Investigations from August

1985 to July

1986 showed that the high concentration area of PO4−P

SiO3−Si and NO3−N gradually reduced with the reduction of the area of the Changjiang River diluted water from summer

autumn to winter

and that the seasonal distributions and variations of the nutrients concentrations were mainly controlled by the river flow and were also related to the growth and decline of phytoplankton. The conservation of SiO3−Si and NO3−N in the estuary in the flood season was poorer than that in the dry season. The behaviour of PO4−P in the estuary shows that aside from biological removal

buffering of PO4−P is possible in the estuary. The highest monthly average concentrations and annual average concentrations

in the river mouth were respectively 0.88 and 0.57 μ mol/L for PO4−P

191.5 and 96.2 μ mol/L for SiO3−Si

and 81.6 and 58.6 μ mol/L for No3−N. The Changjiang’s annual transports of PO4−P

SiO3−Si and NO3−N to the sea were about 1.4×104 tons

204.4×104 tons and 63.6×104 tons respectively. The investigation shows that the seasonal variations of the nutrients transport closely correlate with that of the flow of the Changjiang River.