鄂陵湖浅层冻结湖相沉积物中埋藏植物屑稳定碳同位素组成特征

Carbon isotope composition of buried plant tissues in Ngoring shallow frozen lacustrine sediments

鄂陵湖浅层深2m的冻结湖相沉积物中埋藏植物屑保存完好，植物屑均来源于同一种沉水植物——龙须眼子菜（Potamogetonpectinatus）。碳同位素分析结果表明，剖面中该植物屑的δ13C值在－17.67‰～－11.39‰间变化，比该地生长的陆生植物高。根据δ13C值的变化特征，将湖相沉积分为三个阶段，相应δ13C平均值分别为－16.68‰、－14.48‰和－12.28‰，由下而上呈降低的趋势。沉水植物光合作用中碳同位素分馏的分析表明，沉水植物的δ13C值同水中溶解无机碳的浓度有关，从而与影响其改变的各种因素相关。因此，鄂陵湖湖相沉积物中埋藏植物屑的δ13C特征记录了该地过去环境变化的信息。

The plant tissues, which were well- preserved in 2 m- thick shallow frozen lacustrine sediments of Ngoring, came from the same species of submersed plant, Potamogeton pectinatus. The stable carbon isotopic compositions of these plant tissues range from － 17.67‰ to － 11.39‰ and is higher than that (－ 25.4‰ ) in local terrestrial plant. Three main stages of carbon isotopic change are distinguished according to the obvious shifts of δ 13C values of plant tissues. The mean values of δ 13C are － 16.68‰ , － 14.48‰ and － 12.28‰ , respectively. In general, the δ 13C values have decreasing shifts from bottom to top in Ngoring lacustrine sediment profile. According to the model of stable carbon isotopic fractionation in submerged plant, the concentration of dissolved inorganic carbon (DIC) is an important environmental factor influencing the δ 13C of submerged plants. And the associated factors, for example, temperature and concentration of atmospheric CO2, which can change the concentration of dissolved inorganic carbon, can be recorded in the stable carbon isotopic compositions of these plant tissues.