Air-water CO2 Exchange Fluxes and Its Controlling Mechanism in Modaomen Estuary of the Pearl River, China

Wenkui Tang, Quanzhou Gao, Xiongbo Zheng, Qianzhu Zhang, Zanwen Ma, Chao Zhang, Lifei Ye, Yuan Li, Wei Zheng

Ekoloji, 2018, Issue 106, Pages: 307-318, Article No: e106023


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The seasonal and spatial characterization of dissolved CO2 and its control mechanism in the Modaomen Estuary of the Pearl River (China) were determined by the four underway surveys in April, July, October 2013 and January 2014, respectively. The partial pressure of carbon dioxide (pCO2) was various among different seasons, which may be attributed to the variational runoff among wet and dry seasons. The pCO2 is wet season (April and July) was greatly higher than that of dry season (October and January). The runoff may be regarded as the mainly source of CO2 in the estuary, while the contribution of in situ biologic respiration in the estuary may be limited. The outgassing fluxes of CO2 in the Modaomen Estuary were approximately 30.80 mol C m-2 yr-1. Approximately 2% dissolved inorganic carbon (DIC) in the runoff was emitted into atmosphere during transportation processes in the estuary. The runoff was the key factor for the seasonal variation of CO2 outgassing fluxes in the Modaomen Estuary.


the partial pressure of CO2, CO2 outgassing flux, runoff, Modaomen Estuary, Pearl River


