Change in global aerosol composition since preindustrial times

Abstract

Abstract. To elucidate human induced changes of aerosol load and composition in the atmosphere, a coupled aerosol and gas-phase chemistry transport model of the troposphere and lower stratosphere has been used. The present 3-D modeling study focuses on aerosol chemical composition change since preindustrial times considering the secondary organic aerosol formation together with all other main aerosol components including nitrate. In particular, we evaluate non-seasalt sulfate (nss-SO = 4 ), ammonium (NH + 4 ), nitrate (NO − 3 ), black carbon (BC), sea-salt, dust, primary and secondary organics (POA and SOA) with a focus on the importance of secondary organic aerosols. Our calculations show that the aerosol optical depth (AOD) has increased by about 21% since preindustrial times. This enhancement of AOD is attributed to a rise in the atmospheric load of BC, nss-SO = 4 , NO − 3 , POA and SOA by factors of 3.3, 2.6, 2.7, 2.3 and 1.2, respectively, whereas we assumed that the natural dust and sea-salt sources remained constant. The nowadays increase in carbonaceous aerosol loading is dampened by a 34-42% faster conversion of hydrophobic to hydrophilic carbonaceous aerosol leading to higher removal rates. These changes between the various aerosol components resulted in significant modifications of the aerosol chemical composition. The relative importance of the various aerosol components is critical for the aerosol climatic effect, since atmospheric aerosols behave differently when their chemical composition changes. According to this study, the aerosol composition changed significantly over the different contiCorrespondence to: M. Kanakidou (mariak@chemistry.uoc.gr) nents and with height since preindustrial times. The presence of anthropogenically emitted primary particles in the atmosphere facilitates the condensation of the semi-volatile species that form SOA onto the aerosol phase, particularly in the boundary layer. The SOA burden that is dominated by the natural component has increased by 24% while its contribution to the AOD has increased by 11%. The increase in oxidant levels and preexisting aerosol mass since preindustrial times is the reason of the burden change, since emissions have not changed significantly. The computed aerosol composition changes translate into about 2.5 times more water associated with non sea-salt aerosol. Additionally, aerosols contain 2.7 times more inorganic components nowadays than during the preindustrial times. We find that the increase in emissions of inorganic aerosol precursors is much larger than the corresponding aerosol increase, reflecting a non-linear atmospheric response.

A safe operating space for humanity

“…Human activities since the pre-industrial era have doubled the global concentration of most aerosols (Tsigaridis et al 2006). Aerosols iii directly influence the Earth's radiation balance directly by scattering incoming radiation back to space (Charlson et al 1991(Charlson et al , 1992 or indirectly by influencing cloud reflectivity and persistence (Twomey 1977;Albrecht 1989).…”

Source attributions of hazardous aromatic hydrocarbons in urban, suburban and rural areas in the Pearl River Delta (PRD) region

“…AHs are also most important anthropogenic precursors of secondary organic aerosols (SOA) [12][13][14][15][16][17]. Although estimated SOA from biogenic sources substantially exceeds that from anthropogenic sources on the global scale [18,19], AHs have been identified as dominant SOA precursors in some highly industrialized and densely populated regions, like the Pearl River Delta (PRD) region ( Fig. 1) in south China [20].…”

Global dimming and brightening versus atmospheric column transparency, Europe, 1906–2007

“…In Europe, the continental mean has increased from 0.146 to 0.204, or 40%. Because dust and sea salt aerosols contribute more than 60% to AOD, the total increase in AOD does not entirely reflect the change in the emission of the main anthropogenic aerosol species (sulfate, nitrate, black carbon) whose increase since preindustrial times has been more than a factor of two [Tsigaridis et al, 2006].…”