The impact of PM2.5 sources on the single scattering albedo at a rural site in the south-western Mediterranean region

In the present work, the contribution of PM 2.5 sources to light absorption (σ ap,520 ) and scattering (σ sp,525 ), as well as their impact on SSA values, was analysed. For this, measurements of aerosol optical properties and PM 2.5 chemical composition were conducted at a rural site in southeastern Spain. The sources that significantly contributed to light extinction were: road traffic (TR), biomass burning (BB), mineral dust (MD), and a secondary aerosol source (SA). BB accounted for nearly 50 % of the absorption coefficient (λ = 520 nm), while the SA source exhibited the largest contribution to the scattering process (∼47 % at 525 nm). MD showed the smallest contribution to σ ap,520 and σ sp,525 , although its contribution significantly increased during Saharan dust events (SDEs). SSA daily values showed a clear dependence on the contribution of individual sources to PM 2.5 concentrations. SSA values (λ = 525 nm) exceeding 0.90 were observed when contributions from secondary aerosols were greater than 50 %, while the SSA decreased with the increase in the contribution from road traffic. The contribution from BB was fairly constant for almost all SSA values, although high SSA values (>0.90) were observed when the contribution from this source was very low. The SSA showed a clear spectral dependence that varied according to the aerosol type. So, for BB aerosols the SSA decreased with wavelength, while for mineral dust the opposite trend was observed. • The contribution of PM 2.5 sources to scattering and absorption in a rural site was estimated. • Secondary and biomass burning aerosols were the most contributing sources to σ sp . • Biomass burning and traffic were the most contributing sources to σ ap . • The SSA was highest when the contribution of secondary aerosols to PM 2.5 was greater than 50 %.