Natural Mercury Sources Research Articles

Mercury from Icelandic geothermal activity: High enrichments in soils, low emissions to the atmosphere

Geothermal activity is a natural source of mercury (Hg) to surface environments, but its contributions as part of the larger geogenic flux to the global Hg budget are poorly understood, in part due to large geographic gaps in emissions data where no measurements have been made. In this study we report the results of a field campaign over 2021 and 2022 on the highly active volcanic island country of Iceland. Six geothermal sites across the country were investigated for soil gaseous elemental mercury (GEM) and total Hg (THg) concentrations through a series of measurements made across the diffuse degassing surface. At 10 cm depth, soil GEM concentrations were often hundreds and in some cases thousands of times higher than ambient surface air concentrations. Geothermal soils were also highly enriched in THg due to the sorption of hydrothermal Hg on the characteristically fine, thermally-altered clays and silts. Soil “hotspots” displayed THg concentrations exceeding 100 µg g−1 comparable to levels in areas heavily contaminated by anthropogenic activity and in Hg-rich mineral soils. Strong correlations were observed between soil GEM, THg and soil temperature, and intensive measurements made at small spatial scales (∼1 m2) demonstrated the representativeness of individual sampling points. By adapting an active sampling gradient method for determining soil–air gas fluxes, we estimate an Icelandic geothermal GEM flux of 1.8 kg a−1 and a total Icelandic GEM flux, including non-geothermal areas, of ∼18 kg a−1. This work shows that Icelandic geothermal activity can generate high GEM and THg concentrations in the local soil environment, but its contribution to global Hg cycling appears to be minor.

English

Since the Minamata conference, the scientific and professional worlds (gold industry, metal extraction, health) have come together to conduct research and raise awareness of the effects of mercury (Hg) in the environment, particularly on public health. Africa has not remained on the sidelines of these events, which have a planetary scope due to the long-range transport of various anthropogenic and natural sources of mercury. Since then, scientific data has been produced both in Africa and other continents in the world on the knowledge of the properties of mercury (Hg) as a poison that can migrate through all the links in the food chain. This scientific article is an analysis of mercury (Hg), its sources, its distribution, its health and environmental impacts (terrestrial, aquatic, atmospheric ecosystems, etc.) in Africa. It also aims to present the recent development in this field in the form of a general analysis and to present the measures taken at the political level to control mercury flows in developing countries while highlighting the shortcomings of these policies at the national level in some African countries. Keys words: Mercury, pollution, anthropogenic sources, health effects, Africa.

Mercury Levels in Women and Children from Interior Villages in Suriname, South America.

Natural sources of mercury, historical gold mining, and contemporary artisanal and small-scale gold mining (ASGM) activities have led to mercury contamination in Suriname. Our primary objective was to evaluate mercury levels in hair of women and children from interior villages in Suriname where mercury levels in fish are elevated. We also estimated blood levels of mercury using an established mathematical conversion to facilitate comparison with other biomonitoring programs in the United States. Estimated levels of mercury in the blood of participants from Suriname were significantly higher than those in women from a heavy marine fish-consuming population in southeast Louisiana and estimates of the US national average. This includes women from Surinamese villages well upstream of ASGM activities. Since residents in these areas rely heavily on local fish, this is likely the source of their exposure to mercury. The levels in hair are similar to those seen in women from longitudinal studies finding neurological impairments in children exposed pre- and postnatally. Additional biomonitoring and neurodevelopmental assessments are warranted in these areas, as well as other areas of the Suriname. Mercury levels in hair (Suriname) and blood (southeast LA USA) were determined using cold vapor atomic absorption spectroscopy (CVAAS).

