Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern China

~~Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern China1. Dorale, J. A., Edward, R. L., Ito, E. et al., Climate and vegetation history of mid-continent from 75 to 25 ka: A speleothem record from Crevice Cave, Missouri, USA, Science, 1998, 282(5395): 1871-1874. 2. Li, B., Yuan, D., Qin, J. et al., Oxygen and carbon isotopic char- acteristics of rainwater, drip water and present speleofhems in a cave in Guilin area, and thei…     

Calibration of decomposition of serine to alanine in Bithynia opercula as a quantitative dating technique for Middle and Late Pleistocene sites in Britain

The concentration ratio of the amino acids alanine and serine in calcite opercula of freshwater gastropods of genus Bithynia has been assessed as an age proxy for British Middle and Late Pleistocene sites. Due to decomposition of peptide-bound serine within intra-crystalline protein molecules, alanine/serine ratios increase with sample age, enabling resolution of the marine oxygen-isotope stage of almost all sites and substage resolution for some sites. However, slight overlaps are evident in alanine/serine ratios between some sites from late in one temperate stage and early in the next; this effect results from the low decomposition rates during cold stages, combined with an evident slight dependence of decomposition rates on site conditions. The technique, which can be extended to the Early Pleistocene without technical refinements, is amenable to quantitative calibration using a first-order rate equation, making it feasible in future to present results as numerical ages, subject to an assumed temperature history. Most Pleistocene sites investigated are shown using this technique to have the same ages as previously deduced using biostratigraphy. However, the serine–alanine ages obtained preclude glaciation of southeast England during MIS 16 or of central England during MIS 10.     

The determination of the D/H ratio of non-exchangeable hydrogen in cellulose extracted from aquatic and land plants

A method has been developed for the analysis of D/H ratios of non-exchangeable hydrogen in plant cellulose. Plant samples are nitrated at low temperature and pure cellulose nitrate is extracted by acetone dissolution. Tests of this nitrated product have demonstrated that the nitration-extraction procedure eliminates the OH hydrogen and does not alter the D/H ratio of the cellulose carbon-bound hydrogen. Significant differences exist between δD values of plant total hydrogen and δD values of cellulose nitrate hydrogen. This difference is due to the effect of chemical heterogeneity of the δD value of plant material. Plant-extracted cellulose nitrate D/H ratios are systematically related to the D/H ratios of the associated environmental water. The overall relationship is linear with slope of one and intercept of ?22%. Five aquatic plants which grew at 16–17°C are related isotopically to the water by a linear curve with a slope of 1 and intercept of ?36%. Three plants which grew at 28–29°C have an intercept of ?11%. The general dependence of plant cellulose non-exchangeable hydrogen D/H ratios on the D/H ratios of the associated environmental water suggests that variations of the extracted cellulose nitrate δD values of plants can be used as indicators of climatic change.     

Enzymatic release of amino acids from different humic substances

Humic substances isolated from water, sediment, and soil were characterized by applying elemental analysis, spectroscopic analysis, and gelchromatographic molecular size distribution. In addition, the amounts and pattern of enzymatically released amino acids were determined. Depending on the origin of the humic substances, the percentage of released amino acid nitrogen related to the total nitrogen was in the range of 0.4 to 26.7%. The samples particularly differed in the content of leucine und tyrosine. The total amount of released amino acids was compared with the results obtained from the other characterization methods. This approach indicated that humic substances with a high content of hydrolysable amino acids had high N/C and O/C ratios and low molecular sizes. Beside this, the absorption of these substances in the UV and visible wavelength range was quite low, while the measured ratios of SAK(254)/SAK(436) showed high values. This work leads to the conclusion that the extent of enzymatically releasable amino acids is not only dependant on the nitrogen content of humic substances. Other physical and chemical properties have to be considered for the understanding of the results obtained by the described biochemical characterization method.     

Composition and sources of organic matter and its solvent extractable components in surface sediments of a bay under serious anthropogenic influences: Daya Bay, China

Organic matter of nine surface sediments from the Daya Bay was Soxhlet-extracted with a mixture of 2:1 (v/v) dichloromethane-methanol and separated into five fractions: non-aromatic hydrocarbons, aromatic hydrocarbons, ketones, alcohols, and fatty acids and asphaltenes, and analyzed to determine their bulk and biomarker composition. Marine autogenic input appears to be a major source of organic matter. Generally, non-aromatic hydrocarbons are the most dominant fraction of solvent-extractable organic matter (EOM) followed by the other four fractions in decreasing amounts: fatty acids and asphaltenes, ketones, alcohols and aromatic hydrocarbons. On average, both non-aromatic hydrocarbon fraction and fatty acid and asphaltene fraction account for approximately 40% of EOM. The sources of acyclic methyl ketones, alkanols and fatty acids were examined. For n-alkan-2-ones, allochthonous input is a more important source than marine autogenetic input; the reverse is true for n-fatty acids; for n-alkanols, allochthonous and autogenetic inputs seem comparable. Both n-alkan-2-ones and n-fatty acids in the surface sediments of different areas appear to be derived from common sources.     

