TY - JOUR
T1 - Decomposition of dimethyl polysulfides under solar irradiation in oxic aqueous solutions
AU - Buchshtav, Tamir
AU - Kamyshny, Alexey
N1 - Funding Information:
The authors thank Sarit Melamed for assistance with analyses. They are grateful to Ovadia Lev and Andrey Gavriushin for discussions that helped to improve the manuscript. This work was supported by the Marie Curie Actions CIG PCIG10-GA-2011–303740 (ThioCyAnOx) Grant.
Publisher Copyright:
© 2020 CSIRO.
PY - 2020/8/1
Y1 - 2020/8/1
N2 - The presence of malodorous dimethyl polysulfides (DMPSs) has been documented in marine and limnic systems as well as in tap water distribution systems. These compounds compromise the quality of drinking water. Under oxic conditions and in the absence of radiation, DMPSs with n ≥ 3 sulfur atoms disproportionate into DMPSs with n + 1 and n - 1 sulfur atoms, and, finally, to dimethyl disulfide (DMDS) and S 8 . DMDS, in turn, decomposes to methyl mercaptan (MT) and methanesulfinic acid. Under these conditions, the half-lives of DMPSs vary from months for dimethyl pentasulfide (DM5S) to hundreds of thousands of years for DMDS. In this work, we studied the kinetics and mechanisms of the decomposition reactions of DMPSs with 2-5 sulfur atoms in aqueous solutions in the presence of oxygen and under exposure to solar radiation. The quantum yields of decomposition of DMPSs with 2, 3, 4 and 5 sulfur atoms do not depend on either the concentration of DMPSs or pH, and are 40 ± 10, 2.0 ± 0.2, 35 ± 10 and 10 ± 4 respectively. The quantum yields, which are higher than unity, suggest that under exposure to solar radiation the photochemical decomposition of DMPSs proceeds by a radical chain reaction mechanism. Half-lives of DMPSs in oxic aquatic solutions exposed to solar radiation under a very clear atmosphere and a solar elevation angle of 90 ° were calculated from the quantum yields and were found to be as low as 43 ± 13 s for DMDS, 40 ± 4 s for dimethyl trisulfide (DMTS), 2.1 ± 0.6 s for dimethyl tetrasulfide (DM4S) and 4.2 ± 1.7 s for DM5S.
AB - The presence of malodorous dimethyl polysulfides (DMPSs) has been documented in marine and limnic systems as well as in tap water distribution systems. These compounds compromise the quality of drinking water. Under oxic conditions and in the absence of radiation, DMPSs with n ≥ 3 sulfur atoms disproportionate into DMPSs with n + 1 and n - 1 sulfur atoms, and, finally, to dimethyl disulfide (DMDS) and S 8 . DMDS, in turn, decomposes to methyl mercaptan (MT) and methanesulfinic acid. Under these conditions, the half-lives of DMPSs vary from months for dimethyl pentasulfide (DM5S) to hundreds of thousands of years for DMDS. In this work, we studied the kinetics and mechanisms of the decomposition reactions of DMPSs with 2-5 sulfur atoms in aqueous solutions in the presence of oxygen and under exposure to solar radiation. The quantum yields of decomposition of DMPSs with 2, 3, 4 and 5 sulfur atoms do not depend on either the concentration of DMPSs or pH, and are 40 ± 10, 2.0 ± 0.2, 35 ± 10 and 10 ± 4 respectively. The quantum yields, which are higher than unity, suggest that under exposure to solar radiation the photochemical decomposition of DMPSs proceeds by a radical chain reaction mechanism. Half-lives of DMPSs in oxic aquatic solutions exposed to solar radiation under a very clear atmosphere and a solar elevation angle of 90 ° were calculated from the quantum yields and were found to be as low as 43 ± 13 s for DMDS, 40 ± 4 s for dimethyl trisulfide (DMTS), 2.1 ± 0.6 s for dimethyl tetrasulfide (DM4S) and 4.2 ± 1.7 s for DM5S.
KW - decomposition kinetics
KW - photochemistry
KW - reduced sulfur compounds
KW - volatile organic sulfur compounds
UR - http://www.scopus.com/inward/record.url?scp=85079046556&partnerID=8YFLogxK
U2 - 10.1071/EN19252
DO - 10.1071/EN19252
M3 - Article
AN - SCOPUS:85079046556
SN - 1448-2517
VL - 17
SP - 377
EP - 384
JO - Environmental Chemistry
JF - Environmental Chemistry
IS - 5
ER -
