The Xiamen Symposium on Marine Environmental Sciences (XMAS 2027)

Halomethoxybenzenes (HMBs) recently gained attention due to widespread occurrence and relatively high concentration levels in terrestrial and marine environments as well as structural resemblance to persistent organic pollutants. Here, we report concentrations of four HMBs, i.e., 2,4,6-tribromoanisole (TBA), drosophilin A methyl ether (DAME), tetrachloroveratrole (TeCV) and pentachloroanisole (PCA), in air, water and precipitation collected across Southern Canada from 2019 to 2022 using networks of passive air and water samplers, coupled with active air and deposition samplers. The study region includes Canada's largest cities as well as coastal areas in the St. Lawrence Estuary and Southern Salish Sea region. A total of over 380 samples has been analyzed. The four HMBs have been detected in almost all air samples at levels that were generally higher than reported for Northern Europe. DAME and TBA were most abundant, not only in air but also in precipitation and sea water. Elevated TBA levels in the atmosphere of the St. Lawrence Estuary and coastal British Columbia (BC), higher water concentrations in the open sea, and water/air fugacity ratios that greatly exceed unity are consistent with TBA's marine origin and net volatilization from the ocean. While TBA was also present far from the ocean, e.g., in Toronto and the interior of BC, lower levels and a much weaker temperature dependence than at coastal sites suggest that its potential for long range atmospheric transport. Higher levels of PCA in air from urban sites and in waters in the vicinity of Vancouver and Quebec City suggest dominance of anthropogenic sources, likely related to the use of pentachlorophenol. Despite different sources having been reported for DAME and TeCV, the two tetrachloro-dimethoxy-benzenes display similar spatial patterns in air and no clear spatial trends in water. They both show high seasonal variability in air, with significant correlations with temperature, and have water/air fugacity ratios indistinguishable from unity. The measured data and simulation results from a level III environmental fate model suggest that volatilization from water might be an important process delivering HMBs to the atmosphere, even though some, such as DAME, are believed to be formed by wood-rotting fungi in terrestrial environment.