澜沧江中段水质时空特征分析

Spatio-Temporal Characteristics of Lancangjiang River Water Quality along Middle Reaches

分析水电工程建设前后流域水质时空特征对于研究水电工程对流域水生生态系统以及河岸带生态系统的影响具有重要意义。以澜沧江流域中段为研究区域,通过对10多年的多个断面水质监测资料分析,研究了以铜、铅、锌、镉为代表的金属元素以及氮磷等水质指标的时空分布特征。结果表明:建坝后金属元素的空间分异性比建坝前要明显,但在库区分异性不大;运用ATU(急性毒性度)能更好地反映金属元素指标变化情况,建坝后ATU值小于建坝前,沿干流逐渐减小,时间分异性比建坝前要弱。氮和磷浓度库区比非库区要高,最大值一般出现在大坝出水不远的断面,建坝后具有较明显的营养化趋势,时间分异性也在减弱。表明澜沧江中段水质时空分布受水电工程建设影响明显。

There are water quality changes both the reservoir and downstream alter nyaropower projects construction. Analysis of these changes have important significant in assessing effects of hydropower projects on the aquatic ecosystem and riparian ecosystem. This paper investigates temporal-spatial characteristic of Lancangjiang River water quality along the middle reaches through river section monitoring and sample analyses selecting several representative indices including metals taking Cu, Zn, Pb and Cd for example, NH3- N and P （total phosphorus and/or PO4-P） in the past more than ten years. Results showed that after dams built spatial heterogeneity of metals was more evident than before along the whole middle reaches and not evident along certain reservoir. Moreover, ATUs （Acute Toxic Units） that could assess the changes of metal factors were lower than before and became lower and lower along the middle reaches. Adversely, temporal distribution of metal factors besides NH3 --N and P were more homogeneous. NH3--N and P concentrations in reservoirs were higher whose maximums were tested at site about several kilometers downstream from the dam. There were increasingly eutrophicating after dams built. It was concluded that hydropower projects construction dominantly effected the spatio-temporal distributions of water quality.