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| DOI：10.13522/j.cnki.ggps.2022384 |
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| Change in Water Quality of Ulansuhai Lake after Its Surface Freezing |
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ZHANG Yan, WANG Nan, ZHAO Tongguo, LI Weiping, TIAN Yepeng, YUAN Lingfei
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1. Civil Engineering College, Yantai University, Yantai 264005, China; 2. School of Energy and Environment, Inner Mongolia University of Science and Technology, Baotou 014010, China; 3. Trier Institute of Technology for Sustainable Development,Yantai University, Yantai 264005, China; 4. Yantai Taoziwan Wastewater Treatment Co, Yantai 264013, China
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| Abstract: |
| 【Objective】Chemical quality of surface water bodies is affected by many factors but most of them are driven by oxygen. Bioavailable oxygen in water decreases after the water surface is frozen, and this paper investigates how this impacts water quality in Ulansuhai lake in Inner Mongolia.【Method】Ice and water samples were taken in January 2021 from 10 sites in the lake. Contents of CODMn, nitrate, total phosphorus (TP), total nitrogen (TN), fluoride and copper in each sample were analyzed. They were compared to those measured before the lake was frozen. Change in these chemicals due to freezing was assessed using the single-factor and the comprehensive water quality identification index, as well as the principal component analysis.【Result】① Single factor water quality identification index analysis indicated that the content of all chemicals in fluid water was ranked in the order of water underneath ice≥water before freezing≥melted ice. The pollution degree of the six chemicals was ranked in the order of TN>TP>CODMn>NH3-N>copper>fluoride. The chemicals that resulted in water quality classification change were CODMn, NH3-N and TN. ② Comprehensive water quality identification index analysis showed that freezing worsened the water quality in all 10 sampling sites, though the deterioration varied with sampling sites. Nitrate, TN and TP had the greatest influence on water quality, as increasing nitrogen and phosphorus risked eutrophication. Spatially, water quality in the lake area was ranked in the order of outlet area>middle lake area>inlet area.【Conclusion】Surface freezing in Ulansuhai Lake increased chemical concentrations in the water beneath the ice, leading to water quality deterioration. To ameliorate water pollution, discharge of pollutants to the lake, especially for TN and TP in autumn and winter, should be reduced. |
| Key words: Ulansuhai Lake; icing effect; water quality evaluation; principal component analysis method; water quality identification index |
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