  • Amann T, Weiss A, Hartmann J (2012) Carbon dynamics in the freshwater part of the Elbe estuary, Germany: Implications of improving water quality. Estuar Coast Shelf S., 107: 112-121.
  • Amann T, Weiss A, Hartmann J (2015) Inorganic carbon fluxes in the inner Elbe Estuary, Germany. Estuar Coast, 38: 192-210.
  • Bauer JE, Cai WJ, Raymond PA, Bianchi TS, Hopkinson CS, Regnier PAG (2013) The changing carbon cycle of the coastal ocean. Nature, 504: 61-70.
  • Borges AV (2005) Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean? Estuaries, 28: 3-27.
  • Borges AV, Delille B, Frankignoulle M (2005) Budgeting sinks and sources of CO2 in the coastal ocean: Diversity of ecosystems counts. Geophys Res Lett., 32: 301-320.
  • Borges AV, Delille B, Schiettecatte LS, Gazeau F, Abril G, Frankignoulle M (2004) Gas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt, and Thames). Limnol Oceanogr., 49: 1630-1641.
  • Borges AV, Schiettecatte LS, Abril G, Delille B, Gazeau E (2006) Carbon dioxide in European coastal waters. Estuar Coast Shelf S., 70: 375-387.
  • Cai WJ (2011) Estuarine and coastal ocean carbon paradox: CO2 sinks or sites of terrestrial carbon incineration? Annu Rev Mar Sci., 3: 123-145.
  • Cai WJ, Guo XH, Chen CTA, Dai MH, Zhang L, Zhai WD, Lohrenz SE, Yin K, Harrison PJ, Wang Y (2008) A comparative overview of weathering intensity and HCO3- flux in the world’s major rivers with emphasis on the Changjiang, Huanghe, Zhujiang (Pearl) and Mississippi Rivers. Cont Shelf Res., 28: 1538-1549.
  • Cai WJ, Wang Y (1998) The chemistry, fluxes, and sources of carbon dioxide in the estuarine waters of the Satilla and Altamaha Rivers, Georgia. Limnol Oceanogr., 43: 657-668.
  • Chen CTA, Borges AV (2009) Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2. Deep-Sea Res Pt Ii., 56: 578-590.
  • Chen CTA, Huang TH, Chen YC, Bai Y, He X, Kang Y (2013) Air-sea exchanges of CO2 in the world’s coastal seas. Biogeosciences, 10: 6509-6544.
  • Chen CTA, Huang TH, Fu YH, Bai Y, He XQ (2012) Strong sources of CO2 in upper estuaries become sinks of CO2 in large river plumes. Curr. Opin. Env. Sust., 4: 179-185.
  • Chen CTA, Wang S, Lu X, Zhang S, Lui H, Tseng H, Wang B, Huang H (2008) Hydrogeochemistry and greenhouse gases of the Pearl River, its estuary and beyond. Quatern Int., 186: 79-90.
  • Crosswell JR, Wetz MS, Hales B, Paerl HW (2012) Air-water CO2 fluxes in the microtidal Neuse River Estuary, North Carolina. J Geophys Res-Oceans, 117: C08017.
  • Dai MH, Guo XH, Zhai WD, Yuan LY, Wang BW, Wang LF, Cai PH, Tang T, Cai WJ (2006) Oxygen depletion in the upper reach of the Pearl River estuary during a winter drought. Mar Chem., 102: 159-169.
  • Frankignoulle M, Abril G, Borges A, Bourge I, Canon C, Delille B, Libert E, Théate J (1998) Carbon dioxide emission from european estuaries. Science, 282: 434-436.
  • Guo XH, Dai MH, Zhai WD, Cai WJ, Chen BS (2009) CO2 flux and seasonal variability in a large subtropical estuarine system, the Pearl River Estuary, China. J Geophys Res-Biogeo., 114: G03013.
  • Gupta GVM, Thottathil S, Balachandran KK, Madhu NV, Madeswaran P, Nair S (2009) CO2 Supersaturation and net heterotrophy in a tropical estuary (Cochin, India): influence of anthropogenic effect. Ecosystems, 12: 1145-1157.
  • Han ZY, Tian XP, Liu F (2010) Study on the causes of intensified saline water intrusion into Modaomen Estuary of the Zhujiang River in recent years. Journal of Marine Sciences, 28: 52-59 (In Chinese with English abstract).
  • He BY, Dai MH, Zhai WD, Wang LF, Wang KJ, Chen JH, Lin JR, Han AQ, Xu YP (2010) Distribution, degradation and dynamics of dissolved organic carbon and its major compound classes in the Pearl River estuary, China. Mar Chem., 119: 52-64.
  • Hossler K, Bauer JE (2013) Amounts, isotopic character, and ages of organic and inorganic carbon exported from rivers to ocean margins: 2. Assessment of natural and anthropogenic controls. Global Biogeochemical Cycles, 27: 347-362.
  • Hunt CW, Salisbury JE, Vandemark D (2014) CO2 input dynamics and air-sea exchange in a large new englandestuary. Estuar Coast, 37: 1078-1091.
  • Jiang LQ, Cai WJ, Wang Y, Bauer JE (2013) Influence of terrestrial inputs on continental shelf carbon dioxide. Biogeosciences, 10: 839-849.
