Summary: Groundwater quality is closely linked to human health and ecosystem sustainability, as groundwater serves as a primary source of drinking water and supports numerous terrestrial and aquatic environments worldwide. The occurrence, mobility, and bioavailability of groundwater contaminants are governed by complex interactions among hydrological, geological, biological, and geochemical processes. Natural water–rock interactions, microbial activities, redox transformations, and anthropogenic disturbances can significantly influence the release, transport, and attenuation of potentially harmful elements and compounds, including trace metals, metalloids, nutrients, and emerging contaminants. Understanding these hydro-biogeochemical mechanisms is essential for assessing health risks and developing effective groundwater management strategies.

This session welcomes contributions that investigate: (i) the hydro-biogeochemical processes controlling the occurrence and evolution of groundwater components; (ii) the sources and transformation pathways of groundwater contaminants; (iii) risk assessment of contaminated groundwater. We encourage submissions from diverse regions and research communities focusing on the connections between groundwater systems, environmental processes, and human health.

Summary: Anthropogenic stresses on groundwater quality could be a result of (i) the excessive use of synthetic/organic fertilizers and pesticides in agricultural fields to promote crop growth; (ii) improper industrial disposal of untreated/partially treated wastewater and solid wastes; and (iii) uncontrolled urbanization leading to potential leakage from sewage systems and/or inadequate sanitation systems. In addition, urbanization may also lead to increase in groundwater extraction causing salinization of inland aquifers or aggravating seawater intrusion in coastal aquifers. Understanding the effects of anthropogenic activities on groundwater quality, distinguishing the sources of groundwater contamination, and identifying the processes controlling groundwater quality are fundamentally important for sustainable groundwater resource management. Isotope-based approaches constitute a powerful tool not only for distinguishing the sources of groundwater contamination but also for identifying the processes governing groundwater quality in complex aquifer systems. Overall, we encourage the submission of contributions that use isotope tracers for : (i) demonstrate the influence of anthropogenic activities on groundwater; (ii) investigate the hydro-bio-geo-chemical processes that may affect groundwater quality; (iii) assess the resulting potential impacts on related ecosystems including wetlands, springs, and tributaries; and (iv) develop new methods integrating isotope tracers for investigation of all the above. Overall, we encourage the submission of contributions for a broad geographical representation, and invite all career stage (students, junior, senior, retired, etc.) participants to contribute.

Summary: Groundwater-dependent ecosystems (GDEs), including wetlands, springs, rivers, and riparian environments, rely on groundwater discharge to maintain ecological functions and biodiversity. The chemical composition of groundwater, shaped by water–rock interactions, plays a critical role in regulating the structure, productivity, and resilience of these ecosystems. Understanding the geochemical controls on groundwater-dependent ecosystems is therefore essential for predicting ecosystem vulnerability and supporting sustainable development of groundwater.

This session welcomes contributions that investigate: (i) groundwater discharge and chemical evolution in groundwater-dependent ecosystems; (ii) the impacts of groundwater quality changes on ecosystems; (iii) biogeochemical processes linking groundwater systems and ecosystem functioning. We encourage submissions from diverse geographic regions and research communities addressing the complex relationships between groundwater geochemistry, ecological health, and environmental sustainability.

Summary: Interactions among water, organic matter, and microorganisms are fundamental processes controlling the transformation, transport, and fate of chemical components in aquatic and subsurface environments. Organic matter serves as both an energy source and a reactive medium for microbial communities, influencing redox conditions, mineral dissolution and precipitation, nutrient cycling, and the mobility of contaminants. These coupled hydro-bio-geochemical processes play important roles in ecosystem functioning, carbon cycling, and environmental quality. 

This session welcomes contributions that investigate: (i) the mechanisms governing water–organic matter–microbe interactions across different aquatic systems; (ii) microbial mediation of elemental cycling, mineral transformation, and contaminant attenuation; (iii) the interplay of dissolved organic matter and microbes on groundwater and ecosystem evolution. We encourage submissions from diverse research communities exploring the roles of microbial and organic matter in shaping water quality, ecosystem responses, and environmental sustainability.

Summary: Salinization is a serious environmental concern leading to the deterioration of water quality and perturbation of natural ecosystems. Freshwater salinization could be the result of various natural and anthropogenic sources including seawater intrusion, fertilizer application, road salt products application, sewage wastewater leakage, intense irrigation with water-return, weathering process, dissolution of evaporite deposits, recharge of aerosols from wave activities along the coast, paleo-seawater trapped within aquifers from past marine transgressions, migration of deep saline water through fracture networks or faults into shallow aquifers, etc. Identifying the sources of salinization and understanding the geochemical processes governing freshwater salinization are important for sustainable water resources management and protection. It is in this context that researchers and professionals, investigating freshwater salinization by using isotope tracers, are invited to submit their abstracts to this session. Overall, we encourage the submission of contributions that study freshwater salinization at lab- or/and field-scale, for spatial or/and temporal variations, and this for groundwater and/or surface water.

Summary: It is now well established that atmospheric contaminants affect the climate, ecosystems, and human health, particularly in populated areas where they occur at significant concentrations. Accordingly, substantial research has been conducted over recent decades to chemically characterize these contaminants and identify their major components and formation processes. In this context, isotope geochemistry has demonstrated significant added value when combined with conventional chemical approaches, both for identifying contaminant sources and for characterizing the processes controlling their budgets.

We aim to address current gaps in the application of isotope geochemistry—including measurements of stable and radioactive isotope ratios of trace elements and organic compounds—to environmental research by welcoming original contributions focused on air contaminant characterization, pollution, and environmental change. We also encourage modeling and empirical studies aimed at improving our mechanistic understanding of short- and long-term chemical and isotope variations in global atmospheric systems. Themes of interest include: (i) Emerging issues related to air quality vulnerability and human impacts, including the isotope geochemistry of emerging chemical contaminants; (ii) Advances in isotope analytical techniques for monitoring and identifying the sources and processes controlling the budgets of air contaminants; (iv) Developments in atmospheric processes and atmospheric modeling to investigate air quality vulnerability to human impacts using isotope approaches; (v) Remote sensing applications for air quality vulnerability assessment based on isotope systematics.