Anthropogenic Fingerprints of Sedimentary Deposits in a Himalayan Wetland Ecosystem over the Last 8 Centuries

Understanding sedimentary deposits in wetlands is crucial for their effective management. In this study, we used an integrated approach to estimate the radiocarbon (¹⁴C) chronology, sedimentation rate, and nutrient dynamics of the Khushalsar wetland in the Kashmir Himalaya. A UWITEC gravity corer was used to retrieve a 60 cm sediment core from the wetland. Accelerator mass spectrometer (AMS) facilitated ¹⁴C dating of core sediments revealed that the age of the sediments ranged from 248 ± 30 BP at 15–16 cm depth to 889 ± 27 BP at 59–60 cm depth. The linear increase in ¹⁴C age with depth revealed steady depositional conditions. According to the Constant Rate of Supply model applied to ¹⁴C ages, the sedimentation rate for Khushalsar wetland averaged 0.10 cm per year over the past 829 years, spanning from 1189 to 2018. Physicochemical analysis revealed a high concentration of ionic components in the sediments, wherein the electrical conductivity (EC) ranged from 2230 to 2970 µS cm⁻¹, and organic matter (OM) ranged from 6.6 to 19.8%. The regression model demonstrated significant (p < 0.05) positive and negative associations between the physicochemical parameters. EC explained 91% of the variation in total dissolved solids (TDS) and 89% of the variation in salinity, whereas organic carbon (OC) explained 44% of the variation in nitrogen and 20% of the variation in phosphorus. Depth exhibited a strong positive association with C/N ratio (explaining 17% of the variation) and a negative association with OC, nitrogen, and phosphorus (explaining 59%, 56%, and 50% of the variation, respectively). The study concluded that primary productivity, stormwater runoff, anthropogenic inputs (domestic sewage, raw fecal matter, slaughterhouse wastes), and deforestation in the catchment area are responsible for the increased nutrient concentration and high sedimentation rate in the wetland.