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通过实验室模拟实验,研究了不同pH及富氧、缺氧条件下长江径流淡水和东海外海水在混合过程中磷酸盐(PO4-P)的稀释模式,并结合2006~2007年长江口及邻近海域PO4-P的实际稀释状况,分析了pH及DO对PO4-P在河口混合行为的影响。结果表明:咸淡水混合需要一定的平衡时间,过滤后的长江水与外海水混合后,大约15 h后PO4-P浓度不再变化;未过滤的长江水与外海水混合则需要10 h的平衡时间。在不同pH咸淡水的混合过程中,PO4-P浓度与盐度均呈现出较好的相关性。且在高、低盐度区,PO4-P浓度与pH的变化分别呈现出不同的趋势。在缺氧和富氧状态下,PO4-P浓度均随盐度的增大而降低,且缺氧状态的PO4-P浓度高于富氧状态的PO4-P浓度。此外,根据2006~2007年长江口及邻近海域的现场调查数据可知,PO4-P在河口的实际稀释状况与本研究的实验结果基本相一致。
Through laboratory simulation experiments, the dilution mode of phosphate (PO4-P) in freshwater from the Yangtze River and seawater from the East China Sea under different pH, oxygen-rich and anaerobic conditions was studied. In addition, The actual dilution of PO4-P in the sea area was analyzed. The effect of pH and DO on the PO4-P mixing behavior at the estuary was analyzed. The results showed that the mixture of brackish water and fresh water required a certain amount of equilibration time. After filtering the mixture of the Yangtze River water and the seawater, the concentration of PO4-P did not change after about 15 h. The unfiltered Yangtze River water and seawater mixture required a balance of 10 h time. In the process of mixing different pH salt water, PO4-P concentration and salinity show a good correlation. And in high and low salinity area, PO4-P concentration and pH changes showed different trends. Under hypoxia and oxygen enrichment, PO4-P concentration decreased with the increase of salinity, and PO4-P concentration in hypoxia state was higher than PO4-P concentration in oxygen-enriched state. In addition, based on the field survey data of the Changjiang Estuary and its adjacent sea areas from 2006 to 2007, the actual dilution of PO4-P in estuaries is basically consistent with the experimental results in this study.