Differences between humic substances from riverine, estuarine, and marine environments observed by fluorescence spectroscopy

Sixteen samples of fulvic acids and XAD-4 fractions of riverine, estuarine, coastal, and open ocean origin have been studied by emission and synchronous molecular fluorescence spec- troscopy. Certain features of the molecular fluorescence are related to the nature, the con- tent, and the origin of those aquatic humic substances (HS). Riverine HS appear several times richer in fluorophores than marine HS, which can be well observed by emission fluo- rescence spectroscopy. Synchronous-scan spectra of fulvic acids and of XAD-4 fractions from the aquatic environments studied, emphasized the quality differences of their fluoro- phores.These features are useful as tracers of humic substances related with their natural environment source or even with their anthropogenic origi