Abstract
The study of mercury accumulation in peat cores provides an excellent opportunity to improve the knowledge on mercury cycling and depositional processes at remote locations far from pollution sources. We analyzed mercury concentrations in 150 peat samples from two cores from Rano Aroi (Easter Island, 27° S) and in selected vegetation samples of present-day flora of the island, in order to characterize the mercury cycling for the last ~71 ka BP. The mercury concentrations showed values ranging between 35 and 200 ng g−1, except for a large maxima (~1000 ng g−1) which occurred at the end of the Last Glacial Maximum (LGM, ~20 ka cal BP) in both peat cores. Low temperatures during the LGM would accelerate the atmospheric oxidation of Hg(0) to divalent mercury that, coupled with higher rainfall during this period, most likely resulted in a very efficient surface deposition of atmospheric mercury. Two exceptional short-lived Hg peaks occurred during the Holocene at 8.5 (350 ng g−1) and 4.7 (1000 ng g−1) ka cal BP. These values are higher than those recorded in most peat records belonging to the industrial period, highlighting that natural factors played a significant role in Hg accumulation—sometimes even more so than anthropogenic sources. Our results suggest that wet deposition, linked to atmospheric oxidation, was the main process controlling the short-lived Hg events, both in the mire and in the catchment soils.
Highlights
Mercury (Hg) is a metal of environmental concern due to its high volatility, long atmospheric residence time (1–2 years), and the bioaccumulation of its methylated forms
We found that three of the four main processes controlling Hg concentration depended on climate: wet and dry Hg deposition, as well as local catchment soil erosion owing to precipitation events [29]
The Hg record in the Rano Aroi cores shows a huge range of values between 35–1000 ng g−1, mostly driven by wet precipitation—directly on the mire or through the catchment circuits—essentially during high-rainfall events
Summary
Mercury (Hg) is a metal of environmental concern due to its high volatility, long atmospheric residence time (1–2 years), and the bioaccumulation of its methylated forms. It is released and dispersed in the atmosphere by natural emission sources such as volcanoes, geothermal vents, and Hg-enriched soil, as well as by anthropogenic activities such as mining, coal-fired plants, and chlor-alkali plants [1,2,3]. Gaseous elemental mercury (Hg(0)) is the dominant form of atmospheric Hg, and it is efficiently transported around the globe by long-range atmospheric transport It can be oxidized into highly reactive and water soluble divalent species (Hg(II)), and/or particle-bound Hg (Hg(p)) that can be deposited through wet and dry processes onto surfaces.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
