The Effect Of '98 Yangtze Great Flood And The Three Gorges Project On The Distributions And Transport Of Suspended Organic Matters From Yangtze River

Water column concentrations of total suspended matter(TSM),particulate organic carbon(POC),particulate nitrogen(PN)and their stable isotopic compositions(δ13C andδ15N)are measured at two to five different depths in the Yellow Sea and East China Seas and Yangtze Estuary to clarify the effect of the Yangtze River close off at the Three Gorges project on the distribution of suspended matter in the estuary and the effect of'98 Yangtze great flood on the transport of suspended matter in the Yellow Sea and East China Sea. The results are followed:1. The effect'98 Yangtze great flood on the transport of suspended matter in the Yellow Sea and East China SeaSuspended matters are collected to analyze the distributions of TSM, POC, PN and S throughout the Yellow Sea and East China Sea in the autumn of 1998. There are marked positive correlations (r=0.89～0.98) among TSM, POC and PN, but negative relationships (r=-0.29～-0.59) between TSM and salinity. These results conclude that the POC and PN were controlled primarily by the concentrations of TSM.The C/N ratios of particulate organic matter have a negative linear correlation with PN % (r=-0.44～-0.71), but no correlation with POC %, which suggests C/N ratios are mainly controlled by PN %.There are distinct positive correlations betweenδ15N and POC % or PN % in surface water( r=0.36 and 0.24,p<0.01,respectively), however, the correlation don't exist in more deeper depths. It indicates thatδ15N could be changed by a lot of factors such as nutrient utility, nitrification, denitrification, and different material sources and so on, except decomposition of organic matter.The distributions of C/N ratio andδ13C values of the particulate organic matter suggest that suspended matters from Yangtze River could be transported directly into the Okinawa Trough under the condition of'98 Yangtze great flood, which break through the foregone knowledge obtained under the normal hydrological condition.2. The distributions and source of POM in the water column throughout the Yangtze River Estuary after the Three Gorges There are positive correlations between concentrations of POC and TSM (R=0.708 7) and between concentrations of PN and TSM (R=0.648 4) throughout the turbid Yangtze River Estuary during November and December 2004, it shows the POM has the same source with TSM. Furthermore, Most samples display C:N ratio >12, suggesting the both TSM and POM in this region are mainly of terrestrial origin.Comparing the data of concentrations of TSM and POC in the Yangtze River estuary before and after the Three Gorges project, it indicates that the Yangtze River close off at the Three Gorges has not influenced on the distribution feature of TSM and POC in the Yangtze River estuary.