关中盆地LGT全新世剖面N含量及其环境意义探讨

Total nitrogen and its environmental significance at LGT Holocene profile, Eastern Guanzhong basin

通过对关中盆地LGT全新世剖面的土壤全氮(TN)含量分析研究发现,全氮在黄土、古土壤中的含量明显不同,黄土中均值0.294 0 g/kg,古土壤中均值0.385 6 g/kg,在剖面上呈现出明显的高值和低值交替变化的特征,这种变化与磁化率曲线可进行良好的对比,且与土壤黄土序列对应也良好。认为全氮可作为一个气候替代指标。全氮含量高指示暖湿的生物活动强的气候条件,反之,含量低则指示冷干的生物活动弱的气候条件。

The total content as a climatic proxy is often used in studying of lake and sea deposition condition but hardly used in the Holocene loess-soil sequence on the Loess Plateau. Based on particular survey in the field, LGT Holocene profile in the Eastern Guanzhong basin, Shaanxi, China is selected and total nitrogen content and magnetic susceptibility are measured. The studied results show that total nitrogen content is 0.294 0 g/kg in loess,and 0.385 6 g/kg in soil. What is more, total nitrogen content appears high-low superseded change in the loess profile. At 0～40 cm, 96～196 cm, 210～274 cm, the profile show three high values, corresponding respectively TS, S^1_0, S^2_0,at 40～96 cm, 196～210 cm, 274 ～380 cm appear three low values, corresponding respectively L_0, L_x, L_1. The change of total nitrogen content is in correspondence with magnetic susceptibility curve and the loess-soil sequence. So total nitrogen is offspring of the special climate condition, the content and the distribution is in reference to climate condition. So total nitrogen can be a climatic proxy that recover palaeoclimate. High total nitrogen content shows warm-humid climatic environment, whereas low total nitrogen content shows cold-dry climatic environment.