is a subarctic city with fine particle (PM 2.5 ) concentrations that exceed air quality regulations in winter due to weak dispersion caused by strong atmospheric inversions, local emissions, and the unique chemistry occurring under the cold and dark conditions. Here, we report on observations from the winters of 2020 and 2021, motivated by our pilot study that showed exceptionally high concentrations of fine particle hydroxymethanesulfonate (HMS) or related sulfur-(IV) species (e.g., sulfite and bisulfite). We deployed online particle-into-liquid sampler−ion chromatography (PILS-IC) in conjunction with a suite of instruments to determine HMS precursors (HCHO, SO 2 ) and aerosol composition in general, with the goal to characterize the sources and sinks of HMS in wintertime Fairbanks. PM 2.5 HMS comprised a significant fraction of PM 2.5 sulfur (26−41%) and overall PM 2.5 mass concentration of 2.8−6.8% during pollution episodes, substantially higher than what has been observed in other regions, likely due to the exceptionally low temperatures. HMS peaked in January, with lower concentrations in December and February, resulting from changes in precursors and meteorological conditions. Strong correlations with inorganic sulfate and organic mass during pollution events suggest that HMS is linked to processes responsible for poor air quality episodes. These findings demonstrate unique aspects of air pollution formation in cold and humid atmospheres.

Armor‐grade B4C and SiC specimens were analyzed for phase assemblage, microstructure, and mechanical properties. SiC–N showed the highest four‐point fracture strength, and an ∼50% higher notched beam fracture toughness than solid‐state sintered B4C and SiC. This was attributed to preferential crack propagation along a weaker amorphous aluminosilicate grain‐boundary interphase, which also attenuated the effect of surface flaws on bending strength. Verco B4C showed the highest hardness. That material was phase pure, fully dense, and of finer grain size as compared with pressure‐assisted densification (PAD)‐B4C (hot pressed). Verco SiC showed a hardness equal to (Vickers) or higher than (Knoop) PAD‐B4C, and a comparatively narrow distribution in measured hardnesses. This was attributed to a fine‐grained, fully dense, solid‐state sintered microstructure with a fine and well‐distributed graphite second phase. Hardness of all specimens decreased with increasing applied load.

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• Six samples of core segments from Tank 101-SY, obtained during the window E core sampling, have been analyzed for organic constituents. Four of the samples were from the upper region, or convective layer, of the tank and two were from the lower, nonconvective layer. The samples were analyzed for chelators, chelator fragments, and several carboxylic acids by derivatization gas chromatography/mass spectrometry (GC/MS). The major components detected were ethylenediaminetetraacetie acid (EDTA), nitroso-iminodiacetic acid (NIDA), nitrilotriacetic acid (NTA), citric acid (CA), succinic acid (SA), and ethylenediaminetriacetic acid ('ED3A). The chelator of highest concentration was EDTA in all six samples analyzed. Liquid chromatography (LC) was used to quantitate low molecular weight acids (LMWA) including oxalic, formic, glyeolic, and acetic acids, which are present in the waste as acid salts. From 23 to 61% of the total organic carbon (TOC) in the samples analyzed was accounted for by these acids. Oxalate constituted approximately 40% of the TOC in the nonconvective layer samples. Oxalate was found to be approximately 3 to 4 times higher in concentration in the nonconvective layer than in the convective layer. During FY 1993, LC methods for analyzing LWMA, and two chelators N-(2-hydroxyethyl) ethylenediaminetriacetic acid and EDTA, were transferred to personnel in the Analytical Chemistry Laboratory and the 222-S laboratory.