Program

The marine aerosol plays an important role in global climate regulation and marine biogenic system. Its hygroscopic and optical properties are determined by chemical characteristics, which reflect the interaction of different sources and processes. In this study, chemical composition and sources of marine boundary layer aerosol have been investigated with a series of physical and chemical measurements on the German research vessel Polarstern. Four research cruises were carried out over the Atlantic Ocean in 2011 and 2012, covering spatial range from 53°S to 53°N in two seasons (spring and autumn). 

The chemical composition of non-refractory submicron particles was derived from High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) measurements. Besides, black carbon (BC) mass concentration was provided by a Multi Angle Absorption Photometer (MAAP). On average, non-sea-salt sulfate (nss-sulfate) is the dominant component, contributing 53±13% of the total measured particle mass concentration. Organics (including MSA) are the second most abundant species (25±10%). Ammonium, nitrate, chloride and BC contribute the rest ~20% of total measured mass.

For better understanding the organics sources over the Atlantic Ocean, the positive matrix factorization (PMF) is applied based on high resolution organic mass spectra from HR-ToF-AMS. Five factors have been identified for different sources and processes. Two factors are related to marine biogenic sources: the first one to marine DMS-related emissions and the second one to nitrogen-containing emissions. The other three factors are attributable to continental transport, aged combustion (ship exhausts and biomass burning), and primary sources. Meanwhile, nss-sulfate has been divided into biogenic sulfate and long range transport (LRT) sulfate. All the identified components (including organic and inorganic ones) are sorted by their sources: (1) marine sources correspond to biogenic sulfate, two marine organic factors; (2) aged combustion covers corresponding organic factor and BC; (3) LRT includes continental organic factor, LRT sulfate, ammonium and nitrate; (4)  primary refers to the only primary organic factor. LRT is the main source in general, providing averagely 49% total mass. However, marine sources contribute up to 87% in spring especially in the South Hemisphere (averagely 50%), corresponding to marine air masses as well as biological activities. Contribution of aged combustion sources largely increases to 36% when close to the West Africa, related to ship traffic and wild fires in the West Africa.