Sea-air exchange of bromoanisoles and methoxylated bromodiphenyl ethers in the Northern Baltic

Air-surface exchange of halomethoxybenzenes in a Swedish subarctic catchment

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.

Halomethoxybenzenes in air of the Nordic region

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.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Climate change influence on the levels and trends of persistent organic pollutants (POPs) and chemicals of emerging Arctic concern (CEACs) in the Arctic physical environment - a review

Climate change brings about significant changes in the physical environment in the Arctic. Increasing temperatures, sea ice retreat, slumping permafrost, changing sea ice regimes, glacial loss and changes in precipitation patterns can all affect how contaminants distribute within the Arctic environment and subsequently impact the Arctic ecosystems. In this review, we summarized observed evidence of the influence of climate change on contaminant circulation and transport among various Arctic environment media, including air, ice, snow, permafrost, fresh water and the marine environment. We have also drawn on parallel examples observed in Antarctica and the Tibetan Plateau, to broaden the discussion on how climate change may influence contaminant fate in similar cold-climate ecosystems. Significant knowledge gaps on indirect effects of climate change on contaminants in the Arctic environment, including those of extreme weather events, increase in forests fires, and enhanced human activities leading to new local contaminant emissions, have been identified. Enhanced mobilization of contaminants to marine and freshwater ecosystems has been observed as a result of climate change, but better linkages need to be made between these observed effects with subsequent exposure and accumulation of contaminants in biota. Emerging issues include those of Arctic contamination by microplastics and higher molecular weight halogenated natural products (hHNPs) and the implications of such contamination in a changing Arctic environment is explored.

Uptake, phytovolatilization, and interconversion of 2,4-dibromophenol and 2,4-dibromoanisole in rice plants

The structural analogs, 2,4-dibromophenol (2,4-DBP) and 2,4-dibromoanisole (2,4-DBA), have both natural and artificial sources and are frequently detected in environmental matrices. Their environmental fates, especially volatilization, including both direct volatilization from cultivation solution and phytovolatilization through rice plants were evaluated using hydroponic exposure experiments. Results showed that 2,4-DBA displayed stronger volatilization tendency and more bioaccumulation in aboveground rice tissues. Total volatilized 2,4-DBA accounted for 4.74% of its initial mass and was 3.43 times greater than 2,4-DBP. Phytovolatilization of 2,4-DBA and 2,4-DBP contributed to 6.78% and 41.7% of their total volatilization, enhancing the emission of these two contaminants from hydroponic solution into atmosphere. In this study, the interconversion processes between 2,4-DBP and 2,4-DBA were first characterized in rice plants. The demethylation ratio of 2,4-DBA was 12.0%, 32.0 times higher than methylation of 2,4-DBP. Formation of corresponding metabolites through methylation and demethylation processes also contributed to the volatilization of 2,4-DBP and 2,4-DBA from hydroponic solution into the air phase. Methylation and demethylation processes increased phytovolatilization by 12.1% and 36.9% for 2,4-DBP and 2,4-DBA. Results indicate that phytovolatilization and interconversion processes in rice plants serve as important pathways for the global cycles of bromophenols and bromoanisoles.

Will Climate Change Influence Production and Environmental Pathways of Halogenated Natural Products?

Thousands of halogenated natural products (HNPs) pervade the terrestrial and marine environment. HNPs are generated by biotic and abiotic processes and range in complexity from low molecular mass natural halocarbons (nHCs, mostly halomethanes and haloethanes) to compounds of higher molecular mass which often contain oxygen and/or nitrogen atoms in addition to halogens (hHNPs). nHCs have a key role in regulating tropospheric and stratospheric ozone, while some hHNPs bioaccumulate and have toxic properties similar those of anthropogenic-persistent organic pollutants (POPs). Both chemical classes have common sources: biosynthesis by marine bacteria, phytoplankton, macroalgae, and some invertebrate animals, and both may be similarly impacted by alteration of production and transport pathways in a changing climate. The nHCs scientific community is advanced in investigating sources, atmospheric and oceanic transport, and forecasting climate change impacts through modeling. By contrast, these activities are nascent or nonexistent for hHNPs. The goals of this paper are to (1) review production, sources, distribution, and transport pathways of nHCs and hHNPs through water and air, pointing out areas of commonality, (2) by analogy to nHCs, argue that climate change may alter these factors for hHNPs, and (3) suggest steps to improve linkage between nHCs and hHNPs science to better understand and predict climate change impacts.

