Human-induced addition of dissolved black carbon in the Pearl River Estuary, South China
Qinghua Zhang 1,2, Junfei Zhou 1,2, Weifeng Yang 1,2*, Ziming Fang 1, Min Cheng 1, Yusheng Qiu 1, Minfang Zheng 1
1. College of Ocean and Earth Sciences, Xiamen University, China
2. State Key Laboratory of Marine Environmental Science (Xiamen University)
The environmental behavior of dissolved black carbon (DBC) in the aquatic system can affect the cycling of contaminants have been received worldwide concern. However, its geochemical behavior in urban estuaries and the influence on adjacent coastal sea are not well studied. Herein, DBC samples were determined by the benzene-polycarboxylic acid method to reveal the source and transport in the Pearl River Estuary, South China Sea. The concentration of DBC varied from 0.78 μmol L-1 to 6.84 μmol L-1, with an average of 1.97±1.58 μmol L-1. We find that DOC in the study regions ranged from 72.1 μmol L-1 to 188.0 μmol/L, averaging as 101.1±24.8 μmol L-1. DBC and DOC concentrations were high in the upper of the PRE, and decreased downstream by degree. DOC in the low salinity (<21) region showed a net removal, the distribution characteristics of the DOC suggested an obvious non-conservative behavior along the salinity gradient. DBC was account for 0.42% to 4.68% of DOC, with higher values in the upper of the PRE and lower yields in the downstream, indicating that river-estuary system are an important source of DBC to the coastal sea. We observed the DBC aromatic condensation was significant and continuous decrease seaward direction, the reason may be due to the increase of the photochemical degradation during the waterborne transport. The annual flux of DBC and DOC from PRE to the Northern South China Sea was estimated at 1.7×1010 g C yr-1 and 7.59×1011 g C yr-1, respectively. The large amounts of DBC exported by the Pearl River could indicate a major sink of organic carbon. These results may provide a critical perspective on the role of black carbon in the context of global climate change.
Keywords：dissolved black carbon, Pearl River, South China Sea
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