Journal of Ecology and Rural Environment ›› 2021, Vol. 37 ›› Issue (3): 378-386.doi: 10.19741/j.issn.1673-4831.2020.0553

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Effect of pH on Nitrogen Forms and Ammonia Nitrogen Release Flux in the Bottom Muddy of Plateau Rural Ditches

GONG Yun-hui1, LIU Yun-gen1,2, WANG Yan1,2, YANG Si-lin1, LIU Peng1, ZHANG Jin-long1   

  1. 1. College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China;
    2. Yunnan Key Laboratory of Ecological Environment Evolution and Pollution Control in Mountainous Rural Areas, Kunming 650224, China
  • Received:2020-07-08 Online:2021-03-25 Published:2021-03-18

Abstract: Nitrogen release from ditch sediments in mountainous rural areas induces pollution to water environment of rural ditches, which is affected by changes in overlying water pH values. In this study, indoor simulation experiments with and without sterilization of the sediments and with pH values of the overlying water as 5.5, 7.5, 9.5, and 11.5 were conducted to analyze nitrogen transformation in sediments and ammonia nitrogen release flux at sediment-water interface in typical plateau mountainous rural ditches in the upper reaches of Dianchi Lake. The results show that: (1) Sediment nitrogen content of various forms is in the order of strong oxidant leaching nitrogen (SOEF-N) > ion exchange nitrogen (IEF-N) > weak acid leaching nitrogen (WAEF-N) > strong alkali leaching Nitrogen (SAEF-N). The IEF-N, SAEF-N and SOEF-N contents were decreased while WAEF-N content was increased with the increasing of pH. There is no significant difference between sterilization and non-sterilization of the sediments on nitrogen transformation in rural ditches at the same pH value. (2) The ammonia nitrogen concentration and release flux in the overlying water at acidic (pH=5.5) and strong alkali (pH=11.5) conditions were significantly higher than those at pH=7.5 and 9.5. The ammonia nitrogen release flux in acid and strong alkali conditions without sterilization was 8- and 6-times of that at pH=7.5, while it is 2 times of that at pH=7.5 with sterilization. (3) RDA shows that pH value was positively correlated with IEF-N while negatively correlated with SAEF-N, SOEF-N and WAEF-N under acidic conditions. There is no correlation between pH value and IEF-N, SOEF-N, SAEF-N at pH=7.5, while positively correlated with TN, WAEF-N (pH≥9.5) and negatively correlated with SAEF-N, SOEF-N, IEF-N at alkaline conditions. Besides, DO and Eh are positively correlated with TN and IEF-N. This indicates that the nitrogen release capacity of the sadiments is the strongest in the plateau and mountainous rural ditches under acidic and strong alkaline conditions, while the weakest under pH=7.5. However, under acidic and strong alkali conditions, microorganisms could increase ammonia nitrogen concentration and the flux in overlying water, which was decreased at pH=7.5 and 9.5. The results of the study can provide scientific bases for the improvement of the ecological environment management of rural ditches.

Key words: pH, plateau mountainous countryside, nitrogen form, ammonia nitrogen, ditch sediment, diffusion flux, microorganism

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