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Aquatic environmental chemistry of 2‐(thiocyanomethylthio)benzothiazole and related benzothiazoles
Author(s) -
Brownlee Brian G.,
Carey John H.,
MacInnis Gordia A.,
Pellizzari Ian T.
Publication year - 1992
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.5620110812
Subject(s) - benzothiazole , chemistry , phosphate , environmental chemistry , solubility , hydrolysis , pentachlorophenol , seawater , organic chemistry , oceanography , geology
BUSAN 30WB® is an alternative to pentachlorophenol as an antisapstain agent in the lumber industry. The active ingredient is 2‐(thiocyanomethylthio)benzothiazole (TCMTB). Because very little information is available in the open literature on the fate of TCMTB in aquatic environments, we wish to report our studies on TCMTB and related benzothiazoles, some of which are potential transformation products of TCMTB. We measured the water solubility and octanol/water partition coefficients of TCMTB, benzothiazole (BT), 2‐mercaptobenzothiazole (MBT), and 2‐(meth‐ylthio)benzothiazole (MTBT). The water solubility of TCMTB at 24°C was 40 mg/L, and the log K ow was 3.12. At pH 8 and 24°C in dilute borax‐phosphate buffer, the half‐life of TCMTB was 750 h; in seawater (pH 7.8‐8.0, 24°C) it was about 740 h. Attempts to measure sediment/water partitioning of TCMTB produced traces of MTBT, presumed to result from biological methylation of MBT released by hydrolysis of TCMTB. MTBT was produced directly from MBT in the presence of sediment. In phosphate buffer, TCMTB readily underwent direct photolysis in sunlight to produce MBT, in about 50% yield, and traces of BT. The photochemistry of MBT, the major photolysis product of TCMTB, was studied in some detail. Sunlight quantum yields of TCMTB and MBT are estimated to be 0.01 and 0.002, respectively. Sunlight photolysis of MBT in phosphate buffer with and without dissolved organic matter and in a natural water led to three products: BT (28‐47%), 2‐hydroxybenzothiazole (HOBT) (4‐5%), and an unidentified product. On the basis of our laboratory and field results, in addition to literature reports on the occurrence of benzothiazoles, we propose a partial pathway for this family of benzothiazoles in aquatic environments. TCMTB and MBT are unlikely to persist or bioaccumulate. Stable end products appear to be BT, MTBT, and 2‐hydroxybenzothiazole.