title: Characterization and spacial distribution variability of chromophoric dissolved organic matter (CDOM) in the Yangtze Estuary.
abstract: The spatial characteristics and the quantity and quality of the chromophoric dissolved organic matter (CDOM) in the Yangtze Estuary, based on the abundance, degree of humification and sources, were studied using 3D fluorescence excitation emission matrix spectra (F-EEMs) with parallel factor and principal component analysis (PARAFAC-PCA). The results indicated that the CDOM abundance decreased and the aromaticity increased from the upstream to the downstream areas of the estuary. Higher CDOM abundance and degrees of humification were observed in the pore water than that in the surface and bottom waters. Two humic-like components (C1 and C3) and one tryptophan-like component (C2) were identified using the PARAFAC model. The separation of the samples by PCA highlighted the differences in the DOM properties. Components C1 and C3 concurrently displayed positive factor 1 loadings with nearly zero factor 2 loadings, while C2 showed highly positive factor 2 loadings. The C1 and C3 were very similar and exhibited a direct relationship with A355 and DOC. The CDOM in the pore water increased along the river to the coastal area, which was mainly influenced by C1 and C3 and was significantly derived from sediment remineralization and deposition from the inflow of the Yangtze River. The CDOM in the surface and bottom waters was dominated by C2, especially in the inflows of multiple tributaries that were affected by intensive anthropogenic activities. The microbial degradation of exogenous wastes from the tributary inputs and shoreside discharges were dominant sources of the CDOM in the surface and bottom waters.
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, PR China; State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China. Electronic address: yingwang@bnu.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.forename: Zhenyao
authors.initials: Z
authors.lastname: Shen
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Chenghong
authors.initials: C
authors.lastname: Feng
mesh_terms: D004784:Environmental Monitoring; D063366:Estuaries; D006812:Humic Substances / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis; D025341:Principal Component Analysis; D045483:Rivers / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical
keywords: DOM quality variation; EEM–PARAFAC; Fluorescence comoponents; PCA; Spatial distributions; Yangtze Estuary