scholarly journals Impacts of anthropogenic inputs on hypoxia and oxygen dynamics in the Pearl River estuary

2018 ◽  
Vol 15 (20) ◽  
pp. 6105-6125 ◽  
Author(s):  
Bin Wang ◽  
Jiatang Hu ◽  
Shiyu Li ◽  
Liuqian Yu ◽  
Jia Huang
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
Concentration Changes ◽  
The Pearl River ◽  
Oxygen Dynamics ◽  
Source And Sink

Abstract. In summer, the Pearl River estuary (PRE) experiences hypoxia, largely driven by the high input of fresh water with low dissolved oxygen (DO), abundant nutrients and particulate organic carbon from the Pearl River network. In this study, we used a well-validated physical–biogeochemical model together with a DO species-tracing method to study the responses of hypoxia and oxygen dynamics to the anthropogenic perturbations of riverine inputs (i.e. DO, nutrients, and particulate organic carbon) in July–August 2006. Model results showed that hypoxia in the PRE was most sensitive to riverine inputs of particulate organic carbon, followed by DO concentrations and nutrients. Specifically, a 50 % decrease (increase) in riverine input of particulate organic carbon led to a 47 % decrease (64 % increase) in hypoxic area, with the sediment oxygen demand and water column production being the two most important processes contributing to changes in DO concentration. Changes in the riverine inputs of DO and nutrients had little impact on the simulated hypoxia because of the buffering effects of re-aeration (DO fluxes across the air–sea interface); i.e. the re-aeration responded to the changes in surface apparent oxygen utilization (AOU) associated with river-induced variations of oxygen source and sink processes. The PRE features shallow waters (with averaged depth of 10 m) in which oxygen provided by the re-aeration could penetrate to bottom waters via vertical diffusion and largely offset the changes in DO contributed by other oxygen source and sink processes. This study highlights the importance of re-aeration in reducing hypoxia variability in shallow estuaries.

scholarly journals Impacts of anthropogenic inputs on the hypoxia and oxygen dynamics in the Pearl River Estuary

2018 ◽  
Author(s):  
Bin Wang ◽  
Jiatang Hu ◽  
Shiyu Li ◽  
Liuqian Yu ◽  
Jia Huang
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
River Estuary ◽  
Oxygen Demand ◽  
Pearl River Estuary ◽  
Sediment Oxygen Demand ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
Anthropogenic Inputs ◽  
The Pearl River

Abstract. In summer, the Pearl River Estuary experiences hypoxia, largely driven by the high input of freshwater with low dissolved oxygen (DO) and abundant nutrients and particulate organic carbon from the Pearl River network. In this study, we used a well-validated coupled physical-biogeochemical model to study the response of hypoxia and oxygen dynamics to variations of anthropogenic inputs (i.e. DO, nutrients, and particulate organic carbon). Model results showed that hypoxia in the Pearl River Estuary was confined to the shelf off the Modaomen sub-estuary with a hypoxic area of ~ 200 km2 mainly due to the combined effect of re-aeration and sediment oxygen demand. Numerical experiments suggested that hypoxia in the Pearl River Estuary was most sensitive to riverine inputs of particulate organic carbon , followed by DO concentrations and nutrients. Specifically, a 50 % decrease (increase) in riverine input of particulate organic carbon led to a 47 % decrease (64 % increase) in hypoxic area, with the sediment oxygen demand and water column production being the two most important processes contributing to the changes in DO concentration and hypoxic extent. Changes in the riverine inputs of DO and nutrients had little impact on the simulated hypoxia because of the buffering effects of re-aeration, i.e. the re-aeration compensated the changes in surface apparent oxygen utilization (AOU) associated with river-induced variations of oxygen source and sink processes. The Pearl River Estuary features shallow waters (with averaged depth of 10 m) where oxygen provided by the re-aeration could penetrate to bottom waters via vertical diffusion that largely offset the changes in DO contributed by other oxygen source and sink processes. This study highlights the importance of re-aeration in determining the hypoxic extent and the buffering effects of re-aeration in reducing hypoxia variability in shallow estuary.