Coupling atmospheric mercury isotope ratios and meteorology to identify sources of mercury impacting a coastal urban‐industrial region near Pensacola, Florida, USA

AbstractIdentifying the anthropogenic and natural sources of mercury (Hg) emissions contributing to atmospheric mercury on local, regional, and global scales continues to be a grand challenge. The relative importance of various direct anthropogenic emissions of mercury, in addition to natural geologic sources and reemission of previously released and deposited mercury, differs regionally and temporally. In this study, we used local‐scale, mesoscale, and synoptic‐scale meteorological analysis to couple the isotopic composition of ambient atmospheric mercury with potential sources of mercury contributing to a coastal urban‐industrial setting near a coal‐fired power plant in Pensacola, Florida, USA. We were able to broadly discern four influences on the isotopic composition of ambient atmospheric mercury impacting this coastal urban‐industrial region: (1) local to regional urban‐industrial anthropogenic emissions (mean δ202Hg = 0.44 ± 0.05‰, 1SD, n = 3), (2) marine‐influenced sources derived from the Gulf of Mexico (mean δ202Hg = 0.77 ± 0.15‰, 1SD, n = 4), (3) continental sources associated with north‐northwesterly flows from within the planetary boundary layer (mean δ202Hg = 0.65 ± 0.04‰, 1SD, n = 3), and (4) continental sources associated with north‐northeasterly flows at higher altitudes (i.e., 2000 m above ground level; mean δ202Hg = 1.10 ± 0.21‰, 1SD, n = 8). Overall, these data, in conjunction with previous studies, suggest that the background global atmospheric mercury pool is characterized by moderately positive δ202Hg values; that urban‐industrial emissions drive the isotopic composition of ambient atmospheric mercury toward lower δ202Hg values; and that air‐surface exchange dynamics across vegetation and soils of terrestrial ecosystems drive the isotopic composition of ambient atmospheric mercury toward higher positive δ202Hg values. The data further suggest that mass‐independent fractionation (MIF) of both even‐mass‐ and odd‐mass‐number isotopes, likely generated by photochemical reactions in the atmosphere or during reemission from terrestrial and aquatic ecosystems, can be obscured by mixing with anthropogenic emissions having different MIF signatures.

Distribution of mercury in sediments from Kagoshima Bay, Japan, and its relationship with physical and chemical factors

Kagoshima Bay is located on the south coast of Kyushu Island, Japan. Submarine fumaroles present in the northern area have been identified as a natural source of mercury in the bay. The aim of the present work is to study the spatial distribution of mercury in the bottom sediments of the bay and its relationship with major physicochemical properties that might affect the transport of mercury in the ecosystem surrounding this area. Sediment core samples were collected in the north and central areas in surveys performed during 2011 and 2013. The individual core samples were sliced and processed for the analysis of total mercury (T-Hg), chemical composition, total organic carbon (TOC), particle size and magnetic susceptibility. The horizontal distribution of T-Hg indicates that fumaroles are the primary source of Hg in the area; the results indicate a key role of organic matter binding to Hg. In the area to the west of the fumaroles, the relationship between Hg and TOC is characterized by two linear trends that correspond to the upper and lower sections of the cores. From the physicochemical properties, it was suggested that the two distinct linear relations might be caused by a change of the volcanic activity at the Aira Caldera, which is located at the northern part of the bay. The extent of the bay impacted by the Hg generated from the hydrothermal vents has decreased in recent years and is limited to the vicinity of the emission point.

Volcanic mercury in Pinus canariensis

Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg(-1)) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg(-1)). Thus, mercury emissions originating from the eruption remained only as a mark-in pyroclastic wounds-and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg(-1)) and bark (6.0 μg kg(-1)) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

Mercury deposition in a tidal marsh of south San Francisco Bay downstream of the historic New Almaden mining district, California

A record of mercury deposition was provided by sediment recovered from piston cores of a south San Francisco Bay tidal marsh that is 30 km downstream of the New Almaden mining district, formerly the largest mercury mining district in North America. Pre-mining sediment mercury concentrations were 0.40±0.15 nmol g −1, which are similar to pre-mining concentrations in cores taken from other parts of San Francisco Estuary. Concentrations in the core increase to a maximum of about 6.0 nmol g −1, corresponding to a period in the mid-20th century, nearly 50 years after the peak in mercury production at the mines. The extent of contamination from upstream mining activity appears to reflect the amount of processed ore disposed of at the surface, and also periods when mercury was recovered from reworking these surface ore dumps and open cuts. Transport of this contaminant mercury to the tidal marsh appears to be influenced by hydrologic modifications in the watershed, including dam building and subsidence related to groundwater withdrawal. Although San Francisco Estuary is contaminated with mercury from numerous historic mining sources, including late 19th century hydraulic gold mining in the Sierra Nevada, there is little evidence of pre-mining contamination from natural mercury sources in the southern reach of San Francisco Estuary.