Volatile organic compounds in Arctic snow: concentrations and implications for atmospheric processes

PM2.5 decadal data in cold vs. mild climate airports: COVID-19 era and a call for sustainable air quality policy

Airports are identified hotspots for air pollution, notably for fine particles (PM_2.5) that are pivotal in aerosol-cloud interaction processes of climate change and human health. We herein studied the field observation and statistical analysis of 10-year data of PM_2.5 and selected emitted co-pollutants (CO, NO_x, and O₃), in the vicinity of three major Canadian airports, with moderate to cold climates. The decadal data analysis indicated that in colder climate airports, pollutants like PM_2.5 and CO accumulate disproportionally to their emissions in fall and winter, in comparison to airports in milder climates. Decadal daily averages and standard errors of PM_2.5 concentrations were as follows: Vancouver, 5.31 ± 0.017; Toronto, 6.71 ± 0.199; and Montreal, 7.52 ± 0.023 μg/m³. The smallest and the coldest airport with the least flights/passengers had the highest PM_2.5 concentration. QQQ-ICP-MS/MS and HR-S/TEM analysis of aerosols near Montreal Airport indicated a wide range of emerging contaminants (Cd, Mo, Co, As, Ni, Cr, and Pb) ranging from 0.90 to 622 μg/L, which were also observed in the atmosphere. During the lockdown, a pronounced decrease in the concentrations of PM_2.5 and submicron particles, including nanoparticles_, in residential areas close to airports was observed, conforming with the recommended workplace health thresholds (~ 2 × 10⁴ cm^-3), while before the lockdown, condensable particles were up to ~ 1 × 10⁵ cm^-3. Targeted reduction of PM_2.5 emission is recommended for cold climate regions.

Occurrence of Volatile and Semi-Volatile Organic Pollutants in the Russian Arctic Atmosphere: The International Siberian Shelf Study Expedition (ISSS-2020)

Environmental issues in the Arctic region are of primary importance due to the fragility of the Arctic ecosystem. Mainly persistent organic compounds are monitored in the region by nine stationary laboratories. Information on the volatile (VOC) and semi volatile (SVOC) organic priority pollutants is very limited, especially for the Russian Arctic. Air samples from 16 sites along the Russian Arctic coast from the White Sea to the East Siberian Sea were collected on sorption tubes packed with Tenax, Carbograph, and Carboxen sorbents with different selectivity for a wide range of VOCs and SVOCs in 2020 within the framework of the International Siberian Shelf Study Expedition on the research vessel Akademik Keldysh. Thermal desorption gas chromatography–high-resolution mass spectrometry with Orbitrap was used for the analysis. Eighty-six VOCs and SVOCs were detected in the air samples at ng/m3 levels. The number of quantified compounds varied from 26 to 66 per sample. Benzoic acid was the major constituent, followed by BTEX, phenol, chloroform, bis(2-ethylhexyl) phthalate, and carbon tetrachloride. The study allowed for obtaining the first ever data on the presence of 138 priority pollutants in the air of Russian Arctic, whereas the thorough assessment of their possible sources will be the aim of a next investigation.

Snow microbiome functional analyses reveal novel aspects of microbial metabolism of complex organic compounds

Microbes active in extreme cold are not as well explored as those of other extreme environments. Studies have revealed a substantial microbial diversity and identified cold-specific microbiome molecular functions. We analyzed the metagenomes and metatranscriptomes of 20 snow samples collected in early and late spring in Svalbard, Norway using mi-faser, our read-based computational microbiome function annotation tool. Our results reveal a more diverse microbiome functional capacity and activity in the early- vs. late-spring samples. We also find that functional dissimilarity between the same-sample metagenomes and metatranscriptomes is significantly higher in early than late spring samples. These findings suggest that early spring samples may contain a larger fraction of DNA of dormant (or dead) organisms, while late spring samples reflect a new, metabolically active community. We further show that the abundance of sequencing reads mapping to the fatty acid synthesis-related microbial pathways in late spring metagenomes and metatranscriptomes is significantly correlated with the organic acid levels measured in these samples. Similarly, the organic acid levels correlate with the pathway read abundances of geraniol degradation and inversely correlate with those of styrene degradation, suggesting a possible nutrient change. Our study thus highlights the activity of microbial degradation pathways of complex organic compounds previously unreported at low temperatures.

Diversity of metals and metal-interactive bacterial populations in different types of Arctic snow and frost flowers: Implications on snow freeze-melt processes in a changing climate

Arctic snow has been shown to be a reactive interface for key physical, chemical, and microbiological processes, affecting the Arctic's oxidation, biodiversity, radiation, and climate. To explore the potential links between snow-borne metal contaminants and metal-interactive bacteria, to freezing/melting processes, we performed concurrent chemical characterization, genomic, and morphological analysis of five different Arctic snowpack (accumulated, blowing, fresh falling, surface hoar, and wind pack snow) and frost flower in Utqiaġvik (Barrow), Alaska, using Montreal urban snow as reference. Several complementary analytical techniques, including triple quad ICP-MS/MS along with various chromatography techniques, thermal ionization mass spectrometer (TIMS), high-resolution transition electron microscopy with electron dispersive X-ray spectroscopy (HR-TEM/EDS), and next generation sequencing (NGS), were deployed. Distinct metal composition and bacterial distribution among samples were observed. The concentration of 27 different transition, post-transition, rare, and radioactive metals were determined in molten snow and frost flower, as well as filtered samples. The range of three highest detected metal concentrations among samples were: Hg (3.294-134.485 μg/L), Fe (0.719-34.469 μg/L), and Sr (1.676-19,297.000 μg/L). NGS analysis led to the identification of metal interacting bacteria in all types of snow and frost flowers in the Arctic (blowing snow (1239), surface hoar snow (2243), windpack (2431), frost flowers (1440)), and Montreal urban snow (5498)) with specific bacterial genera such as: Acinetobacter, Arcenicella, Azospirillum (surface hoar snow), Arthrobacter, Paenibacillus (blowing snow), and Cycloclasticus, OM182 clade (frost flower). Several types of bacteria with confirmed or associated ice nucleation activity were observed in different types of snow, and frost flower including Pseudomonas genera (e.g., Pseudomonas fluorescens), Flavobacterium, Corynebacterium, and Pseudoxanthomonas. The implications of the above findings to snow-air interactions including nanoparticles, namely during melting and freezing cycles, and to probe the impact of various natural and anthropogenic activities are herein discussed.