Seasonal and air mass trajectory effects on dissolved organic matter of bulk deposition at a coastal town in south-western Europe

Rainwater contains a complex mixture of organic compounds which may influence climate, terrestrial and maritime ecosystems and thus human health. In this work, the characteristics of DOM of bulk deposition at a coastal town on the southwest of Europe were assessed by UV-visible and three-dimensional excitation-emission matrix fluorescence spectroscopies and by dissolved organic carbon (DOC) content. The seasonal and air mass trajectory effects on dissolved organic matter (DOM) of bulk deposition were evaluated. The absorbance at 250 nm (UV(250 nm)) and integrated fluorescence showed to be positively correlated with each other, and they were also positively correlated to the DOC in bulk deposition, which suggest that a constant fraction of DOM is likely to fluoresce. There was more chromophoric dissolved organic matter (CDOM) present in summer and autumn seasons than in winter and spring. Bulk deposition associated with terrestrial air masses contained a higher CDOM content than bulk deposition related to marine air masses, thus highlighting the contribution of terrestrial/anthropogenic sources.

Authors acknowledge funding from the Portuguese FCT (Foundation for Science and Technology) to CESAM (Centre for Environmental and Marine Studies). The FCT fellowship given to P.S.M. Santos (Ref. SFRH/BPD/75350/2010) is also acknowledged. Authors would like to gratefully thank the Group of Organic Chemistry of University of Aveiro for making available to us the use of their Fluoromax 3 equipment of molecular fluorescence spectrophotometer. TOC analyses were carried out at the “Administração Regional de Saúde” (Aveiro) and authors wish to here express their gratitude to this Centre and especially to Dra. Ana Maria Félix and Dra. Rosário Figueiredo. The authors also wish to thank Professor Maria Dolores Orgaz from the Department of Physics at the University of Aveiro for meteorological information support.

published