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Assessing the hydroxyl radical and volatilization roles in aquatic fate estimations of sulfur heterocycles: Dibenzothiophene derivatives
Author(s) -
Saranjampour Parichehr,
Armbrust Kevin L.,
Marx Brian D.
Publication year - 2017
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.3745
Subject(s) - dibenzothiophene , chemistry , reaction rate constant , steric effects , alkyl , hydroxyl radical , sulfur , organic chemistry , environmental chemistry , radical , physics , quantum mechanics , kinetics
Abstract Polycyclic aromatic sulfur heterocycles (PASHs) and their alkyl derivatives can be released into aquatic systems via crude oil spills or runoff from petroleum‐treated areas, such as asphalt. Dibenzothiophene (DBT) and its derivatives (C1‐DBT, C2‐DBT, and C4‐DBT) were chosen as model compounds to investigate the relative impact of volatilization and hydroxyl radical degradation on estimates of their overall dissipation after entry into aquatic ecosystems as a function of depth using the exposure analysis modeling system (EXAMS). The hydroxyl radical rate constant (K · OH ) and Henry's law constant of PASHs were determined in distilled water. The analogue C1‐DBT reacted fastest with · OH relative to other PASHs. The C2‐DBT and C4‐DBT analogues had higher Henry's law constants compared with other derivatives. Steric hindrance by alkyl substituents on the sulfur moiety most strongly impacted measured rate and Henry's law constants between DBT and individual alkyl derivatives. These steric effects do not appear to be considered in the physical property estimation software EPI Suite. Simulated dissipation of PASHs using EXAMS suggests that volatilization is a dominant fate pathway for the higher molecular weight and less polar C2‐DBT and C4‐DBT at all depths and DBT and C1‐DBT at 0.1‐m. However, model scenarios suggest that hydroxyl radical degradation may significantly contribute to the degradation of more polar DBT and C1‐DBT at 1‐m and 2‐m depths. Environ Toxicol Chem 2017;36:1998–2004. © 2017 SETAC