Reference conditions and threshold values for nitrate-nitrogen in New Zealand groundwaters.

ABSTRACT: Management of groundwater quality is assisted by an understanding of reference conditions, which describe the concentration ranges expected for key substances in the absence of human impact. This study evaluates reference conditions for NO₃-N in New Zealand groundwater based on three complementary methods: hierarchical cluster analysis, relationships to groundwater age, and regression against a measure of land-use impact. The three methods result in very similar national-scale estimates of reference conditions for NO₃-N concentration in oxic, minimally impacted groundwater, with the 80th, 90th and 95th percentiles found to be 1.65 ± 0.12, 1.97 ± 0.14 and 2.32 ± 0.14 mg/l, respectively (weighted average ± 95% confidence level), in good general agreement with previous s

SUBMITTER: Daughney CJ 

PROVIDER: S-EPMC11619017 | biostudies-literature | 2025

REPOSITORIES: biostudies-literature