Appendix 12: NOF Environmental Limits for Attributes for Freshwater Boffa Miskell Ltd | Waihi North Project: Freshwater Ecological Assessment | [Subject] Table 12-1: Environmental limits for ammonia toxicity (as ammoniacal-nitrogen) for ecosystem health values in freshwater in New Zealand (from NPS-FM 2020). Ammonia (toxicity) Value (and component) Ecosystem health (Water lit ) Freshwater body type Rivers and lakes Attribute unit mg NH4-N/L (milligrams ammoniacal-nitrogen per litre) Attribute band and description Numeric attribute state Annual median Annual maximum A 99% species protection level: No observed effect on any species tested. ≤0.03 ≤0.05 B 95% species protection level: Starts impacting occasionally on the 5% most sensitive species. >0.03 and ≤0.24 >0.05 and ≤0.40 National bottom line 0.24 0.40 C 80% species protection level: Starts impacting regularly on the 20% most sensitive species (reduced survival of most sensitive species). >0.24 and ≤1.30 >0.40 and ≤2.20 D Starts approaching acute impact level (that is, risk of death) for sensitive species. >1.30 >2.20 Numeric attribute state is based on pH 8 and temperature of 20°C. Compliance with the numeric attribute states should be undertaken after pH adjustment.
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