Studies on the transport mechanisms and behaviors of six trace metals (Fe, Mn, Cd, Cu, Pb and Zn) in the Tsengwen river and estuary were per rmed r the high- ow and low- ow seasons. Dis­ solved metals in the Tsengwen river are slightly higher than those in the pristine rivers but much lower than those in the heavily polluted rivers of the world. The riverborne dissolved Fe, Mn, Cu, Pb and Zn exhibited signi cant removals in the early estuarine transport; r Cd, however, this was likely controlled by the mixing process in the estuary. Particulate and sediment metals, similar to dissolved metals, showed elevated concentrations in the middle river, but there was little di erence throughout estuarine locations. The enriched levels of par­ ticulate and sediment metals with re rence to backgrounds (shale's metals) were und in a sequence of Pb, Cd> Zn, Cu> Fe, Mn.
Trace metals were principally transported by suspended particu­ lates, accounting r over 93 % of the total gross uxes. Particulate Fe and Pb are mostly concentrated in the Fe-Mn hydroxides and crys­ talline actions. Particulate Mn, Cu, Zn and Cd distribute rather signi cantly, in addition to Fe-Mn hydroxides and crystalline frac­ tions, in exchangeable and carbonate phases, carbonate and organic phases, carbonate phase, and exchangeable phase, respectively. The particulate speciation shows little di erence between riverwater and estuarine water. The net uxes of metals out of the estuary are mod­ eled to be approximately 56 %, 76 %, 114 %, 67 %, 84 % and 73 % of dissolved in uxes as well as 35 %, 32 %, 28 %, 29 %, 39 % and 50 % of particulate in uxes, respectively r Fe, Mn, Cd, Cu, Pb and Zn. The imbalance of metals between the dissolved and particulate phases is thought to result from metal deposition in the estuary.