Long-Term Changes in Water Quality and Eutrophication of China’s Liujiang River
Baiyang Jiang1,2, Jianhua Chen3, Qiqing Luo4, Junxiang Lai5, Huixin Xu6, Yinghui Wang1, Kefu Yu1
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1School of Marine Sciences, Guangxi University, Nanning 530004, China
2School of Environment, Guangxi University, Nanning 530004, China
3School of Resources and Metallurgy, Guangxi University, Nanning 530004, China
4The Department of Science and Technology, Guangxi University, Nanning 530004, China
5Guangxi Academy of Sciences, Nanning 530007, China
6Water Conservancy Bureau of Liuzhou City, Liuzhou 545000, China
Submission date: 2015-09-16
Final revision date: 2015-12-02
Acceptance date: 2016-02-16
Publication date: 2016-05-25
Pol. J. Environ. Stud. 2016;25(3):1033–1043
Long-term changes (2003-14) of water temperature, DO, pH, TN, NH4-N, TP, and CODMn were examined at eight sampling stations along the Liujiang River. Water quality parameters showed considerable spatial and temporal variability. Annual averages of those parameters were 22.1ºC, 7.8 mg/L, 7.58, 1.35 mg/L, 0.27 mg/L, 0.06 mg/L, and 1.7 mg/L, respectively. An increasing trend for TN/TP and a decreasing trend for pH were observed in all parts of the Liujiang. Pollution levels were generally higher in the lower Liujiang than in the upper and middle parts of the river due to the impact of urban sewage. All indicators reached level III water quality standards except TN, which suggests that the control of nitrogen emissions should be strengthened. Relatively high N/P ratios in the Liujiang contribute to a potential for phosphorus limitation of phytoplankton. The average concentration of Chlorophyll-a was 1.2 μg/L in 2014. The TLI index indicated that the eutrophication state of the Liujiang was mesotrophic, while the downstream water was polluted due to its nutrient inputs from agriculture and urban sources. The water quality of the river keeps well by comparison to other major rivers of the world, which provided the basis for urban development and river protection in Liuzhou City.