三峡水库运行期支流沉积物营养盐污染评价

Nutrients Distribution and Pollution Evaluation for Top-layer Sediments in Tributaries of Three Gorges Reservoir during Water Storage Period

通过对三峡库区7条支流表层沉积物中总氮(TN)、总磷(TP)、钾(K)及有机质(OM)的含量进行测定,分析其空间分布特征,评价其污染水平,揭示其污染来源。结果表明,7条支流pH值平均值(7.91±0.53),按照支流沿程分布,表层沉积物各营养盐含量基本呈上升趋势,回水断面和断面营养盐含量较高。仅澎溪河(PX)上游断面表层沉积物各营养盐含量较高,按沿程逐渐降低,到支流回水末端又呈升高趋势。7条支流均未出现有机污染,但受到有机氮污染胁迫;除OM外,25个断面的营养盐(TN、TP)含量基本超过了加拿大安大略省环境和能源部发布的沉积物中能引起水环境生态风险效应的营养物含量评价标准,沉积物已受到污染,但仍属于多数底栖生物可以承受的污染水平。

Seven tributaries in the Three Gorges Reservoir were investigated focusing on the top-layer sediments with the purpose to reveal the paths of pollution into them,thus TN,TP,K and organic matter（OM） were measured,the spatial distributions of those pollutants were analyzed and the pollution levels evaluated. The investigation showed that average value of pH was（7.91±0.53）,and the trophic salts content increased along those tributaries flowing into the reservoir;in addition,the backwaters of those tributaries had higher content of trophic salts,with the exception of the Pengxi River in which trophic salts content gradually decreased along its path into the reservoir,however showing upward in its backwater end. In general,pollution of OM was not a problem though still stressed by organic nitrogen. Compared with the relative standards of Otario in Canada,the situation of the seven tributaries in terms of TN and TP concentrations（except for OM）in 25 sampling crosssections was not good,exceeding the limits of evaluation standard set by the environment department of Ontario for controlling content of trophic salts which will cause ecological risks. In this way, the sediments of those tributaries had been contaminated;however,the situation was not so bad to menace the existence of most of the benthos.