Appendix 12: NOF Environmental Limits for Attributes for Freshwater Boffa Miskell Ltd | Waihi North Project: Freshwater Ecological Assessment | [Subject] Table 12-2: Environmental limits for nitrate toxicity (as nitrate-nitrogen) for ecosystem health values in freshwater in New Zealand (from NPS-FM 2020). Table 6 – Nitrate (toxicity) Value (and component) Ecosystem health (Water quality) Freshwater body type Rivers Attribute unit mg NO3 – N/L (milligrams nitrate-nitrogen per litre) Attribute band and description Numeric attribute state Annual median Annual 95th percentile A High conservation value system. Unlikely to be effects even on sensitive species. ≤1.0 ≤1.5 B >1.0 Some growth effect on up to 5% of species. and ≤2.4 >1.5 and ≤3.5 National bottom line 2.4 3.5 C Growth effects on up to 20% of species (mainly sensitive >2.4 species such as fish). No acute effects. and ≤6.9 >3.5 and ≤9.8 D Impacts on growth of multiple species, and starts approaching acute impact level (that is, risk of death) for sensitive species at higher concentrations (>20 mg/L). >6.9 >9.8 This attribute measures the toxic effects of nitrate, not the trophic state. Where other attributes measure trophic state, for example periphyton, freshwater objectives, limits and/or methods for those attributes may be more stringent.
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