南海中部深海沉积物的~(14)C年龄测定

本文根据南海中部海区17个样品的~(14)C年龄测定结果,叙述了深海沉积物的~(14)C测年方法和步骤;同时对南海中部深海沉积物中生物碳酸盐中的无机碳和有机碳所测定的~(14)C年龄差别进行了讨论。认为南海中部深海沉积物中的无机碳~(14)C年龄偏老于有机碳的~(14)C年龄,但偏老程度不大。认为有机碳的~(14)C年龄是可靠的。     

黄土-古土壤序列14C年代学研究进展

^14C年龄的可靠性在于测年物质的可靠。木质样品被认为是最可靠的测年物质,但在黄土序列中不易发现。最常用的测年物质是有机质,其含量低于2％,并受到农业施肥和现代植物根系渗透的影响,造成^14C年龄偏年轻,本实验室采用新的前处理法能有效地分离年轻污染物。在稳定沉积的古土壤中,孢粉可作为可靠的测年物质。黄土中的蜗牛吸收了不同放射性比度的^14C,如果用于测年能影响年龄的准确性,通常挑选蜗牛文石进行测年。加速器质谱测年技术的运用使得黄土序列^14C年代研究更快捷、更灵敏,但研究重点仍集中在可靠测年物质的选择和提取方法上。     

天目山千亩田泥炭腐殖化度记录的中全新世气候变化

以14C测年为基础,构建了天目山千亩田地区泥炭沼泽剖面年龄-深度模式曲线,通过该区的腐殖化度与烧失量分析研究,发现两者呈现出很好的相关性,共同记录了该地区4 200 aBP以来的气候变化,可划分出3个主要阶段:早期(4 135±40~3 200 aBP)泥炭腐殖化度偏低,指示气候湿热;中期(3 200~630 aBP)泥炭腐殖化度偏高,指示气候温凉偏干;晚期(630 aBP以来),泥炭腐殖化度偏低,气候温凉湿润。     

西沙石岛风成灰岩的ESR和^14C年龄

采用ESR技术测定了西沙石岛风成灰岩地表样品的年龄,进一步证实这些风成灰岩是末次冰期的产物。通过ESR年龄和~(14)C年龄的对比,对于受到现代污染的样品,ESR方法似乎比~(14)C方法要可靠些;此外,对ESR测年中年剂量率的确定及ESR年龄的地质意义也进行了一些讨论。     

稀释技术^14C测年可靠性的研究

稀释技术~(14)C测年的关键在于本底气的稳定,稀释技术测定的最大年限取决于样品的含碳量。同一样品无机碳部分和有机碳部分的对比实验和不同测年方法的对比实验,都证明稀释技术测定的~(14)C年龄不但复现性好而且可靠。     

中国东南入海河流沉积物的稀土元素地球化学特征

系统采集了浙闽三条中小河流的代表性表层沉积物和悬浮物样品,用1N盐酸淋滤样品,研究稀土元素(REE)在酸溶及酸不溶相态中的组成特征。浙闽河流沉积物酸溶组分中的REE在总REE中的占比可达32%~82%,其中Fe-Mn氧化物和黏土矿物吸附态是细粒沉积物酸溶组分REE的主要赋存形式。浙闽河流沉积物酸溶组分的REE组成反映其遭受化学风化的信息;酸不溶组分主要由硅酸盐造岩矿物和稳定副矿物组成,尤其是锆石对REE组成有重要贡献。酸不溶相REE组成揭示,当地流域风化物质与潮流作用带入的长江源细颗粒是浙闽河口沉积物的主要来源。REE在风化及水动力分选过程中会发生分异,使得沉积物全岩组成不直接继承其源岩的REE组成特征,运用于物源判别时候需要慎重。中国东南河流沉积物显示Gd异常,这不是人类活动引起的Gd输入所致,而只反映中国东部物质的组成特征。     

红树植物红海榄叶化学组成研究

对红树植物红海榄叶的基本化学成分水分,灰分,灰分中酸不溶物,灰分中S(SO42-),粗蛋白,粗脂肪等及氨基酸和微量元素的组成和含量进行了系统的分析测定。其基本化学组成各成分含量分别为:水分(69.18%),灰分(3.04%),灰分中酸不溶物(0.094%),灰分中S(SO42-)(0.052%),粗脂肪(7.75%),粗蛋白(7.14%);测得了红海榄叶中17种氨基酸,其总含量为10.7mg/g,其中人体必须氨基酸有7种,占所含氨基酸总量约26%;采用全谱直读等离子体原子发射光谱仪对红海榄叶进行了31种微量元素的分析测定,测得了其中18种元素的含量,红海榄叶中含有丰富的人体必须的矿物质元素。     

~(14)C测年常规方法的小苯量测量——用FH-1915低本底液体闪烁计数器试验

本文报道了常规方法小苯量~(14)C测年试验结果,说明利用国产FH-1915低本底液体闪烁计数器对0.5ml左右的样苯进行~(14)C年代测定,其结果能满足地质年代学要求,从而为样品量少或含碳量低的样品进行~(14)C测年提供了可能性。     

