Atmospheric mercury emissions from substrates and fumaroles associated with three hydrothermal systems in the western United States

Abstract

[1] This paper quantifies atmospheric mercury (Hg) emissions from substrates and fumaroles associated with three hydrothermal systems: Lassen Volcanic Center, California (LVC); Yellowstone Caldera, Wyoming (YC); and Dixie Valley, Nevada (DV). Substrate Hg fluxes were measured using field chamber methods at thermal and nonthermal sites. The highest Hg fluxes (up to 541 ng m À2 h À1 ) were measured at thermal active areas. Fluxes from altered and unaltered nonthermal sites were <10 ng m À2 h À1 and were comparable to those measured in natural low-Hg background regions for YC and DV, and at LVC they were slightly elevated. Similarly, reactive gaseous mercury concentrations were higher in thermal active areas. Using a Geographic Information System framework for scaling, estimated area-average Hg emissions from substrates were 0.9-3.8 ng m À2 h À1at LVC, 0.8-2.8 ng m À2 h À1 at YC, and 0.4-0.5 ng m À2 h À1 at DV. At LVC, nonthermal areas were the primary substrate source of atmospheric Hg (>98%). At YC, substrate Hg emissions were dominated (50 to 90%) by acidically altered thermal areas. Substrate emissions at DV were low and primarily from nonthermal areas (66% to 75%). Fumarole emissions at LVC (91-146 kg yr À1 ) and YC (0.18-1.6 kg yr À1 for Mud Volcano) were estimated by applying Hg:H 2 O and Hg:CO 2 ratios in hydrothermal gas samples to H 2 O and CO 2 emissions. Applying total area-average emissions from substrates and thermal features at LVC, YC, and DV to similar systems across the conterminous United States, yearly atmospheric Hg emissions from active hydrothermal systems are projected to be 1.3-2.1 Mg.

Mercury emissions from soils and fumaroles of Nea Kameni volcanic centre, Santorini (Greece)

“…We find a system blank value (GEM blank ~0.13 ng m -3 ) in agreement with those reported in literature (~0.2 ng GEM m -3 ; Gustin et al, 1999;Eckley et al, 2010;Engle et al, 2006). These measurements, thought limited to only five investigated sites, allow us to make a first order assessment of diffuse GEM emissions from soils, which we infer are in the range of 1.3-4.8 × 10 -2 ng m -2 s -1 (~47-173 ng m -2 h -1 ).…”

“…Measurements at the far higher-temperature (250°C) fumaroles of La Fossa Crater, Vulcano island, indicated GEM/CO 2 mass ratio of 6.0 × 10 -8 . Our data are also close to those reported by Engle et al (2006) for the fumaroles at Yellowstone Caldera, a hydrothermal system with temperatures ranging from 85°t o 95°C and in the presence of H 2 S (1.6 to 2.6 × 10 -9 ; Engle et al, 2006).…”

“…1b), and we argue that these different temperature environments may have a role in controlling the patterns of Hg release. In the soil system, remobilization of previously deposited Hg will take place during the daylight hours, when solar irradiation promotes photochemical reduction reactions (Zhang et al, 2001;Witt et al, 2008b;Fu et al, 2008;Engle et al, 2006;Gustin, 2003), a process that could well justify the increased soil GEM/CO 2 ratios (relative to fumaroles). Emission of this secondary (re-mobilized) GEM from soil will likely be suppressed upon approaching the fumaroles, because the higher thermal flux prevailing there will act against development of Hg deposition/re-volatilization cycles: at site NKS5, the closest to NK1 fumarole, we obtain a low GEM/CO 2 ratio, in all similar to the fumarolic ratio (Fig.…”

Investigation of factors affecting mercury emission from subtropical forest soil: A field controlled study in southwestern China

“…Earlier studies supposed that the amount of mercury emitted from soil to the chamber at the short TOTs associated with the high flow rates was quickly diluted such that ΔC approached the value of zero (Eckley et al, 2010;Engle et al, 2006;Lin et al, 2012). But high flushing flow rates may alter the chemical/physical conditions within the chamber beyond those expected under normal surface conditions resulting in an enhancement in surface emissions.…”

“…Instead, slow flushing flow rates may suppress the mercury emission potential due to the excessive buildup of mercury within the chamber. Engle et al (2006) suggested that while high flow rates and short TOTs are appropriate for measuring flux from soils with high mercury concentrations, lower flow rates and TOTs were more appropriate for low mercury content soils and Eckley et al (2010) proposed that the optimal flow for measuring mercury flux was at the beginning of the stable ΔC period, which was chosen as a compromise between competing criteria aimed at creating conditions inside the chamber similar to the outside. The relative stable ΔC concentrations were about 1.8 ng m −3 , and the corresponding flushing flow rate was 5 L min −1 and TOT was 0.94 min in this field study.…”