Dissolved Black Carbon in North Cascades Snow, Meltwater and a Downstream River
Journal Article
Overview
abstract
Abstract; ; Quantification of black carbon on snow in the Cascade Range is needed due to increasing wildfire intensity and frequency. Here, the benzenepolycarboxylic acid (BPCA) molecular method was used to measure dissolved black carbon (DBC) in snow, nearby rivers, streams, and supraglacial melt collected in 2022 and 2023 from Mount Baker and Mount Rainier. The average DBC concentration in snow was 9 ± 4 μg‐C/L and 10 ± 6 μg‐C/L in stream, river, and supraglacial meltwater samples. The DBC method provides black carbon source identification via BPCA characterization. DBC concentrations and BPCA proportions were compared to modeled smoke deposition from the Navy Aerosol Analysis and Prediction System reanalysis model. In both years, total deposition from May through October was approximately 670 mg/m; 2; . However, early season smoke deposition (May through July) was four times higher in 2023 than 2022, indicating seasonal variability in the timing of deposition. Dry deposition accounted for over 80 percent of total late season smoke deposition (August through October) in both 2022 and 2023, while wet deposition accounted for 75 and 30 percent of total early season deposition in 2022 and 2023, respectively. The largest smoke deposition events on Mount Baker coincided with precipitation events and enrichment of benzenepentacarboxylic acid, a marker of biomass burning, in snow. Using the Snow, Ice, and Aerosol Radiative model, we estimated an average albedo of 0.68 ± 0.03. The resulting instantaneous radiative forcing attributable to the presence of BC in snow ranged from 3 to 16 W/m; 2; , with an average of 7.47 ± 3.3 W/m; 2; .;
