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1. An investigation into the chemistry of HONO in the marine boundary layer at Tudor Hill Marine Atmospheric Observatory in Bermuda

   https://doi.org/10.5194/acp-22-6327-2022  

   Zhu, Yuting; Wang, Youfeng; Zhou, Xianliang; Elshorbany, Yasin F.; Ye, Chunxiang; Hayden, Matthew; Peters, Andrew J. (January 2022, Atmospheric Chemistry and Physics)

   Abstract. Here we present measurement results of temporal distributions of nitrous acid (HONO) along with several chemical and meteorologicalparameters during the spring and the late summer of 2019 at Tudor Hill Marine Atmospheric Observatory in Bermuda. Large temporal variations inHONO concentration were controlled by several factors including local pollutant emissions, air mass interaction with the island, andlong-range atmospheric transport of HONO precursors. In polluted plumes emitted from local traffic, power plant, and cruise ship emissions,HONO and nitrogen oxides (NOx) existed at substantial levels (up to 278 pptv and 48 ppbv, respectively),and NOx-related reactions played dominant roles in daytime formation of HONO. The lowest concentration of HONO wasobserved in marine air, with median concentrations at ∼ 3 pptv around solar noon and < 1 pptv during thenighttime. Considerably higher levels of HONO were observed during the day in the low-NOx island-influenced air([NO2] < 1 ppbv), with a median HONO concentration of ∼ 17 pptv. HONO mixing ratios exhibiteddistinct diurnal cycles that peaked around solar noon and were lowest before sunrise, indicating the importance of photochemical processes forHONO formation. In clean marine air, NOx-related reactions contribute to ∼ 21 % of the daytime HONOsource, and the photolysis of particulate nitrate (pNO3) can account for the missing source assuming a moderate enhancement factorof 29 relative to gaseous nitric acid photolysis. In low-NOx island-influenced air, the contribution from bothNOx-related reactions and pNO3 photolysis accounts for only ∼ 48 % of the daytime HONOproduction, and the photochemical processes on surfaces of the island, such as the photolysis of nitric acid on the forest canopy, might contributesignificantly to the daytime HONO production. The concentrations of HONO, NOx, and pNO3 were lowerwhen the site was dominated by the aged marine air in the summer and were higher when the site was dominated by North American air in the spring,reflecting the effects of long-range transport on the reactive nitrogen chemistry in background marine environments. 

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2. Evidence of heterogeneous HONO formation from aerosols and the regional photochemical impact of this HONO source

   https://doi.org/10.1088/1748-9326/aae492  

   Lu, Xingcheng; Wang, Yuhang; Li, Jianfeng; Shen, Lu; Fung, Jimmy C (November 2018, Environmental Research Letters)
3. Sharp contrasts between freshwater and marine microbial enzymatic capabilities, community composition, and DOM pools in a NE Greenland fjord

   https://doi.org/10.1002/lno.11253  

   Balmonte, John Paul; Hasler‐Sheetal, Harald; Glud, Ronnie N.; Andersen, Thorbjørn J.; Sejr, Mikael K.; Middelboe, Mathias; Teske, Andreas; Arnosti, Carol (July 2019, Limnology and Oceanography)

   Abstract Increasing glacial discharge can lower salinity and alter organic matter (OM) supply in fjords, but assessing the biogeochemical effects of enhanced freshwater fluxes requires understanding of microbial interactions with OM across salinity gradients. Here, we examined microbial enzymatic capabilities—in bulk waters (nonsize‐fractionated) and on particles (≥ 1.6μm)—to hydrolyze common OM constituents (peptides, glucose, polysaccharides) along a freshwater–marine continuum within Tyrolerfjord‐Young Sound. Bulk peptidase activities were up to 15‐fold higher in the fjord than in glacial rivers, whereas bulk glucosidase activities in rivers were twofold greater, despite fourfold lower cell counts. Particle‐associated glucosidase activities showed similar trends by salinity, but particle‐associated peptidase activities were up to fivefold higher—or, for several peptidases, only detectable—in the fjord. Bulk polysaccharide hydrolase activities also exhibited freshwater–marine contrasts: xylan hydrolysis rates were fivefold higher in rivers, while chondroitin hydrolysis rates were 30‐fold greater in the fjord. Contrasting enzymatic patterns paralleled variations in bacterial community structure, with most robust compositional shifts in river‐to‐fjord transitions, signifying a taxonomic and genetic basis for functional differences in freshwater and marine waters. However, distinct dissolved organic matter (DOM) pools across the salinity gradient, as well as a positive relationship between several enzymatic activities and DOM compounds, indicate that DOM supply exerts a more proximate control on microbial activities. Thus, differing microbial enzymatic capabilities, community structure, and DOM composition—interwoven with salinity and water mass origins—suggest that increased meltwater may alter OM retention and processing in fjords, changing the pool of OM supplied to coastal Arctic microbial communities. 

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4. Nitrous Acid (HONO) Formation from the Irradiation of Aqueous Nitrate Solutions in the Presence of Marine Chromophoric Dissolved Organic Matter: Comparison to Other Organic Photosensitizers

   https://doi.org/10.1021/acsearthspacechem.1c00292  

   Mora Garcia, Stephanie L.; Pandit, Shubhrangshu; Navea, Juan G.; Grassian, Vicki H. (November 2021, ACS Earth and Space Chemistry)
5. FREEDOM: Engineering a State-of-the-Art DOM Fuzzer

   https://doi.org/10.1145/3372297.3423340  

   Xu, Wen; Park, Soyeon; Kim, Taesoo (October 2020, Proceedings of the 27th ACM Conference on Computer and Communications Security (CCS 2020))