LI Yangzheng1, REN Jintong1,YANG Yanli1,2, TIAN Luyin1,3, KONG Fangxiang1, DENG Haolei1, WU Xiuhua1
(1.School of Ecological Engineering, Guizhou University of Engineering Science, Bijie, Guizhou 551700, China;
2.School of Geography and Environment Science, Guizhou Normal University, Guiyang 550059, China;
3.School of Environment and Resources, Guangxi normal university, Guilin, Guangxi 541004, China)
Abstract: In order to explore the distribution of three inorganic nitrogen species and the environmental conditions of nitrogen transformations in the karst area of southwest China, and to provide the theoretical support for water protection and utilization in the karst area, we studied the water quality in the karst area from both aspects of space and time. Contents of ammonia, nitrite and nitrate, DO, CODcr, TP, TN and other related indicators were analyzed using standard methods. The results showed: ① The more closed are the environments, the smaller are the annual variations of inorganic nitrogen contents, especially, nitrite. ② Concentrations of ammonia, nitrite and nitrate in sealed underground waters were below the detection limit, 0.012 mg/L and 1.472 mg/L, respectively, which is closely related to natural conditions in the subtropical karst area of Guizhou, China, such as, ubiquitous occurrence of dissolved fissure and funnel in carbonate bedrocks and high adsorptive ability of alfisols to ammonia; the highest concentrations of nitrite were found in early autumn instead of in summer because that a lag period of 2-3 months may exist, in which nitrite introduced by agricultural fertilization in summer can infiltrate into the groundwater. ③ Concentrations of ammonia and nitrite in the Qingheyuan pond, a semi-open surface water, were lowest in summer. The ammonia concentration is low in winter because of the low temperature, which restrains the activity of Ammonia-oxidizing bacteria (AOB). Compared with summer and winter, temperature and precipitation in spring and autumn are moderate, so concentrations of ammonia were found to be relatively high in both seasons. The annual concentration curve of nitrate showed stable in summer, suggesting that, instead of temperature, DO is the controlling factor of the Nitrite-oxidizing bacteria (NOB) proliferation. ④ The concentration of ammonia in the reach of Liucangqiao, an open water system, was low in summer, which mainly related to the precipitation dilution and the preference absorption of ammonia by aquatic plants. Since of the poor adapt ability of NOB to environment changes, the proliferation of NOB is largely limited in the dramatically changed natural environment of summer, e.g. habitat mutation, lack of carbon source etc., consequently, nitrite was accumulated significantly. Annually, the higher concentration of nitrite and the lower concentration of nitrate occurred simultaneously. Moreover, to stimulate the NOB activity in open surface waters, the concentration of DO and the atmospheric temperature should be greater than 4 mg/L and 10℃, respectively.
Key words: ammonia; nitrite; nitrate; Ammonia-oxidizing bacteria; Nitrite-oxidizing bacteria; karst water; Bijie city
EARTH AND ENVIRONMENT Vol.47, No.3, Tot No.329, 2019, Page 246-253