Molecular structure of kerogens from source rocks of the Tarim Basin: A study by Py-GC-MS and methylation-Py-GC-MS

Kerogen is the organic matter in sediments that isneither soluble in common organic solvents nor in hy-drous alkaline solvents[1]. It is the most important or-ganic matter on the earth and regarded as the majorsource of natural gas and petroleum. Being the mac-romolecule, kerogen is not readily to be contaminatedby other organic matter. It is the most reliable indige-nous organic matter in sediments[2]. The structure of kerogen is one of the key sub-jects of organic geochemical studies in…     

Carbon isotopic study of individual alcohol compounds in modern sediments from Nansha Islands sea area, China

Carbon isotopic compositions of individual n-alkanols and sterols in modern sediments from the Nansha Islands sea area are measured after derivatization to trimethylsilyl ethers by the new isotopic analytical technique of GC/C/IRMS. The effects of the three added silyl carbon atoms in every alcohol molecule on these compound isotopic compositions and the characteristics of their carbon isotopic compositions are studied. Then their biological sources are discussed using their carbon isotopic compositions. Project supported by the National Natural Science Foundation of China and Project of the Multidisciplinary Oceanographic Expedition of Chinese Academy of Sciences to Nansha Islands.     

The extent of hydrocarbon contamination in the marine environment from a research station in the Antarctic

Low level hydrocarbon contamination is measurable in the vicinity of Antarctic stations, N-alkane and polycyclic aromatic hydrocarbon (PAH) concentrations in seawater and sediment at Signy Station, South Orkney Islands indicated contamination was confined to within a few hundred metres of the station. Total n-alkane concentrations in seawater decreased from 7.6 to 2.6 μg l⁻¹ within 500 m of the station. All n-alkane values in seawater were within the limits of variation for oceanic waters proposed by cripps (1992), although the distribution pattern suggested pollution from the station. The total PAH concentration in seawater varied between 110 and 216 ng l⁻¹. These values showed no trend with distance from the station and were all slightly higher than for the open ocean. The n-alkane and PAH concentations in the surface sediment declined to low levels within 375 m of the station. This indicates that a large proportion of the hydrocarbons entering Factory Cove was deposited from the water column. Sediment n-alkane concentrations were similar at all depths of the cores when collected more than 125 m from the station. PAH levels in the sediment appeared to be due to local input, including a small spill in 1965.     

腾冲火山活动的时代和岩浆来源问题

47个腾冲火山岩样品的K-Ar年龄值域在0.09和17.84Ma之间。4条火山岩的⁴⁰Ar/³⁶Ar-⁴⁰K/³⁶Ar等时线年龄分别为2.93、0.81、0.31和0.13Ma。火山喷发的时代从中新世到更新世,喷发的高潮在晚更新世。腾冲火山目前还不是死火山,而腾冲及其邻区的热事件（侵入-热变质-喷发）又是连续发生的。20个样品的Rb和Sr含量、稳定Sr同位素初始比（0.70578-0.71437）以及其它地球化学资料还表明,这些火山岩是属于板块碰撞带生成的高钾钙碱性岩浆系列。火山岩的母岩浆来源于地幔的玄武岩浆,但在上升过程中受到过富含放射性成因Sr的地壳物质的强烈渐进混染。     

Carbon isotope ratios of C_4 plants in loess areas of North China

Recent stable carbon isotope studies have shown that the occurrence of C4 plants on the Earth was much later than that of C3 plants and there was a global ex-pansion of C4 biomass around 5―8 million years ago[1]. Although far fewer species use the C4 pat…     

Marine87Sr/86Sr ratios from the Jurassic to Pleistocene: evidence from groundwaters in Israel

Oceanic⁸⁷Sr/⁸⁶Sr ratios during Jurassic to Pleistocene have been determined by analysing fresh waters from marine limestone and dolomite aquifers. The results are in good agreement with published data from well preserved fossil material. The⁸⁷Sr/⁸⁶Sr ratios obtained are 0.7070 for Lower to Middle Jurassic, 0.7075 for Late Cretaceous, 0.7080 for Lower to Middle Eocene and 0.7087 for Pleistocene aquifer waters. The value of⁸⁷Sr/⁸⁶Sr for the Eimer and Amend isotopic standard was 0.7082.     

Relationships between bacterial-algal proliferating and mass extinction in the Late Devonian Frasnian-Famennian transition: Enlightening from carbon isotopes and molecular fossils

The five major mass extinctions which occurred in the transition of the Ordovician-Silurian (440 Ma), Late Devonian Frasnian-Famennian (F-F) (370 Ma), Permian-Triassic (250 Ma), Triassic-Jurassic (205 Ma) and Cretaceous-Paleogene (65 Ma) are significant phenomena in the Phanerozoic global environment and organic evolution. Their corresponding extinction rates of marine invertebrate at the level of genus and family are 60% (genus) and 26% (family), 57% and 22%, 82% and 51%, 53% and 22%, …     

Carbon isotopic characteristics and their genetic relationships for individual lipids in plants and sediments from a marsh sedimentary environment

