| The well known'Three Gorges Project'(TGP) of the Changjiang started in 1994, and two cofferdams of the TGD were closed on November 8, 1997, with the first filling stage of the reservoir completed in June 2003. Slated to begin full-scale operations in 2009, this dam will be the largest dam in the world. The TGP will have far-reaching effects on environmental and human health issues over the drainage basin and the adjacent East China Sea. After the filling to 135m of the reservoir, we took water and suspend matter samples over the Three Gorges Reservoir (TGR) and the main channel of the Changjiang in April 2006 and September to October 2006. In this paper we aimed at the distribution of phosphorus species and update background data of nutrient concentrations in the Changjiang after the construction of TGD. The chemistry of phosphorus in the water of TGR was studied, based on the data in April 2006. The results showed that no obviously variation of phosphorus species in the TGR. Phosphate was the predominant species of the total phosphorus (TP).Particulate phosphorus concentration was low. Suspended particulate matter, dissolved oxygen, chlorophyll a and particulate phosphorus concentrations were higher at surface than those of at bottom in Xiangxi River. Phosphate, dissolved organic phosphorus, dissolved total phosphorus concentrations decreased gradually along the current, all the above distribution were caused by the algal adsorption and the dilution of the main channel of the Changjiang.The chemistry of phosphrous in water and suspended matter in the main channel of Changjiang was studied, based on the data in April 2006 and September to October. The results showed that suspended particulate matter decreased sharply from station Fuling to station Wanzhou, then decreased slowly from station Wanzhou to Gezhou Dam, after the Gezhou Dam, it began to increase. The phosphorus species'concentrations in the main channel of Changjiang varied obviously throughout the basin. Phosphate was the predominant species of the dissolved total phosphorus (DTP) and DTP was the predominant species of the TP in both investigations. There are obviously season variations of phosphate, DTP and TP in the main channel of Changjiang. Phosphate concentration was higher in April than September to December in the upper reaches (from Fuling to Gezhou Dam), while higher in September to December than that of April from Gezhou Dam to estuary. DTP and TP varied slightly from Fuling to Gezhou Dam, while higher in September to December than that of April from Gezhou Dam to estuary. Partuculate phosphorus concentration was higher in April than that of September to December in the main channel above Dongting Lake. Fluxes calculation at each station indicated that the fluxes of phosphorus increased from upstream to downstream.The research on the morphology of particulate phosphorus in the Yangtze River in September 2006 showed that authigenic apatite phosphorus was the main form except to Anqing and Datong station. Bio-available phosphorus had a high percent in total phosphorus, which was 27.7-69.0%. Loosely adsorbed phosphorus was affected by the adsorption of the particulate and grain sizes of the particulate, and increased first, then decreased along the Yangtze River. The distribution of organic phosphorus was the same as the chlorophyll a, which was mainly controlled by biological activities. Iron-bound phosphorus which was affected by the redox conditions decreased first and then increased. Authigenic apatite phosphorus distributed evenly except to Anqing and Datong stations. The distribution of detrital phosphorus took on a trend that increased at first and then decreased. Residue phosphorus had no significant changes in the entire valley. The concentration of Bio-available phosphorus in the front of the Xiangxi River was low and increased in the back of the river.
|
PDF Full Text Request