Time trends of persistent organic pollutants (POPs) and Chemicals of Emerging Arctic Concern (CEAC) in Arctic air from 25 years of monitoring.

The long-term time trends of atmospheric pollutants at eight Arctic monitoring stations are reported. The work was conducted under the Arctic Monitoring and Assessment Programme (AMAP) of the Arctic Council. The monitoring stations were: Alert, Canada; Zeppelin, Svalbard; Stórhöfði, Iceland; Pallas, Finland; Andøya, Norway; Villum Research Station, Greenland; Tiksi and Amderma, Russia. Persistent organic pollutants (POPs) such as α- and γ-hexachlorocyclohexane (HCH), polychlorinated biphenyls (PCBs), α-endosulfan, chlordane, dichlorodiphenyltrichloroethane (DDT) and polybrominated diphenyl ethers (PBDEs) showed declining trends in air at all stations. However, hexachlorobenzene (HCB), one of the initial twelve POPs listed in the Stockholm Convention in 2004, showed either increasing or non-changing trends at the stations. Many POPs demonstrated seasonality but the patterns were not consistent among the chemicals and stations. Some chemicals showed winter minimum and summer maximum concentrations at one station but not another, and vice versa. The ratios of chlordane isomers and DDT species showed that they were aged residues. Time trends of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were showing decreasing concentrations at Alert, Zeppelin and Andøya. The Chemicals of Emerging Arctic Concern (CEAC) were either showing stable or increasing trends. These include methoxychlor, perfluorohexane sulfonic acid (PFHxS), 6:2 fluorotelomer alcohol, and C9-C11 perfluorocarboxylic acids (PFCAs). We have demonstrated the importance of monitoring CEAC before they are being regulated because model calculations to predict their transport mechanisms and fate cannot be made due to the lack of emission inventories. We should maintain long-term monitoring programmes with consistent data quality in order to evaluate the effectiveness of chemical control efforts taken by countries worldwide.

Multi-year Analyses Reveal Different Trends, Sources, and Implications for Source-Related Human Health Risks of Atmospheric Polycyclic Aromatic Hydrocarbons in the Canadian Great Lakes Basin.

Polycyclic aromatic hydrocarbons (PAHs) are of high concern to public health due to their carcinogenic and mutagenic properties. Here, we present the first comprehensive and quantitative analysis of sources, potential source regions according to source sectors and source-related human health risks of multi-year atmospheric measurements of PAHs in the Canadian Great Lakes Basin (GLB). The highest PAH concentrations were observed at a rural residential site (Egbert), followed by two regionally representative remote sites [Point Petre (PPT) and Burnt Island]. The levels of most PAHs in the GLB atmosphere significantly decreased between 1997 and 2017, broadly consistent with the decreasing trends of anthropogenic emissions. Coal, liquid fossil fuel, and biomass burning were the most common potential sources. The potential source regions for most source sectors were identified south or southwest of the sampling sites. Risk assessment suggests potential health risks associated with the inhalation of atmospheric PAHs. On a positive note, health risks from coal combustion, liquid fossil fuel combustion, and petrogenic sources at PPT significantly decreased, directly demonstrating the success of emission control in reducing health impacts. In contrast, the health risk from forest fire-related PAH emissions may play an increasing role in the future due to climate change.

PM10-bound trace elements in the Great Lakes Basin (1988-2017) indicates effectiveness of regulatory actions, variations in sources and reduction in human health risks.

Limited studies focus on the effectiveness of regulatory actions on changes in sources and temporal trends of human health risks for trace elements in atmospheric particles < 10 µm (PM10). To address this knowledge gap, PM10 samples were collected at three stations in the Great Lakes Basin over a thirty-year time span and analyzed for 19 representative elements. Temporal trends of trace elements in PM10 were derived using the Digital Filtration Technique and sources of these elements were determined using multiple statistical techniques, namely enrichment factor analysis, positive matrix factorization (PMF) and potential source contribution function (PSCF). Non-carcinogenic and carcinogenic risks by chronic exposure were assessed using US EPA reference concentrations and inhalation unit risk. Our results showed a strong relationship between element concentrations and local populations, which suggested that the emissions of trace elements were anthropogenically-related and was confirmed by the enrichment factor analysis. The concentrations of most elements were significantly decreasing with halving times ranging from 10 to 48 years in response to national and international regulatory actions. Specific origins of atmospheric trace elements were from the copper refining industry, refuse incineration, coal combustion, vehicle emissions, oil/coal-fired power plants, and crustal/soil dust. Potential source region analysis indicates dominant sources south of the sampling sites in the US, associated with a higher population and more industrial and transportation activities. The possibility of non-cancer health effects due to inhalation were mostly within acceptable levels. However, potential cancer risk posed by inhalation of some elements cannot be ignored, with values approaching or higher than the acceptable level. Considering that the sampling locations are remote and regionally-representative, our finding emphasizes the importance of continued monitoring of metals in air to assess the effectiveness of control strategies.

