›› 2014, Vol. 24 ›› Issue (1): 143-158.doi: 10.1007/s11442-014-1078-2

• Research Articles • Previous Articles     Next Articles

Sources and transport of organic carbon from the Dongjiang River to the Humen outlet of the Pearl River, southern China

FU Yingchun1, TANG Congguo2, LI Jun3, ZHAO Yaolong1, ZHONG Wei1, ZENG Xiantie1   

  1. 1. School of Geography, South China Normal University, Guangzhou 510631, China;
    2. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang 550002, China;
    3. Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal University, Tianjin 300387, China
  • Received:2012-12-25 Revised:2013-09-17 Online:2014-02-15 Published:2014-02-15
  • Contact: Zhao Yaolong, PhD and Professor, specialized in geographical information science. E-mail:yaolong@scnu.edu.cn E-mail:yaolong@scnu.edu.cn
  • About author:Fu Yingchun, PhD and Associate Professor, specialized in geographical information science. E-mail:fuyc@scnu.edu.cn
  • Supported by:

    National Natural Science Foundation of China, No.41101152; No.40901090; No.41172315; The Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry; The talents introduced into Universities Foundation of Guangdong Province of China; The China Scholarship Council (CSC) funding in 2013; The Universities Disciplinary and Special Construction Funds of Guangdong Province Foundation, No.C10092; The Scientific Research Foundation of Graduate School of South China Normal University

Abstract:

Transport of organic carbon via rivers to estuary is a significant geochemical process in the global carbon cycle. This paper presents bulk total organic carbon (TOC) from the Dongjiang catchment to the adjacent Humen outlet, and discusses the applicability of δ13C and ratio of carbon to nitrogen (C/N) as indicators for sources of organic matter in the surface sediments. Survey results showed that organic carbon concentration in summer were higher than in the winter. An elevated trend of TOC occurred along the river to the Humen outlet in both surveys, and the highest mean values of dissolved and particular organic carbon (DOC~279 μmol L-1 and POC~163 μmol L-1) were observed in the urban deltaic region in summer flood flow. Winter samples had a wide range of δ13C and C/N (δ13C -24.6‰ to -30.0‰, C/N 4-13), and summer ones varied slightly (δ13C -24.2‰ to -27.6‰, C/N 6-18). As results suggest that POC in the three zones of upstream-delta-outlet dominantly came from riverbank soil, phytoplankton and agricultural C3 plants in winter, whereas main sources were from the riverbank and mangrove soil in summer. Moreover, anthropogenic sewage inputs had 11% and 7% contribution to POC in the deltaic and outlet. Transport accompanied with seasonal freshwater variation, phytoplankton production and degradation, and removal behavior caused variation of organic carbon concentration. The results also discovered that TOC export bulk in Dongjiang was approximately one quarter of Humen flux in the dry flow, and anthropogenic activity significantly impacted the river export contribution.

Key words: Dongjiang River, Humen outlet, total organic carbon, flux, δ13C, C/N