Nitrate contamination in New Zealand's domestic drinking water with a focus on rural groundwater-sourced self-supplies

作者：Karyne M. Rogers, Diane Bradshaw, Phil Scadden, Conny Tschritter, Stuart Sanderson, Jannine Cooper, Andy Phillips, Jennifer Pannell, Julia Thern, Steve Abel, Michael Joy, Xing Liu, Tim Chambers · 发表于：The Science of The Total Environment · 年份：2025 · DOI：10.1016/j.scitotenv.2025.180549 · 被引用次数：8 · 研究领域：Soil and Water Nutrient Dynamics

Nitrate contamination is a major threat to freshwater quality with serious implications for ecological and human health. We report on New Zealand's largest drinking water nitrate investigation with more than 3800 samples collected nationally between 2022 and 2024. New Zealand's drinking water standards (NZDWS) do not require chemical testing of domestic rural groundwater self-supplies (from bores and springs), so are more vulnerable to nitrate contamination due to reliance on shallower groundwater and proximity to livestock in rural areas. This study overwhelmingly confirms that Canterbury has the largest percentage of elevated groundwater nitrates in New Zealand. NZDWS has a maximum acceptable value for nitrate‑nitrogen (MAV of 11.3 mg/L NO 3 -N) which was exceeded in 6.8 % of rural samples from Canterbury, while 43.1 % exceeded ½ MAV (5.65 mg/L NO 3 -N). Waikato and Southland (each with 15.0 % and 39.9 % of samples exceeding ½ MAV, and 2.9 % and 4.6 % exceeding MAV, respectively) had the highest maximum nitrate values (34.0 and 140 mg/L NO 3 -N). The national database also signals emerging regions of concern, including Bay of Plenty, Hawke's Bay, Taranaki, Manawatū-Whanganui, Wellington, Nelson, Tasman and Otago with 9.4 % to 24.5 % of samples exceeding ½ MAV, and up to 7.5 % exceeding MAV. Using a dual nitrate isotope approach ( δ 15 N NO3 and δ 18 O NO3 ), dairy effluent is identified as a primary cause of high nitrate levels found in these groundwaters. In this nationall...