No evidence for large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet.

In the current Matters Arising we present results from verifying control measurements of dissolved mercury (Hg) in glacial meltwater from the Greenland Ice Sheet (GrIS), which significantly challenges the conclusions of the recent publication by Hawkings et al. (2021). By direct measurements of meltwater in the same glacial catchment area, we demonstrate that the input Hg concentration for the regional upscaling in Hawkings et al (2021) is likely vastly over-estimated with major implications for the validity of the asserted extreme yield of Hg from the GrIS. In addition, we present a plausible explanation for the high Hg concentration values in the study, namely hitherto unidentified cross-contamination of water samples by mercury chloride (HgCl2), which was present and used for other purposes during field work. Together, the result of our control study potentially invalidates the suggested implications of geologically sourced Hg under the southwestern margin of the GrIS on the Arctic ecosystem in both current and future climate conditions.

Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

The Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

Discontinuous Geochemical Monitoring of the Galleria Italia Circumneutral Waters (Former Hg-Mining Area of Abbadia San Salvatore, Tuscany, Central Italy) Feeding the Fosso Della Chiusa Creek

The Galleria Italia waters drain the complex tunnel system of the former Hg-mining area of Abbadia San Salvatore (Tuscany, central Italia) and feed the 2.5 km-long Fosso della Chiusa creek. The mining exploitation was active for more than one century and more than 100,000 tons of liquid mercury were produced by roasting processes of cinnabar (HgS). In this work, a discontinuous geochemical monitoring of the Galleria Italia circumneutral waters was carried out from February 2009 to October 2020, during which the main physicochemical parameters, main and minor dissolved species and trace elements (including Hg) were determined. In the observation period, significant variations in the water chemistry were recorded, particularly when flooding waves, due to intense precipitations, occurred, with the two main events being recorded in February 2009 and January 2010. The chemical composition of the Galleria Italia waters was Ca(Mg)-SO4 and related to congruent dissolution of gypsum/anhydrite at which a contribution from carbonatic and silicatic minerals and partial solubilization of CO2 and and H2S oxidation is to be added. Regarding the trace elements, Al, Mn and Fe were up to 1500, 768 and 39520 μg L−1, with these elements also showing high contents in the sediment precipitating by the Galleria Italia waters. In most cases, dissolved mercury was below the instrumental detection limit (<0.1 μg L−1), although occasionally it reached >1 μg L−1. Considering a mean flow rate of 40 L s−1 of the discharged water, the amount of dissolved mercury released from Galleria Italia was computed, although most mercury was occurring in the sediment (1.2 mg kg−1). A more realistic computation of mercury released from Galleria Italia should involve a sampling network along the Fosso della Chiusa before entering the riverine system of the Tiber basin, into which dissolved and suspended mercury are to be determined along with that occurring in the sediments.

HR3DHG version 1: modeling the spatiotemporal dynamics of mercury in the Augusta Bay (southern Italy)

The biogeochemical dynamics of Hg, and specifically of its three species Hg0, HgII, and MeHg (elemental, inorganic, and organic, respectively), in the marine coastal area of Augusta Bay (southern Italy) have been explored by the high-resolution 3D Hg (HR3DHG) model, namely an advection–diffusion–reaction model for dissolved mercury in the seawater compartment coupled with a diffusion–reaction model for dissolved mercury in the pore water of sediments in which the desorption process for the sediment total mercury is taken into account. The spatiotemporal variability of the mercury concentration in both seawater ([HgD]) and the first layers of bottom sediments ([HgDsed] and [HgTsed]), as well as the Hg fluxes at the boundaries of the 3D model domain, have been theoretically reproduced, showing acceptable agreement with the experimental data collected in multiple field observations during six different oceanographic cruises. Also, the spatiotemporal dynamics of the total mercury concentration in seawater have been obtained by using both model results and field observations. The mass balance of the total Hg species in seawater has been calculated for the Augusta Harbour, improving previous estimations. The HR3DHG model could be used as an effective tool to predict the spatiotemporal distributions of dissolved and total mercury concentrations, while contributing to better assessing hazards for the environment and therefore for human health in highly polluted areas.

Amalgam and Dissolved Mercury Removal A system not just a Separator

&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Abstract&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Title: Amalgam and Dissolved Mercury Removal&amp;#160; A system not just a Separator&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Content&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Packs Solutions LLC has developed an amalgam and dissolved mercury system that significantly reduces the mercury discharge from the dental practice. The US American Dental Association estimates that 50% of the mercury entering the waste treatment facility is from dental practices. &amp;#160;The system consists of an innovative chairside trap, use of pH neutral vacuum line cleaners and disinfectants, and advanced technology separator that removes the dissolved mercury from the office discharge. &amp;#160;The system is currently in use in the United States and is rapidly gaining popularity with wastewater treatment authorities.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The presentation provides data taken from dental offices and the affect of pH on the dissolving of amalgam in water. The average dental office generates over 14,000 ng/L of dissolved mercury that can not be removed by traditional waste treatment processes.&amp;#160; The system has proven to reduce the discharge to &lt;1,000 ng/L on average.&amp;#160; The system requires no changes in office routine or equipment. The separator is maintenance free and the chairside trap is custom made to fit in any brand of trap.&amp;#160; The average annual cost in the United States is as low as $420 for one chair practice to $1300 for a 6 chair practice.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Bill Purves&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Packs Solutions LLC&lt;/p&gt;

HR3DHG version 1: modelling the spatio-temporal dynamics of mercury in the Augusta Bay (southern Italy)

The biogeochemical dynamics of Hg, and specifically of its three species Hg0, HgII, and MeHg (elemental, inorganic, and organic, respectively) in the marine coastal area of Augusta Bay (southern Italy) have been explored by the high resolution 3D Hg (HR3DHG) model, namely an advection-diffusion-reaction model for the dissolved mercury in the seawater compartment coupled with i) a diffusion-reaction model for dissolved mercury in the pore water of sediments and ii) a sorption/de-sorption model for total mercury in the sediments. The spatio-temporal variability of dissolved and total mercury concentration both in seawater ([HgD] and [HgT]) first layers of bottom sediments ([HgsedD] and [HgsedT]), and the Hg fluxes at the boundaries of the 3D model domain have been theoretically reproduced, showing an excellent agreement with the experimental data, collected in multiple field observations during six different oceanographic cruises. The mass-balance of the different Hg species in seawater has been calculated for the Augusta Harbor, improving previous estimations. The HR3DHG model includes modules that can be implemented for specific and detailed exploration of the effects of climate change on the spatio-temporal distribution of Hg in highly contaminated coastal-marine areas.

Mercury in the water of small rivers of the Onega Bay basin of the White Sea

The results of the expeditionary studies of the mercury behavior in the water of small rivers of the Onega Bay basin of the White Sea are presented. Priority forms of mercury migration have been identified and the forms of its location along the trunk of the Kyanda River have been calculated. The relationship between the content of various forms of mercury on the one hand and salinity, pH, Eh waters on the other has been analyzed. The influence of hydrological phases on the transformation of inorganic forms of mercury has been revealed. Differences in the levels of content of dissolved mercury and its connection with the salinity in the extuar areas of the marginal filters of the Subarctic rivers in natural conditions and the environment of anthropogenic impact were established.