Apportioning and modeling the anthropogenic fingerprints in a Himalayan freshwater lake over the last ∼ 3.7 ka: Insights into pollution chronology and future policy implications

Lack of systematic monitoring and increasing pollution trends in Himalayan Lake sediments highlights the need for evaluating increasing anthropogenic fingerprints with advanced multi-dimensional analytical approaches to understand potential risks to aquatic life and broader ecosystem. Therefore, this study investigated and modelled the chronological and quantitative shifts in heavy metals and bulk organic parameters in Dal Lake core sediments for last ∼3700 years using optically stimulated luminescence (OSL) dating, inductively coupled plasma mass spectrophotometry (ICP-MS), elemental and time series forecasting analysis. Due to the limited scientific literature available on the temporal trends and forecasting of heavy metals and nutrients in the bottom sediments of the lake, incorporating such a multi-dimensional approach facilitates accurate historical reconstruction, detailed elemental characterization, and predictive insights into future contamination, providing a thorough understanding of sediment composition and environmental changes over time. The findings of study revealed substantial variations in heavy metals and organic parameters within the lake from ∼12.5 to ∼3719 years before present (BP). Sediment pollution indices showed anthropogenic pressures on lake between ∼567 to ∼12.5 years BP, indicating moderate to strong pollution in upper sediment layers. Potential ecological risk index highlighted moderate risks up to ∼216 years BP and low risks from ∼285 to ∼3719 years BP. Organic parameters, such as total organic carbon, nitrogen, phosphorus, and C/N ratios indicated rising eutrophication from ∼476 to ∼12.5 years BP. Multivariate statistical analysis highlighted a strong positive relationship between heavy metals and organic parameters, depicting common environmental pathways and sources of contamination in Dal lake. Time series analysis using auto-regressive moving average model confirmed continuous anthropogenic alterations on lake and predicted increasing pollution trends in the coming decades. The model forecasted zinc concentration in Dal Lake over next 35 years to increase by ∼15 times, iron (∼35), manganese (∼24), lead (∼76), arsenic (∼239), mercury (∼100), cadmium (∼16), chromium (∼5), molybdenum (∼27), copper (∼10), cobalt and nickel (∼14) times from current observed concentrations. Similarly, total organic carbon in Dal Lake top sediment layers is expected to increase by ∼20 times, total nitrogen ∼37 and total phosphorous ∼36 times, indicating potential hyper-eutrophic conditions in coming decades. Novel insights provided by present study could have significant policy implications beyond regional context offering a framework for understanding the long-term anthropogenic fingerprints in Himalayan and global lake ecosystems.