Assessment of Incubation Experiments Using Isotopically Enriched Mercury Compounds in Seawater including Dissolved Gaseous Mercury
Year: 2024
Type: article
Abstract: The main drivers of mercury (Hg) compound distribution in seawater are poorly understood, calling for novel spatial and seasonal observations of potential transformations. However, scientific progress is hindered by a lack of intercomparability among incubation studies and the infrequent inclusion of dissolved gaseous mercury species (DGM = elemental Hg (Hg(0)) + dimethyl Hg (DMHg)) despite their importance in the biogeochemical cycle of Hg. We perform a comprehensive quality assessment on our proposed incubation protocol at near ambient concentrations (∼10 × ambient background) including the formation of DGM on three distinct coastal seawaters and discuss intercomparability with previous experimental approaches. We establish an excellent mass balance for tracer isotopes both excluding DGM ( 199 Hg = 99.5% and 201 Hg = 100.4%, median) and including DGM ( 199 Hg = 100.3% and 201 Hg = 101.7%, median). We find a good median relative standard deviation for experimental triplicates ( 199 Hg(II) ∼ 1.7%, MM 201 Hg ∼ 1.5%, 199 DGM ∼ 10%, 201 Hg(II) ∼ 13%, and 201 DGM ∼ 22%), enabling the accurate determination of methylation, demethylation, and reduction rate constants at femtomolar concentration levels. We observed Hg(0) formation from MMHg, potentially indicating reductive demethylation. This study highlights the practicability and importance of incorporating DGM species (here, Hg(0), eventually DMHg) in future incubation studies.
Source: ACS ES&T Water
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
Funder: Agence Nationale de la Recherche
Award: E2S
OpenAlex ID: W4405334071