三峡库区次级河流营养状态及营养盐输出影响

Trophic States and Nutrient Output of Tributaries in Three Gorges Reservoir Area

通过对三峡库区15条次级河流TP、TN、Chla、高锰酸盐指数、SD和浮游植物的测定,分析了次级河流的营养状态及营养盐输出状况.结果表明,次级河流TN、TP、高锰酸盐指数、Chla含量和SD差异较大,SD范围为0.45～1.5m,TN含量范围为0.65～4.27mg.L-1,TP含量范围为0.011～0.432mg.L-1,高锰酸盐指数范围为0.657～5.37mg.L-1,Chla值范围为0.57～12.2mg.m-3.次级河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3条达到轻度富营养化,2条为贫营养,10条河流为中营养.次级河流藻类7门67属129种,种类数以硅藻、绿藻和蓝藻最多.浮游植物的群落类型以硅-绿藻型、硅-蓝藻型和蓝-绿藻型为主,种类和数量随水域不同而呈现差异,水体营养特征为浮游植物响应型.15条次级河流年排放TN、TP和高锰酸盐指数分别为3.14×105t、1.76×104t和2.74×105t.三峡水库完工后,由于次级河流河口区水体流速减缓,富营养化趋势可能加重.

TP, TN, chlorophyll a, potassium permanganate index and secchi depth （SD） and phytoplankton were determined in 15 tributaries of Three Gorges Reservoir. Trophie 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 Chla were different in each tributary. SD, ＇IN, TP, potassium permanganate index and Chla value are 0.45 - 1.5 m, 0.65 - 4.27 mg·L^-l , 0.011 - 0.432 mg·L^-l , 0.657 - 5.37 mg·L^-l and 0.57 - 12.2 mg·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 are limited by TP. Utilizing the method of integrated nutrition state index, it assessed the trophie states degree of tributaries. All of the studied tributaries, 3 tributaries are eutropher, 10 tributaries are mesotropher and 2 tributaries are oligotropher respectively. 129 species of phytoplankton are identified, which belongs to 7 division and 67 genera. The dominant species are Bacillariophyceae, Chiorophyceae and Cyanophyta. The type of phytoplankton community is Bacillariophyceae-Chlorophyceaetype, Bacillariophyceae-Cyanophytatype and Cyanophyta-Chlorophyceaetype. The species and numbers of phytoplankton are various in different tributaries. The nutritive peculiarity belongs to responding type of phytoplankton. The nutrient fluxes load was calculated by discharge and concentration of each tributary. The nutrient fluxes load of TN ,TP and potassium permanganate index are 3.14 × 10^5 t, 1.76 × 10^4 t and 2.74 × 10^5 t respectively in one year. After the Three Gorges Dam was completed in 2009, eutrophication trend of tributaries estuaries would be more serious with the decreasing of flow velocity.