Source discrimination of sedimentary PAHs in the Orkhon River Basin, Central Asia: a geochemical record of anthropogenic contributions

Abstract

Sediment cores are critical proxies for understanding the historical pollution dynamics of stable environmental contaminants, with their accumulation influenced by complex interactions between anthropogenic activities and environmental factors. This study focused on sediment records of polycyclic aromatic hydrocarbons (PAHs) in the Orkhon River Basin in Mongolia. Using 210Pb-based sediment chronology, a strong correlation between PAH concentration trends and regional economic development was identified. The historical contributions of petroleum evaporation, coal combustion, biomass burning, and traffic emissions to PAH levels were quantified using absolute principal component scores-multivariate linear regression (APCS-MLR) and positive matrix factorization (PMF) models. Furthermore, random forest (RF) and partial least squares structural equation modeling (PLS-SEM) were employed to assess the influence of 26 natural and anthropogenic drivers on PAH variation. Results demonstrated that sediment physicochemical properties were the primary direct drivers of PAH distribution, while socioeconomic factors (GDP, population) exerted net positive impact by promoting energy consumption and traffic activities. Comparative pathway analysis revealed distinct driver frameworks for PAHs (socioeconomic-energy-traffic) and conventional air pollutants (socioeconomic-energy). This integrated approach provides multidimensional evidence for PAH source tracing in the Orkhon River Basin, supporting regional water environment management and policy formulation.