浙江沿海~(14)C测年与全新世以来的海平面变化

本文对浙江沿海所采集的40个泥炭、贝壳、海滩岩、木头、淤泥和粘土样品进行了~(14)C年代测定。根据测定结果对浙江沿海全新世以来海平面的变化和全新世底界的年代进行初步讨论。     

西沙群岛珊瑚礁测年与解析

采用~(14)C、~(230)Th/~(234)U和电子自旋共振(ESR)等多种测年方法对西沙群岛珊瑚礁的年龄进行了对比研究,发现不同测年方法得到的年龄差别很大。应用不同测年方法的原理对年龄进行了解析,结合珊瑚礁的矿物组成,推算出石岛珊瑚礁样品的原生珊瑚形成时间约为30 000 aBP;在6 000～7 000 aBP,随着海平面的下降,珊瑚矿物组分开始发生变化,并在约5 000 aBP通过碳酸盐胶结形成较为致密的珊瑚礁。本研究解释了测年方法不同得出的年龄不一致的问题,为今后珊瑚礁测年研究提供了一种较为合理的解决思路。     

The occurrence of high molecular weight humic material in recent organic-rich sediment from the Namibian shelf

The molecular size distribution of humic substances has been investigated in two recent sediment samples of different ages taken from a single core sample collected off Walvis Bay, south-west Africa. Extractable humic acids were found to be by far the major form of organic carbon in both sediments, the near-surface younger sample containing predominantly high molecular weight (>100 000 molecular weight) humic acids and little fulvic acids whilst the deeper, older sample contained relatively less humic acid and relatively more fulvic acid of a range of molecular weights. A significant age difference was found between the >300 000 molecular weight and the <30 000 molecular weight fractions of the near-surface sample, the lower molecular weight fraction being older than the higher molecular weight fraction.The data suggest that in this rapidly accumulating, organic-rich sediment the first step en route from the planktonic matter to the humic complexes is direct and rapid incorporation of the biogenic material into high molecular weight humic acids.     

HUMIC SUBSTANCES IN SEDIMENTS

In this paper the chemical characteristics of humic substances (humic acid and fulvic acid) from East China Sea surficial sediment are studied through combination of chemical and physical methods. Results show that humic acids have less aromatic hydrocarbon and more alkane structure.The contents of amino acids from hydrolyzate of humic substances are different. The amount of various amino acids (such as acidic, neutral or basic amino aicd) of fulvic acid is higher than that of humic acid. The distribution order of amino acid abundance in various kinds of sediments is neutral amino acid>aromatic amino acid> basic amino acid.In addition, mathematical statistic method is also used to study their distribution. All samples show similar regularities, i. e., the contents of glycine, alanine, aspartic and glutamic are very high and those of cystine and methionine are very low or even disappear.The above results further confirm that humic acid and fulvic acid have similar composition and structure.     

Chemical characterization of humic substances isolated from mangrove swamp sediments: The Qinglan area of Hainan Island,China

In order to improve the understanding of structural and reactive features of sediment organic matter from mangrove swamp as well as evaluate the relationship between such features and the impact from different sources (marine and terrestrial), humic and fulvic acids were isolated from two mangrove swamp sediments located in the Qinglan harbors on Hainan Island, China. One is a forest surface sediment site (WWM2), and the other is an estuary subaqueous sediment site (BMW). The humic and fulvic acids were characterized and compared using chemical and spectroscopic methods, including elemental analysis, thermogravimetric analysis (TGA), Fourier Transformed Infrared Spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C NMR) and potentiometric titrations. The results indicated that there were less aliphatic compounds but more aromatic compounds and oxygen-containing functional groups in fulvic acids. Humic acids contained more long-chain hydrocarbons and nitrogen compounds. Comparison of the C/N ratios and δ¹³C values for the humic substances at both sites indicated a larger marine and/or microbial contribution to the BMW site. Humic substances at the WWM2 site have more acidic functional groups than those of the BMW site. Compared to the literature, more phenolic groups existed in the samples of both sites, which may be due to the autochthonous contribution of mangrove plants.     

Sedimentary humic substances in the northern Adriatic sea (Mediterranean sea)

Humic compounds were determined in sediments collected in an area of the Adriatic sea receiving fresh waters from the river Po. Sediment cores (10 cm) were sectioned into four layers which were analysed separately for redox potential (Eh), total phosphorus (TP), total organic carbon (TOC), humic (HA) and fulvic acid (FA) content. The structure of HA and FA was also investigated. The results showed that the TOC and TP content decreased from the coast to the open-sea stations. Humic and fulvic acid concentrations were also inversely correlated to the distance from the coast. Moreover, the humic and fulvic acids were closely correlated to the total organic content and to the total phosphorus content. The correlations found between humic substances (HS) and TOC and TP, respectively, could be explained both by an in situ formation due to the high content of nutrients and organic matter, and by a common source of HS, TOC and TP, namely the River Po discharge. The predominant presence of aliphatic carbon in the humic structures, the low degree of substitution and the high nitrogen content suggest that primarily humified compounds were formed in situ. Nevertheless, the River Po can act both as supplier of organic matter of which decomposition products lead to the formation of humic compound and as carrier of humified compounds.     

