Effects of Holocene climate change on mercury deposition in Elk Lake, Minnesota: The importance of eolian transport in the mercury cycle

Abstract

Sediments in Elk Lake, Minnesota, consist of 10,400 varve layers that provide a precise chronology for Holocene fluctuations in climate and biota recorded in the strata. Progressively greater concentrations and accumulation rates of mercury since ca. A.D. 1875 reflect deposition of anthropogenic mercury additions to the atmosphere. Within the Ho-locene record are numerous short intervals in which mercury concentrations and accumulation rates exceed the modern values. The highest mercury concentrations formed ca. 8 ka, coincident with a rapid change from cool, moist conditions to warm, dry conditions. A related change in flora from pine forest to prairie caused destruction of organic forest soils and the release of mercury that had been sequestered in them, resulting in a short-lived pulse of mercury to the lake. Accumulation rates of mercury were highest during the 4 k.y. mid-Holocene dry interval and show a correlation with periods of rapid depo-sition of eolian dust. The mercury was probably bound to wind-borne mineral particles, which were derived from an unidentified mercury-rich source region west of Elk Lake.

The Role of Climate: 71 ka of Atmospheric Mercury Deposition in the Southern Hemisphere Recorded by Rano Aroi Mire, Easter Island (Chile)

“…The mid-Holocene Hg peak in the Aroi peat record is also in agreement with the maximum Hg accumulation recorded at 4.2 ka cal BP in varved Elk Lake (North America) [68]. These authors found a causative factor between increased aeolian dust transport and deposition from remote locations with Hg-enriched soils.…”

Natural and anthropogenic variations in atmospheric mercury deposition during the Holocene near Quelccaya Ice Cap, Peru

“…We first test the hypothesis that atmospheric deposition is the primary source of Hg to Yanacocha by comparing Hg concentrations and sedimentology in the Yanacocha record during the entire record (12.3 to 0 ka) and just the preanthropogenic period (defined and used herein as 12.3 to 3.5 ka, based on previous records and historical information [ Nriagu , ; Martínez‐Cortizas et al ., ; Cooke et al ., ]). Previous millennial‐scale Hg records in lake sediments relate changes in Hg fluxes to groundwater level [ Jacobson et al ., ], lithogenic input from weathering within the catchment [ Thevenon et al ., ], and mobilization of Hg from soils [ Cannon et al ., ]. However, the lack of correlations of Hg concentration with LOI 550 and with Ti (Figure ) shows that organic matter and lithogenic input, respectively, do not have significant effects on Hg deposition in Yanacocha.…”

Prediction of Holocene Mercury Accumulation Trends by Combining Palynological and Geochemical Records of Lake Sediments (Black Forest, Germany)

“…Long-term records encompassing Hg deposition over several thousands of years suggest a natural variability in the background values comparable to the recent anthropogenic forcing of the atmospheric Hg cycle [28,32,57,58]. Potential factors controlling pre-industrial Hg variations in lake sediments are natural changes in atmospheric fluxes.…”