title: Photo- and bio-reactivity patterns of dissolved organic matter from biomass and soil leachates and surface waters in a subtropical wetland.
abstract: Dissolved organic carbon (DOC) measurements and optical properties were applied to assess the photo- and bio-reactivity of dissolved organic matter (DOM) from different sources, including biomass leaching, soil leaching and surface waters in a subtropical wetland ecosystem. Samples were exposed to light and/or dark incubated through controlled laboratory experiments. Changes in DOC, ultraviolet (UV-Vis) visible absorbance, and excitation-emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC) were performed to assess sample degradation. Degradation experiments showed that while significant amounts of DOC were consumed during bio-incubation for biomass leachates, a higher degree of bio-recalcitrance for soil leachate and particularly surface waters was displayed. Photo- and bio-humification transformations were suggested for sawgrass, mangrove, and seagrass leachates, as compared to substantial photo-degradation and very little to almost no change after bio-incubation for the other samples. During photo-degradation in most cases the EEM-PARAFAC components displayed photo-decay as compared to a few cases which featured photo-production. In contrast during bio-incubation most EEM-PARAFAC components proved to be mostly bio-refractory although some increases and decreases in abundance were also observed. Furthermore, the sequential photo- followed by bio-degradation showed, with some exceptions, a "priming effect" of light exposure on the bio-degradation of DOM, and the combination of these two processes resulted in a DOM composition more similar to that of the natural surface water for the different sub-environments. In addition, for leachate samples there was a general enrichment of one of the EEM-PARAFAC humic-like component (Ex/Em: <260(305)/416 nm) during photo-degradation and an enrichment of a microbial humc-like component (Ex/Em: <260(325)/406 nm and of a tryptophan-like component (Ex/Em: 300/342 nm) during the bio-degradation process. This study exemplifies the effectiveness of optical property and EEM-PARAFAC in the assessment of DOM reactivity and highlights the importance of the coupling of photo- and bio-degradation processes in DOM degradation.
authors.affiliation: Southeast Environmental Research Center and Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
authors.forename: Meilian
authors.initials: M
authors.lastname: Chen
authors.affiliation: Southeast Environmental Research Center and Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA. Electronic address: jaffer@fiu.edu.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Jaffé
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D005431:Florida; D006812:Humic Substances / Q000032:analysis*; D010782:Photolysis; D012989:Soil Pollutants / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000528:radiation effects; D053833:Wetlands
chemical_list: D006812:Humic Substances; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical
keywords: Bio-reactivity; DOM; EEM-PARAFAC; Fluorescence; Photo-reactivity; Wetland