三峡库区消落带草本植物碳氮磷释放及影响因素

以三峡库区消落带优势草本植物狗牙根(Cynodon dactylon)、牛鞭草(Hemarthriaaltissima)、稗草(Echinochloacrusgalli)、狗尾草(Setariaviridis)和马唐(Digitariasanguinalis)为试验植物,在室内进行了为期60 d的淹水模拟试验,并对消落带优势草本植物淹水后TOC、TN和TP的释放特征及影响因素进行了研究. 结果表明:5种优势草本植物淹水后均可导致水中pH降低,TOC、TN和TP的U_max(最大单位累积释放量)分别为21.03~43.65、0.50~3.23和0.54~2.69 mg/g,U_max出现在淹水第15~20天,并且TOC、TN和TP的R(释放速率)差异显著；水体中微生物、水体温度和上覆水中ρ(TOC)、ρ(TN)、ρ(TP)对植物淹水后TOC、TN和TP的释放均有一定影响. 在对消落带植被调查研究的基础上,根据淹水试验植物的U_max,对蓄水后三峡库区消落带植被TOC、TN、TP的释放量进行了估算,在蓄水后20 d内,消落带植被可向水体释放大量的TOC、TN和TP,蓄水初期可能会引起库区局部水域水质恶化,影响水库的水环境安全. 

Characteristics of Carbon, Nitrogen and Phosphorus Release from Dominant Herbaceous Plants in Water-Level Fluctuation Zone of the Three Gorges Reservoir

Five dominant herbaceous species, Cynodon dactylon, Hemarthriaaltissima, Echinochloacrusgalli, Setariaviridis and Digitariasanguinalis, in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) were investigated. In order to determine how total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) are released while the plants are submerged in water, the stems and leaves of these plants were collected and submerged in water for 60 days in a laboratory. The results showed that the decomposition of the soaked plants caused a decrease in pH of the water. The maximum unit cumulative release amounts of TOC, TN and TP were 21.03-43.65,0.50-3.23 and 0.54-2.69 mg/g, respectively, which occurred between the 15^th and 20^th days. Furthermore, the maximum unit cumulative release rates of the plants varied significantly. Microbial activity, temperature and concentration of overlying water impacted the release of TOC, TN and TP. Based on previous reports on the vegetation of WLFZ and the maximum unit cumulative release amounts, the release amounts of TOC, TN and TP in the WLFZ during the impounding period of TGR were estimated. It was estimated that large amounts of TOC, TN and TP could be released within the 20 days during impoundment, which could result in a deterioration of local water quality and have an impact on water environment security during the initial period of impoundment.