摘要
根据高分辨率的湖泊沉积物粒度、Rb/Sr比、磁化率的综合分析 ,结合区域降水、历史记载资料 ,重建了内蒙古岱海地区近 5 0 0年来以小冰期为特征的、具有 10 0年准周期 (经谱分析 )的古环境变迁及受其制约发生的尘暴事件历史。结果表明 ,湖泊沉积物中Rb/Sr比值很好地反映了流域陆地受古环境状态变化控制的化学风化率的历史 ,而尘暴事件则主要是受冬、夏季风的相对强弱制约的。大量尘暴事件频发于小冰期干冷的气候条件下 ,表现为流域化学风化强度减弱、沉积物中粗颗粒含量高、中值粒径大。在转暖的现代气候下 ,尘暴事件很少 ,化学风化增强 ,沉积物中的粗颗粒含量及中值粒径也随之降低。但是近十几年 ,在化学风化仍相对较强的气候条件下 ,尘暴事件却呈上升趋势 。
Based on high-resolution analysis of grain size, Rb/Sr ratio and magnetic susceptibility of the lake sediments,combined with reconstructed historical data of regional precipitation from tree ring and with frequency of dust storms in China and with historical documentary records, we reconstructed the paleoenvironmental change and dust storm history in the Daihai Lake during the last 500 years including the Little Ice Age. The variation of Rb/Sr ratios shows quasi 100 years periodicity. Our results indicate that the variations of Rb/Sr ratios in lake sediments can be used as a good indicator of chemical weathering in watershed and that dust storm events were controlled mainly by the intensity of the summer and winter monsoons. Major dust fall events are generally associated with dry and cold climate during the Little Ice Age,when chemical weathering became weak in watershed and the median grain size of the lake sediments became larger with high contents of coarse grain (>100 μm). At time of warm conditions after the Little Ice Age, enhancement of chemical weathering resulted decrease both in the contents of coarse grain (>100 μm) and the median grain size, when dust storm events were limited. During the last one to two decades, however, dust storm events increased gradually though chemical weathering was still intense, related partly with greenhouse and more desertificated soil by human activity.
出处
《西安工程学院学报》
2001年第4期6-10,共5页
Journal of Xi'an Engineering University
基金
中国博士后基金 ( 5 0 30 30 2 )项目
国家自然科学基金( 4 0 0 0 30 0 1)项目
