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Concentrations of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) were analyzed and investigated in surficial sediment collected in 2018 from ten different nearshore sites in Lake Ontario and the St. Lawrence River influenced by inputs from varying urban and historical land uses. Sites were grouped into two categories of tributary and lake according to their location. Results show that tributary sites had higher concentrations of total chlorinated paraffin (CP) than lake sites. Humber Bay, a lake site, had the highest total CP concentration (55,000 ng/g TOC ) followed by Humber River, a tributary site (50,000 ng/g TOC ). The lowest concentrations were found in eastern Lake Ontario and Lake St. Francis in the St. Lawrence River (540 ng/g TOC ). Higher concentrations of chlorinated paraffins (CPs) were found where runoff and wastewater inputs from urban areas, current industrial activities, and population were the greatest. Levels of MCCPs were higher than SCCPs at all sites but one, Lake St. Francis. Among the SCCPs, C 13 and among the MCCPs C 14 were the dominant chain length alkanes, with C 14 being the highest among both groups. The SCCPs and MCCPs profiles suggest that they can be used to distinguish between sites impacted by local sources vs. sites impacted by short-/long-range transport of these chemicals., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

PM 2.5 was sampled over a seven-year period (2013-2019) at two locations ∼50 km apart in Southern Ontario (concurrently for five years: 2015-2019). One is a heavily industrialized site (Hamilton), while the other was a rural site (Simcoe). To assess the impact of industrialization on the composition and sources of PM affecting air quality in these two locations, positive matrix factorization coupled with dispersion normalization (DN-PMF) was used to identify six and eight factors at Simcoe and Hamilton, respectively. The Simcoe factors in order of diminishing PM mass contribution were: particulate sulphate (pSO4), secondary organic aerosol (SOA), crustal matter, particulate nitrate (pNO3), biomass burning, and vehicular emissions. At Hamilton, the effects of industrialization were observed by the ∼36% higher average ambient PM 2.5 concentration for the study period as well as the presence of factors unique to metallurgy, i.e., coking and steelmaking, compared to Simcoe. The coking and steelmaking factors contributed ∼15% to the PM mass at Hamilton. Seasonal variants of appropriate nonparametric trend tests with the associated slopes (Sen's) were used to assess statistically significant changes in the factor contributions to PM 2.5 over time. Specifically at Hamilton, a significant decline in PM contributions was noted for coking (-0.03 μg/m³/yr or -4.1%/yr) while steelmaking showed no statistically significant decline over the study period. Other factors at Hamilton that showed statistically significant declines over the study period were: pSO4 (-0.27 μg/m³/yr or -12.6%/yr), biomass burning (-0.05 μg/m³/yr or -9.02%/yr), crustal matter (-0.03 μg/m³/yr or -5.28%/yr). These factors mainly accounted for the significant decline in PM 2.5 over the study period (-0.35 μg/m³/yr or -4.24%/yr). This work shows the importance of long-term monitoring in assessing the unique contributions and temporal changes of industrialization on air quality in Ontario and similarly affected locations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Ltd. All rights reserved.)

Ambient fine particulate matter (PM 2.5 ) data were collected in the lower City of Hamilton, Ontario to apportion the sources of this pollutant over an 18-month period. Hamilton has complex topographical features that may result in worsened air pollution within the lower city, thus, dispersion-normalized, multi-time resolution factor analysis (DN-MT-FA) was used to identify and quantify contributions of factors in a manner that reduced the influence of local meteorology. These factors were secondary organic aerosols type 1 (SOA_1), particulate nitrate (pNO3), particulate sulphate (pSO4), primary traffic organic matter (PTOM), Steel/metal processing and vehicular road dust emissions (Steel & Mobile) and, secondary organic aerosols type 2 (SOA_2) with origins ranging from mainly regional to mainly local. Factors that were mainly local (PTOM, Steel & Mobile, SOA_2) contributed up to 17% of the average PM 2.5 mass while mixed local/regional factors (pNO3, pSO4) made up 43% on average, indicating the potential for further reduction of harmful PM concentrations locally. Of particular interest from a health protection perspective, was the composition of PM 2.5 on days when an exceedance of the 24-hr WHO air quality guideline for this pollutant was observed. In general, SOA_1 was found to drive summer exceedances while pNO3 dominated in the winter. During the summer period, SOA_1 was attributable to wildfires in the northern parts of Canada while local traffic sources in winter contributed to the high levels of pNO3. While local, industrial factors only had minor relative mass contributions during exceedances, they are high in highly oxidized organic species (SOA_2) and toxic metals (Steel & Mobile). Thus, they are likely to have more impacts on human health. The methods and results described in this work will be useful in understanding prevalent sources of particulate matter pollution in the ambient air in the presence of complex topography and meteorological effects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Ltd. All rights reserved.)