Perfluoroalkyl Acids in Great Lakes Precipitation and Surface Water (2006-2018) Indicate Response to Phase-outs, Regulatory Action, and Variability in Fate and Transport Processes.

The concentrations of perfluoroalkyl acids (PFAAs) were determined in precipitation from three locations across the Great Lakes between 2006 and 2018 and compared to those in surface water. Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) concentrations generally decreased in precipitation, likely in response to phase-outs/regulatory actions. In comparison, concentrations of shorter-chained PFAA, which are not regulated in Canada did not decrease and those of perfluorohexanoate and perfluorobutanoate (PFBA) recently increased, which could be due to their use as replacements, as the longer-chained PFAAs are being phased-out by industry. PFOS and PFOA concentrations were greater in Lake Ontario precipitation than in precipitation from more remote locations. In comparison, PFBA concentrations were comparable across locations, suggesting greater atmospheric transport either through its more volatile precursors and/or directly in association with particles/aerosols. In Lake Ontario, the comparison of PFAAs in precipitation to those in surface water provides evidence of sources (e.g., street dust and wastewater effluent) in addition to wet deposition to surface water, whereas wet deposition appears to be dominant in Lakes Huron and Superior. Our results suggest that source control of shorter-chained PFAAs may be slow to be reflected in environmental concentrations due to emissions far from the location of detection and continued volatilization from existing in-use products and waste streams.

Polycyclic Aromatic Hydrocarbons Not Declining in Arctic Air Despite Global Emission Reduction.

Two decades of atmospheric measurements of polycyclic aromatic hydrocarbons (PAHs) were conducted at three Arctic sites, i.e., Alert, Canada; Zeppelin, Svalbard; and Pallas, Finland. PAH concentrations decrease with increasing latitude in the order of Pallas > Zeppelin > Alert. Forest fire was identified as an important contributing source. Three representative PAHs, phenanthrene (PHE), pyrene (PYR), and benzo[ a]pyrene (BaP) were selected for the assessment of their long-term trends. Significant decline of these PAHs was not observed contradicting the expected decline due to PAH emission reductions. A global 3-D transport model was employed to simulate the concentrations of these three PAHs at the three sites. The model predicted that warming in the Arctic would cause the air concentrations of PHE and PYR to increase in the Arctic atmosphere, while that of BaP, which tends to be particle-bound, is less affected by temperature. The expected decline due to the reduction of global PAH emissions is offset by the increment of volatilization caused by warming. This work shows that this phenomenon may affect the environmental occurrence of other anthropogenic substances, such as more volatile flame retardants and pesticides.

Temporal trends of halogenated flame retardants in the atmosphere of the Canadian Great Lakes Basin (2005-2014).

