To date, no baseline assessment of emerging organic contaminant (EOC) occurrence in New Zealand groundwaters has been undertaken. Recognition of the significance of EOC in NZ groundwaters is increasing but analytical capability remains limited. EOCs comprise an increasing number of compounds originating from a range of origin and use. EOCs ubiquitous occurrence in groundwater has been demonstrated in numerous International studies. The impact of EOCs on freshwater quality, human and aquatic health is yet to be characterised for most compounds. Where negative impact has been demonstrated, EOCs are selectively banned or restricted.
To inform future monitoring, we conducted the first regional EOC baseline survey in New Zealand groundwater using a novel sampling design: State of Environment (SOE) monitoring sites were selected randomly from a groundwater mean residence time (MRT) stratified site list. Forty-seven SOE sites representing young (1-11 yrs MRT), intermediate (11-50 yrs MRT) and old (50-250 yrs MRT) groundwaters were screened for a wide EOCs suite (723); including ten targeted sites located close to known EOC sources for comparison.
Five EOC categories were detected at 91% of the SOE sites: pesticides (48 compounds), pharmaceuticals (11), industrial (10), preservatives/food additives (3) and personal care products (1). EOC concentrations ranged from 0.1 to 11000 ng/L and were generally lower that those reported in overseas groundwaters. Concentrations above the EU maximum admissible concentration for total pesticides (100 ng/L) were measured at 28 SOE sites. Young groundwater exhibited higher EOC concentrations and a wider range of compounds, however detections occurred in all MRT groups.
Seven EOC categories were detected at targeted sites. The two categories found only at targeted sites were drugs of abuse and life-style compounds. Concentrations ranged from to 0.2 to 14000 ng/L. Pesticide concentrations were generally lower at SOE sites than at targeted sites, but concentration of other categories were higher at targeted sites.
The survey results were used to: review current pesticide monitoring; propose complementary monitoring; identify potential EOC groundwater tracers and identify compounds for which cost-effective New Zealand laboratory capability is needed.