Spatial Distribution Patterns, Hotspots of Contaminants of Emerging Concern and Driving Factors in a River Network of Xizang Plateau

This study encompasses the explication of systematic spatial distribution patterns and identification of hotspots of contaminants of emerging concern (CECs) across the network of rivers, including Yarlung Tsangpo River and its tributaries in Xizang Plateau. A total of 16 CECs were detected in wide range of frequencies and concentrations ranging from below limit of detection (BLD) - 163.13 ng/L across the river network, indicating widespread spatial heterogeneity. The systematic spatial distribution pattern suggested a positive spatial autocorrelation with Moran's Index values of 0.35, 0.15, 0.42 for diclofenac acid, bisphenol AF and trimethoprim, respectively. Subsequently, hotspots of CECs were identified in the upper reaches of Parlung Tsangpo River and Zayu River, and lower reaches of Lhasa River by using Getis-Ord Gi* statistics coupled with inverse distance weighted interpolation. Geodetector was used to elucidate the driving factors responsible for the spatial heterogeneity. The q-statistics identified rivers, dissolved oxygen, human population density, and land use types as major factors associated with the spatial heterogeneity of CECs. Besides, the interaction between these factors produced enhanced bivariate and nonlinear effects on the spatial heterogeneity of CECs, compared to their individual impacts. The specific levels of the environmental and physicochemical parameters associated with the higher CECs concentrations justified the hotspots. This study provided a comprehensive understanding of the CEC contamination in riverine environments along with an exploration into driving factors responsible for spatial heterogeneity and hotspots that may pose high risks to human health and aquatic ecosystem.