Registration Dossier
Registration Dossier
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EC number: 233-321-1 | CAS number: 10117-38-1
Endpoint summary
Administrative data
Description of key information
Potassium sulfite is an inorganic compound and is not subject to biodegradation. However, sulfite substances, including potassium sulfite, can be transformed by microbial activity.
Sulfites are unstable in the environment and become part of the natural sulfur cycle. Microorganisms have a controlling influence on the oxidation state of sulfur, capable of either oxidation or reduction depending on microbial species and environment. Inorganic sulfur compounds are metabolized by physiologically and phylogenetically diverse microorganisms as electron donor or acceptor, playing a predominant role in the sulfur biogeochemical cycle in the environment.
Under oxygen-rich conditions, sulfites are rapidly oxidized catalytically by (air) oxygen or by microbial activity to sulfate. Microbial oxidation of reduced sulfur species including elemental sulfur (S), sulfide (HS-), sulfite (SO32-) and thiosulfate (S2O32-) is an energetically favorable reaction carried out by a wide range of organisms, i.e. sulfur oxidizing microorganisms (SOM) resulting in ultimate transformation into sulfate (SO42-, Simon and Kroneck, 2013).
Under highly reduced conditions, reduction to sulfides may take place with subsequent formation of solid-phase minerals and metal sulfides of very low bioavailability/solubility, including FeS, ZnS, PbS and CdS (Lindsay, 1979, Finster et al., 1998). Thus, under anoxic conditions, sulfate is readily reduced to sulfide by sulfate-reducing bacteria (SRM) that are common in anaerobic environments. Other sulfur-containing microbial substrates such as dithionite (S2O42-), thiosulfates (S2O32-) or sulfite (SO32-) may also be anaerobically utilised, ultimately resulting in the reduction to sulfide (H2S).
Accordingly, available literature data on sulfite transformation processes in water, sediment and soil show rapid transformation to sulfate when added to the respective environmental compartment, i.e. > 97% of added sulfite (30 – 150 µM SO32-) transformed within three days in sediments and marine waters, respectively.
Additional information
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