如同137Cs和210Pbex核尘埃,土壤和坝库沉积物中的孢粉也源于大气沉降,是否能用于侵蚀产沙的示踪研究?在陕北吴旗周湾水库采集了一些表层土壤和现代淤地坝、古代聚湫坝沉积泥沙的样品,尝试土地利用/覆被变化和侵蚀产沙的孢粉示踪研究。初步研究表明:草地表土孢粉丰富,平均浓度为26077粒/g;有33个科属的花粉,孢粉组合反映了当地以蒿属为主的半干旱温带草原植被;坡耕地表土的孢粉组合和草地一致,但孢粉平均浓度远低于草地,仅5844粒/g。坝库沉积剖面中,和137Cs核素一样,孢粉也富集于每一洪水沉积旋迴的上部层位,可用于沉积旋迴的区分。现代沉积旋迴的孢粉平均浓度,远低于草地和坡耕地表土,这表明草地和坡耕地土壤不是沉积泥沙的主要来源。古代沉积物的孢粉平均浓度高于现代沉积,表明流域内300年前的植被好于现代,或300年前沟谷地的相对产沙量低于现代。古代孢粉组合中十字花科花粉比例高达36·85%,明显高于现代的0·58%含量,这表明草地退化严重,十字花科植物比例急剧降低。孢粉示踪技术在植被环境恢复,沉积旋迴区分,和泥沙来源确定等方面具有一定的潜力,但应建立针对土地利用/覆被变化和侵蚀产沙研究的孢粉示踪技术方法。 Like the 137Cs and 210Pbex nuclear dusts, the sporopollen in the sediments of soil and dams also originated from the atmospheric subsidence and could be used for tracing the sediment yield erosion. Some surface soils and modern Silt dam, sediment samples collected from ancient polygamy, and attempted sporopollen tracing studies on land use / cover change and erosion and sediment yield. Preliminary studies have shown that the topsoil is rich in spores and the average concentration is 26077 grains per gram. The pollen and sporopollen assemblages of 33 genera reflect the local semi-arid temperate steppe vegetation, The combination is consistent with grassland, but the average sporopollen concentration is much lower than that of grassland, with only 5844 grains / g. Like the 137Cs, the sporopollen also accumulates in the upper stratigraphic cycle of each flood depositional cycle and can be used for the differentiation of sedimentary cycles. The average pollen concentration of modern sedimentary cycles is much lower than that of grassland and sloping farmland, which indicates that grassland and sloping farmland are not the main source of sediment. The average concentration of sporopollen in ancient sediments is higher than that of modern sediments, indicating that the vegetation in the basin 300 years ago is better than the present or that the relative sediment yield in the valley 300 years ago is lower than that in modern times. The percentage of cruciferous pollen in ancient sporopollen assemblages is as high as 36.85%, which is significantly higher than the modern level of 58.8%. This indicates that grassland degradation is serious and the proportion of cruciferous plants is drastically reduced. Sporopollen tracer technology has some potential in the aspects of restoration of vegetation environment, sedimentary cycle differentiation, and determination of sediment source. However, spore powder tracing techniques for land use / cover change and erosion and sediment production should be established.