湖北梁子湖沉积物正构烷烃与多环芳烃对环境变迁的记录

Response of the n-alkanes and polycyclic aromatic hydrocarbons records in sediments from Lake Liangzi to the environmental change

对梁子湖沉积柱91～345cm段中正构烷烃和17种多环芳烃含量进行了分析,发现在整个沉积柱中,长碳链正构烷烃的比例和17种多环芳烃含量的变化具有良好的一致性,二者都是从181～194cm(14C定年显示其对应的沉积年代为我国历史上的春秋战国时期)开始突然增高,指示了陆源有机质输入的剧增。认为这种变化正是春秋战国时期我国自然环境条件的改变以及由此引起的人类活动的增加在湖泊沉积记录中的反映。

Lake Liangzi is located in the southeastern part of Hubei Province and adjacent to the Tonglushan ancient copper ore site. In order to reconstruct the history of the environmental change in this area and identify the impact of anthropogenic activities on the sediment records of Lake Liangzi, a systematic study was made of the organic composition of sediments from the lake. A sediment core 345 cm long was collected in 2002 from the central part of the lake, sliced into 1 cm sections and analyzed by GC for nalkanes, and by GCMS for PAHs (polycyclic aromatic hydrocarbons). The data reveal that sedimentation in Liangzi Lake has changed through time. It’s found that an abrupt upward increase of the contents of nalkanes and PAHs from depth 181～194 cm exists in the sediment core, and the diagnostic ratios of nalkanes indicate that the proportion of landderived longchained components has increased dramatically from depth 181 cm in core too, implying that the increase in the contents of organic matter in sediments is mainly attributed to the increase of the landderived organic matter inputs from 181 cm in core, which corresponds to the Spring &Autumn Period (770 B.C.-476 B.C.) and the Warring States Period (475 B.C.-221 B.C.) in China’s history according to 14C dating. It’s suggested that the variations along the core are most probably related to the climatic evolution of this area and the consequent anthropogenic influences on the organic geochemical records in Lake Liangzi.