三峡水库成库后支流库湾营养状态及营养盐输出

三峡水库成库后,对受成库影响的12条主要支流库湾营养状态及营养盐输出状况进行了初步研究.结果表明,支流库湾总氮(TN)、总磷(TP)、高锰酸盐指数、叶绿素a含量和透明度差异较大,透明度范围为0.10～3.5 m,TN含量范围为0.535～7.47 mg·L-1,TP含量范围为0.016～0.835 mg·L-1,高锰酸盐指数范围为1.55～5.88 mg·L-1,叶绿素a范围为1.38～23.7 mg·m-3.支流受到不同程度污染,水体中N含量丰富,部分次级河流富营养化的限制因子为P.利用相关分析方法,分析了叶绿素a与营养盐之间的关系,叶绿素a与高锰酸盐指数呈显著正相关(r=0.6242,p＜0.01).利用综合营养状态指数法评价了次级河流富营养化程度,结果表明,5月和6月份分别有5条和8条支流达到富营养化水平,其余河流为中营养.三峡水库蓄水后,支流库湾的富营养化程度较成库前严重.12条次级河流排放TN、TP、高锰酸盐指数和NH4 -N分别为668、26.7、890和99.2 g·s-1.三峡水库完工后,因支流库湾区水体流速进一步减缓,富营养化趋势将加重.

Nutrient Output of Tributaries Bay in Three Gorges Reservoir After Impoundment

After the Three Gorges Reservoir storaged water in June 2003, total phosphorus (TP), total nitrogen (TN), chlorophyll a (Chl-a), potassium permanganate index and Secchi depth (SD) were determined in 12 tributaries bay in Three Gorges Reservoir. Trophic states were assessed and output fluxes of TN, TP and potassium permanganate index were calculated. The results showed that value of TN,TP, potassium permanganate index, SD and Chl-a were different in each tributary bay. SD, TN, TP, potassium permanganate index and Chl-a value were 0.10-3.5m, 0.535-7.47 mg x L(-1), 0.016-0.835 mg x L(-1), 1.55-5.88 mg x L(-1) and 1.38-23.7 mg x m(-3) respectively. The water body of tributaries is polluted at various levels. The concentration of TN is abundant. The rate of TN and TP showed that a part of tributaries eutrophication were limited by TP. The correlation of nutrient and Chl-a were researched. It indicated there was a significant positive correlation (r = 0.6242) between chlorophyll a and potassium permanganate index. Utilizing the method of integrated nutrition state index, it assessed the trophic states degree of tributaries bay. The integrated nutrition state index ranged from 33.3 to 66.1. Among all of the studied tributaries, 5 tributaries are eutrophic in May and 8 tributaries are eutrophic in June. The rest of tributaries are mesotrophic. The degree of eutrophication is more serious than before the Three Gorges Reservoir impoundment. The nutrient fluxes load was calculated by discharge and concentration of each tributary. The nutrient fluxes load of TN, TP, potassium permanganate index and NH4(+)-N are 668, 26.7, 890 and 99.2 g x s(-1) respectively. After the Three Gorges Dam was completed in 2009, eutrophication trend of tributaries estuaries will be more serious with the more slow flow velocity.