China national water quality criteria for the protection of freshwater life: Ammonia

Ammonia is one of the two mandatory indexes for China's water environment pollution control. The current China ammonia water quality standard does not reflect the effect of water quality parameters on ammonia toxicity. The Ministry of Ecology and Environment of China just released the China National Aquatic Life Criteria Report for ammonia. This paper discusses the technical route, formulation process and results of the national ammonia criteria. Based on China's own technical guidelines, a total of 259 acceptable acute and 44 acceptable chronic data for ammonia were adopted. The temperature of the water body corresponding to the ammonia criteria was divided into 6 grades, and the pH was divided into 12 grades, which constitutes 72 groups of water quality conditions. Based on the empirical formulas recommended by USEPA, the ammonia toxicity data was adjusted, and the optimal fitting model was used to derive the 72 short-term criteria and the 72 long-term criteria for ammonia. In terms of criteria derivation, the method used by the USEPA to extrapolate at the criteria level has been improved and replaced with extrapolation at the species level, making the final criteria value more accurate. (C) 2020 Elsevier Ltd. All rights reserved.