| Some physical and chemical factors of water quality ,the plankton , the primary productivity and the concentrations of the chlorophyll a (chla) in the water area, in which a cage culture boat was set up, of Fujiang river in Hechuan, Chongqing, were studied from January in 2004 to February in 2006. Six sampling stations were selected in this research. Station I was in the 50m ahead the nose of the boat, station II was in the net cage (12m from the right bank), station III was in the section 50m behind the rear of the boat and in the middle of the river, station IV was also in the section 50m behind the rear of the but 12m from the right bank, station V in the section 150m behind the rear of the boat and in the the middle of the river, station VI was also in the section 50m behind the rear of the but 12m from the right bank.The main results were as follows:1. The fluctuation of the physical and chemical factors and the concentration of chla in the waterAmong 6 sampling stations, the average concentrations of the inorganic nitrogen (EN)were 1.55mg.L-1, 1.304mg.L-1, 1.029mg.L-1, 0.839mg.L-1, 1.091mg.L-1, 1.071mg.L-1 respectively. The average contents of total phosphorus (TP) were 0.154mg.L-1, 0.191mg.-1, 0.204mg.L-1, 0.215mg.L-1, 0.204mg.L-1, 0.347mg.L-1 respectively. The concentrations of HPO42- were 0.102mg.L-1, 0.101mg.L-1, 0.118mg.L-1, 0.101mg.L-1, 0.118mg.L-1, 0.143mg.L-1 respectively on average. The concentrations ofthe chla were 0.011ug·L-1, 0.011 ug·L-1, 0.013ug·L-1, 0.012ug·L-1, 0.010ug·L-1, 0.010ug·L-1 on average. The COD were 28.62mgO2·L-1,30.27mgO2·L-1, 28.62mgO2·L-1, 27.88 mgO2·L-1, 31.90mgO2·L-1, 28.91mgO2·L-1 respectively, the contents of dissolved oxygen were 9.3 mgO2·L-1, 9.00mgO2·L-1, 9.4mgO2·L-1, 9.2mgO2·L-1, 9.3mgO2·L-1, 9.4mgO2·L-1 respectively. The water temperature observed during the period were 8.8℃-27.7℃; the pH of the water were 5.9- 9.1.The concentration of the nitrogen of station II was higher than other 5 spots.The contents of TP...
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