Bromoanisoles and methoxylated bromodiphenyl ethers in macroalgae from Nordic coastal regions

Marine macroalgae are used worldwide for human consumption, animal feed, cosmetics and agriculture. In addition to beneficial nutrients, macroalgae contain halogenated natural products (HNPs), some of which have toxic properties similar to those of well-known anthropogenic contaminants. Sixteen species of red, green and brown macroalgae were collected in 2017-2018 from coastal waters of the northern Baltic Sea, Sweden Atlantic and Norway Atlantic, and analyzed for bromoanisoles (BAs) and methoxylated bromodiphenyl ethers (MeO-BDEs). Target compounds were quantified by gas chromatography-low resolution mass spectrometry (GC-LRMS), with qualitative confirmation in selected species by GC-high resolution mass spectrometry (GC-HRMS). Quantified compounds were 2,4-diBA, 2,4,6-triBA, 2'-MeO-BDE68, 6-MeO-BDE47, and two tribromo-MeO-BDEs and one tetrabromo-MeO-BDE with unknown bromine substituent positions. Semiquantitative results for pentabromo-MeO-BDEs were also obtained for a few species by GC-HRMS. Three extraction methods were compared; soaking in methanol, soaking in methanol-dichloromethane, and blending with mixed solvents. Extraction yields of BAs did not differ significantly (p > 0.05) with the three methods and the two soaking methods gave equivalent yields of MeO-BDEs. Extraction efficiencies of MeO-BDEs were significantly lower using the blend method (p < 0.05). For reasons of simplicity and efficiency, the soaking methods are preferred. Concentrations varied by orders of magnitude among species: ∑2BAs 57 to 57 700 and ∑5MeO-BDEs < 10 to 476 pg g-1 wet weight (ww). Macroalgae standing out with ∑2BAs >1000 pg g-1 ww were Ascophyllum nodosum, Ceramium tenuicorne, Ceramium virgatum, Fucus radicans, Fucus serratus, Fucus vesiculosus, Saccharina latissima, Laminaria digitata, and Acrosiphonia/Spongomorpha sp. Species A. nodosum, C. tenuicorne, Chara virgata, F. radicans and F. vesiculosus (Sweden Atlantic only) had ∑5MeO-BDEs >100 pg g-1 ww. Profiles of individual compounds showed distinct differences among species and locations.

Seasonal variation, air-water exchange, and multivariate source apportionment of polycyclic aromatic hydrocarbons in the coastal area of Dalian, China

The concentrations and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in air and seawater dissolved samples from the coastal area of Dalian were investigated, as well as their air-water exchanges. The average concentrations of PAHs were 27.5 ± 14.6 ng/m³ and 49.5 ± 20.5 ng/L in the air and water, respectively. Phenanthrene was the dominant congener in both air and water dissolved phase. Seasonality was discovered in the air with the concentrations higher in winter than in summer, but not in the water dissolved phase. Air-water exchange trends also displayed apparent seasonality with 3-4 ring PAHs generally being volatilization or equilibrium in summer but deposition in winter, which highlighted the important influence of temperature on the air-water exchange direction of PAHs. The air-water exchange fluxes of individual PAH congeners ranged from -24331 to 6541 ng/m²/d, and the highest deposition and volatilization fluxes both appeared at the industrial areas, which emphasized the influence of point source emission to the magnitude of air-water diffusion flux of PAHs. Multivariate source apportionment approaches, including principle component analysis, diagnostic ratios, and positive matrix factorization, were conducted, which suggested that PAHs in water originated from multiple sources. Frequent port transport correlated vehicle/ship emission rather than coal combustion may be the primary contributor of PAHs to the coastal air and water.

