Characterization of black carbon-containing particles from soot particle aerosol mass spectrometer measurements on the R/V Atlantis during CalNex 2010

We presentmass spectrometrymeasurements of black carbon-containing particlesmade on board the R/V Atlantis during the CalNex (California Research at the Nexus of Air Quality and Climate Change) 2010 study using an Aerodyne Research Inc. soot particle aerosol mass spectrometer (SP-AMS). The R/V Atlantis was deployed to characterize airmassesmoving offshore the California coast and to assess emissions fromsources in urban ports. This work presents a first detailed analysis of the size-resolved chemical composition of refractory black carbon (rBC) and of the associated coating species (NR-PM_BC). A colocated standard high-resolution aerosolmass spectrometer (HR-AMS) measured the total nonrefractory submicron aerosol (NR-PM₁). Our results indicate that, on average, 35% of the measured NR-PM1 mass (87% of the primary and 28% of the secondary NR-PM1, as obtained from the mass-weighted average of the NR-PM_BC species) was associated with rBC. The peak in the average size distribution of the rBC-containing particles measured by the SP-AMS in vacuum aerodynamic diameter (d_va) varied from ~100 nm to ~450 nm d_va, with most of the rBC mass below 200 d_va. The NR-PM_BC below 200 nm d_va was primarily organic, whereas inorganics were generally found on larger rBC-containing particles. Positive matrix factorization analyses of both SP-AMS and HR-AMS data identified organic aerosol factors that were correlated in time but had different fragmentation patterns due to the different instruments vaporization techniques. Finally, we provide an overview of the volatility properties of NR-PM_BC and report the presence of refractory oxygen species in some of the air masses encountered.