scholarly journals Remote Sensing Observation of Particulate Organic Carbon in the Pearl River Estuary

2015 ◽  
Vol 7 (7) ◽  
pp. 8683-8704 ◽  
Author(s):  
Dong Liu ◽  
Delu Pan ◽  
Yan Bai ◽  
Xianqiang He ◽  
Difeng Wang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

scholarly journals Distribution and sources of particulate organic carbon in the Pearl River Estuary in summer 2010

2012 ◽  
Vol 32 (14) ◽  
pp. 4403-4412 ◽  
Author(s):  
刘庆霞 LIU Qingxia ◽  
黄小平 HUANG Xiaoping ◽  
张霞 ZHANG Xia ◽  
张凌 ZHANG Ling ◽  
叶丰 YE Feng
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

scholarly journals Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions

2010 ◽  
Vol 7 (2) ◽  
pp. 2889-2926 ◽  
Author(s):  
B. He ◽  
M. Dai ◽  
W. Huang ◽  
Q. Liu ◽  
H. Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Surface Sediments ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Outer Shelf ◽  
Pearl River ◽  
Terrestrial Organic Matter ◽  
The Pearl River Estuary ◽  
The Pearl River

Abstract. Organic matter in surface sediments from the upper reach of the Pearl River Estuary and Lingdingyang Bay, as well as the adjacent northern South China Sea shelf was characterized by a variety of techniques, including elemental (C and N), stable carbon isotopic (δ 13C) composition, as well as molecular-level analyses. Total organic carbon (TOC) content was 1.61±1.20% in the upper reach down to 1.00±0.22% in Lingdingyang Bay and to 0.80±0.10% on the inner shelf and 0.58±0.06% on the outer shelf. δ13C values ranged from −25.11‰ to −21.28‰ across the studied area, with a trend of enrichment seaward. The spatial trend in C/N ratios mirrored that of δ13C, with a substantial decrease in C/N ratio from 10.9±1.3 in the Lingdingyang Bay surface sediments to 6.5±0.09 in the outer shelf surface sediments. Total carbohydrate yields ranged from 22.1 to 26.7 mg (100 mg OC)−1, and typically followed TOC concentrations in the estuarine and shelf sediments, suggesting that the relative abundance of total carbohydrate was fairly constant in TOC. Total neutral sugars as detected by the nine major monosaccharides (lyxose, rhamnose, ribose, arabinose, fucose, xylose, galactose, mannose, and glucose) yielded between 4.0 and 18.6 mg (100 mg OC)−1 in the same sediments, suggesting that a significant amount of carbohydrates were not neutral aldoses. The bulk organic matter properties, isotopic composition and C/N ratios, combined with molecular-level carbohydrate compositions were used to assess the sources and accumulation of terrestrial organic matter in the Pearl River Estuary and the adjacent northern South China Sea shelf. Results showed a mixture of terrestrial riverine organic carbon with in situ phytoplankton organic carbon in the areas studied. Using a two end-member mixing model based on δ13C values and C/N ratios, we estimated that the terrestrial organic carbon contribution to the surface sediment TOC was ca. 57±13% for Lingdingyang Bay, 19±2% for the inner shelf, which decreased further to 4.3±0.5% on the outer shelf. The molecular composition of the carbohydrate in surface sediments also suggested that the inner estuary was rich in terrestrial-derived carbohydrates but that the contribution of terrestrial-derived carbohydrates decreased offshore. Terrestrial organic carbon accumulation flux was estimated as 1.37±0.92×1011 g yr−1 in Lingdingyang Bay, which accounted for 37±25% of the terrestrial organic carbon transported to the Bay. The burial efficiency of terrestrial organic matter was markedly lower than that of suspended particulate substance (~71%) suggesting that the riverine POC undergoes significant degradation and replacement during transportation through the estuary.

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