巢湖沉积物δ13Corg和δ15N记录的生态环境演化过程

通过对巢湖2处柱状沉积物样品中δ¹³C_org、δ　¹⁵N、C/N比值、TOC和TN含量的测定,分析了近百年来巢湖沉积物有机质的来源,探讨受人类活动影响的湖泊生产力变化和富营养化过程.结果表明,巢湖沉积物有机质的主要来源是水生藻类,陆生有机质的输入量较少,但是城市污染物的输入与农业面源污染的影响是不可忽视的.巢湖沉积物剖面上,δ¹³C_org、δ¹⁵N、TOC和TN含量变化按沉积深度可以明显划分为2个阶段：①10 cm以下,H3点δ¹³C_org波动在-21.74‰～-19.34‰的范围内,其余数据表现相对平缓,湖泊内的生物物种是固氮植物和非固氮植物共存,2个采样点具有不同的湖泊营养化进程;②10 cm至表层段,2个剖面的δ¹³C_org迅速减小,δ¹⁵N、TOC和TN则是显著增大,巢湖闸的建成使得内源营养物质快速积累,湖泊初始生产力水平迅速提高,富营养化加剧.

Record of ecosystem evolvement processes provided by delta 13C(org) and 6 delta 15N values in Chaohu Lake sediments

Variations of delta 13C(org) and delta 15N values, C/N ratios, TOC and TN contents in Chaohu Lake sediments reflect the sources of organic matter in lake sediments, evolution of lake productivity and the eutrophic status in Chaohu Lake during last 100 years. Our results suggest that the sedimentary organic matter was derived mainly from aquatic algae and partly from land matter. However, the input of the pollutants from city and agriculture into the lake could not be neglected. Two stages can be found in the sediments cores according to the profiles of delta 13C(org), delta 15N values, TOC and TN contents. Below 10cm, delta 13C(org) values vary between - 21.74 per thousand and - 19.34 per thousand. Nitrogen fixing and non-nitrogen fixing phytoplankton coexist together. Two cores show different nutrition processes. Above 10cm, in both profiles, the values of delta 13C(org) start to decrease sharply, but delta 15N, TOC and TN increase. The construction of Chaohu Gate leads to the enhancement of lake productivity and development of eutrophication.