Human Activity Driven Spatial Heterogeneity of Pollutants in a Highland River Basin Revealed by Non-Target Screening and Improved PBT Evaluation: A Case Study from the Yalong River on the Qinghai-Tibet Plateau,China

Abstract

Emerging pollutants are becoming increasingly diverse, raising concerns about contamination in plateau river systems and the need for efficient assessment frameworks. In this study, non-targeted screening (NTS) was conducted at 17 sites along the Yalong River, identifying 158 waterborne pollutants including human drugs, veterinary drugs, antibiotics, pesticides, and others. An improved PBT (Persistence, Bioaccumulation, Toxicity) evaluation framework was developed by incorporating toxicity data from green algae, daphnia, and fish to enhance ecological relevance. The basin was divided into three land use regions-industrial-agricultural production area (IAPA), alpine canyon area (ACA), and alpine meadow area (AMA)-for spatial analysis. Human drugs were the dominant category (55.70%) in both number and total peak area and exhibited the highest average PBT score (0.745). Non-metric multidimensional scaling (NMDS) and random forest modeling revealed significant differences in pollutant compositions across land use regions (p < 0.05), and a strong alignment between pollutant profiles and land use characteristics. These findings indicate that pollutant composition and spatial distribution were significantly influenced by human activities and resource utilization patterns. This study proposes a region-specific framework integrating NTS, improved PBT evaluation, and spatial analysis to support pollution management in high-altitude river basins.