Echoes of change: deciphering environmental history through biomarkers investigation in sediment core from a Central Himalayan Lake

The dynamics and scale of anthropogenically induced environmental changes in the Indian Himalayas remain largely unexplored, presenting a complex and enigmatic challenge. To tackle this, we investigated the pollution, eutrophication and fire history of the last century by analyzing the concentration, compositional variation, and temporal trends in polycyclic aromatic hydrocarbons (PAHs), monosaccharide anhydrides, fecal biomarkers and other aliphatic hydrocarbons (n-alkanes, acyclic isoprenoids and botryococcenes) from a lake sediment core in the Central Himalayas at 2084 m asl. The study revealed that the concentration of total PAHs increased steadily with a compositional change after 1970, paralleling an increase in socio-economic activities in the region. The PAHs diagnostic ratios revealed that pyrogenic sources accounted for the majority of the sedimentary PAHs and the high correlation between PAHs and fecal stanols (r = 0.84, p < 0.05) indicated the active role of humans in the catchment. The total concentrations of botryococcenes (C31-34) and n-alkanes showed an increasing trend in eutrophication with greatest values recorded during the 1980s, coinciding with a compositional change between long (nC26-36), mid (nC21-25) and short chain (更多