Per- and polyfluoroalkyl substances (PFAS) are globally distributed in the natural environment, and their persistent and bioaccumulative potential illicit public concern. The production of certain PFAS has been halted or controlled by regulation due to their adverse effect on the health of humans and wildlife. However, new PFAS are continuously developed as alternatives to legacy PFAS. Additionally, many precursors are unknown, and their metabolites have not been assessed. To better understand the PFAS profiles in the Lake Ontario (LO) aquatic food web, a quadrupole time-of-flight mass spectrometer (QToF) coupled to ultrahigh-performance liquid chromatography (UPLC) was used to generate high-resolution mass spectra (HRMS) from sample extracts. The HRMS data files were analyzed using an isotopic profile deconvoluted chromatogram (IPDC) algorithm to isolate PFAS profiles in aquatic organisms. Fourteen legacy PFAAs (C5-C14) and 15 known precursors were detected in the LO food web. In addition, over 400 unknown PFAS features that appear to biomagnify in the LO food web were found. Profundal benthic organisms, deepwater sculpin( Myoxocephalus thompsonii ), and Mysis were found to have more known precursors than other species in the food web, suggesting that there is a large reservoir of fluorinated substances in the benthic zone.

This work presents the first assessment of temporal trends (2005-2016) for perfluoroalkyl acids (PFAAs) in top predator fish of the Laurentian Great Lakes except Lake Ontario, for which we provide a post-2008 update. Lake trout (Salvelinus namaycush) or walleye (Sander vitreus; Lake Erie only) collected annually from 2005 to 2016 were analyzed for 12 perfluoroalkyl carboxylic acids (PFCAs) and 4 perfluoroalkyl sulfonic acids (PFSAs) with carbon chain lengths between 4 and 16 (C4-C16). Individual analyte concentrations generally decreased in fish basin-wide between 2005 and 2016, including Lake Ontario lake trout previously found to lack declining PFAA concentrations up until 2008. Declining fish PFAA burden reflects a positive response to the industrial phase-outs of these chemicals. Notable exceptions to this general decline included most analytes in lake trout collected from Lake Superior near Keweenaw Point and C6 and C8 PFSAs and C9 PFCAs in Lake Erie lake trout and walleye, which exhibited constant or increasing concentrations in recent years. Recent increases in Lake Superior shoreline development and mobilization from increased sediment resuspension and contamination from biosolids-amended agricultural soils in the Lake Erie watershed are plausible explanations for these cases. However, data scarcity prohibits confirmation of these suspected causes. The lingering lack of declining concentrations noted in this study together with the ongoing evolution of the fluorinated chemical industry emphasize the vigilance needed to better understand how past and future emissions will affect the Great Lakes and global ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Fish have been used for decades as bioindicators for assessing toxic contaminants in the Great Lakes ecosystem. Routine environmental monitoring programs target predetermined compounds that do not reflect the complete exposure of chemicals to biota and do not provide the complete halogenated fingerprint of the biota. In the current work, a nontargeted screening method was developed using a two-dimensional gas chromatograph coupled to a high-resolution time-of-flight mass spectrometer and was applied to 149 edible fish fillets from different species in the Great Lakes to characterize a more robust set of halogenated organic compounds across species and among lakes. Lake Ontario had the largest number of novel halogenated organic compounds (NHOCs). Seven NHOCs were observed in species from all lakes, indicating that this regional signature was not species-dependent. Hierarchical cluster analysis showed identical NHOC profiles between bottom dwelling and pelagic species. The NHOCs were grouped into seven clusters with similar structures and potentially similar environmental behaviors. Seven of the 29 NHOCs likely containing methoxy or ethoxy groups on a benzene or benzene-methanol backbone were clustered into one group with similar retention times. Five NHOCs were clustered with legacy contaminants that likely have similar structures or are their degradation products.

