Isotopic Tracing of Atmospheric and Groundwater Sulfur Dynamics

Isotopic tracing of sulfur integrates stable and cosmogenic isotope measurements to unravel the sources, transport pathways and transformation processes of sulfur in the atmosphere and subsurface water. In the atmosphere, oxidation of sulphur dioxide to sulphate involves mass-dependent fractionation of 34S/32S ratios, while in the stratosphere cosmogenic production of 35S generates a time-sensitive tracer that is delivered to the troposphere by precipitation. Once deposited, sulphate migrates through soils and aquifers, where microbial activity and mineral interactions can further alter isotopic signatures. By analysing δ34S and δ33S values alongside 35S activities, researchers can distinguish anthropogenic emissions from volcanic or biogenic sources, quantify deposition rates, and establish residence times of water in recharge zones. These methods inform assessments of acid deposition, industrial pollution control and the sustainability of groundwater resources. Advances in mass spectrometric resolution and sample preparation have improved detection limits for both stable and radioactive isotopes, expanding the applicability of isotopic tracing to diverse climatic regions. Integrating atmospheric chemistry with hydrogeological modelling now enables robust predictions of sulphur fluxes at regional and global scales, with direct implications for managing water quality, evaluating ecosystem responses and guiding environmental policy.

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Isotopic Tracing of Atmospheric and Groundwater Sulfur Dynamics publication trend

The graph below shows the total number of articles in isotopic tracing of atmospheric and groundwater sulfur dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Stable sulphur isotopes (δ34S, δ33S): Ratios of non-radioactive 34S and 33S to 32S used to trace sulphur sources and reaction pathways.

Cosmogenic 35S: A radioactive isotope of sulphur produced in the upper atmosphere, with an 87.4-day half-life, used as a time-sensitive tracer.

Isotopic fractionation: The partitioning of isotopes between substances or phases due to physical or chemical processes, leading to characteristic isotope ratio shifts.

Managed Aquifer Recharge (MAR): Deliberate infiltration of surface or recycled water into aquifers to enhance groundwater resources and quality.

Mass spectrometry: Analytical technique for measuring isotope ratios by separating ions based on mass-to-charge ratio.

Input function: The temporal profile of isotope concentration entering a system, required for accurate residence time calculations.

References

1. Quantifying Apparent Groundwater Ages near Managed Aquifer Recharge Operations Using Radio-Sulfur (35S) as an Intrinsic Tracer. Water (2016).
2. Variability of Cosmogenic 35S in Rain—Resulting Implications for the Use of Radiosulfur as Natural Groundwater Residence Time Tracer. Water (2020).