Distribution of chromophoric dissolved organic matter in Yellow Sea by Fluorescence Excitation-Emission matrix Regional Integration

Fluorescence Excitation Emission Matrix (FEEM) is often used to characterize the composition and properties of Chromophoric Dissolve Organic Mater (CDOM) in the freshwater and seawater. This research adopted Fluorescence Regional Integration (FRI) to assess the dynamics of CDOM in the Yellow Sea. FEEMs were delineated into five Excitation-Emission regions (five fluorophores): tyrosine-likematerial (Region I, λ
Ex
/λ
Em
=240–250nm/250–330nm), tryptophan-likematerial (Region II, λ
Ex
/λ
Em
240–250nm/330–380nm), fulvic acid-like materials (Region III, λ
Ex
/λ
Em
=240–250nm/380–580nm), microbial byproduct-like material (Region IV, λ
Ex
/λ
Em
=250–480nm/250–380nm) and humic acid-like material (RegionV, λ
Ex
/λ
Em
=250–480nm/380–580nm). The total fluorescence regional integration (Ф
T,n
) of FEEMs can be used as a good index for CDOM concentration, which is better than the traditional one-point fluorescence method. Fluorescence regional integration value of each fluorophore (Ф
i,n
) also was a good index to characterize CDOM composition and distribution. Fluorescence regional integration proportion of humic acid-like material (V) decreased gradually from coastal to coast, suggesting that fluvial input was the primary source of CDOM in the coastal, while fluorescence regional integration proportion of protein-like fluorophores (I and II) and microbial byproduct-like material (Region IV) increased, indicating an obvious contribution of biological activity within this area. For fulvic acid-like materials (III), there was a large high-value area, which indicated that both fluvial input and biological activity had contributions. All fluorescents, especially the protein-like fluorescence peaks (I and II) in the middle layer were higher than those from the surface layer and bottom layer, suggesting that the vertical distribution of CDOM in those stations were controlled by CDOM photochemistry or biological activity.