冲绳海槽沉积物干酪根特征

本文采用元素分析、镜下观察、红外光谱、扫描电镜和热解分析等技术,分析了冲绳海槽柱状样中腐植酸、富里酸和干酪根的化学、物理特征,并探讨了它们之间的成因关系和干酪根类型。沉积物的产烃能力甚差,每吨沉积物仅能生成0.49～1.18kg烃类物质。     

Cadmium, copper, and zinc interactions with marine humus as a function of ligand structure

The interactions in seawater of cadmium, copper, and zinc with natural levels of marine humus (fulvic and humic acids) were studied using differential pulse anodic stripping voltammetry (DPASV). Interactions with Cu were also examined by ultraviolet spectrophotometry. The degree of interaction relates to the structure of the particular fulvic or humic acid tested. Marine fulvic and humic acids with different equivalent weights and varying degrees of aromaticity and heteroatom substitution were tested to assess the relative importance of these fundamental structural features in determining the degree of interaction. An index of heteroatom substitution, derived from proton magnetic resonance spectra of these materials, when combined with equivalent weights correlated with the nature and degree of metal interaction. Both marine fulvic and humic acids appreciably interacted with Zn. In contrast, the extent of interaction of fulvic acids with Cu appears to be related to their structure while humic acids appear to interact with Cu regardless of structure. Cadmium interacts only with mature, highly crosslinked humic acids.     

Molecular weight and trace metal distributions in fulvic and humic acid fractions of coastal marine sediments

Molecular weight and trace metal distributions of fulvic and humic acid fractions of marine sediments from the Seto Inland Sea were investigated by using a gel filtration technique in combination with atomic absorption and emission spectrometries. A binary molecular weight distribution was found both in the fulvic acid fraction and in the humic acid fraction. The fulvic acid fractions with molecular weights of less than 1.5×10³ and of 5×10³?10⁴ accounted for 38–57 % and 25–41 % of the total fulvic acids, respectively, and the humic acid fractions with molecular weights of 10²?10⁴ and of over 2×10⁵ accounted for 58–73 % and 16–27 % of the total humic acids, respectively. The components with molecular weights of over 1.5×10³ contained 54 %, on average, of the Fe, Zn and Cu in the fulvic acid fraction, and the components with molecular weights of over 10⁴ contained 58 %, on average, of these metals in the humic acid fraction.     

Characterization of humic and fulvic acids isolated from marine sediments of Sagami and Suruga Bays with C-13 and proton nuclear magnetic resonance

The C-13 and proton NMR spectra of marine humic and fulvic acids isolated from sediments of Sagami and Suruga Bays and Aldrich humic acid were obtained using pulse Fourier transform mode. The C-13 and proton NMR spectra, which clarified the differences in chemical characteristics among the various humic substances, showed that the marine humic acids had more aliphatic and less aromatic character than the Aldrich humic acid, and the marine fulvic acids had polysaccharide-like character. The C-13 NMR spectra of the marine humic substances, in particular, had many relatively well-resolved peaks with significant intensities, indicating the presence of variously bonded carbon atoms in them.     

沙漠黄土边界带湖相沉积糜地湾剖面红外释光测年

通过对糜地湾剖南红外释光测年结果与^14C测年结果（校正年代）比较，认为红外释光测年方法应用于沙漠黄土边界带湖相沉积物的年代测定可取得理想结果。 介绍了适合红外释光测年的粗颗粒钾长石矿物的分离，对粗颗粒钾长石红外释光信号的光晒退、残留信号和回授等性质作了初步研究，对测量等效剂量和附加剂量法和再生法进行了比较，同时还介绍了中国科学院黄土与第四纪地质国家重点实验室释光测年实验室从样品采集开始到年代值计算的整个测年实验流程。     

Carbohydrates in humic and fulvic acids from Hiroshima Bay sediments

A core of 75 cm length from Hiroshima Bay, Seto Inland Sea in Japan, has been analyzed for the carbohydrate content of the humic and fulvic acids. These carbohydrates were found by gel filtration to be in the high molecular weight range. Carbohydrates were more abundant in fulvic acids than in humic acids. A comparison of carbohydrates in humic acids with those in fulvic acids showed that the former did not undergo diagenetic loss any faster than the latter. Identification of most alditol acetate in monosaccharides is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. However, the compositional differences between carbohydrates in humic and fulvic acids were greater in the top section of 0–20 cm than in the 50–70 cm section. The processes which produce the humic-acid carbohydrates are operative either prior to or shortly after deposition.