三峡水库成库后水体中COD_(Mn)、BOD_5空间变化

Spatial variation of BOD_5 and COD_(Mn) in the Three Gorges Reservoir

根据2004年2、5、8月,三峡水库成库后6个水平断面、4个垂直断面采样分析,对水体水质参数、DO以及COD_(Mn)和BOD_5的水平分布和垂直分布进行了研究．研究结果表明,成库后BOD_5达到国家地表水Ⅰ类标准,COD_(Mn)不同季节变化较大,水质范围在Ⅱ-Ⅳ类标准．BOD_5、COD_(Mn)变化范围分别在0．1-1．3 mg/L．1．8-6．3 mg/L,受三峡水库成库的影响,水平分布上,DO、COD_(Mn)、BOD_5在成库区域低于上游区；COD_(Mn)含量丰水期＞平水期＞枯水期；BOD_5浓度降低主要与污染物停留时间变长有关,COD_(Mn)主要是与泥沙沉积有关．垂直分布上,污染物3个层次变化不显著,未出现分层现象．枯水期、平水期、丰水期颗粒态含量占总COD_(Mn)范围分别为5．5%-27．3%,9．1%-28．8%,48．6%-78．3%．三峡水库对COD_(Mn)、BOD_5有净化作用,枯水期成库区域通量COD_(Mn)、BOD_5比上游区降低44%、76%,平水期降低13．5%,32%,丰水期降低31．8%、19．1%．各采样站点有机物通量和流量有显著的相关性．大宁河库湾受浮游藻类生长的影响,DO饱和率高于干流库区．

Through sampling and analysis of 6 horizontal stations and 4 vertical stations in the Three Gorges area, the spatial variation of water quality parameter, dissolved oxygen （ DO）, biochemical oxygen demand （ BOD5 ） and permenganate index of oxygen demand （ CODM. ） were revealed in Feb. , May and Aug. , 2004. Concentration of BOD5 were retained low level which preceded surface water standard I and CODMn changed from Ⅱ- Ⅳ in diverse season. The variation of BOD5 and CODMn ranged from 0. 1 - 1.3 mg/L and 1.8 - 6.3 mg/L respectively. Horizontal concentration of DO, BOD5 and CODM. in reservoir area were lower than upstream area. In flood season, coneentration of CODMn were higher than normal and dry season. In reservoir area, the lower concentration of BOD5 were due to long retension time and COD due to particulate deposition. The vertical variation of BOD5 and CODMn were not notable and organic pollutant were not layered. Particle CODMn rate in total CODMn in dry, normal and flood season ranged from 5.5% -27.3% ,9.1% -28.8% and 48.6% -78.3% respectively. Water quality was improved when passing through reservoir. Flux of CODMn and BOD5 decreased 44% and 76% in dry season, 13. 5% and 32% in normal season, 31.8% and 19.1% in flood season respectively. There was significant correlation between organic pollutant load and water discharge. Because of algae growth, the saturated rate of DO in Daning river bay is higher than in the main stream of reservoir.