Comparison of black carbon, primary and secondary brown carbon light absorption and direct solar absorption at the foothill and summit of Mt. Hua, China.

Atmospheric black carbon (BC), primary and secondary brown carbon (BrC and BrC) are the light-absorbing carbonaceous aerosol components. The vertical changes in the BC and BrC distributions are not generally known. Here, we presented a study of the spectral light absorption properties, direct solar absorption, and potential source areas of BC and BrC at the foothill (375 m a.s.l.) and summit (2060 m a.s.l.) of Mt. Hua, China. More than tripled BC and BrC light absorption coefficient were observed at the foothill compared to the summit. The dominant carbonaceous light-absorbing was attributed to BC with the percentages of 77 % (foothill) and 79 % (summit), respectively. The light absorption coefficient and direct solar absorption of BrC were much higher than those of BrC at foothill, especially in winter. The enhancing contributions of BrC light absorption coefficient and direct solar absorption were observed with high RH and visibility at the summit. The light absorption properties of BC, BrC, and BrC may be attributed to the emissions, meteorological conditions, and photochemical oxidation. The inferred potential source spatial distributions of BC and BrC showed different patterns at the foothill and summit. The results underlined the primary emission effects (including BC and BrC) at the foothill and the importance of BrC at the summit, respectively.