A multi-method comparison of Atchafalaya Basin surface water organic matter samples.

Surface water organic matter (OM) was isolated from two distinct sites within the Atchafalaya Basin using a combination of XAD-8 and XAD-4 non-ionic macroporous resins and characterized by a suite of analytical methods, including elemental analysis, (13)C cross polarization magic angle spinning nuclear magnetic resonance, attenuated total reflectance Fourier transform infrared, luminescence spectroscopy including parallel factor analysis, and ultraviolet-visible spectroscopy. The major findings of the study are (i) despite the large differences in hydrology, optical properties, iron content, dissolved oxygen, and degree of human exploitation, the spectral and elemental signatures of the hydrophobic acids and transphilic acids fractions of the isolated OM for the different sites were remarkably similar; (ii) the luminescence characteristics of the four studied fractions provided information on the relative contributions from terrestrial and microbial input sources, as well as the degree of humification; and (iii) a detailed analysis of the total luminescence data led to a new dual excitation model based on quinone exciplexes for long wavelength emissions.