太湖湖滨湿地沉积物营养元素分布特征及其环境意义

针对当前修复湖滨湿地去除氮磷营养盐长期效果的不确定性,以东太湖自然湖滨湿地与东部滨岸区、竺山湾修复湖滨湿地为代表,采用放射性核素210Pb计年法测定湖滨湿地沉积物的年代,据此计算出沉积速率,并结合沉积物柱中粒度组成与碳氮磷的含量变化,推算出自然湖滨湿地沉积物中碳氮磷的平均蓄积量.结果表明:太湖自然湖滨湿地与修复湖滨湿地沉积物的颗粒组成均以粉砂粒为主.东太湖自然湖滨湿地沉积物的平均沉积速率为:芦苇群落,0.74cm/a;茭草群落,0.69cm/a;香蒲群落,1.24cm/a;牛鞭草群落,1.27cm/a;荷群落,0.81cm/a.近40a来,东太湖自然湖滨湿地单位面积(cm2)沉积物中碳氮磷的蓄积量平均为:总有机碳1408.0mg,总氮138.2mg,总磷14.31mg.对于修复湖滨湿地而言,随着植物群落的发育演替,营养元素在修复湖滨湿地系统内可以不断累积,其沉积物库的蓄积量潜力很大,在控制外源污染输入的前提下,湖滨湿地具有净化水质的长期环境效应.

Nutrients distribution characteristics and their environmental significance of Taihu lakeside wetland sediments

Lakeside wetland is an important transition zone between the aquatic ecosystem and the adjacent terrestrial ecosystem. In recent years, extensive lakeside wetland restoration projects of Lake Taihu have been carried out. However, the long-term function and sustainability of lakeside wetland restorations remain largely unexplored. Taking the natural lakeside wetland in Dongtaihu Bay, the restored lakeside wetland in the Eastern Shoreline and Zhushan Bay as a case, this paper calculated sedimentation rates with high-resolution radionuclide timing (210Pb-date to age-depth profile translation), and combined with grain-size and vertical distribution characteristics of TOC, TN, TP to analyze accumulations of TOC, TN, TP in the natural lakeside wetland sediments. The results showed that the sediments were mainly compromised of silt in either natural lakeside wetland or restored one. The average sedimentation rates of natural lakeside wetland in Dongtaihu Bay were: 0.74cm/a of Phragmites communis, 0.69cm/a of Zizania caduciflora, 1.24cm/a of Typha orientalis, 1.27cm/a of Hemarthria altissima, 0.81cm/a of Nelumbo nucifera. In recent 40years, the accumulations of TOC, TN, TP (per cm2) in natural lakeside wetland sediments of Dongtaihu Bay were: TOC 1408.0mg, TN 138.2mg, TP 14.31mg. For the restored lakeside wetland, with development of vegetation, the accumulations of nutrients in the restored lakeside wetland would be increasing. There is a large potential in sediment pool. As the external pollution under control, the lakeside wetland has a long-term function of purifying water.