湿碱消解-等离子体发射光谱法测定海洋沉积物中的生物硅

利用湿碱式化学提取技术和电感耦合等离子体发射光谱仪,优化样品碱式消解方法,确定仪器最佳工作条件,建立了测定海洋沉积物中不同含量级别生物硅的方法。结果表明,仪器检出限为0.724μmol/L,方法检出限为0.942μmol/L。用于测定硅酸盐-硅溶液成分分析国家一级标准物质(GBW08648和GBW 08649,标准值分别为50.0μmol/L和100.0μmol/L),测定值分别为(49.888±0.275)μmol/L、(99.578±0.651)μmol/L,相对标准偏差为0.443%、0.527%;对于不同生物硅含量级别海洋沉积物样品的平行、独立测量,其相对标准偏差8.9%。方法快速、简便、准确,可满足古海洋学不同时空尺度气候和环境分析的应用。     

The role of diagenetic carbonate concretions in the preservation of the original sedimentary record

The Upper Cretaceous organic rich limestones and marls of the Tarfaya basin of southwest Morocco contain numerous calcite concretions, which formed during early diagenesis. Relative textural similarities are observed both in the concretions and in the host sediments. However, the biological content of the concretions is considerably higher than in the host marls and limestones. Evidence for fossil dissolution in the host marls, and the absence of concretions in some fossil-rich zones, suggest that the difference in fossil abundance between the concretions and host rock is a function of dissolution, rather than preferential precipitation in fossil-rich areas. Consequently, the carbonate concretions appear to represent the 'memory' of the sediment and allow quantification of the original biological components and are potential tools for estimating the original biological material deposited in the soft sediments.     

Preliminary paleolimnological study of rocha lagoon, SE Uruguay

Physical, chemical and biological data from a sedimentary profile of Rocha lagoon (Uruguay) are presented. Analyses of silica remains showed that opal phytoliths, diatoms, sponge spicules and chrysophyte cysts were the most important contributors to biogenic silica. Organic matter, total nitrogen and total phosphorus were used to infer past trophic development. Physical analysis of sediments allowed us to identify five lithological units related to sea level variation and climatic events.     

川北高燕锰矿的锰质岩类型和生物成矿作用

川北高燕陡山沱组锰矿的锰质岩有四种主要类型：由富藻层和碎屑层组成的叠层石锰质岩，由藻屑，鲕屑组成的藻屑锰质岩和由锰质内碎屑与各种基质组成的内碎屑锰质岩。根据矿层中赋存的大量藻类遗体及其与矿石的密切共生关系来看．生物特别是藻类参与了锰矿的成矿作用。     

Contribution to the atmospheric NH3 budget

The paper deals with recent measurements of NH₃ applying an improved Indophenolblue method after Bertheolot. Aircraft measurements show a marked difference of the absolute concentration of NH₃ between summer and winter. This seasonal difference indicates the effectiveness of biogenic NH₃ sources during the summer months. Quantitative analysis of the source strength of different soils show the influence of the temperature at the ground and of the pH-value of the soil. The main sources of NH₃ are continental, but microbiological activity in the soil alone cannot fully explain the NH₃ flux into the atmosphere.     

Temporal dynamics and productivity of biogenic soil crusts in the central Karakum desert, Turkmenistan

Biogenic soil crusts (BSCs), consisting of different combinations of mosses, lichens, liverworts, fungi and cyanobacteria, are a widespread phenomenon in arid and semi-arid environments. BSCs are found throughout those areas unaffected by grazing and other anthropogenic activities. Current economic conditions in the newly Independent Central Asian States favor the development of BSCs, which may significantly influence plant communities. The data from 40-years of field observations in a protected area in the Karakum Desert, Turkmenistan, together with a sequence of aerial photographs of the same area may contribute to the study of the establishment of BSCs and understanding their role in vegetation communities. The fenced-off Karrykul area can serve as a model for the current processes in the vast desert areas in Central Asia, which are underused due to the financial constraints. It is hypothesized that after some 15 years, the role of BSCs changes from a positive (rehabilitating) effect on the first stages of protection, to a negative effect on the structure and biomass of vegetation communities. Therefore, undergrazing, as well as overgrazing, should be considered as a desertification factor.     

