Source attribution of water-soluble organic aerosol by nuclear magnetic resonance spectroscopy.

The functional group compositions of atmospheric aerosol water-soluble organic compounds were obtained employing proton nuclear magnetic resonance ((1)H NMR) spectroscopy in a series of recent experiments in several areas of the world characterized by different aerosol sources and pollution levels. Here, we discuss the possibility of using (1)H NMR functional group distributions to identify the sources of aerosol in the different areas. Despite the limited variability of functional group compositions of atmospheric aerosol samples, characteristic (1)H NMR fingerprints were derived for three major aerosol sources: biomass burning, secondary formation from anthropogenic and biogenic VOCs, and emission from the ocean. The functional group patterns obtained in areas characterized by one of the above dominant source processes were then compared to identify the dominant sources for samples coming from mixed sources. This analysis shows that (1)H NMR spectroscopy can profitably be used as a valuable tool for aerosol source identification. In addition, compared to other existing methodologies, it is able to relate the source fingerprints to integral chemical properties of the organic mixtures, which determine their reactivity and their physicochemical properties and ultimately the fate of the organic particles in the atmosphere.