Organic pollutants have been monitored in the atmosphere of the Great Lake Basin (GLB) since the 1990s in support of the Canada-US Great Lakes Water Quality Agreement and to determine the effectiveness of source reduction measures and factors influencing air concentrations. Air samples were collected between 2005 and 2014 at three sites with different geographical characteristics (Burnt Island, Egbert and Point Petre) in the Canadian GLB using high-volume air samplers and the air samples were analyzed for polybrominated diphenyl ethers (PBDEs) and several other non-PBDE halogenated flame retardants (HFRs). Spatial and temporal trends of total concentrations of HFRs were examined. BDE-47, BDE-99, and BDE-209 were the dominant PBDE congeners found at the three sites. For the non-PBDE HFRs, allyl 2,4,6-tribromophenyl ether (TBP-AE), hexabromobenzene (HBBz), pentabromotoluene (PBT), anti-dechlorane plus (anti-DDC-CO) and syn-dechlorane plus (syn-DDC-CO) were frequently detected. High atmospheric concentrations of PBDEs were found at the Egbert site with a larger population, while lower levels of PBDEs were detected at Point Petre, which is close to urban centers where control measures are in place. The strong temperature dependence of air concentrations indicates that volatilization from local sources influences atmospheric concentrations of BDE-28 and BDE-47 at Point Petre and Burnt Island, while long-range atmospheric transport (LRAT) was important for BDE-99. However, a weaker correlation was observed between air concentrations and ambient temperature for non-PBDE HFRs such as TBP-AE and HBBz. Atmospheric PBDE concentrations are decreasing slowly, with half-lives in the range of 2-16 years. Faster declining trends of PBDEs were observed at Point Petre rather than at Burnt Island. As Point Petre is closer to urban centers, faster declining trends may reflect the phase out of technical BDE mixtures in urban centers while LRAT influences the air concentrations at Burnt Island. The levels of syn-DDC-CO and anti-DDC-CO are decreasing at Point Petre and the levels of other non-PBDE HFRs such as TBP-AE, PBT and HBBz are increasing. Long-term declining trends of PBDEs suggest that regulatory efforts to reduce emissions to the GLB environment have been effective but that continuous measurements are required to gain a better understanding of the trends of emerging chemicals in the atmosphere of the GLB.

Atmospheric concentrations and loadings of organochlorine pesticides and polychlorinated biphenyls in the Canadian Great Lakes Basin (GLB): Spatial and temporal analysis (1992-2012).

Long-term air monitoring data for POPs are required to determine the effectiveness of source reduction measures and factors controlling air concentrations. Air samples were collected between 1992 and 2012 at three sites with different geographical characteristics (Burnt Island, Egbert and Point Petre) in the Canadian Great Lakes Basin (GLB) using high-volume samplers and analyzed for organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Spatial and temporal trends of gas-phase concentrations of OCPs, selected PCB congeners and Æ©PCBs (84 congeners) were assessed. Egbert had the highest concentrations of some OCPs due to historical [dichlorodiphenyltrichloroethanes (DDTs), dieldrin, γ-hexachlorocyclohexane (γ-HCH)] and current (endosulfan) applications of these pesticides in the surrounding agricultural cropland. This shows that agricultural areas are a source of OCPs to the GLB. High o,p'-/p,p'-DDT ratios were determined and an increasing trend was observed at Point Petre and Burnt Island up to 2004; indicating that the GLB is influenced by dicofol-type DDT sources, which have higher o,p'-/p,p'-DDT ratios than technical DDT. Atmospheric PCB concentrations at Egbert and Point Petre are higher than those measured at Burnt Island, likely due to urban influence and greater populations. Loadings calculations suggest that the atmosphere is a source of α-endosulfan and p,p'-DDT to the lakes and the opposite is true for p,p'-DDE. Long-term decreasing trends were observed for both OCPs and PCBs; consistent with control measures implemented in North America. Atmospheric PCB concentrations are decreasing relatively slowly, with halflives in the range of 9-39 years. Chlordane, α-endosulfan, ß-endosulfan, dieldrin, and DDT-related substances showed halflives in the range of 7-13 years. α-HCH and γ-HCH were decreasing rapidly in air, with halflives of 5 years. Long-term declining trends of PCBs and OCPs suggest that regulatory efforts to reduce emissions to the GLB environment have been effective, but emissions from primary and secondary sources might limit future declines.

Findings from quality assurance activities in the Integrated Atmospheric Deposition Network.

A series of experiments were conducted among the laboratories participating in the Integrated Atmospheric Deposition Network (IADN) monitoring program to evaluate comparability of the reported persistent organic pollutant concentrations. This quality assurance activity is essential because a variety of methods are currently used for sample collection, extraction, and analysis by the IADN laboratories. The experiments included analyses of a common reference standard (CRS), analyses of split samples, and analyses of samples collected with co-located samplers at the Point Petre IADN measurement station. The analytes included polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs). For virtually all compounds, the laboratories produced generally comparable results for the CRS samples, the split samples and the co-location samples, although some differences were observed. Analysis of the methods may pinpoint areas where variations in the methods will result in the differences observed in the reported data. These differences can be due to the field sampling process, the analytical method, field blank values, or a combination of all these factors. This study points out the importance of QA activities at every step of an environmental monitoring process so that areas where improvements may be needed or where inconsistencies may exist can be identified.