Polyselenylsulfides as neglected central intermediates in Selenium cycling
Year: 2025
Type: article
Abstract: Selenium (Se) is an essential yet toxic trace element; it has one of the narrowest nutritional optimums of all elements. The speciation of Se significantly influences its mobility, toxicity, bioavailability, and bioaccumulation. Se environmental cycling has been generally understood as a sequence of bidirectional redox processes of Se species. Elemental Se (Se 0 ) is considered a central species that is thermodynamically favoured in the redox conditions found in most environments. This study reports the identification of a novel group of dissolved species called polyselenylsulfides (with the general formula Se x S y 2− ). These species form upon the reaction of Se 0 with sulfide. Using derivatisation and ultrahigh-performance liquid chromatography electrospray ionisation quadrupole time-of-flight mass spectrometry, polysulfides (S x 2− , x = 2–6), selenide (Se 2− ), polyselenides (Se x 2− , x = 2–3), and previously undetected polyselenylsulfides (SeS 2− , SeS 2 2− , Se 2 S 2− , and SeS 3 2− ) were identified. The reaction was spontaneous and proceeded rapidly at alkaline pH (completed within <24 h). A slower and incomplete reaction was observed at circumneutral pH. The fast and spontaneous reaction down to circumneutral pH suggests the ubiquitous importance of polyselenylsulfides in sulfidic environments and calls for revising the environmental fate of Se. The existence of polyselenylsulfides challenges the traditional ‘selenocentric’ view, which focuses on specific, bidirectional redox reactions that only involve Se species. Moreover, the perception of Se 0 as a terminal, insoluble species in many anoxic environments is questioned. The adoption of a ‘chalcogenic’ perspective is proposed, wherein the selenium and sulfur cycles are closely interconnected and the fate of Se is governed by the presence of sulfide. • Elemental selenium nanoparticles dissolves spontaneously in sulfide solutions. • Polyselenylsulfides and selenide identified as reaction products by HPLC-qTOF-MS. • The reaction occurs from neutral to alkaline pH. • The highlighted reaction might be ubiquitous in sulfidic environments.
Source: Chemosphere
Authors: Mathieu Martinez, Markus Lenz
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,010
OpenAlex ID: W4416890824