At the air−ice interface, some aromatic compounds such as benzene and anthracene are surprisingly unreactive toward OH. This may be a consequence of the poor solvation of these compounds at the interface, resulting in clustering there. We test this hypothesis by comparing the reaction of OH with pyrene, a 4ring polyaromatic hydrocarbon (PAH), to reactions of OH with the more water-soluble compounds coumarin and 7-hydroxycoumarin (7OHC). We observe that OH reacts readily with coumarin and 7OHC at both liquid and frozen air−water interfaces. Pyrene, a much less soluble compound, reacts with OH at the liquid surface but not at the air−ice interface. We report evidence of pyrene aggregation at the ice surface based on its broadened and redshifted emission spectrum alongside fluorescence mapping of anthracene, a closely related 3-ring PAH, which shows bunching at the ice surface. By contrast, fluorescence mapping shows that coumarin is fairly homogeneously distributed at the air−ice interface. Together, these results suggest that the limited reactivity of some compounds toward OH at the ice surface may be a consequence of their propensity to self-aggregate, demonstrating that chemical morphology can play an important role in reactions at the ice surface.
In recent decades, contamination of the environment with microplastics and micro bers has been recognized as a pervasive and ubiquitous issue of global concern. While much research in this eld has been undertaken in marine environments, more recent studies have identi ed rivers as major conveyors of plastic pollution from terrestrial into marine systems. However, reports on the levels and composition of microplastic and micro ber contamination in rivers of the Canadian prairie region, speci cally the South Saskatchewan River (SSR), are scarce, which leaves this vital source of water for societies and ecosystems in a vulnerable state. To ll this gap, we obtained samples from seven sites along the Saskatchewan portion of the SSR, as well as three stormwater retention ponds (SRP) in the city of Saskatoon during the spring, summer, and fall of 2020. We used optical and Raman microscopy to enumerate and characterize particles in these samples. Total levels of particles and bers in all samples ranged from 32 to 116 particles m − 3 . Most particles (approx. 77%) were natural bers, while polymers accounted for the remaining 33%. Average microplastic levels were lower (3.18 ± 3 particles m − 3 ) downstream of Lake Diefenbaker, a large reservoir on the SSR, compared to upstream (12.0 ± 9 particles m − 3 ). Retention of microplastics in the reservoir could explain the lower mean microplastic concentration of 4.43 ± 3 particles m − 3 recorded in the SSR compared to mean concentrations of 26.2 ± 18 particles m − 3 reported in the North Saskatchewan River, which is not dammed. This study is among the rst to describe microplastic and micro ber levels in the SSR and thereby helps improve our understanding of this pervasive environmental contaminant on the Canadian prairies.
In recent decades, contamination of the environment with microplastics and microfibers has been recognized as a pervasive and ubiquitous issue of global concern. While much research in this field has been undertaken in marine environments, more recent studies have identified rivers as major conveyors of plastic pollution from terrestrial into marine systems. However, reports on the levels and composition of microplastic and microfiber contamination in rivers of the Canadian prairie region, specifically the South Saskatchewan River (SSR), are scarce, which leaves this vital source of water for societies and ecosystems in a vulnerable state. To fill this gap, we obtained samples from seven sites along the Saskatchewan portion of the SSR, as well as three stormwater retention ponds (SRP) in the city of Saskatoon during the spring, summer, and fall of 2020. We used optical and Raman microscopy to enumerate and characterize particles in these samples. Total levels of particles and fibers in all samples ranged from 32 to 116 particles m− 3. Most particles (approx. 77%) were natural fibers, while polymers accounted for the remaining 33%. Average microplastic levels were lower (3.18 ± 3 particles m− 3) downstream of Lake Diefenbaker, a large reservoir on the SSR, compared to upstream (12.0 ± 9 particles m− 3). Retention of microplastics in the reservoir could explain the lower mean microplastic concentration of 4.43 ± 3 particles m− 3 recorded in the SSR compared to mean concentrations of 26.2 ± 18 particles m− 3 reported in the North Saskatchewan River, which is not dammed. This study is among the first to describe microplastic and microfiber levels in the SSR and thereby helps improve our understanding of this pervasive environmental contaminant on the Canadian prairies.
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