Seasonal assessment of water quality and water quality index (WQI) variations, in Jiangsu Kunshan Tianfu National Wetland Park, China

Seasonal variations in surface water quality are essential for assessing temporal variations in wetlands pollution due to natural or anthropogenic inputs from both point and non-point sources. The goal of this study was to use established methodologies to estimate the water quality of the Tianfu National Wetland Park based on physicochemical features; sampling was done from eight monitoring locations throughout the wetland region in the summer of 2019 and winter of 2020. The water quality index (WQI) is calculated using the following parameters: Turbidity (NTU), Nitrate, Chlorophyll, TOC, DOC, COD, BOD, Chroma, Ammonium nitrogen, pH, Electric Conductivity, and Total Phosphorus. One-way ANOVA and Tukey's pairwise comparisons with a 5% significance level were used to compare water quality parameters among the monitoring point's data. T-test analysis was used to compare the parameters between summer 2019 and winter 2020 and the difference between the water inlet and the water outlet. Cluster analysis was done on the WQI results using Ward's linkage approach. The analyses of variance (ANOVA) of data revealed statistically significant differences between points of sampling (p < 0.05). The paired t-test revealed significant differences in parameters between summer 2019 and winter 2020; however, all parameters in summer show higher values in the water inlet than water outlet. In winter, TOC, DOC, COD, BOD, Chroma, pH, and Electric Conductivity showed higher values than Turbidity (NTU), Nitrate, Chlorophyll, Ammonium Nitrogen, and Total Pospurus. In general, summer showed higher pollution than winter, and water inlets were more polluted than water outlets indicating that other factors may affect the water quality, such as vegetation cover, temperature, water level, and activities in the wetland during the seasons.