Mercury records covering the past 90 000 years from lakes Prespa and Ohrid, SE Europe
<p>The element mercury (<span class="inline-formula">Hg</span>) is a key pollutant, and much insight has been gained by studying the present-day <span class="inline-formula">Hg</span> cycle. However, many important processes within this cycle operate...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-01-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/21/531/2024/bg-21-531-2024.pdf |
| Summary: | <p>The element mercury (<span class="inline-formula">Hg</span>) is a key pollutant, and much insight has been gained by studying the present-day <span class="inline-formula">Hg</span> cycle. However, many important processes within this cycle operate on timescales responsive to centennial- to millennial-scale environmental variability, highlighting the importance of also investigating the longer-term <span class="inline-formula">Hg</span> records in sedimentary archives. To this end, we here explore the timing, magnitude, and expression of <span class="inline-formula">Hg</span> signals retained in sediments over the past <span class="inline-formula">∼</span> 90 <span class="inline-formula">kyr</span> from two lakes, linked by a subterranean karst system: Lake Prespa (Greece, North Macedonia, and Albania) and Lake Ohrid (North Macedonia and Albania). Results suggest that <span class="inline-formula">Hg</span> fluctuations are largely independent of variability in common host phases in each lake, and the recorded sedimentary <span class="inline-formula">Hg</span> signals show distinct differences first during the Late Pleistocene (Marine Isotope Stages 2–5). The <span class="inline-formula">Hg</span> signals in Lake Prespa sediments highlight an abrupt, short-lived peak in <span class="inline-formula">Hg</span> accumulation coinciding with local deglaciation. In contrast, Lake Ohrid shows a broader interval with enhanced <span class="inline-formula">Hg</span> accumulation and, superimposed, a series of low-amplitude oscillations in <span class="inline-formula">Hg</span> concentration peaking during the Last Glacial Maximum, which may result from elevated clastic inputs. Divergent <span class="inline-formula">Hg</span> signals are also recorded during the Early and Middle Holocene (Marine Isotope Stage 1). Here, Lake Prespa sediments show a series of large <span class="inline-formula">Hg</span> peaks, while Lake Ohrid sediments show a progression to lower <span class="inline-formula">Hg</span> values. Since <span class="inline-formula">∼</span> 3 <span class="inline-formula">ka</span>, anthropogenic influences overwhelm local fluxes in both lakes. The lack of coherence in <span class="inline-formula">Hg</span> accumulation between the two lakes suggests that, in the absence of an exceptional perturbation, local differences in sediment composition, lake structure, <span class="inline-formula">Hg</span> sources, and water balance all influence the local <span class="inline-formula">Hg</span> cycle and determine the extent to which <span class="inline-formula">Hg</span> signals reflect local- or global-scale environmental changes.</p> |
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| ISSN: | 1726-4170 1726-4189 |