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1. Isolation and Identification of Mercury–Dissolved Organic Matter Complexes in Mercury–Humic Acid Suspensions

   https://doi.org/10.1002/rcm.9986  

   Qasim, Ghulam Hussain; Harris, Lisa; Mangal, Vaughn; Montesdeoca, Mario; Todorova, Svetoslava; Driscoll, Charles (January 2025, Rapid Communications in Mass Spectrometry)

   ABSTRACT RationaleThe complexation with dissolved organic matter (DOM) is a pivotal factor influencing transformations, transport, and bioavailability of mercury (Hg) in aquatic environments. However, identifying these complexes poses a significant challenge because of their low concentrations and the presence of coexisting ions. MethodsIn this study, mercury–dissolved organic matter (Hg‐DOM) complexes were isolated through solid‐phase extraction (SPE) from Hg–humic acid suspensions, and complexes were putatively identified using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS). ResultsDissolved organic carbon (DOC) and total Hg analysis before and after SPE showed an increase in DOC:Hg ratio. The DOC:Hg ratio was lower in extracts from cartridges with silica structure bonded with hydrocarbon chains (C18) than priority pollutant (PPL) cartridges at circumneutral pH, indicating that C18 was more effective at extracting DOM complexed Hg. These results were confirmed with FTICR‐MS analysis, where two Hg‐DOM complexes were putatively identified from PPL extracts as opposed to eight from C18 (Winnow score > 75%). In addition, C₈H₁₃HgN₂O₂S, a molecular formula with am/zratio of 403.04, was identified across three separate extractions using a C18 cartridge, suggesting that the complexes were preserved during extraction and, presumably, electrospray ionization. ConclusionsThe results highlight the effectiveness of the methodology developed in this study—SPE coupled with FTICR‐MS for isolating and identifying Hg‐DOM complexes. This approach allows for the exploration of the elemental and structural composition of Hg‐DOM complexes, which affects Hg speciation, bioavailability, and transformations in aquatic ecosystems. SynopsisA methodology was developed to identify Hg‐DOM complexes at low concentrations to gain insight into mercury bioavailability, transformations, and transport in the environment. 

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2. Mercury speciation and stable isotopes in emperor penguins: First evidence for biochemical demethylation of methylmercury to mercury-dithiolate and mercury-tetraselenolate complexes

   https://doi.org/10.1016/j.jhazmat.2024.136499  

   Manceau, Alain; Bustamante, Paco; Richy, Etienne; Cherel, Yves; Janssen, Sarah E; Glatzel, Pieter; Poulin, Brett A (March 2025, Journal of Hazardous Materials)
3. Aqueous Elemental Mercury Production versus Mercury Inventories in the Lake Michigan Airshed: Deciphering the Spatial and Diel Controls of Mercury Gradients in Air and Water

   https://doi.org/10.1021/acsestwater.0c00187  

   Lepak, Ryan F.; Tate, Michael T.; Ogorek, Jacob M.; DeWild, John F.; Peterson, Benjamin D.; Hurley, James P.; Krabbenhoft, David P. (January 2020, ACS ES&T Water)

   null (Ed.)

   Atmospheric delivery of mercury (Hg) is important to the Upper Great Lakes, and understanding gaseous Hg exchange between surface water and air is critical to predicting the effects of declining mercury emissions. Speciated atmospheric Hg, dissolved gaseous Hg (DGM), and particulate and filter passing total Hg were measured on a cruise in Lake Michigan. Low mercury levels reflected pristine background conditions, especially in offshore regions. In the atmosphere, reactive and particle-associated fractions were low (1.0 ± 0.5%) compared to gaseous elemental Hg (1.34 ± 0.14 ng m–3) and were elevated in the urbanized southern basin. DGM was supersaturated, ranging from 17.5 ± 4.8 pg L–1 (330 ± 80%) in the main lake to 33.2 ± 2.4 pg L–1 (730 ± 70%) in Green Bay. Diel cycling of surface DGM showed strong Hg efflux during the day due to increased winds, and build-up at night from continued DGM production. Epilimnetic DGM is formed from photochemical reduction, while hypolimnetic DGM originates from biological Hg reduction. We found that DGM concentrations were greatest below the thermocline (30.8 ± 13.6 pg L–1), accounting for 68–92% of the total DGM in Lake Michigan, highlighting the importance of nonphotochemical reduction in deep stratified lakes. 

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4. Quantum Chemical Investigation of Snow–Mercury Interactions and Their Implication of Mercury Deposition in the Arctic

   https://doi.org/10.1021/acs.jpca.2c08551  

   Ali, Emaan; Patel, Nandini; Patel, Shrina; Asaduzzaman, Abu (March 2023, The Journal of Physical Chemistry A)
5. Interaction of reactive mercury with surfaces and implications for atmospheric mercury speciation measurements

   https://doi.org/10.1016/j.atmosenv.2023.120240  

   Allen, Natalie; Gačnik, Jan; Dunham-Cheatham, Sarrah M.; Gustin, Mae Sexauer (February 2024, Atmospheric Environment)

   Accurate measurement of atmospheric reactive mercury (RM) presents analytical challenges due to its reactivity and ultra-trace concentrations. In the last decade, use of the University of Nevada, Reno – Reactive Mercury Active System (RMAS) for RM measurements has increased since it has been shown to be more accurate than the industry standard, the Tekran 2537/1130/1135 system. However, RMAS measurements also have limitations, including long time resolution and sampling biases associated with membranes used for RM sampling. We therefore investigated the use of higher sampling flow rates to reduce sampling time and tested alternative membrane materials using both ambient air sampling and controlled laboratory experiments with a gaseous oxidized mercury (GOM) calibrator. Results indicated that increasing the RMAS sampling flow had a negative impact on determined RM concentrations. RM concentrations at 2 L min−1 were 10% and 30–50% lower than at 1 L min−1 in spring/summer and winter, respectively. However, the chemical composition of RM captured on membranes was not impacted by the increased flow rate. Membranes currently used in the RMAS performed better than numerous alternatives with similar composition, retaining Hg more efficiently. Both ambient air sampling and laboratory experiments revealed that membranes designed to retain only particulate-bound mercury (PBM) also retained significant amounts of GOM. PBM membranes based on borosilicate glass designs retained more than 70% of GOM. 

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