Title : Seasonal Variability of Water Vapor Dynamics in the Semi-Arid Region of Western India - revelations from isotopic investigation at Mt. Abu, Rajasthan.

Abstract

This study presents the first continuous year-long measurement of stable isotopes (d18O, dD, and d-excess) in atmospheric water vapor over semi-arid western India. Continuous in-situ observations captured isotopic variations from daily to seasonal scales to identify key controlling processes. Temporal changes in vapor isotopes are governed by shifts in moisture sources and the influence of recycled moisture, producing a distinct seasonal isotopic baseline. A pronounced isotopic depletion precedes rainfall events by several days, suggesting its potential as a precursor to precipitation. A sharp isotopic transition observed in late April indicates a major shift in vapor source. The dominant moisture sources—northern and southern Arabian Sea, arid terrestrial regions of Iraq–Iran–Afghanistan–Pakistan, and the wetter eastern landmass of India and the Bay of Bengal—each impart distinct isotopic characteristics, enabling the identification of seasonal vapor origins and their hydrometeorological implications.

Title : Nitrogen fluxes and primary productivity in Archaean Ocean

Abstract

The most oxidised form of nitrogen - Nitrate (NO3⁻) - serves as an essential and often limiting nutrient for life in the modern well-oxygenated ocean. However, ~3 billion years ago (Archean eon) the Earth’s surface environment and oceans were largely deprived of oxygen. Nitrogen isotopic composition (δ¹⁵N) of sedimentary rocks of that time suggests ammonium (NH4+) dependent anaerobic nitrogen cycling. In an attempt to quantify nitrogen fluxes and productivity in such ammonium-based ecosystem, we have developed a numerical two-box model that simulates Archean nitrogen cycling under ammonium-dependent conditions. In this seminar I will be discussing the results of the model and evaluate the Archean nitrogen isotopic record.