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Polyurethane foam (PUF) is widely used for active air sampling (AAS) of gaseous semivolatile organic compounds (SVOCs). PUF efficiently collects SVOCs with moderate to low volatility, but applications are limited for the more volatile SVOCs due to breakthrough from the PUF trap. The collection efficiency can be predicted by frontal chromatography theory with knowledge of several parameters: the sampled air volume, the breakthrough volume which depends on the PUF/air partition ratio (K_PA), and the number of theoretical plates (N) in the PUF trap. Here we evaluate data from two Canadian air monitoring programs in which front and back PUF traps (P1 and P2) were used to check for breakthrough, as indicated by the back/front ratio (P2/P1) of collected SVOCs. A frontal chromatography model was used to relate collection efficiency of hexachlorobenzene (HCB) and α-hexachlorocyclohexane (α-HCH) to their observed P2/P1 ratios under assumed scenarios of K_PA and N, and apparent N-values for the PUF traps were derived. Results were applied to correcting observed air concentrations of HCB for breakthrough loss. The choice of K_PA greatly influenced the adjusted air concentrations and their variation with temperature.

Measuring dissolved concentrations of polybrominated diphenyl ethers (PBDEs) and non-BDE flame retardants on a global scale provides critical insights into the effectiveness of the Stockholm Convention. In the present study, we deployed passive sampling devices at 43 seawater and freshwater sites covering 21 countries from 2016 to 2020. The detection frequencies were 20−94% for BDE congeners and 33−42% for dechlorane plus, higher than those (0−20%) for other target compounds. The median concentrations of dissolved Σ₉PBDE (sum of BDE-28, -47, -66, -85, -99, -100, -153, -154, and -183) were 0.28 and 0.64pg L−1 in seawater and freshwater, respectively. The concentrations of dissolved Σ₉PBDE, along with published data, slightly increased before 2016 and remained steady from 2016 to 2018, indicating delayed effects of the global phase out of technical Penta- and Octa-BDEs. The log-transformed concentrations of individual BDE congeners were better correlated with regional gross domestic product than with population density. The potential ecological risk of BDE-47 was low, and there was a lack of key risk indicators for other compounds. The present study documented the delayed response of the aquatic environment to the regulatory actions on reducing PBDE emissions.

Halomethoxybenzenes (HMBs), including 2,4-dibromoanisole (DBA), 2,4,6-tribromoanisole (TBA), and droso-philin A methyl ether (1,2,4,5-tetrachloro-3,6-dimethoxybenzene; DAME) are bioaccumulative halogenatedcompounds with natural and anthropogenic sources. This study characterized these three HMBs in seawater andDAME in air in the Bering and Chukchi Seas. The goal was to describe and explain distributions of HMBs asseasonal ice retreated in spring. The results show that concentrations of individual HMBs are sensitive to distinctenvironmental processes. DBA decreased during spring blooms, while spring freshwater brought DAME into thesystem. Net volatilization of DAME occurred at a freshwater-influenced site, while all other site samplesdemonstrated net deposition of DAME from the atmosphere to seawater or equilibrium with respect to gas ex-change. The highest concentrations of TBA occurred near freshwater, but there were no statistically significanttrends in the levels of this compound. Arctic sampling did not show evidence of a buildup of HMBs under icefrom possible production by ice algae or bacteria. The different trends in concentrations of individual HMBs andtheir sensitivity to environmental variables over a short timescale complicates comparisons across systems,evaluations of ecological function, and potential risk assessments.

Halomethoxybenzenes (HMBs) and related halomethoxyphenols are produced naturally in the marine and terrestrial environment and some also have anthropogenic origins. They are relatively volatile and water soluble and undergo atmospheric exchange with water bodies and soil. Here we report air-surface exchange of HMB compounds brominated anisoles and chlorinated dimethoxybenzenes in a Subarctic lake and catchment in Sweden during September 2022. HMBs were isolated from water on solid-phase extraction cartridges and from ground litter/soil by solvent extraction and determined by capillary gas chromatography - quadrupole mass spectrometry. Identified compounds in lake and stream water in the 10–100 pg L⁻¹ range were 1,2,4,5-tetrachloro-3,6-dimethoxybenzene (DAME) > 2,4-dibromoanisole (DiBA) ≥ 2,4,6-tribromoanisole (TriBA) > 1,2,3,4-tetrachloro-5,6-dimethoxybenzene (tetrachloroveratrole, TeCV). DAME and the related compound 2,3,5,6-tetrachloro-4-methoxyphenol (DA) are reported in Subarctic litter/soil in the range 0.005–1.1 mg kg⁻¹ dry weight (dw), whereas DiBA and TriBA were not detected in any litter/soil sample and TeCV in only one. Exchanges were assessed from concentrations in water and soil, air concentrations from a monitoring station at Pallas, Finland, and the physicochemical properties of the HMBs. Fluxes to and from the lake were estimated using the two-film gas exchange model. Net loadings (deposition minus volatilization) for the month of September were − 23, −15 and − 68 g for DiBA, TriBA and DAME, respectively, which amounted to about 4–7 % of the estimated lake inventory. An exchange assessment for DAME from litter/soil showed significant net volatilization at five sites, net deposition at one site and near-equilibrium at one site. The Torneträsk catchment appeared close to steady state with respect to HMB exchange during September 2022. The situation could be different during the warmer and colder seasons, and extending the study to cover these periods is a suggested next step.

