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The formation of brown carbon (BrC) in aqueous atmospheric aerosols is well-documented and often attributed to aldehyde-ammonia reactions. However, many studies have focused on individual aldehyde precursors, overlooking the complex composition of organic aerosols, which comprise a diverse mix of organic and inorganic compounds. To address this, a complex BrC system was investigated by generating aqueous atmospheric aerosol mimics containing glyoxal (Gly), glycolaldehyde (GAld), and ammonium sulfate. Structural analysis using supercritical fluid chromatography−mass spectrometry (SFC-MS) showed that adjusting the Gly:GAld mole ratio leads to variations in the composition and abundance of BrC products formed. Notably, aromatic heterocycles (e.g., imidazoles and pyrazines) as well as acyclic carbonyl oligomers were identified to form at different concentrations depending on the Gly:GAld mole ratio. UV−visible spectroscopy analysis demonstrated that light absorption in these mixed Gly + GAld + AS systems cannot be modeled as a simple weighted average of the Gly:GAld mole ratio; observed changes in light absorbance can be explained by compositional changes in solution. These observations indicate that cross-reactions are occurring between the Gly and GAld in solution, potentially leading to changes in the physical properties of the aerosol. Given the thousands of reactive compounds found in atmospheric aerosol, these findings could have important implications for our understanding of organic reactions within the aerosol. 

Research cruises were conducted to sample the invertebrate community along the shelf off the central coast of Oregon from 2010 to 2018. A large marine heatwave (MHW) hit the northeast Pacific in fall 2014 and persisted locally through 2015. Here, we assessed the caloric content changes of Crangon alaskensis (a common sandy shrimp) before, during, and after the 2014–2015 MHW. We found significant reductions in the caloric density of shelf populations of C. alaskensis during summer 2015. Oceanographic indices like the Biologically Effective Upwelling Transport Index (BEUTI) and the Pacific Decadal Oscillation (PDO) had greater predictive power for caloric density and biomass than in situ conditions, although bottom temperature and dissolved oxygen were also significantly correlated with caloric density. Caloric density of C. alaskensis was highest in 2018, indicating favorable conditions after the intense MHW of 2014–2015 allowed the caloric density to rebound. 

Abstract The DArk Matter In CCDs at Modane (DAMIC-M) experiment is designed to search for light dark matter (m_χ< 10 GeV/c²) at the Laboratoire Souterrain de Modane (LSM) in France. DAMIC-M will use skipper charge-coupled devices (CCDs) as a kg-scale active detector target. Its single-electron resolution will enable eV-scale energy thresholds and thus world-leading sensitivity to a range of hidden sector dark matter candidates. A DAMIC-M prototype, the Low Background Chamber (LBC), has been taking data at LSM since 2022. The LBC provides a low-background environment, which has been used to characterize skipper CCDs, study dark current, and measure radiopurity of materials planned for DAMIC-M. It also allows testing of various subsystems like readout electronics, data acquisition software, and slow control. This paper describes the technical design and performance of the LBC.