The carbon isotopic compositions of individual lip-ids can provide the genetic information about sedi-mentary lipids so that it has extensively applied pros-pects in geochemically studied field[1―8]. However, this applied research relies heavily on the accumula-tion of studied data in the genetic relationships between carbon isotopic compositions of individual lipids and their biological precursors in different sedi-mentary environments. Recently, the useful δ 13C data of individual lipids f…     

Climate variability recorded by n-alkanes of paleolake sediment in Qaidam Basin on the northeast Tibetan Plateau in late MIS3

Here we combine n-alkanes preserved in a shell bar section from Qarhan paleolake, Qaidam Basin with the other sedimentary proxies to elucidate the lake evolution process during the period 39.7 to 17.5 14C ka BP (calibrated age ranges from 43.5 to 22.4 cal. ka BP). In different stages, the n-alkane homologues exhibited different distribution modes indicative of variations in the surrounding vegetation and the hydrologic condition of the lake. The n-alkanes proxies (CPIh, ACLh, Paq) have the same trends as th...     

Oxygen isotope compositions of quartz grains (4—16μm) from Chinese eolian deposits and their implications for provenance

In recent years, the researches of inland Asia aridification since late Cenozoic have attracted much attention in the paleoclimate community. Rea et al.[1] studied a 12 Ma eolian record in North Pacific and associated it with the aridification of northwes…     

The influence of plants on atmospheric carbon monoxide and dinitrogen oxide

It is shown by laboratory experiments and extensivein-situ measurements that higher plants (Vicia faba, Platanus acerifolia, Fagus silvatica, andPinus silvestris) produce carbon monoxide. The measurements were carried out under natural conditions with respect to the concentrations of O₂ and H₂O, and temperature. The CO₂- and CO-mixing ratios were varied in the ranges 350 to 530 ppm and 3–270 ppb, respectively. The CO-production rates were found to be light dependent with an average value per cm² of leaf area of 3×10^–13 g/sec for a radiation intensity of 5×10⁴ erg/cm² sec. The production rates are independent of the CO₂- and CO-mixing ratios employed in the test atmosphere. Considering the production rate of 3×10^–13 g/cm² sec to be representative for global conditions the total CO-production by plants is estimated to be 0.5–1.0×10¹⁴ g/year. In contrast to carbon monoxide atmospheric dinitrogen oxide is not influenced by plants in the same manner.     

Characteristics and distributions of humic acids in two soil profiles of the southwest China Karst area

Characteristics and distributions of humic acid(HA) and soil organic matter(SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area. The results showed that characteristics and distribution of SOM along the two soil profiles were notably different. Total organic carbon(TOC) contents of soil samples decreased just slightly along the limestone soil profile but sharply along the yellow soil profile. TOCs of the limestone soils were significantly higher than those of the corresponding yellow soils, and C/N ratios of SOMs showed a similar variation trend to that of TOCs, indicating that SOM can be better conserved in the limestone soil than in the yellow soil. The soil humic acids were exhaustively extracted and further fractionated according to their apparent molecular weights using ultrafiltration techniques to explore underlying conservation mechanisms. The result showed that C/N ratios of HAs from different limestone soil layers were relatively stable and that large molecular HA fractions predominated the bulk HA of the top soil, indicating that HA in the limestone profile was protected while bio and chemical degradations were retarded. Combined with organic elements contents and mineral contents of two soils, weconcluded that high calcium contents in limestone soils may play a key role in SOM conservation by forming complexation compounds with HAs or/and enclosing SOMs with hypergene CaCO_3 precipitation.     

闽南沿海晚更新世地层的初步研究

本文对闽南沿海晚更新世沉积的分布特征和主要的地层剖面进行了描述,并根据野外沉积与地貌观察及~(14)、微体古生物与孢粉分析资料,对上述地层与沉积的年代、成因与古气候状况进行了分析与讨论     

Hydrocarbons in coastal sediments from the Mediterranean sea (Gulf of Fos area, France)

Sedimentary hydrocarbons have been studied quantitatively and qualitatively in 11 coastal stations located in the Gulf of Fos (French Mediterranean coast). Hydrocarbon levels ranged from 10 to 260 mg kg(-1) sed. dry weight. A new parameter "NAR" (Natural n-alkane ratio) is proposed to evaluate the contribution of terrestrial inputs of hydrocarbons in the sediments. The origins of hydrocarbons are multiple: terrestrial inputs, biogenic, pyrolytic (industry emissions mainly steel and iron industries, ship and road traffic). Generally, the main source of contamination is not petroleum. Several ratios between parent polycyclic aromatic hydrocarbons show that the sources of hydrocarbons in the sediments are generally much more pyrolytic than petrogenic.     

The characteristics of Quaternary activity of faults in the sea area near the Yangtze River mouth

Introduction As far as the frequency and magnitude are concerned, the earthquakes in the sea area to the east of Shanghai are far more strong than in land area with the largest one in the sea area near the Yangtze River mouth being MS=436, while in land, only MS=434 occurred on Sept. 1, 1624. As a moderately strong earthquake active area, the sea area near the Yangtze River mouth, may cause a potential risk to Shanghai. In 1971 and 1996, earthquakes with MS=5~6 occurred in this area. Geo…