Chen,G., Cao,X., Song,C. and Zhou,Y.(2010): Adverse effects of ammonia on nitrification process: the case of Chinese shallow freshwater lakes. Water Air Soil Pollut., 210, 297-306.

『硝化過程へのアンモニアの逆効果：中国の浅い淡水湖の場合』

『Abstract
　Nitrification is a process in which ammonia is oxidized to nitrite (NO2-) that is further oxidized to nitrate (NO3-). The relations between these two steps and ambient ammonia concentrations were studied in surface water of Chinese shallow lakes with different trophic status. For the oxidations of both ammonia and NO2-, more eutrophic lakes generally showed significantly higher potential and actual rates, which was linked with excessive ammonia concentrations. Additionally, both potential and actual rates for ammonia oxidation were higher than those for NO2- oxidation in the more eutrophic lakes, while in the lakes with lower trophic status, both potential and actual rates for ammonia oxidation were almost equivalent to those for NO2- oxidation. This can be explained by the excessive unionized ammonia (NH3) concentration that inhibits nitrite-oxidizing bacteria in the more eutrophic lakes. The laboratory experiment with different ammonia concentrations, using the surface water in a eutrophic lake, showed that ammonia oxidation rates were proportional to the ammonia concentrations, but NO2- oxidation rates did not increase in parallel. Furthermore, NO2- oxidation was less associated with particles in natural water of the studied lakes. Without effective protection, it would be selectively inhibited by the excessive ammonia in hypereutrophic lakes, resulting in NO2- accumulation. Shortly, the increased concentrations of ammonia cause a misbalance between the NO2--producing and the NO2--consuming processes, thereby exacerbating the lake eutrophication.

Keywords: Nitrification process; Ammonia concentration; Nitrite accumulation; Chinese shallow lakes』

1. Introduction
2. Materials and methods
　2.1. Description of the four study lakes
　2.2. Sampling and chemical analysis
　2.3. measurement of potential and actual rates of ammonia and NO2- oxidation
　2.4. Size fractionation of ammonia and NO2- oxidation rates
　2.5. Laboratory experiment with different NH3 concentrations
　2.6. Statistical analysis
3. Results
　3.1. Water quality parameters
　3.2. Potential and actual rates of ammonia and NO2- oxidation in surface water
　3.3. Size fractionation of ammonia and NO2- oxidation rates
　3.4. Laboratory experiment with different NH3 concentrations
4. Discussion
5. Conclusion
Acknowledgments
References

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