Effects of Historical and Modern Mining on Mercury Deposition in Southeastern Peru

Abstract

Both modern anthropogenic emissions of mercury (Hg), primarily from artisanal and small-scale gold mining (ASGM), and preindustrial anthropogenic emissions from mining are thought to have a large impact on present-day atmospheric Hg deposition. We study the spatial distribution of Hg and its depositional history over the past ~400 years in sediment cores from lakes located regionally proximal (~90–150 km) to the largest ASGM in Peru and distal (>400 km) to major preindustrial mining centers. Total Hg concentrations in surface sediments from fourteen lakes are typical of remote regions (10–115 ng g−1). Hg fluxes in cores from four lakes demonstrate preindustrial Hg deposition in southeastern Peru was spatially variable and at least an order of magnitude lower than previously reported fluxes in lakes located closer to mining centers. Average modern (A.D. 2000–2011) Hg fluxes in these cores are 3.4–6.9 μg m−2 a−1, compared to average preindustrial (A.D. 1800–1850) fluxes of 0.8–2.5 μg m−2 a−1. Modern Hg fluxes determined from the four lakes are on average 3.3 (±1.5) times greater than their preindustrial fluxes, similar to those determined in other remote lakes around the world. This agreement suggests that Hg emissions from ASGM are likely not significantly deposited in nearby downwind regions.

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

“…We therefore calculate a best approximation of the Hg flux ratio in the Yanacocha record as time-weighted mean post-A.D. 1980 fluxes (4.0 μg m À2 a À1 ) over pre-3.5 ka fluxes (1.4 μg m À2 a À1 ), yielding a flux ratio of 3.0 ± 1.5. This flux ratio, which accounts for total anthropogenic Global Biogeochemical Cycles 10.1002/2013GB004780 modification to the global Hg cycle during the Holocene, is in good agreement with sediment records that use the period A.D. 1800 to 1850 as background fluxes from two other lakes in southeastern Peru (i.e., 4.0 ± 1.0) [Beal et al, 2013] and from lakes around the world (i.e., on average 3.5) [Biester et al, 2007]. The discrepancy between our Holocene Hg flux ratio (3.0 ± 1.5) and the modeled 7.5-fold enrichment since 2000 B.C.…”

“…Decreased Hg concentrations and fluxes in the Yanacocha record from ~ A.D. 1650 to 1750 are followed by a general increase coincident in timing with estimated maximum Hg 0 emissions in South and Central America from ~ A.D. 1750 to 1810 [ Nriagu , ]. However, increasing Hg fluxes are not evident during this period in Laguna Negrilla (Figure ) or in two lakes ~65 km west of Yanacocha [ Beal et al ., ]. The spatially inconsistent signal of Hg fluxes in this region suggests that mining dust continued to contribute significant amounts of Hg to certain lakes and that any increase in Hg deposition due to anthropogenic Hg 0 emissions was relatively negligible during the preindustrial period.…”

“…1750 to 1810 [Nriagu, 1993]. However, increasing Hg fluxes are not evident during this period in Laguna Negrilla (Figure 7) or in two lakes~65 km west of Yanacocha [Beal et al, 2013]. The spatially inconsistent signal of Hg fluxes in this region suggests that mining dust continued to contribute significant amounts of Hg to certain lakes and that any increase in Hg deposition due to anthropogenic Hg 0 emissions was relatively negligible during the preindustrial period.…”

Diatom ooze—A large marine mercury sink

“…The amount of Hg emitted to the atmosphere by colonial gold mining was probably too low to be detectable in remote Antarctica. Similarly, the increase in global atmospheric Hg loads, as revealed by our Antarctic marine sediment cores, attributed to all-time anthropogenic activities, is only about a factor of 2.2, which is slightly lower than in most Hg records from terrestrial archives (14,(30)(31)(32) but distinctly lower than current model predictions. This might be due to the fact that most anthropogenic Hg has been emitted in the Northern Hemisphere so that a larger Hg portion is sequestered there.…”

Observational and Modeling Constraints on Global Anthropogenic Enrichment of Mercury

“…Some recent work suggests releases to the atmosphere are only a small fraction of the total Hg consumed 13, 29 and impacts are restricted to the local environment. 30,31 The objective of this review is to bracket plausible scenarios for global anthropogenic enrichment of Hg based on current estimates of primary emissions and rates of exchange between environmental reservoirs. Global anthropogenic Hg enrichment is important because it directly affects future environmental responses to changes in anthropogenic emissions, and we discuss the implications of various uncertainty scenarios here.…”