Observationally-constrained carbonaceous aerosol source estimates for the Pearl River Delta area of China

Abstract. We simulated elemental carbon (EC) and organic carbon (OC) aerosols over the Pearl River Delta (PRD) area of China and compared the results to seasonal surface measurements, with the aim of quantifying carbonaceous aerosol sources from a "top-down" perspective. Our regional model was driven by current-best estimates of PRD EC (39.5 Gg C yr⁻¹) and OC (32.8 Gg C yr⁻¹) emissions and included updated secondary organic aerosol formation pathways. The simulated annual mean EC and OC concentrations were 4.0 and 7.7 μg C m⁻³, respectively, lower than the observed annual mean EC and OC concentrations (4.5 and 13.1 μg C m⁻³, respectively). We used multiple regression to match the simulated EC against seasonal mean observations. The resulting top-down estimate for EC emission in the PRD area was 52.9 ± 8.0 Gg C yr⁻¹. We estimated the OC emission in the PRD area to be 60.2 ± 10.3 Gg C yr⁻¹, based on the top-down EC emission estimate and the primary OC / EC ratios derived from bottom-up statistics. Using these top-down emission estimates, the simulated average annual mean EC and OC concentrations were improved to 4.4 and 9.5 μg C m⁻³, respectively, closer to the observations. Secondary sources accounted for 42 % of annual mean surface OC in our top-down simulations, with biogenic VOCs being the most important precursors.