Occurrence and concentrations of halogenated natural products derived from seven years of passive water sampling (2007-2013) at Normanby Island, Great Barrier Reef, Australia

Polydimethylsiloxane (PDMS) based passive water samplers deployed at Normanby Island, Great Barrier Reef (Australia) from 2007 to 2013 were analyzed for halogenated natural products (HNPs). Altogether, 38 samples, typically deployed for 30 days, were studied. Five HNPs (Q1, 2'‑MeO-BDE 68, BC-10, 2,4‑dibromoanisole and 2,4,6‑tribromoanisole) were detected in all samples. Most samples (>90%) featured 2,2'‑diMeO-BB 80, 6‑MeO-BDE 47, 2',6‑diMeO-BDE 68 and 2,4‑dibromophenol. In addition, tetrabromo‑N‑methylpyrrole (TBMP) was detected in ~80% and Cl₆-DBP in ~30% of the samples. Estimated time weighted maximum water concentrations were >150 pg Q1 and 60 pg 2'‑MeO-BDE 68 per L seawater. Typically, the concentrations were varying from year to year. Moreover, time weighted average water concentration estimates did not reveal consistent maximum trend levels within a given year. Additional screening analysis via GC/MS indicated the presence of several polyhalogenated 1'‑methyl‑1,2'‑bipyrroles (PMBPs), 1,1'‑dimethyl‑2,2'‑bipyrroles (PDBPs), and 1‑methylpyrroles (PMPs) along with four brominated N‑methylindoles and several other polyhalogenated compounds at Normanby Island.

Mass-flow-based removal and transformation potentials for TBBPA, HBCDs and PBDEs during wastewater treatment processes

At a sewage treatment plant, 27 polybrominated diphenyl ethers, 17 methoxylated brominated diphenyl ethers, nine hydroxylated brominated diphenyl ethers, three hexabromocyclododecane diastereomers, and tetrabromobisphenol A were monitored at five major treatment stages (the influent, primary settlement stage, biological reaction stage, secondary settlement stage, and the UV irradiation disinfection stage). Hexabromocyclododecanes were the dominant chemicals, contributing 40% of the total concentrations of the chemicals in the dissolved phase of the sewage. Brominated flame retardant mass flow in the wastewater was lower after than before the biological reaction stage, and more than 70% of the inflowing mass load was removed from the mainstream wastewater by becoming associated with the sludge. More than half of mass loads of parent brominated flame retardants in the wastewater were removed after the treatments, but up to 10% of the initial mass loads remained in the final effluent and was expected to be released into the aquatic environment. The hydroxylated and methoxylated brominated diphenyl ether concentrations decreased by <25%, much less than the polybrominated diphenyl ethers. It is possible that hydroxylated and methoxylated polybrominated diphenyl ethers formed through the transformation of polybrominated diphenyl ethers during the biological reactions of treatment processes.

