TY - JOUR
T1 - Kinetics and mechanism of the abiotic decomposition of dimethyl polysulfides with three, four and five sulfur atoms under dark, oxic conditions
AU - Buchshtav, Tamir
AU - Amrani, Alon
AU - Said-Ahmad, Ward
AU - Kamyshny, Alexey
N1 - Publisher Copyright:
© 2019 CSIRO.
PY - 2019
Y1 - 2019
N2 - The presence of malodorous dimethyl polysulfides (DMPSs) has been documented in various aquatic systems. In this work, we studied the kinetics and mechanisms of the chemical decomposition of DMPSs with 3-5 sulfur atoms in aqueous solutions in the presence of oxygen and absence of light. DMPSs are shown to undergo reaction with hydroxyl ions, which results in their decomposition. The orders of the decomposition reactions with respect to dimethyl trisulfide (DMTS), dimethyl tetrasulfide (DM4S) and dimethyl pentasulfide (DM5S) are 2.0 ± 0.3, 1.7 ± 0.3 and 2.0 ± 0.2, respectively. The reaction orders with respect to OH- are 0.59 ± 0.06, 0.56 ± 0.08 and 0.58 ± 0.11, respectively. The activation energies of these reactions are 170 kJ mol-1 K-1, 114 kJ mol-1 K-1 and 75 kJ mol-1 K-1, respectively. The initial products of the decomposition are Me2Sn-1 and Me2Sn+1 and the apparent final products are elemental sulfur and dimethyl disulfide (DMDS). DMDS, which is formed during the decomposition of DMTS, is depleted in 34S (ϵ = -13.2 ‰), while the DM4S is enriched 34S (ϵ = 4.7 ‰). A mechanism for the decomposition of DMPSs is proposed based on the results. Under these conditions, half-lives for the decomposition of DMPSs in Lake Kinneret vary from 2 months for DM5S to 100 000 years for DMTS. The relatively short time scale of the reported odour episodes indicates that other chemical, photochemical or biological processes are responsible for the decomposition of DMTS and DM4S.
AB - The presence of malodorous dimethyl polysulfides (DMPSs) has been documented in various aquatic systems. In this work, we studied the kinetics and mechanisms of the chemical decomposition of DMPSs with 3-5 sulfur atoms in aqueous solutions in the presence of oxygen and absence of light. DMPSs are shown to undergo reaction with hydroxyl ions, which results in their decomposition. The orders of the decomposition reactions with respect to dimethyl trisulfide (DMTS), dimethyl tetrasulfide (DM4S) and dimethyl pentasulfide (DM5S) are 2.0 ± 0.3, 1.7 ± 0.3 and 2.0 ± 0.2, respectively. The reaction orders with respect to OH- are 0.59 ± 0.06, 0.56 ± 0.08 and 0.58 ± 0.11, respectively. The activation energies of these reactions are 170 kJ mol-1 K-1, 114 kJ mol-1 K-1 and 75 kJ mol-1 K-1, respectively. The initial products of the decomposition are Me2Sn-1 and Me2Sn+1 and the apparent final products are elemental sulfur and dimethyl disulfide (DMDS). DMDS, which is formed during the decomposition of DMTS, is depleted in 34S (ϵ = -13.2 ‰), while the DM4S is enriched 34S (ϵ = 4.7 ‰). A mechanism for the decomposition of DMPSs is proposed based on the results. Under these conditions, half-lives for the decomposition of DMPSs in Lake Kinneret vary from 2 months for DM5S to 100 000 years for DMTS. The relatively short time scale of the reported odour episodes indicates that other chemical, photochemical or biological processes are responsible for the decomposition of DMTS and DM4S.
KW - decomposition kinetics
KW - isotope fractionation
KW - reduced sulfur compounds
KW - volatile organic sulfur compounds
UR - http://www.scopus.com/inward/record.url?scp=85068372917&partnerID=8YFLogxK
U2 - 10.1071/EN19076
DO - 10.1071/EN19076
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AN - SCOPUS:85068372917
SN - 1448-2517
VL - 16
SP - 495
EP - 504
JO - Environmental Chemistry
JF - Environmental Chemistry
IS - 7
ER -