Zhuo Hai-Hua, Lou Bao-Feng, Wu Yun-Li, Wang Rui-Lin, Chen Jie, Lan Jing
Yangtze River Basin Ecological Environment Monitoring and Scientific Research Center, Yangtze River Basin Ecological Environment Supervision and Administration Bureau, Ministry of Ecological Environment, Wuhan 430010, China.
Huan Jing Ke Xue. 2020 Dec 8;41(12):5371-5380. doi: 10.13227/j.hjkx.202005108.
After the completion of the Three Gorges Reservoir and the upstream reservoir group of the Yangtze River, new water and sediment conditions appeared in the middle and lower reaches of the Yangtze River, and its influence on the phosphorus concentrations in water has attracted much attention. Therefore, the spatial and temporal distributions of total phosphorus (TP) concentrations in the middle and lower reaches of the mainstem under the new water and sediment conditions were studied. The results show that:① after the construction of the Three Gorges Reservoir, the concentrations of TCP (samples were allowed to settle for 30 min) in the middle and lower reaches of the Yangtze River fluctuates between 0.10 and 0.15 mg·L, and generally increased during 2004-2010 and then decreased during 2014-2019, and increases along the flow direction. The concentrations of dissolved total phosphorus (TDP) have slowly increased with time. ② The settleable solids influence the phosphorus content to varying degrees. The median values of TCP/TP ratio in Nanjinguan, Hankou, and 23 km below Wusongkou, are 0.900, 0.720, and 0.609, respectively, which decreases successively from upstream to downstream. The proportion of TPP (total particulate phosphorus)/TP shows an increasing trend along the flow direction. The median values of TPP/TP ratios in Nanjinguan, Hankou, and 23 km below Wusongkou were 0.439, 0.567, and 0.738, respectively. ③ According to the "Environmental quality standard for surface water GB 3838-2002", the water quality was assessed using TCP concentrations, and the assessment results showed that the water quality of the middle and lower reaches of the Yangtze River was generally good. However, considering the influence of settleable solids, the water quality categories assessed based on TP concentrations would be worse, especially near estuaries. ④ In the middle and lower reaches of Yangtze River, there is little difference in the phosphorus concentration of different monitoring sites in the upper section of main stream; however, the difference is obvious near the estuary. ⑤ The concentration of TCP in the coastal waters of the urban river section of the middle and lower reaches of the Yangtze River is significantly higher than that of the main channel, and there are obvious coastal pollution zones in the coastal waters of the urban river section.
三峡水库及长江上游水库群建成后，长江中下游出现了新的水沙条件，其对水体中磷浓度的影响备受关注。因此，研究了新水沙条件下长江中下游干流总磷（TP）浓度的时空分布。结果表明：①三峡水库建成后，长江中下游水体中30分钟沉降态总磷（TCP）浓度在0.10～0.15mg·L之间波动，2004—2010年总体呈上升趋势，2014—2019年呈下降趋势，且沿程升高。溶解性总磷（TDP）浓度随时间缓慢上升。②可沉降固体对磷含量有不同程度的影响。南津关、汉口、吴淞口以下23km处TCP/TP比值的中位数分别为0.900、0.720、0.609，自上游向下游依次降低。总颗粒态磷（TPP）/TP比例沿程呈上升趋势。南津关、汉口、吴淞口以下23km处TPP/TP比值的中位数分别为0.439、0.567、0.738。③依据《地表水环境质量标准GB 3838—2002》，采用TCP浓度对水质进行评价，评价结果表明长江中下游水质总体良好。但考虑可沉降固体的影响，基于TP浓度评价的水质类别会变差，尤其是在河口附近。④长江中下游干流上段不同监测点的磷浓度差异较小；但在河口附近差异明显。⑤长江中下游城市河段近岸水域TCP浓度显著高于主槽，城市河段近岸水域存在明显的近岸污染带。
