Mercury Partitioning in two Different Types of Waterbodies

Author(s): Christof Plessl, Christiane Christian, Thomas Zechmeister, Bernhard Keppler, Franz Jirsa
Abstract: Mercury (Hg) is one of the most frequently and globally occurring pollutants and is listed as a priority substance in the field of water policy within the European Union. In a previous study, we measured unexpectedly high Hg levels in plants and fish from Lake Neusiedl, an alkaline, saline, seston-rich, shallow lake in Eastern Austria. Hg concentrations in sediment were far below the Austrian background levels. No point source for Hg in the lake has been described before, therefore, atmospheric deposition is considered to be the main source for the Hg budget in the lake. The question of an enhanced Hg turnover due to the specific chemical properties of the lake arose. To shed light on the physico-chemical processes involved, we performed lab experiments comparing water samples from Lake Neusiedl with samples from Panozzalacke, a small freshwater waterbody within the catchment of the Danube River, representing an average European freshwater body. Mesocosm experiments using Hg spiked water samples, without and with undisturbed sediment were conducted to observe Hg partitioning between water, air, sediment and particulate matter over time. The results showed a significantly faster Hg removal from the water phase in Lake Neusiedl and a clear enhancement of the removal of Hg from the water phase in the presence of sediment in both samples. In addition, a negative correlation between the emission of Hg into the air and the share of particular bound Hg, which was higher in Lake Neusiedl, was detected. This is a strong hint, that Hg that enters the waterbody is bound to particular matter much faster, and to a higher degree in Lake Neusiedl, depriving it from deposition into the sediment and enhancing its bioavailability. Ongoing field experiments should confirm these observations under natural conditions.
Organisation(s): Department of Inorganic Chemistry
External organisation(s): University of Vienna, University of Johannesburg (UJ)
Publication date: 07-2018
Austrian Fields of Science 2012: 104023 Environmental chemistry, 104003 Inorganic chemistry
Portal url: https://ucrisportal.univie.ac.at/en/publications/5a52b9cb-07e6-4c72-be34-2f78b6cdfba0