Mass and Number Size Distributions of rBC in Snow and Firn Samples From Pine Island Glacier, West Antarctica

An extended‐range Single Particle Soot Photometer (SP2) coupled to a Marin‐5 nebulizer was used to measure the refractory black carbon (rBC) mass and number size distributions in 1,004 samples from a West Antarctica snow/firn core. The SP2 was calibrated using Aquadag and a Centrifugal Particle Mass Analyzer for BC particles ranging from 0.5 to 800 fg. Our results indicate a significant contribution of rare, large particles of mass‐equivalent diameter (DBC) \u3e 500 nm to the total rBC mass (36%), while small particles (DBC \u3c 100 nm) are abundant but contribute \u3c8% to total rBC mass. We observed a primary mass median diameter of 162 ± 40 nm, smaller than reported for snow in other regions of the globe but similar to East Antarctica rBC size distributions. In addition, we observed other modes at 673, 1,040, and \u3e1,810 nm (uncontained mode). We compared two sets of samples from different seasons (wet vs. dry) and observed that dry season concentrations are 3.4 and 2 times that of the wet season in the ranges of 80 nm \u3c DBC \u3c 500 nm (small particles) and 500 nm \u3c DBC \u3c 2,000 nm (large particles), respectively, while number of particles in the dry season is 3.5 and 2 times that of the wet season for the same size ranges. Millimeter thick melt layers have been observed in some samples, although they did not change the observed median diameter. This study provides the first detailed rBC mass and number size distribution from West Antarctica