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| Spatial-temporal variation of inflow river water quality under land use effect |
| Received:August 16, 2019 |
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| KeyWord:inflow river;temporal and spatial change;spatial autocorrelation;geographically weighted regression |
| Author Name | Affiliation | E-mail | | XIANG Song | Research Center of Lake Environments, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Chinese Research Academy of Environmental Sciences, Beijing 100012, China | | | WAN Ling | Research Center of Lake Environments, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China | | | PANG Yan | Research Center of Lake Environments, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
National Engineering Laboratory for Lake Pollution Control and Ecological Restoration, Chinese Research Academy of Environmental Sciences, Beijing 100012, China | 190068749@qq.com |
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| Abstract: |
| This study analyzes the water quality variation of inflow rivers directly affecting lake. Focusing on the three major river systems of the Lake Erhai basin, the effects of inflow rivers on the water quality of Erhai Lake and its change trend under land-use changes in 2014 were studied with spatial analysis method, statistical analysis method and model. Results indicated that the chemical-oxygen demand (COD), total nitrogen(TN), total phosphorus(TP), and ammonia nitrogen of inflow rivers in 2014 exceeded class Ⅱ levels; the main pollutants were the TN and TP. Water quality indexes of inflow rivers showed significantly spatial-temporal variation among the three river systems. The overall river quality was poorer in the rainy season than in the dry season. The contamination of the TN and TP in the Boluojiang river system was the most serious, followed by the Cangshanshibaxi river system. In spite of the low concentrations of TN and TP, significant temporal variation occurred in the Beisanjiang river system. The spatiotemporal association of the river quality between the river and Erhai Lake was significant, especially in the rainy season. The pollutant concentration, excluding TN, in Erhai Lake was higher in the areas with the most polluted inflow rivers. The COD and vegetation area percentage had a significant negative correlation(P<0.05). Furthermore, the river TN and TP had significant positive correlations with the construction land area percentage(P<0.01) as well as a significant negative correlation with other land use in the basin scale(P<0.05). COD, TP and ammonia nitrogen of inflow rivers showed significant spatial autocorrelation. A geographical weighted regression(GWR) model showed that there were significant spatial variations in the regression relationship between the vegetation area proportion and COD. This changed to a negative relationship and the fitting degree increased from the south to the north. The regression relationship of the area proportion of construction land and TP also showed a spatial difference but remained positive throughout the entire basin. The highest fitting degree of the two occurred in the west Cangshanshibaxi basin and north inflowing area. Suggestions regarding pollution regulation in Erhai Lake basin were made to focus on nonpoint pollution control in the rainy season, strengthen the comprehensive treatment of nonpoint pollution in the Boluojiang river system, and control the construction land surface flow in the Cangshanshibaxi river system. Furthermore, more attention should be paid to optimize the ecological land functions of interception and purification on runoff in the Beisanjiang river system. |
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