Absorption and fluorescence characteristics of chromophoric dissolved organic matter in the Yangtze Estuary

摘要

The Yangtze Estuary is heavily influenced by coast-continent geochemical processes and anthropogenic ac tivity; thus, the source and distribution of chromophoric dis solved organic matter (CDOM) in the estuary are strongly impacted by these processes. Here, a series of samples were collected from across the Yangtze Estuary to investigate the source and spatial dynamics of CDOM and its components throughout the system. Three indices (a(355), spectral slope, and fluorescence) were then calculated and interpreted. The results indicated that the distribution of CDOM was dominat ed by allochthonous input, conservative mixing, and phase transfer. The contribution of biogenic CDOM to total CDOM increased with salinity, and three individual CDOM compo nents were identified upon fluorescence excitation emission matrix spectroscopy and parallel factor analysis of the water samples: Cl, corresponding to humic substance-like CDOM, C2, corresponding to tryptophan-like CDOM, and C3, corre sponding to tyrosine-like CDOM. Cl primarily originated from a terrestrial source, C2 had widespread origins, none of which played a dominant role, and C3 mainly originated from allochthonous input in the medium salinity area. Unexpected ly, no marine humic-like component was found in the surface water of the Yangtze Estuary, possibly because turbidity decreased the depth of sunlight penetration, limiting produc tion of this component.