Occurrence, sources, and controlling factors of emerging organic pollutants in a freshwater lake system in the NW Himalayas

The occurrence, sources, and spatial distribution of phthalate esters (PAEs), polycyclic aromatic hydrocarbons (PAHs), and faecal stanols were simultaneously investigated in surface sediments from Manasbal Lake, NW Himalayas. The concentrations of Σ₄PAEs ranged from 9.08 μg/g to 194.42 μg/g, while Σ₁₆PAHs varied from non-detectable (n.d.) to 250.1 μg/g. Sewage markers such as coprostanol and epi-coprostanol were detected, with concentrations ranging from 0.05 to 0.4 µg/g (mean = 0.17 µg/g) and 0.05 to 1.18 µg/g (mean = 0.26 µg/g), respectively, indicating significant faecal pollution. Detected PAEs included diethyl phthalate, di-isobutyl phthalate, dibutyl phthalate isomers, and di(2-ethylhexyl) phthalate. The primary sources of PAEs in the sediments were domestic waste from nearby villages, garbage disposal from residential areas, and built-up regions. Three-factor modeling using positive matrix factorization identified fuel combustion as the most significant source of PAHs, contributing 40.4 % of the pollution, followed by biomass combustion, which accounted for approximately 33.1 %. The highest concentrations of Σ₁₆PAEs, Σ₄PAEs, and stanols compounds were observed in the eastern part near the inlet, suggesting that their distribution is strongly influenced by proximity to pollution sources. Conversely, there was no significant relationship between these organic contaminants and sediment characteristics (grain size and TOC content) or water depth. The significant correlation between Σ₄PAEs and microplastic abundance indicates that PAEs can serve as effective markers for identifying plastic pollution in sediments. This study enhances the baseline characterization of emerging contaminants in Himalayan freshwater systems and contributes to a better understanding of the potential sources and controls on their distribution in aquatic systems globally.