Polycyclic aromatic hydrocarbons (PAHs), released from petrogenic, pyrogenic or diagenetic sources (degradation of wood materials), are of global concern due to their adverse effects, and potential for long-range transport. While dissolved PAHs have been frequently reported in the literature, there has been no consistent approach of sampling across water bodies. Passive samplers from the AQUA/GAPS-MONET initiative were deployed at 46 sites (28 marine and 18 freshwater), and analyzed for 28 PAHs and six polycyclic musks (PCMs) centrally. Freely dissolved PAH concentrations were dominated by phenanthrene (mean concentration 1500 pg L^-1; median 530 pg L^-1) and other low molecular weight compounds. Greatest concentrations of phenanthrene, fluoranthene, and pyrene were typically from the same sites, mostly in Europe and North America. Of the PCMs, only galaxolide (72% of samples) and tonalide (61%) were regularly detected, and were significantly cross-correlated. Benchmarking of PAHs relative to penta- and hexachlorobenzene confirmed that the most remote sites (Arctic, Antarctic, and mountain lakes) displayed below average PAH concentrations. Concentrations of 11 of 28 PAHs, galaxolide and tonalide were positively correlated (P < 0.05) with population density within a radius of 5 km of the sampling site. Characteristic PAH ratios gave conflicting results, likely reflecting multiple PAH sources and postemission changes.

Fungi and substrates undergoing fungal decomposition were collected from forests in northern and southernSweden and analyzed for chlorinated dimethoxybenzenes (DMBs). Specimens were fungi fruiting bodies, rottingwood, forest litter and underlying humus. Targeted compounds were DAME (1,2,4,5-tetrachloro-3,6-DMB) andrelated fungal secondary metabolites. A screening procedure was developed which involved soaking the speci-mens in ethyl acetate followed by analysis by capillary gas chromatography – mass spectrometry with mass selec-tive detection (GC-MSD). DAME was the most frequently found (62% of 47 specimens) and often the most abun-dant target compound, with range and mean ± SD concentrations of <0.0017–3.81 and 0.21 ± 0.63 mg kg−1ww. Based on log-log correlations of partition coefficients of hydrophobic compounds between fungal biomass/water (KD) and octanol/water (KOW), five species of fungi are suggested to produce DAME de novo versus bioaccu-mulation from forest runoff water. Full-scan mass spectra of some high-concentration specimens indicated thepresence of a Cl2DMB and a Cl3DMB, which could not be identified further due to lack of standards, anddrosophilin A (DA = 2,3,5,6-tetrachloro-4-methoxyphenol), the precursor to DAME. Tetrachloroveratrole(TeCV = 1,2,3,4-tetrachloro-5,6-DMB) was found in only a few specimens. This study supports our hypothesis offungi as a source of DAME in terrestrial runoff and indicates that other chlorinated secondary metabolites arepresent. DAME is widely distributed globally, and it would be good to have a better understanding of its sourcesand pathways as a marker of terrestrial organochlorines and their availability for bioaccumulation

Halomethoxybenzenes (HMBs) are a group of compounds with natural and anthropogenic origins. Here we extend a 2002–2015 survey of bromoanisoles (BAs) in the air and precipitation at Råö on the Swedish west coast and Pallas in Subarctic Finland. New BAs data are reported for 2018 and 2019 and chlorinated HMBs are included for these and some previous years: drosophilin A methyl ether (DAME: 1,2,4,5-tetrachloro-3,6-dimethoxybenzene), tetrachloroveratrole (TeCV: 1,2,3,4-tetrachloro-5,6-dimethoxybenzene), and pentachloroanisole (PeCA). The order of abundance of HMBs at Råö was ΣBAs > DAME > TeCV > PeCA, whereas at Pallas the order of abundance was DAME > ΣBAs > TeCA > PeCA. The lower abundance of BAs at Pallas reflects its inland location, away from direct marine influence. Clausius-Clapeyron (CC) plots of log partial pressure (P_air)/Pa versus 1/T suggested distant transport at both sites for PeCA and local exchange for DAME and TeCV. BAs were dominated by distant transport at Pallas and by both local and distant sources at Råö. Relationships between air and precipitation concentrations were examined by scavenging ratios, SR = (ng m⁻³)_precip/(ng m⁻³)_air. SRs were higher at Pallas than Råö due to greater Henry's law partitioning of gaseous compounds into precipitation at colder temperatures. DAME is produced by terrestrial fungi. We screened 19 fungal species from Swedish forests and found seven of them contained 0.01–3.8 mg DAME per kg fresh weight. We suggest that the volatilization of DAME from fungi and forest litter containing fungal mycelia may contribute to atmospheric levels at both sites.

