Evaluating elemental mercury outgassing from soil-groundwater systems using passive air samplers: method development and implementation (EMOSGROW Project).

• Applicant: Professor Harald Biester, Ph.D., since 12/2021
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Soil Sciences
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495149255

Mercury (Hg) is a redox active element in soils and groundwater, readily partitioning between oxidised (Hg2+) and reduced (Hg0) species. Elemental Hg (Hg0) is highly volatile and when produced favours partitioning from condensed phases (solids and liquids) to the gas phase, where it is persistent. This process leads to atmospheric emissions of mercury that increase active pool of Hg in the global Hg cycle and can lead to human and environmental health effects. Such concerns are heightened in soil-groundwater systems that have been contaminated by Hg. Peatlands are a unique soil-groundwater system that can store large amounts of atmospherically derived Hg in which high and variable groundwater levels (at or near the surface) and peat decomposition can lead to extreme redox gradients, and production of both Hg0 and highly toxic methyl-Hg. Despite our awareness of Hg0 production in these soil-groundwater systems, very little is known about Hg0 outgassing from groundwater, deep soil layers andpeatlands and there is no existing method that can assess the production and presence of gas phase Hg0. Here we present a novel research approach to examine this critical process in the Hg biogeochemical cycle. The method of assessing Hg0 outgassing from groundwater and subsurface soils and peat will be based on a novel, time-averaged passive (non-electrical) sampling approach using Hg passive air samplers (MerPAS; developed by the project Antragsteller) deployed within groundwater wells and sampling containers buried within soil/peat profiles. Method development will require full calibration specific to these unique applications using co-located automated/pumped Hg0 measurements and a complete description of the method uncertainty assessed through both laboratory and field studies. Measurements are to be carried out in the area of the three Hg contaminated sites in southern Germany and Switzerland and peatlands in Northern Germany and the Julian Alps (Slovenia).

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: David McLagan, Ph.D., until 11/2021