Occurrence of selected halogenated flame retardants in Belgian foodstuff

This paper reports on the occurrence of halogenated flame retardants (HFRs), namely PBDEs, HBCDs, TBBPA, brominated phenols (BrPhs), dechlorane plus (DP) and emerging FRs in a variety of Belgian foodstuffs. A total of 183 composite food samples were analyzed by GC-MS and LC-MS/MS techniques for the presence of HFRs. The analyses revealed that 72% of the samples was contaminated with HFRs to some extent. The highest number of contaminated samples was observed within the group 'Potatoes and derived products', 'Fish and fish products' and 'Meat and meat products', while the least contaminated group was 'Food for infants and small children'. The total HFR content ranged from <LOQ to 35.4 ng/g ww with an average content of 1.2 ng/g ww and median of 0.25 ng/g ww. The samples with the highest total HFR levels were canned king crab, fresh mackerel, Emmental cheese, fresh eel and plaice. The most frequently detected HFRs were PBDEs and BrPhs being present in almost all food groups, and among the individual HFRs, the most frequently found compounds were BDE-47 (53%), BDE-209 (46%) and 246-TBP (40%). TBBPA, DPs, TBPH and γ-HBCD occurred with a frequency of less than 5%. TBBPS, 26-DBP, HBB, TBB and BTBPE were not detected in any of the analyzed food samples.

Atmospheric Transport and Deposition of Bromoanisoles Along a Temperate to Arctic Gradient

Bromoanisoles (BAs) arise from O-methylation of bromophenols, produced by marine algae and invertebrates. BAs undergo sea-air exchange and are transported over the oceans. Here we report 2,4-DiBA and 2,4,6-TriBA in air and deposition on the Swedish west coast (Råö) and the interior of arctic Finland (Pallas). Results are discussed in perspective with previous measurements in the northern Baltic region in 2011-2013. BAs in air decreased from south to north in the order Råö > northern Baltic > Pallas. Geometric mean concentrations at Pallas increased significantly (p < 0.05) between 2002 and 2015 for 2,4-DiBA but not for 2,4,6-TriBA. The logarithm of BA partial pressures correlated significantly to reciprocal air temperature at the coastal station Råö and over the Baltic, but only weakly (2,4-DiBA) or not significantly (2,4,6-TriBA) at inland Pallas. Deposition fluxes of BAs were similar at both sites despite lower air concentrations at Pallas, due to greater precipitation scavenging at lower temperatures. Proportions of the two BAs in air and deposition were related to Henry's law partitioning and source regions. Precipitation concentrations were 10-40% of those in surface water of Bothnian Bay, northern Baltic Sea. BAs deposited in the bay catchment likely enter rivers and provide an unexpected source to northern estuaries. BAs may be precursors to higher molecular weight compounds identified by others in Swedish inland lakes.

Chlorinated pesticides and natural brominated anisoles in air at three northern Baltic stations

Polyurethane foam (PUF) disk passive samplers were deployed at one inland and two island locations in the Bothnian Bay region of the northern Baltic Sea. Uptake was linear over 81-147 d and a temperature range of -2.6 to 14.2 °C for organochlorine pesticides (OCPs) and current-use pesticides (CUPs) having log K_OA ≥9 at ambient temperatures. Partial saturation of the PUF disks occurred for the more volatile OCPs hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), and for bromoanisoles (BAs), which are products of bromophenols released by natural and anthropogenic sources. Correction for nonlinear uptake of these was made using experimentally measured PUF-air partition coefficients. Passive-derived air concentrations of pesticides were uniform over the bay and agreed within a factor of 2 or better with levels determined by active (pumped) sampling at one of the island stations. Levels of OCPs were similar to those reported at background sites in the European and Canadian Arctic and at monitoring stations in the central Baltic and southern Scandinavia, indicating long-range transport. The insecticide chlorpyrifos was 10 times lower at bay stations than in the Canadian Arctic. Insight to sources and processes was gained by examining compound profiles. Fractions F_alpha = α-HCH/(α-HCH + γ-HCH) and F_TC = trans-chlordane/(trans-chlordane + cis-chlordane) at bay stations were higher than in the Norwegian and Finnish Arctic and similar to those at the southern monitoring stations. Volatilization of chlordanes from Baltic seawater may also modify F_TC. Higher F_TriBA = 2,4,6-TriBA/(2,4,6-TriBA + 2,4-DiBA) distinguished local volatilization from the Baltic Sea versus lower F_TriBA found at the inland site and reported in air on the Norwegian coast, suggesting westerly transport from the Atlantic across Norway and Sweden.