Direct Measurements of Dry and Wet Deposition of Black Carbon Over a Grassland

The atmospheric lifetime of black carbon (BC) is controlled by wet and dry deposition, which are poorly constrained by observations. We show that the single‐particle soot photometer can measure surface‐atmosphere exchange fluxes of refractory BC (rBC) particle mass (mrBC) and number (NrBC) by eddy covariance. We report field measurements of rBC dry and wet deposition rates during summer 2017 at the Southern Great Plains site in Oklahoma. On average, dry deposition of rBC is 0.3 ± 0.2 mm/s. We estimate a wet deposition flux of 2,600 ng·m−2·hr−1 over the 148.5 mm of rainfall observed. These data indicate a composite lifetime of 7–11 days. Key Points First direct measurements of black carbon by SP2 and eddy covariance over grassland suggest a dry deposition velocity of 0.3 ± 0.2 mm/s Wet deposition is the dominant process of black carbon loss, but dry deposition can significantly impact black carbon lifetime Measurements suggest that current atmospheric model parameterizations capture the atmospheric lifetime of black carbon reasonably well