Abstract
Characterization of dissolved organic matter (DOM) is useful in understanding environment quality and carbon cycling in the lake system. In this study, the fluorescence of DOM, major ions, and nutrients in water were investigated to understand the sources and the transformation of DOM in Dianchi Lake, the sixth largest freshwater lake in China. The dissolved organic carbon content in water above the deposition layer was higher than 5 mg C∙L−1 but lower than that in pore water. Two primary components of humic (C1) and protein-like components (C2) were identified using parallel factor (PARAFAC) modeling on sample fluorescence spectra. Organic components were related to mineral structures, and encapsulation of bacterial or algal cells into particulates could be disintegrated to release DOM. The aromaticity and the hydrophobicity of optical properties were regulated by percentages of chromophores (CDOM) of DOM in surface water, whereas by percentages of fluorophores (FDOM) in DOM in pore water, the underlying water layer was defined as a belt of transition. The molecular weight enhanced with percentages of C1 in CDOM increased in water above the sediment layer and the pore water at the northern lake site, but molecular weight attenuated with percentages decreased in pore water at the southern lake site. DOM not only originated from particulate decomposition but also derived from internal transformation among different, dissolved organic molecules. Small molecules were aggregated into larger ones, and, conversely, large molecules decomposed into small sizes. Another speculation is that dissolved molecules adsorbed or were encapsulated into particulates or were degraded and released into dissolved phases. The precise factors regulated composition, structure, and spectral properties of dissolved organic matter in the Dianchi Lake. This study highlights that sources of DOM and transformation mechanisms in the lake water could be correlated with nutrients and primary geochemical factors for mobility and distribution in different water compartments.
Highlights
Dissolved organic matter (DOM) plays an important role in carbon biogeochemical cycling and the evolution of water quality in the aquatic system [1,2,3]
The results indicated that fluorescent substances regulated properties of DOM greatly in biogeochemical processes; the larger percentages of fluorescent components in DOM resulted in the more stable properties of DOM
This study investigated the fluorescence of DOM, major ions, and nutrients in waters of Dianchi
Summary
Dissolved organic matter (DOM) plays an important role in carbon biogeochemical cycling and the evolution of water quality in the aquatic system [1,2,3]. DOM fraction in aquatic ecosystems, controlling the photochemical reactions of the surface water and nutrient and light availability for aquatic organisms [11,13,14]. The transformations of DOM have been found to induce chemical interaction, cycling and production of inorganic carbon, nitrogen and phosphorus compounds, numerous low molecular weight organic compounds, as well as toxic chemicals throughout the environment [15,16]. During transformations of DOM, a detailed chemical and physical characterization of DOM is useful for understanding the fate, the water properties, and the ecological effects in the aquatic environment
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