Spatial distribution of per- and polyfluoroalkyl substances in the Yellow River basin: Role of suspended sediment on the PFAS partition and accumulation.

The widespread occurrence of per- and polyfluoroalkyl substances (PFAS) and emerging substitutes in riverine environments has raised growing concern, particularly perfluoroalkyl ether carboxylic acids (PFECAs). The Yellow River (YR) is the 2nd longest river in China with the highest sediment content. However, PFAS behaviors and ecological impacts remain poorly understood in this sediment-laden river. A large spatial scale investigation was conducted to elucidate the spatial heterogeneity and driving mechanisms of PFAS in YR, with emphasis on species-specific responses of fish with different feeding strategies. Following the confluence of Wei River (434.7 ng/L), PFECAs exhibited a pronounced substitution trend (from 57.1 to 329.9 ng/L). Along the downstream reaches, rising turbidity and sediment flux coincided with increasing PFAS concentrations in water (from 117.3 to 289.3 ng/L), sediment (0.14-2.07 ng/g dw) and fishes (3.71-61.8 ng/g dw), likely driven by cumulative discharge, long-range transport and sluggish hydrodynamics. Geographically weighted regression analysis revealed land-use patterns, industrial activities and population density dominated PFAS heterogeneity among socioeconomic indicators. The heavy sediment load enhanced PFAS partitioning and deposition, particularly within elevated hanging-river section, where fine particles and higher organic matter content facilitated accumulation. Suspended sediment acted as dynamic traps, accelerating PFAS sequestration and redistribution, with Random Forest highlighting its pivotal role. Elevated sedimentary PFAS levels increased exposure risks for benthic/filter-feeding fish inhabiting the lower water column. This study proposed a hybrid analytical framework integrating source apportionment, driver identification, and pollution prediction-advancing machine learning-based approaches for assessing trace organic contaminants in turbid river system.