Persistent organic pollutants (POPs) are recognized as pollutants of global concern, but so far, information on the trends of legacy POPs in the waters of the world has been missing due to logistical, analytical, and financial reasons. Passive samplers have emerged as an attractive alternative to active water sampling methods as they accumulate POPs, represent time-weighted average concentrations, and can easily be shipped and deployed. As part of the AQUA-GAPS/MONET, passive samplers were deployed at 40 globally distributed sites between 2016 and 2020, for a total of 21 freshwater and 40 marine deployments. Results from silicone passive samplers showed α-hexachlorocyclohexane (HCH) and γ-HCH displaying the greatest concentrations in the northern latitudes/Arctic Ocean, in stark contrast to the more persistent penta (PeCB)- and hexachlorobenzene (HCB), which approached equilibrium across sampling sites. Geospatial patterns of polychlorinated biphenyl (PCB) aqueous concentrations closely matched original estimates of production and use, implying limited global transport. Positive correlations between log-transformed concentrations of Σ7PCB, ΣDDTs, Σendosulfan, and Σchlordane, but not ΣHCH, and the log of population density (p < 0.05) within 5 and 10 km of the sampling sites also supported limited transport from used sites. These results help to understand the extent of global distribution, and eventually time-trends, of organic pollutants in aquatic systems, such as across freshwaters and oceans. Future deployments will aim to establish time-trends at selected sites while adding to the geographical coverage.

Introduction: Thousands of halogenated natural products (HNPs) are generated in the ocean and on land. A subset of these, halomethoxybenzenes (HMBs), are released from both natural and anthropogenic sources. Here we consider: 1. Brominated anisoles (BAs), transformation products of bromophenols. 2. Drosophilin A methyl ether (DAME: 1,2,4,5-tetrachloro-3,6-dimethoxybenzene), a secondary metabolite of terrestrial fungi. 3. Tetrachloroveratrole (TeCV: 1,2,3,4-tetrachloro-5,6-dimethoxybenzene), a lignin byproduct found in bleached kraft mill effluent. 4. Pentachloroanisole (PeCA), a metabolite of the wood preservative pentachlorophenol.

Methods: We examined several ecosystem compartments to determine sources and exchange processes for these HMBs: air, precipitation, rivers, forest fungi and litter, and water from northern Baltic estuaries and offshore. Samples were analyzed for HMBs by capillary gas chromatography – quadrupole mass spectrometry.

Results and discussion: All four types of HMBs were found in air, and BAs, DAME and TeCV were also present in precipitation. BAs and DAME were common in rivers and estuaries, whereas TeCV was low and PeCA was below detection. DAME was identified in several species of fungi and in forest litter; TeCV was occasionally present, but BAs and PeCA were below detection. Concentrations of BAs were higher in estuaries than in rivers or offshore waters, showing that estuaries are hot spots for production. BAs were negatively or not correlated with chlorophyll-a, suggesting contribution by heterotrophic bacteria as well as known production by phytoplankton and macroalgae. DAME was negatively or not correlated with BAs and did not appear to be produced in the estuaries; fungi and forest litter containing fungal mycelia are suggested as sources. HMBs volatilize from sea and land, disperse through the atmosphere, and return via precipitation and rivers. Production and biogeochemical cycles are influenced by climate change and we suggest BAs and DAME for following partitioning and exchange processes.

Hexachlorobenzene (HCB) was used in the United States from 1945 to 1966 as a fungicide on wheat, while octachlorostyrene (OCS) was never marketed. However, both HCB and OCS continue to be emitted into the atmosphere as byproducts of several industrial processes. We have measured the atmospheric concentrations of HCB and OCS in samples collected every 12 days at five sites on the shores of the North American Great Lakes since 1991. The geometric mean concentrations of HCB and OCS are ∼60 and 0.7 pg/m3, respectively, at all sites regardless of the local population, and these concentrations have not changed significantly over time. The concentrations of HCB measured here are similar to those reported by other studies of the northern troposphere and are ∼3 times those reported in the southern troposphere, suggesting that HCB sources are largely in the Northern Hemisphere. It is apparent that direct and recycled emissions of HCB and OCS into the northern troposphere are widespread in scope and, despite the elimination of HCB as a fungicide, have not changed in a meaningful way in the past 20–30 years. This is unlike the case for other legacy chemicals, for which global restrictions on their use have been more effective.