  • Jiang LQ, Cai WJ, Wang YC (2008) A comparative study of carbon dioxide degassing in river- and marine-dominated estuaries. Limnol Oceanogr., 53: 2603-2615.
  • Jiao SL, Gao QZ, Liu K (2009) Salinity freshwater mixing characteristics and the variations of the partial pressure of carbon dioxide along the Modao Gate waterway in the Xijiang River in China in drought season. Acta Oceanol Sin, 31: 40-47 (In Chinese with English abstract).
  • Jiao SL, Liu K, Gao QZ (2007) Variation of pCO2 in the surface water along the waterway of the Xijiang River inner estuary in fall. Acta Scientiae Circumstantiae, 28: 356-361(In Chinese with English abstract).
  • Laruelle GG, Durr HH, Slomp CP, Borges AV (2010) Evaluation of sinks and sources of CO2 in the global coastal ocean using a spatially-explicit typology of estuaries and continental shelves. Geophys Res Lett., 37: L15607.
  • Liu B, Lv HB, Wu CY, Bao Y, Ren J (2014) The evalution simulation and dynamic geomorphic process analysis of Modaomen Estuary from the 1960s to 1970s. Acta Oceanol Sin, 36: 75-80 (In Chinese with English abstract).
  • Liu Z, Zhang L, Cai WJ, Wang L, Xue M, Zhang X (2014) Removal of dissolved inorganic carbon in the Yellow River Estuary. Limnol Oceanogr., 59: 413-426.
  • Ludwig W, Amiotte Suchet P, Probst JL (1996) River discharges of carbon to the world’s oceans: Determining local inputs of alkalinity and of dissolved and particulate organic carbon. Cr Acad Sci Ii A., 323: 1007-1014.
  • Muduli PR, Kanuri VV, Robin RS, Charan Kumar B, Patra S, Raman AV, Nageswarara Rao G, Subramanian BR (2012) Spatio-temporal variation of CO2 emission from Chilika Lake, a tropical coastal lagoon, on the east coast of India. Estuar Coast Shelf S., 113: 305-313.
  • Noriega C, Araujo M (2014) Carbon dioxide emissions from estuaries of northern and northeastern Brazil. Sci Rep-Uk, 4: 6164.
  • Noriega CED, Araujo M, Lefevre N (2013) Spatial and temporal variability of the CO2fluxes in a tropical, highly urbanized estuary. Estuar Coast, 36: 1054-1072.
  • Raymond PA, Bauer JE, Cole JJ (2000) Atmospheric CO2 evasion, dissolved inorganic carbon production, and net heterotrophy in the York River estuary. Limnol Oceanogr., 45: 1707-1717.
  • Reum JCP, Alin SR, Feely RA, Newton J, Warner M, McElhany P (2014) Seasonal carbonate chemistry covariation with temperature, oxygen, and salinity in a fjord estuary: Implications for the design of ocean acidification experiments. Plos One, 9: e89619.
  • Sarma VVSS, Kumar NA, Prasad VR, Venkataramana V, Appalanaidu S, Sridevi B, Kumar BSK, Bharati MD, Subbaiah CV, Acharyya T, Rao GD, Viswanadham R, Gawade L, Manjary DT, Kumar PP, Rajeev K, Reddy NPC, Sarma VV, Kumar MD, Sadhuram Y, Murty TVR (2011) High CO2 emissions from the tropical Godavari estuary (India) associated with monsoon river discharges. Geophys Res Lett., 38: L08601.
  • Takahashi T, Olafsson J, Goddard JG, Chipman DW, Sutherland SC (1993) Seasonal-variation of CO2 and nutrients in the high-latitude surface oceans - a comparative-study. Global Biogeochem Cy., 7: 843-878.
  • Takahashi T, Sutherland SC, Sweeney C, Poisson A, Metzl N, Tilbrook B, Bates N, Wanninkhof R, Feely RA, Sabine C, Olafsson J, Nojiri Y (2002) Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Res Pt Ii., 49: 1601-1622.
  • Wanninkhof R, McGillis WR (1999) A cubic relationship between air-sea CO2 exchange and wind speed. Geophys Res Lett., 26: 1889-1892.
  • Weiss RF, Price BA (1980) Nitrous-oxide solubility in water and seawater. Mar Chem., 8: 347-359.
  • Xiao HW, Long AM, Sun LY (2013) The fluorescence excitation emission matrix spectroscopy of CDOM in Modaomen Estuary of the Pearl River. Marine Sciences, 46: 41-46 (In Chinese with English abstract).
  • Yao GR, Gao QZ, Wang Z, Huang X, He T, Zhang Y, Jiao S, Ding J (2007) Dynamics Of CO2 partial pressure and CO2 outgassing in the lower reaches of the Xijiang River, a subtropical monsoon river in China. Sci Total Environ., 376: 255-266.
  • Yu PS, Zhang HS, Zheng MH, Pan JM, Bai Y (2013) The partial pressure of carbon dioxide and air-sea fluxes in the Changjiang River Estuary and adjacent Hangzhou Bay. Acta Oceanol Sin., 32: 13-17.
  • Zhai WD, Dai MH, Guo XG (2007) Carbonate system and CO2 degassing fluxes in the inner estuary of Changjiang (Yangtze) River, China. Mar Chem, 107: 342-356.