Atmospheric mercury (Hg) presents significant analytical challenges due to its ultra-trace concentrations, complex behavior and diverse sources. This session addresses critical advancements in the determination of atmospheric mercury, with a focus on speciation, isotopic fingerprinting, and modeling. Accurate mercury speciation is essential for understanding the distinct roles of elemental, particulate-bound, and reactive gaseous mercury in atmospheric chemistry and deposition processes. New advanced techniques are needed for precise Hg speciation, enabling researchers to distinguish between different forms of mercury and their respective environmental impacts. Isotopic fingerprinting of mercury provides valuable insights into the sources and transformation processes of mercury in the atmosphere. Utilizing cutting-edge methods, like multi-collector inductively coupled plasma mass spectrometry, mercury emissions can be tracked to their origins and understand the isotopic fractionation that occurs during atmospheric transport and deposition. This approach enhances our ability to identify anthropogenic and natural sources of mercury and track its movement through the environment. Integrating speciation and isotopic data into atmospheric models is a key focus of this session. Environmental models aim to improve predictions of mercury distribution and its environmental impacts, offering a comprehensive understanding of mercury in the atmosphere. By combining detailed chemical and isotopic information with advanced modeling techniques, the fate and transport of mercury in the environment can be better predicted, thus informing policy decisions and mitigation strategies. Accordingly, this session aims to provide a comprehensive overview of current methodologies, challenges, and future directions in atmospheric mercury research. The aim is to address the complex analytical challenges of mercury determination and contribute to the development of more effective strategies for managing mercury pollution on a global scale. Participants will gain insights into the latest advancements in mercury speciation, isotopic fingerprinting, and modeling, as well as the practical applications of these techniques in environmental monitoring and assessment.