Fig. 2: Seasonal trends in COD and DO concentrations across China’s ten major river basins from 2006 to 2020.
From: Natural and anthropogenic imprints on seasonal river water quality trends across China
Maps illustrating the spatial distribution of seasonal trends in COD (a) and DO (b) concentrations across sub-watersheds during this period (p < 0.05). Red and blue colors represent increasing and decreasing trends, respectively, with deeper shades indicating more significant changes. Grouped bar charts show the proportions of sub-watersheds with significant and non-significant seasonal trends in COD (c) and DO (e) for spring, summer, autumn, and winter. Dark colors indicate significant trends (p < 0.05), while lighter shades denote non-significant trends (p > 0.05); red and blue represent increasing and decreasing trends, respectively. Depict the average trend levels (p < 0.05) in COD (d) and DO (f) concentrations across northern and southern basins in different seasons. Bars represent the mean trends, colored hollow circles denote changes in sub-watershed concentrations. The curves to the right of the bars display the normal distribution of the data points. The horizontal bars represent 1.5 times the standard deviation (SD).
