Preliminary study on the dissolved and colloidal organic carbon in the Zhujiang River estuary |
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| Authors: | Dai Min-han Jean-Marie Martin Hong Hua-sheng Zhang Zu-lin |
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| Institution: | (1) Environmental Science Research Centre, Xiamen University, 361005 Xiamen, China;(2) Joint Research Center, Environment Institute, I-21020 Ispra, Italy |
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| Abstract: | This paper reports data on the dissolved and colloidal organic carbon in the Zhujiang (Pearl) River estuary. DOC concentration
was 142 to 239 μmol/L in the freshwater taken in March 1997 from the four Zhujiang River tributaries flowing into the Lingdingyang
estuary. High concentration was observed in the Humen tributary located near Guangzhou. The rapidly increased DOC concentration
at low salinities (∼5) may be attributed to the exchange between macroparticulate and dissolved organic matter during the
early stage of estuarine mixing. DOC concentration overall followed the mixing line until salinity 25, where the Deep Bay
is located and where DOC was elevated. This elevated DOC may suggest a local organic matter source from Shenzhen. Using a
cross-flow ultrafiltration (CFF) system equipped with a Millipore Prep-scale CFF 1 kD regenerated cellulose membrane, we also
separated the colloidal organic matter from the truly dissolved fraction (<1 kD). CFF membranes were carefully evaluated for
their applicability (retention characteristics, blank level and mass balance) to separate colloidal organic matter. COC in
the study area ranged from 5 to 85 μmol/L, representing 3%–32% of DOC. The highest COC percentage was found at low salinities
(<5) in both winter and summer. Evidence suggests in-situ production of colloidal material at this salinity range. Beyond
this point, a very modest removal was observable until high salinities. Again, an increase in COC concentration was shown
in the samples taken from the Deep Bay.
This work was supported by European Commission under contract CI1*-CT94-0136. |
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| Keywords: | dissolved organic carbon colloidal organic carbon Zhujiang River estuary |
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