Carbon inputs and distribution in estuaries of turbid rivers: the Yang Tze and Yellow rivers (China)

Particulate and dissolved organic and inorganic carbon concentrations were measured in the Yang Tze (Changjiang) and Huanghe (Yellow) river estuaries, during two different seasons. During the winter, the organic matter in the suspended load of both estuarine systems was dominantly of terrestrial origin, while in the summer, there were significant contributions from aquatic production. In these turbid rivers, there is a strong positive correlation between the concentrations of total suspended matter and particulate organic carbon, probably because biological production is inhibited when turbidity exceeds a certain limit. Dissolved organic carbon (DOC) does not exhibit a conservative behavior in these estuarine systems. High dissolved organic carbon values in bottom water samples suggest remobilization of DOC from near-surface, bottom sediments. Dissolved inorganic carbon concentrations were very high in the Huanghe River, and the trend in the calculated saturation indices for calcite suggests precipitation of carbonate in this estuarine system. There is no such evidence for carbonate precipitation in the Yang Tze River.