Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (2): 495-505.DOI: 10.13745/j.esf.sf.2022.2.86

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Temporal and spatial distribution characteristics of nitrogen and phosphorous in the water of Qionghai Lake, Sichuan Province and their response to ecological environment

SHI Yao1,2(), ZHANG Lei1,2, QIN Yanwen1,2,*(), MA Yingqun1,2, YANG Chenchen1,2, LIU Zhichao1,2, ZHU Huailin3   

  1. 1. State Key Laboratory of Environmental Criteria and Risk Assessment,Chinese Research Academy of Environmental Sciences, Beijing 100012,China
    2. Institute of Water Ecology and Environment,Chinese Research Academy of Environmental Sciences, Beijing 100012, China
    3. Environmental Technology Engineering Co., Ltd, China Academy of Environmental Sciences, Beijing 100012, China
  • Received:2022-04-15 Revised:2022-05-23 Online:2023-03-25 Published:2023-01-05
  • Contact: QIN Yanwen

Abstract:

The aim of this article was to explore the characteristics of nitrogen and phosphorus pollution in the Qionghai Lake. We analyzed the temporal and spatial distribution characteristics of TN, NH 4 +-N and TP concentrations of water samples from 11 lake sampling sites in 2020. The relationships between nitrogen/phosphorus and chlorophyll-a concentrations were discussed, and the eutrophication status of the Qionghai Lake was evaluated in order to strengthen the prevention and control of lake eutrophication and ensure the safety of the lake water source. The results showed that TN concentrations ranged from 0.315-0.500 mg·L-1, with a mean value of 0.399 mg·L-1, and NH 4 +-N concentrations ranged from 0.063-0.171 mg·L-1, with a mean value of 0.098 mg·L-1, both meeting the standard for grade Ⅱ surface water of lake and reservoir; while TP concentrations also met the standard, with a range of 0.019-0.035 mg·L-1 and a mean value of 0.023 mg·L-1. Both nitrogen and phosphorus concentrations in the Qionghai Lake show temporal and spatial differences: TN, NH 4 +-N and TP concentrations varied significantly with time and were higher in dry season than in wet season; they have similar spatial distribution patterns, with high concentration areas mainly observed at station 1 (Haihekou) and 10 (Gaojian Bay) in the northwestern part of the lake, and were all higher in the northwest than in the east of the lake. The average TN/TP ratio was higher in the dry season, characterized by phosphorous limitation, than in the wet season, characterized by nitrogen and phosphorus limitation. TN, TP and NH 4 +-N concentrations positively correlated with Chla concentration, indicating nitrogen and phosphorous could promote the algae growth. Evaluation of eutrophication in the Qionghai Lake showed that the average trophic status index (TSI) value for the lake was 38.011; and the study area was in a mesotrophic state as a whole, with a higher TSI value for the northwest and a lower TSI value for the east.

Key words: Qionghai Lake, nitrogen, phosphorus, temporal and spatial distribution, chlorophyll-a, eutrophication

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