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Keeping a watch on freshwater contaminants

Emerging Organic Contaminants are a recently-recognised class of chemicals that can affect freshwater quality, and human and aquatic health.

People walking on boardwalk past pond. Photo: Margaret Low

Contaminant types include pesticides, pharmaceuticals and industrial compounds. Photo: Margaret Low


“This is definitely a great piece of work that is going to be very useful for informing further work in this area.”

John Caldwell, Senior Scientist for Science and Strategy, Waikato Regional Council


Our groundwater team partnered with the Waikato Regional Council and the British Geological Survey to examine aquifers in the Waikato. The pilot project sampled more than 50 bores throughout Waikato, testing for the presence of these contaminants. 

The contaminants are natural or manufactured chemicals that are commonly found in household and personal care products, pharmaceuticals and agrichemicals. They are classed as ‘emerging’ as a result of improved analytical techniques and better monitoring. Our survey provides the first region-wide measurement of these contaminants in New Zealand groundwater to inform future monitoring beyond standard tests for pesticide presence.

The Waikato pilot survey screened groundwater samples for the presence of 723 compounds to establish a baseline and to inform future monitoring regimes. Seventy-three compounds were detected at 91% of sites, with rates ranging between one and 31 compounds per site. Twentyeight compounds were measured at concentrations above the EU maximum admissible levels for total pesticides for drinking water. 

Dominant contaminant types identified include pesticides, pharmaceuticals, industrial compounds, preservatives/food additives, and personal care products. Concentrations were similar to those found in groundwaters overseas, where regulatory organisations are placing restrictions and bans on the use of selected contaminants. 

GNS Science now wants to extend the survey to other regions in New Zealand. Our groundwater scientists anticipate there will be regional differences in contaminant makeup and concentrations based on land use and the mix of industries in particular areas.