She recently completed her PhD studying the process of denitrification on four South Island estuaries, the pristine Tautuku in the Catlins and the less pristine Waikouaiti, Tokomairiro and the Avon-Heathcote near Christchurch.
Estuaries trap sediments and nutrients from land before they are carried to the coast and then return the nitrogen to its stable form back into the atmosphere, she said.
"Bacteria in estuary sediments naturally remove nitrogen from land, much like sewage treatment plants that strip nitrogen out of sewage before it is discharged at sea."
It could also release the environmentally harmful nitrous-oxide gas, which was 310 times more potent than the greenhouse gas CO2.
In a first, she also measured and compared the amount of the gas released in the more pristine catchment (Tautuku) with the other estuaries which were more affected by urban and farm run-off.
Dr Gongol found Tautuku produced "minuscule" amounts of nitrous oxide. the Avon-Heathcote produced gas at levels eight times greater.
The three estuaries more affected by human activity were still relatively efficient at performing denitrification, but Tautuku was "slightly more efficient".
The environmental message from her work was clear, she said.
"Lowering the nutrient loading in estuaries would be a way to reduce the amount of nitrous oxide being produced."
She hoped her research would enable others to make decisions about the management of their ecosystems.
However, nutrient levels in New Zealand estuaries were low compared to those in Europe or North America where populations were much greater, she said.
