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

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（δ13C）、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，可以划分出以下阶段：9 400~7 300 cal. a BP期间，δ15N值偏低且剧烈波动，暗示了气候状况较为干旱且不稳定；7 300~5 900 cal. a BP期间，δ15N值偏高，指示气候相对湿润；5 900~3 100 cal. a BP期间，δ15N由相对高值降为低值，指示气候环境由湿转干；3 100~1 100 cal. a BP期间，δ15N总体呈现相对高值，但后期呈下降趋势，指示了此阶段中气候特征由相对湿润转向干旱；但在1100~0 cal. a BP期间偏高的δ15N值，则可能受到了增强的人类活动的影响．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．

Study on the Climatic and Environmental Implication of Stable Nitrogen Isotopes from the Lacustrine Sediments in Typically Westerly-Influenced Balikun Lake in Xinjiang

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‰ to 22.9‰ with an average value of 12.0‰. Supported by multi-proxy records including bulk organic carbon isotopes (δ13Corg), organic matter content (OM), and the ratio of TOC and total nitrogen (C/N), higher δ15N values could reflect relatively wet conditions, whereas lower δ15N suggests relatively dry conditions is inferred. Based on the δ15N record, five climatic periods in the past 9400 years could be identified, i.e., relatively dry condition from 9400 cal. a BP to 7300 cal. a BP; relatively wet conditions between 7300 cal. a BP and 5900 cal. a BP; relatively dry period between 5900 cal. a BP and 3100 cal. a BP; a wetter period from 3100 cal. a BP to 1100 cal. a BP, and after 1100 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 Xinjiang, NW China.