Synchronous scan and excitation-emission matrix fluorescence spectroscopy of water-soluble organic compounds in atmospheric aerosols

Three-dimensional excitation-emission matrix (EEM) fluorescence spectra of water-soluble organic compounds (WSOC) from aerosol samples were measured and compared with those reported in the literature for natural dissolved organic matter. The EEM profiles of the WSOC presented three characteristic excitation/emission (lambda(Exc)/lambda(Em)) peaks: 240/405 nm, 310/405 nm and 280/340 nm. The fluorescence intensities at lambda(Exc)/lambda(Em)approximate to240/405 nm and lambda(Exc)/lambda(Em)approximate to310/405 nm are located at wavelengths shorter than those reported for aquatic humic substances, indicating a smaller content of both aromatic structures and condensed unsaturated bond systems in the WSOC fraction. The EEM profiles of fractions obtained by the isolation procedure of the WSOC by the XAD resins showed that a fractionation has occurred and the XAD-8 eluate is highly representative of the total WSOC of collected aerosol. Synchronous scan spectra were more detailed than conventional fluorescence emission spectra, appearing more suitable for studying multicomponent samples such as the WSOC from atmospheric aerosols.