Water Quality Assessment and Spatial Analysis of River System in Suburban Area of Hangzhou, China

Water quality degradation caused by excess nutrient inputs is a major issue facing urban wetlands. This study aimed to characterize the spatiotemporal variations in water quality and identify main pollution sources in a degraded urban wetland in Hangzhou, China. Water samples were collected from 14 locations along the Xianlin and Wutong Rivers in from September to March. Concentrations of nitrogen, phosphorus, dissolved oxygen, and other water quality parameters were measured. Single-factor assessment indicated the main pollutants were total nitrogen (TN) and ammonia nitrogen (NH3-N), with average concentrations of 4.20 mg/L and 2.76 mg/L in the Xianlin River. Nutrient concentrations displayed significant seasonal variations, with higher levels in winter months. Spatial heterogeneity was also evident, with the highest pollution levels observed at convergent and downstream sections influenced by external sources. Based on the results, agricultural runoff and municipal wastewater are likely major contributors to the excessive nitrogen and phosphorus inputs to the wetland. Hydrologic restoration to improve water circulation may help reduce nutrient accumulation. This study provides a detailed characterization of water quality issues and identifies priorities for remediation in the study wetland.