Varved lake sediments as archives of environmental impacts following large volcanic eruptions

Major volcanic eruptions may have severe societal impacts as shown by ash dispersal and sulphur emissions from recent Icelandic eruptions. However, ice-core sulphur records demonstrate that these events were minor as compared to historical events of much larger magnitude.

We still lack a sufficient understanding of the environmental impacts of such colossal eruptions, which take place on average once per century. By sampling of annually laminated (varved) lake sediments at well-documented sites, we aim at estimating the extent of such sulphate deposition events, their typical duration and effects on aquatic biota, catchment vegetation and soils, including the potential release of methyl mercury to lake waters. We will target six major events of known origin during the last millennium and analyse their physical, chemical and biological impacts at annual resolution, using an advanced freeze corer and established palaeolimnological and geochemical methods. As part of ongoing efforts to establish instrumentation for synchrotron light-based analyses of unaltered, frozen sediment records at the MAX IV facility in Lund, we will also perform high-resolution S and Fe speciation analyses of the sediments, using X-ray absorption near-edge spectroscopy. Apart from deeper insights into ecosystem responses to massive sulphur deposition and associated ashfall events, the proposed research will pave the way for future applications of synchrotron light-based techniques within palaeolimnology.