Spatial Heterogeneity and Ecological Risk Patterns of Wastewater Discharge in a Rapidly Urbanizing Watershed

Accurately resolving the spatial configuration and pollution-load clustering of fixed wastewater sources is critical for ecological protection in rapidly urbanizing watersheds. However, the spatial heterogeneity of discharge patterns and their interactions with sensitive aquatic systems remain insufficiently understood. Using a 2023 inventory of operational discharge points in Jinjiang City, we integrated Ripley’s K-function, hot spot analysis, and standard deviational ellipse to characterize multi-scale spatial patterns and associated ecological risks. Results show pronounced clustering of point sources in the western and central zones, with four distinct aggregation typologies ranging from strong clustering to quasi-random distributions. Buffer analysis identifies rivers as the dominant receptors within 1,000 m of discharge outlets, implying higher ecological vulnerability relative to reservoirs and lakes. Pollution-load source apportionment based on chemical oxygen demand (COD), ammonia nitrogen (NH₃–N), and total nitrogen further delineates 15 priority industries into three functional archetypes: centralized treatment–dominated, industrial-driven, and composite industrial–livestock forms. Spatially, COD and NH₃–N hotspots co-occur in the southeastern region, whereas cold spots are concentrated in the north. Overall, this study uncovers the complex spatial heterogeneity and key high-risk zones of industrial wastewater emissions, providing an ecological basis for optimizing industrial spatial layout and implementing targeted watershed-scale pollution control strategies.