为探究梯级水库建设下澜沧江流域电导率和浊度变化规律,以澜沧江干流和梯级水库作为研究对象,在2016年10月、2017年2月、2017年6月、2018年1月进行水质参数监测.通过对澜沧江流域电导率、浊度等指标进行监测分析,以表征梯级水库建设对澜沧江水环境的累积效应.由Pearson相关性分析结果表明,电导率与浊度相关性显著.空间上,自上游至下游,自然河段电导率沿程逐步下降,水库河段电导率缓慢降低,其中在大型水库坝前坝后波动较大;浊度自上游至下游先上升后下降,自然河流段先增高后降低,水库河段浊度变化范围较小.时间上,平水期电导率因汛后富集作用整体上高于其它时期,自然河段丰水期电导率最低,水库河段变化范围与趋势几乎一致;自然河段丰水期浊度显著高于其他时期,水库河段在不同时期沿程总体在90 FNU以下.梯级水库建设使流速减缓,电导率和浊度累积效应明显.小湾水库不同时期浊度垂向变幅在10 FNU以内,电导率因水体滞留时间增大随水温出现分层现象;功果桥水库、苗尾水库不同时期水体滞留时间短,浊度垂向变幅较小湾水库大,垂向掺混使电导率变幅较小.

通过对已建水库河流的沉积物磷形态与未建水库河流进行对比,揭示建有水库河流与自然河流沉积物磷形态的差异,并分析其差异的原因.结果发现:怒江、澜沧江自然河段TP含量分别在510.68～624.61 mg·kg-1、528.79～629.40 mg·kg-1之间变化,澜沧江水库段383.50～1044.13 mg·kg-1之间变化.沉积物6种磷形态中,自然河道段Ex-P、Fe-P、Al-P、OP、Ca-P、Res-P含量分别在0.87～5.02 mg·kg-1、19.13～44.4 mg·kg-1、8.81～33.97 mg·kg-1、73.74～142.75 mg·kg-1、325.22～493.51 mg·kg-1、34.67～76.84 mg·kg-1之间变化;而澜沧江水库段Ex-P、Fe-P、Al-P、OP、Ca-P、Rest-P含量分别在0.72～4.41 mg·kg-1、28.68～81.01 mg·kg-1、11.52～377.03 mg·kg-1、40.61～160.78 mg·kg-1、46.91～349.83 mg·kg-1、23.49～92.84 mg·kg-1之间变化.与自然河道相比,水库段沉积物Fe-P、Al-P含量上升,Ca-P(除坝下沉积物含较高外)在库区的含量下降.水库段沉积物Fe-P、Al-P含量上升,其可能的原因是沉积物中的Ca-P释放产生的磷酸盐,较深部位沉积物层的铁磷矿物还原溶解释放溶解磷酸盐以及较小粒径的沉积物吸附水体中的磷酸盐与沉积物中铁铝的(氢)氧化物结合而沉积下来.

The ecological problems due to reservoir construction are causing unprecedented concern. To reveal the differences in organic carbon distribution characteristics and sediment sources of total organic carbon (TOC) between the old and new reservoirs, water samples, and sediment samples from reservoirs constructed in the three different periods of Miaowei, Gongguoqiao, and Dachaoshan were collected in November 2017. The temperature (T), dissolved oxygen (DO), TOC, redox potential (ORP), total nitrogen (TN), and total phosphorus (TP) of the water samples were measured. The isotopes 15N and 13C were used as indicators with IsoSource software to analyze the contributions of TOC sources and their source materials to the corresponding reservoir sediments, in order to explore the carbon cycle mechanism and evolution mode of reservoir. The results showed that the average concentrations of organic carbon in the waters of the Miaowei, Gongguoqiao, and Dachaoshan Reservoirs were 0.95 mg·L-1, 1.97 mg·L-1, and 4.64 mg·L-1, respectively. The range of organic carbon content in the corresponding sediments was 4.41-81.63 g·kg-1, 18.30-28.42 g·kg-1, and 9.16-14.46 g·kg-1, respectively. The cascade construction of the reservoirs resulted in a difference between the sediment sources of the new and old reservoirs and the surrounding recharge area, meaning that the TOC of the new and old reservoirs were significantly different. For the TOC of waterbodies, the difference between the thermodynamic state of water and dissolved oxygen indirectly affects the distribution trend of TOC. The sediments mainly reflect the influence of source elements, that is, the ability of the sedimentary environment to preserve organic matter was the main cause of the vertical distribution of DCS, MV, and GGQ sediments. In the evolution mode of cascade reservoir, the research shows that it can be preliminarily set as three stages. Firstly, due to the short age of MV, it is in the first stage and mainly accumulates the TOC from the upstream. GGQ is longer than the age of MV, and it is mainly used to decompose the upstream TOC, so it is defined as in the second stage. Finally, as an old reservoir, DCS mainly accumulates TOC sources around the reservoir, which can be regarded as the third stage.