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Thiosulfate Production in Cysteine‐Amended Soil
Author(s) -
Zhong T.,
Morra M. J.
Publication year - 1994
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1994.03615995005800030028x
Subject(s) - thiosulfate , chemistry , soil water , cysteine , biogeochemical cycle , sulfur , reagent , incubation , tetrathionate , nuclear chemistry , environmental chemistry , chromatography , biochemistry , organic chemistry , biology , ecology , enzyme
Thiol‐labile compounds are produced in cysteine‐amended soil, as evidenced by the production of H 2 S following addition of reagents containing free sulfhydryl groups (−SH). Thiosulfate (S 2 O 2− 3 ) is a likely reactant candidate because it is an intermediate in biogeochemical S cycling and is reduced to H 2 S by ‐SH, but its presence in cysteine‐amended soils has not been documented previously. Four soils were amended with l ‐cysteine (15 mmol kg −1 soil) incubated at 0.033 MPa soil water suction or under saturated conditions, and then extracted with 0.1 M LiCl. Colorimetric analysis of the extracts using cyanolysis with and without addition of a Cu 2+ catalyst indicated the presence of S 2 2− 3 and a polythionate such as S 4 O 2− 6 ; positive interferences from the cyanolysis of S 2− were minimal. Ion chromatographic analysis of the extracts showed a well‐resolved peak with the same retention time as S 2 O 2− 3 and yielded concentration estimates similar to those obtained by colorimetry, providing positive identification of S 2 O 2− 3 in cysteine‐amended soils. Thiosulfate production occurred under both saturated and unsaturated conditions, varied among soils from 0 to 35.2 mg S 2 O 2− 3 ‐S kg −1 , and was nearly eliminated by autoclaving the soil before incubation or by addition of NaN 3 . Although the exact pathway for S 2 O 2− 3 production is unknown, it is likely that H 2 S formation and subsequent oxidation are responsible.