining influences. These sites also displayed high bisphenol A and caffeine concentrations. The identified EOC threshold values have potential applications to assess anthropogenic pollution at local level. This type of approach could be extended and form the basis for developing regional thresholds for better water resource management.