scholarly journals Distribution, seasonality, optical characteristics, and fluxes of dissolved organic matter (DOM) in the Pearl River (Zhujiang) estuary, China

2018 ◽  
Author(s):  
Yang Li ◽  
Guisheng Song ◽  
Philippe Massicotte ◽  
Fangming Yang ◽  
Ruihuan Li ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Fluorescent Dissolved Organic Matter ◽  
Organic Carbon Concentration ◽  
Parallel Factor ◽  
Zhujiang Estuary ◽  
The Pearl River

Abstract. Dissolved organic carbon concentration in the Pearl River estuary (PRE) of China was measured in May, August, and October 2015 and January 2016. Chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) in the latter three seasons were characterized by absorption and fluorescence spectroscopy. Parallel factor analysis of the fluorescence spectra identified two protein-like, two humic-like, and one oxidized quinone-like FDOM components. The seasonality of average DOM abundance varied as follows: DOC: May (156 μmol L−1) > January (114 μmol L−1) ≈ August (112 μmol L−1) > November (86 μmol L−1); CDOM absorption at 330 nm: August (1.76 m−1) > November (1.39 m−1) ≈ January (1.30 m−1); FDOM expressed as the sum of the maximum fluorescence intensities of all FDOM components: November (1.77 R.U.) > August (1.54 R.U.) ≈ January (1.49 R.U.). Average DOM abundance in surface water was higher than in bottom water, their difference being marginal (0.1–10 %) for DOC in all seasons and for CDOM and FDOM in November and January, and moderate (16–21 %) for CDOM and FDOM in August. DOC showed little cross-estuary variations in all seasons while CDOM and FDOM in January were higher on the west side of the estuary than in the middle and on the east side. All three variables exhibited large variations and/or rapid drawdowns at the head of the estuary (salinity 

Distribution of dissolved organic matter in the Pearl River Estuary, China

2004 ◽  
Vol 89 (1-4) ◽  
pp. 211-224 ◽  
Author(s):  
Julie Callahan ◽  
Minhan Dai ◽  
Robert F Chen ◽  
Xiaolin Li ◽  
Zhongming Lu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

scholarly journals Distribution, seasonality, and fluxes of dissolved organic matter in the Pearl River (Zhujiang) estuary, China

2019 ◽  
Vol 16 (13) ◽  
pp. 2751-2770 ◽  
Author(s):  
Yang Li ◽  
Guisheng Song ◽  
Philippe Massicotte ◽  
Fangming Yang ◽  
Ruihuan Li ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Average Concentration ◽  
Spatiotemporal Variability ◽  
Pearl River ◽  
Head Region ◽  
The Pearl River ◽  
Protein Rich

Abstract. Dissolved organic carbon (DOC) concentration in the Pearl River estuary (PRE) of China was measured in May, August, and October 2015 and January 2016. Chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) in the latter three seasons were characterized by absorption and fluorescence spectroscopy. CDOM and FDOM exhibited negligible seasonal variations, while DOC displayed a significant seasonality, with the average concentration being highest in May (156 µmol L−1), lowest in November (87 µmol L−1), and comparable between January (118 µmol L−1) and August (112 µmol L−1). Although DOC, CDOM, and FDOM in surface water were generally higher than in bottom water, the difference between the two layers was statistically insignificant. DOC showed little cross-estuary variations in all seasons, while CDOM and FDOM in January were higher on the west side of the estuary than on the east side. All three variables showed rapid drawdowns in the head region of the estuary (salinity <5); their dynamics in the main estuary were primarily controlled by conservative mixing, leading to linearly declining or relatively constant (for DOC in May and November only) contents with increasing salinity. The decrease in FDOM with salinity was 5 %–35 % faster than that of CDOM, which in turn was 2–3 times quicker than that of DOC. Salinity and CDOM absorption coefficients could serve as indicators of DOC in August and January. Freshwater endmembers in all seasons mainly contained fresh, protein-rich DOM of microbial origin, a large part of it likely being pollution-derived. Protein-like materials were preferentially consumed in the head region but the dominance of the protein signature was maintained throughout the estuary. Exports of DOC and CDOM (in terms of the absorption coefficient at 330 nm) into the South China Sea were estimated as 195×109 g and 266×109 m2 for the PRE and 362×109 g and 493×109 m2 for the entire Pearl River Delta. The PRE presents the lowest concentrations and export fluxes of DOC and CDOM among the world's major estuaries. DOM delivered from the PRE is, however, protein-rich and thus may enhance heterotrophs in the adjacent coastal waters. Overall, the PRE manifests lower abundance and smaller spatiotemporal variability of DOM than expected for a sizable estuary with a marked seasonality of river runoff due supposedly to the poorly forested watershed of the Pearl River, the rapid degradation of the pollution-derived DOM in the upper reach, and the short residence time of freshwater.

Molecular composition and spatial distribution of dissolved organic matter (DOM) in the Pearl River Estuary, China

2020 ◽  
Vol 17 (3) ◽  
pp. 240 ◽  
Author(s):  
Chen He ◽  
Qiong Pan ◽  
Penghui Li ◽  
Wei Xie ◽  
Ding He ◽  
...  
Keyword(s):  
Organic Matter ◽  
Spatial Distribution ◽  
Dissolved Organic Matter ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Molecular Composition ◽  
Pearl River ◽  
Terrestrial Organic Matter ◽  
The Pearl River Estuary ◽  
The Pearl River

Environmental contextEstuaries play an important role in global carbon cycling in terms of transforming dissolved organic matter (DOM). We describe the molecular composition and spatial distribution of DOM in the Pearl River Estuary, an area severely impacted by anthropogenic activities, and show how DOM composition gradually changes with salinity. The results will help our understanding of the sources and transformations of anthropogenic DOM discharged to the coastal seas. AbstractThe Pearl River is the second-largest river in China in terms of water discharge and brings enormous amounts of nutrients and terrestrial organic matter to the South China Sea, which makes the Pearl River Estuary (PRE) highly eutrophic. However, the molecular composition and distribution of dissolved organic matter (DOM) in the PRE have scarcely been investigated. In this study, solid-phase extraction (SPE) was performed to collect DOM samples from PRE along a salinity gradient. The samples were characterised by negative-ion electrospray ionisation (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyse their molecular composition and spatial distribution. The FT-ICR MS results showed that the terrestrial organic matter was gradually diluted and/or degraded during the migration from the river to the coastal ocean. Furthermore, both sulfur containing and unsaturated molecules were highly abundant in the upper stream samples, which indicated that anthropogenic input might be another important source of the assigned DOM in PRE. A group of bio-refractory molecules, characterised as carboxylic-rich alicyclic-like molecules, was found to accumulate with the increase of salinity. The composition of the SPE-DOM showed a gradual variation with the salinity and spatial changes; however, the variation was slightly different from those in pristine estuaries. This study demonstrates that the molecular composition of DOM is crucial for elucidating its source and transformation in an estuary.

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