黄土剖面中氧化物的比值和相对淋溶、积聚值在地质上的意义

As have been determined, the ratios of oxides and the contents of CaCO3 show a tendency to increase from bottom to top in Luochuan loess section, whereas an opposite tendency is observed for the relative values of weathering leaching or accumulation of loess, Moreover, the limits of oxide ratios from less to greater than the average value coincide with the boundary between Wucheng and Lishi loess strata, as well as with the boundary of magnetic polarity reversal. The ratios of oxides and the variations of relative weathering-leaching or accumulation extents are synchronous with the fluctuation of CaCO3 contents. From this investigation, it is shown that the ratios of oxides in the superimposed loees and paleosols from the loess profile are found rhythmically varied. These Characteristics might be explained by the hypothesis of repeated climatic fluctuation from dry (loess) to humid (paleosol) during the Quaternary period.     

Geochemical Characteristics and Sedimentary Environment of the Salawusu Section

The chemical compositions of and the contents of CaCO3, free Fe2O3 and REE in the sediments of the Salawusu section have been analyzed to investigate the geochemical features of different sedimentary facies and explore their sedimentary enironmetnts during the Late Pleistocene.The con-tents of CaCO3, free Fe2O3 and ∑REE in lacustrine deposits of the middle part of the section are higher than those in the other parts ,except SiO2 which shows an opposite trend.According to the distribution characteristics of the components mentioned above, the section may be divided into four parts which are equivalent to those divided in terms of lithologic characters and sedimentary facies.More remarkable characteristics were observed with respect to the distribution of CaCO3, free Fe2O3,∑REE and SiO2/Al2O3 and FeO/Fe2O3 ratios, which can be adopted as the geochemical indices for paleoclimate division.From the above, four paleoclimate stages have been distinguished for the deposition process.The first stage ,dated at 0.20-0.15Ma, is characterized by a dry and cold climate,the second stage, ranging from 0.15 to 0.07 Ma ,by a warm and slightly dry climate,the third stage ,about 0.07-0.01Ma ,by a cold and humid climate;and prevailing in the last ten thorsand years is the fourth stage,with the climate changing graduall from warm-humid to warm-dry.     

黄土中铁的形态分布及其组合特征研究

通过对采自陕西各地马兰黄土上部样品中８种形态铁和全铁含量以及碳酸盐、有机质、ｐＨ等有关因素分析,发现黄土中不同形态铁的含量差异很大。其中铝硅酸盐矿物铁、晶形铁和无定形铁是黄土中铁的主要存在形态,三者的含量合计可占全铁量的９９．８％以上,其余代换态铁、松结有机铁、碳酸盐结合铁、氧化锰结合铁和紧结有机铁５者的含量合计不到全铁量的０．２％。黄土各形态铁的含量变化具有同步消长特征,而全铁含量是各形态铁含量的主要制约因素,在区域上黄土碳酸盐和全铁含量的极显著正相关关系主要与颗粒和矿物成分的变化有关,黄土有机质的积累过程不但有益于有机结合铁形成,同时亦有益于其他各形态铁以及全铁富集,而黄土的碱化作用过程不利于铁的形态分异。     

磁黄铁矿催化分解苯酚反应动力学及其产物特征

本文用批量实验法研究了天然磁黄铁矿在过氧化氢参与下催化分解苯酚的动力学反应。结果表明,在pH=3.81～5.88时,苯酚都可被有效的分解,分解速率k=4.0～212h-1(g/L)-1,高于氧化铁矿物类催化剂,可与Fenton试剂相比拟。同时它具有反应速率可控、催化剂与反应产物易于分离和回收等优点。对反应液中Fe(II)、Fe(Ⅲ)浓度和紫外光谱分析表明,反应过程与Fenton反应类似,苯酚先是被快速转化成多酚类化合物,接着被分解成羧酸类化合物。溶液pH不同,产物不同,总有机碳(TOC)矿化率也不同,一般可达50%～58%。     

铅在高岭石表面的吸附模式

采用表面络合模式,研究了高岭石表面的酸碱性质以及高岭石表面对铅的吸附行为。结果表明,高岭石表面在不同ｐＨ条件下对质子和铅离子的吸附反应可以用单一表面基团、无静电表面络合模式来描述。高岭石表面酸度常数拟合值分别为ｐＫａ１＝２．７５和ｐＫａ２＝５．５２,电荷零点ｐＨｚｐｃ＝４．１铅在高岭石表面的吸附量随ｐＨ值的升高而增加,吸附铅的两种表面化合态〉ＳＯＰｂ＾＋和〉ＳＯＰｂＯＨ的浓度也随ｐＨ值的变化而变化     

铜(Ⅱ)在高岭石表面的吸附

在天然水体系中,铜、铅、镉等重金属元素的形态分布、迁移、归宿和生物有效性强烈取决于重金属元素在水体颗粒物表面的分配趋势.本文对铜(Ⅱ)在常见的重要粘土矿物--高岭石表面的吸附进行了实验和模式研究,结果表明,在同时考虑自由水合离子CU2+和羟基金属离子CuOH+与高岭石表面络合的情况下,单一表面基团、无静电表面络合模式能很好地描述铜(Ⅱ)的吸附行为.拟合得到的CuoH+的络合常数比Cu2+的大得多. 铜(Ⅱ)在高岭石表面的吸附量随pH值的升高而增加.吸附铜的两种表面化合态,>SOCu+和>SOCuOH的浓度在实验的pH范围内,也随pH值升高而增加,并且以>SOCu+为主.     

第四纪沉积地球化学研究的若干进展

第四纪沉积地球化学是研究第四纪时期化学元素及其同位素在地壳中的分布与演化规律的科学。它着重研究元素及其同位素在不同成因类型的第四纪沉积物中分市、分配、迁移和富集的规律。距今2—3Ma以来的第四纪是地球历史的最新篇章。第四纪沉积物作为第四纪地质过程在特定的地质环境中所形成的产物,留下了许多自然环境变迁的遗迹,含有它们形     

The Paleoclimatic Variation Records of Carbonate and Iron Oxides in the Weinan Loess Section

The contents and distributions of CaCO3,Fe2O3.FeO and free Fe2O3 in the Weinan loess section of Shaanxi Province of China were investigated through dense sampling.The results show that the contents of CaCO3 and the ration of Fe2O3/FeO may be chosen as proxy in dices for the precipitation and temperature changes in the formation time of the strata,respectively.According to these geochemical indices,six stages of plaeoclimate evolution are proposed in this region since 142 ka B.P.,and secondary climate changes are discussed as well based on the curves of geochemical indices.     

末次间冰期以来渭南黄土剖面地球化学指标所反映的古气候变化

渭南剖面由全新世土壤Ｓ０，末次冰期黄土Ｌ１及末次间期古土壤Ｓ１和组成。其中，Ｌ１可以进一步划分为三层黄土和两层弱发育的土壤；Ｓ１由三层土壤组成。碳酸盐，游离铁及有机质含旺在渭南剖面上的变化表明上述化学成分可以用作缺气候的替代性指标，并能反映古气候的变化。