新疆巴里坤湖全新世湖泊沉积物稳定氮同位素的气候与环境意义研究

Study on the Climatic and Environmental Implication of Stable Nitrogen Isotopes from the Holocene Lacustrine Sediments in Balikun Lake in Xinjiang

选择位于西风环流显著影响的新疆巴里坤湖作为研究对象，结合对位于湖心部位的人工开挖剖面的多指标（包括有机碳同位素（δ1C）、有机质含量（OM）和碳氮比（C／N））的对比分析和验证，发现该湖泊沉积物的δ15N记录较好地响应了过去9400年以来气候环境的变化，依据其波动变化特征划分出以下阶段：9400～7300cal．aBP期间，气候状况较为干旱且不稳定；7300～5900cal．aBP期间，气候相对湿润；5900～3100cal．aBP期间，气候环境由湿转干；3100～1100cal．aBP期间，气候特征由相对湿润转向干旱；但在1100～0cal．aBP期间偏高的δ15N值，可能受到了人类活动的影响．本研究表明，巴里坤湖沉积物δ15N记录对于恢复研究区全新世气候与环境变化的特征与历史等方面具有较好的应用潜力和前景．

The significance of climatic implication of the sediments nitrogen isotopes from Balikun Lake, which is located in typically westerly-influenced northeastern Xinjiang, is studied in this paper. Values of δ15N values of a 250 cm-deep section which is located at the center of the lake, fluctuate from 6. 0%0 to 22.9%0 with an average val- ue of 12.0%0. Supported by multi-proxy records including bulk organic carbon isotopes （ δ13 Corg ） , organic matter content （OM）, and the ratio of TOC and total nitrogen （C/N）, higher δ15N values could reflect relatively wet con- ditions, whereas lower δ15N suggests relatively dry conditions is inferred. Based on the δ15N record, five climatic periods in the past 9 400 years could be identified, i.e. , relatively dry conditions from 9 400 cal. a BP to 7 300 cal. a BP; relatively wet conditions between 7 300 cal. a BP and 5 900 cal. a BP; relatively dry period between 5900cal. aBPand3 100 cal. aBP; a wetter period from 3 100cal, aBPtol 100cal. aBP, and afterl 100 cal. a BP, strengthened human activity may exert strong influence on nitrogen isotopes. The results indicate that the nitrogen isotopes bear valuable potential to indicate past climatic changes in the westerly-influenced arid Xin- jiang, NW China.