Legacy halogenated contaminants have been monitored in the Great Lakes for decades, but there are many additional unknown halogenated contaminants potentially affecting the Great Lakes ecosystem. To address this concern, lake trout ( Salvelinus namaycush ) were collected in 2005/2006 and 2015/2016 from each lake and screened for previously unidentified compounds. The isotopic profile deconvoluted chromatogram algorithm was used to isolate unknown halogenated components using high-resolution mass spectrometry data files generated by an atmospheric pressure gas chromatography-quadrupole time-of-flight mass spectrometer operated in positive and negative modes. The temporal and spatial differences in the newly detected features were used to isolate new potential contaminants. Decadal differences in the unknown halogenated compounds (or features) were compared with the total polychlorinated biphenyl concentration trends. Greater than 2000 unknown halogenated features were detected. As expected, Lake Superior contained the lowest number of unknown halogenated features, whereas Lake Ontario contained the highest. Unknown features tended to have fewer Cl and/or Br atoms compared to traditional legacy contaminant features typically monitored. Diverse patterns of unknown halogenated compounds between lakes suggested that there continues to be unidentified sources of halogenated contaminants in the Great Lakes missed by current monitoring programs.

Hexabromocyclododecane (HBCDD) is a hazardous, persistent, bioaccumlative brominated flame retardant. To investigate how its use has affected the Great Lakes, total HBCDD (∑HBCDD) concentrations and temporal trends in homogenized whole fish samples from the Great Lakes region (1978 to 2016) were determined. ∑HBCDD concentrations (ng/g ww) for each lake are Erie (0.49-2.60), Ontario (3.12-8.90), Michigan (3.91-9.01), Superior (5.69-13.1), and Huron (5.57-13.7). Early years (1978 to 1992) showed no significant trend. However, recent trends (2004 to 2016) suggest concentrations are increasing in Lakes Erie and Ontario, decreasing in Lakes Superior and Michigan, and not changing in Lake Huron. Decreasing trends for Lakes Superior and Michigan are likely the result of decreased usage of the compound globally, regionally, and locally. For the other lakes, increasing or zero trends are consistent with food web changes due to invasive species and climate change, which has caused more intense storms and less ice cover leading to increased sediment resuspension.

Our research reports polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CP-PCBs) concentrations and age-corrected trends for lake trout and walleye in the Great Lakes over the 2004-2014 period. We determined that age-contaminant corrections are required to accurately report contaminant trends due to significant lake trout age structure changes. The age-trend model (ATM) described here uses a lake-specific age-contaminant regression to mitigate the effect of a fluctuating lake trout age structure to directly improve the log-linear regression model. ATM results indicate that half-life (t 1/2 ) and percent decreases for PCDD/Fs, CP-PCBs, and toxic equivalence (TEQ) (average -56 to 70%) were fairly uniform and consistent across the Great Lakes over the 2004-2014 period. The vast majority of TEQ associated with all Great Lakes lake trout and walleye samples is due to the nonortho CP-PCBs (average = 79%) as compared with PCDD/Fs (average = 21%). On average, CP-PCB_126 individually accounted for over 95% of the total CP-PCB TEQ. A retrospective analysis (1977-2014) of 2378-TCDF and 2378-TCDD raw concentrations in Lake Ontario lake trout revealed decreases of 94% and 96%, respectively. Tissue residue guidelines for wildlife protection based on lake trout and walleye total TEQ were uniformly exceeded in all the Great Lakes.

Continuous measurements of particle number concentrations were performed in Rochester, NY, and Toronto, Ontario, Canada during the 2003 calendar year. Strong seasonal dependency in particle number concentration was observed at two sites. The average number concentration of ambient particles was 9670 +/- 6960 cm(-3) in Rochester, whereas in Toronto the average number of particles was 28,010 +/- 13,350 cm(-3). The particle number concentrations were higher in winter months than in summer months by a factor of 1.5 in Rochester and 1.6 in Toronto. In general, there were also distinct diurnal variations of aerosol number concentration. The highest weekdays/weekends ratio of number concentration was typically observed during the rush-hour period in winter months with a ratio of 2.1 in Rochester and 2.0 in Toronto. The correlation in the total particle number concentrations between the two urban sites was stronger in winter because of the common urban traffic patterns, but weaker in summer because of local sulfur dioxide (SO2)-related particle formation events in Rochester in the summer. Strong morning particle formation events were frequently observed during colder winter months. Good correlations between particle number and carbon monoxide (CO) as well as temperature suggested that motorvehicle emissions lead to the formation of new particles as the exhaust mixes with the cold air. Regional nucleation and growth events frequently occurred in April. Local SO2-related particle formation events most frequently occurred in August. SO2 and UV-B were highly correlated with particle concentration, suggesting a high association of photochemical processes with these local events. A high directionality in a northerly direction was observed for particle number and SO2, indicating the influence of point sources located north of Rochester.