Natural dissolved organic matter is a complex assemblage of continuously changing molecules that experience different fates and impact on the global biogeochemical cycles. Sunlight photo-irradiation is one of the most important ways of DOM alteration, with organic compounds partly being completely degraded to CO2 (and other greenhouse gases), and the rest being mainly transformed to new structures. We have studied the variability of photochemical reactivity and transformation of terrigenous organic matter from nine aquatic environments including a lake, six rivers, and two swamps. We used a variety of traditional and advanced analytical techniques to provide a comprehensive understanding of the observed photo-degradation. Carbon and nitrogen contents, one-dimensional 1H NMR, optical analyses (spectrophotometry and spectrofluorometry), and ultrahigh resolution mass spectrometry (ESI-FT-ICR-MS) provided insights for photochemical changes from different analytical perspectives. These data were supplemented by compound-specific measurements of condensed aromatic carbon (using benzenepolycarboxylic acid markers), metals (Fe, Ca, Mg), and N-and P-containing nutrients (NH4+, NO3-, NO2-, PO43-). Clear variability in photochemical reactivity was observed by employing principal component analysis on the different types of data, and it correlated with sample composition parameters. Our results show that terrigenous organic matter across a diverse range of chemical composition undergoes photochemical degradation and transformation, on both quantitative and qualitive scales, and becomes more like oceanic DOM with increasing irradiation. Results from this study allow us to better understand the fate of terrigenous organic matter in different sunlit environments, as well as learn the importance of DOM source and matrix species in aquatic photochemistry.

Photochemical variability of terrigenous organic matter from different near-shore environments

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.