【摘要】 沙漠环境下,风成沉积物可溶盐的组成、分布和成因可为理解地表过程及环境与气候系统间的相互作用提供重要证据。本研究通过对塔克拉玛干、库姆塔格、巴丹吉林和腾格里四大沙漠的风成沙样品的水溶盐研究,提供了中国北方沙漠带风成沙可溶盐的组成、含量、分布的基础数据,并讨论了风成沙可溶盐的来源、地理分布、成因及其对沙漠固碳的环境意义。风成沙可溶盐的含量介于0.05‰～1.86‰之间(平均0.42‰),盐水溶液的pH值介于8.4～9.6之间并与含碳可溶盐组分的含量显著相关,指示了中国北方沙漠风成沙处在土壤积盐的初级阶段,沙漠土壤的碱性环境受无机碳盐的主导。氯化钠和碳酸钠是可溶盐的主要化学组成,在空间分布模式上具有高度的区域一致性和区间递变性。可溶盐含量和组成的空间变化与区域气候参数(降水和温度)有明显的对应关系,并受风成分异作用的影响,而与区域水文地质条件差异显著。经论证,大气沉降过程控制着沙漠风成沙可溶盐的主体来源;土壤含碳无机盐的含量、属性及沙漠固碳潜力,指示中国北方沙漠在未来全球变暖背景下可能对全球碳循环具有潜在贡献。几个二元沉积结构剖面的可溶盐案例分析表明,在应用二元或多元沉积序列的可溶盐指标重建沙漠区域的古环境变化历史时存在不确定性,需要结合沉积学指标的应用。更多还原

【Abstract】 In the desert environment,aeolian-sand soluble salt composition,distribution and formation in modern land surface are critical to understanding the interactions between earth surface processes and environmental and climatic systems.In this study,four large sandy seas in northern China,the Taklamakan,Kumutag,Badanjilin and Tenggeli deserts,were investigated for geochemical variations of soluble salts in aeolian sands in order to(1)provide basic data about the concentrations and chemistries of soluble salts in deserts of northern China and(2)discuss the origins and causes of geographical distribution associated with the significance of atmospheric-carbon fixation in desert environment.The total concentrations of soluble salt in the aeolian sands of four sand seas range between 0.05‰and 1.86‰,with pH ranging between 8.4 and 9.6 and highly correlate to the carbon-bearing salt contents, indicating a primary degree of salt accumulation and alkaline soil conditions controlled principally by inorganic carbon salts in the desert lands of northern China.Sodium chloride and bicarbonate are the major chemical species, existing a highly regional homogeneity and an inter-regional gradation in spatial distribution of chemical composition.The geographical variations in salt content correlate with regional climatic parameters,such as precipitation and temperature,and aeolian-sedimentary differentiation processes,but have weak linkage with regional hydrological conditions,indicating the regional aridity have a significant influence on the soluble salts in aeolian sands.The sedimentation of soluble salts via atmospheric processes,which are closely associated with dry deposition,are the major source of soluble salts in aeolian sands.To a certain extent,the sandy deserts in northern China,as inferred from the carbon-bearing salts and the alkalinity of the sandy soils,appear to have potential to provide a significant contribution to the global carbon cycle during global warming.Case studies from the Taklamakan and Badanjinlin deserts suggest that variations in salt content in sedimentary sequences,interlaid by aeolian and lacustrine sediments,should be interpreted with care for palaeo-environmental changes,and combination of salt with sedimentary proxy is necessary.更多还原