Competition between enzymatic and abiotic reduction of uranium(VI) under iron reducing conditions

Reduction of U(VI) under iron reducing conditions was studied in a model system containing the dissimilatory metal-reducing bacterium Shewanella putrefaciens and colloidal hematite. We focused on the competition between direct enzymatic uranium reduction and abiotic reduction of U(VI) by Fe(II), catalyzed by the hematite surface, at relatively low U(VI) concentrations (< 0.5 μM) compared to the concentrations of ferric iron (> 10 mM). Under these conditions surface catalyzed reduction by Fe(II), which was produced by dissimilatory iron reduction, was the dominant pathway for uranium reduction. Reduction kinetics of U(VI) were identical to those in abiotic controls to which soluble Fe(II) was added. Strong adsorption of U(VI) at the hematite surface apparently favored the abiotic pathway by reducing the availability of U(VI) to the bacteria. In control experiments, lacking either hematite or bacteria, the addition of 45 mM dissolved bicarbonate markedly slowed down U(VI) reduction. The inhibition of enzymatic U(VI) reduction and abiotic, surface catalyzed U(VI) reduction by the bicarbonate amendments is consistent with the formation of aqueous uranyl-carbonate complexes. Surprisingly, however, more U(VI) was reduced when dissolved bicarbonate was added to experimental systems containing both bacteria and hematite. The enhanced U(VI) reduction was attributed to the formation of magnetite, which was observed in experiments. Biogenic magnetite produced as a result of dissimilatory iron reduction may be an important agent of uranium immobilization in natural environments.     

Diatom Paleolimnological Record of Holocene Climatic and Environmental Change in the Altai Mountains, Siberia

The sedimentary diatom records of three shallow lakes in the Altai Mountains, southern Siberia, were examined to assess the nature and timing of Holocene environmental changes. Few paleoenvironmental records, especially reconstructions not based on pollen, have been reported from this region. The lakes differ in elevation, annual precipitation, and catchment vegetation. Diatom assemblages in all lakes were dominated for the entire period of record by small benthic species of Pseudostaurosira Williams & Round, Staurosira Ehrenberg, and Staurosirella Williams & Round. Planktonic taxa only occur in very low abundances (<5%). The most diverse diatom flora was found in Dzhangyskol, which is situated at the lowest elevation within a forested catchment. A lack of detailed information on the ecological preferences of the dominant taxa and the complexity of environmental drivers make direct interpretation of the diatom record difficult. However, other proxies suggest that dramatic shifts in dominance between Staurosira elliptica and Staurosirella pinnata in Grusha Ozero reflect millennial-scale variability in climate. Together, chironomids and diatoms provide evidence of a cooling possibly correlative to the Younger Dryas Stade and subsequent early-Holocene warming consistent with pollen evidence of afforestation, which also is likely linked to increased humidity. By ~6000 cal year BP, the transition to a cooler, more continental climate had begun. The diatom record of Akkol shows significantly less variation in diatom community composition, but biogenic silica accumulation rates, a proxy for diatom productivity, appear to reflect climatic variability driven by insolation trends over the past 8000 years. Long-term variability in Dzhangyskol is not clearly linked to climate.     

Potential deposition of biogenic silica source sediment in the Paleo-Yangtze Grand Underwater Delta estimated with satellite remote sensing

Biogenic silica sediment constitutes one of the critical sources of particle income in the oceans. In this paper, satellite remote sensing of primary production, sinking flux, and molar ratio of Si/C were utilized to elucidate potential biogenic silica sediment in the Paleo-Yangtze Grand Underwater Delta. Primary production retrieval showed that daily primary production in the Paleo-Yangtze Grand Delta was 3.3–10.8?Mt?d^?1, with 5.8?Mt?d^?1 on average. Sinking flux, retrieved with in situ observations and satellite remote sensing, was within the range of 109–657?mg?Cm^?2?d^?1, or about 23% of total primary production, on average. A molar ratio of Si/C of 0.11–0.45 interval was used in the area, for the Paleo-Yangtze Grand Delta was similar to coastal water and affected by many factors. Considering that phytoplankton in the Paleo-Yangtze Grand Underwater Delta is mainly diatom (80% on average), about 0.21–0.88 billion tons of biogenic silica source sediment is produced in the area annually. With the reduction of land source sediment occurring in recent years in the area, biogenic silica sediment may be one of the dominant sediment sources for maintaining the future stability of the Paleo-Yangtze Grand Underwater Delta.     

Natural background and anthropogenic inputs of polycyclic aromatic hydrocarbons (PAH) in sediments of South-Western Barents Sea

Polycyclic aromatic hydrocarbons (PAH) were measured in sediment cores from 13 locations in South-Western Barents Sea as part of a detailed study of the Norwegian seabed under the MAREANO program. The generally low PAH levels found, an average around 200 ng g⁻¹ dry weight for sum PAH, indicate low inputs of petroleum hydrocarbons to the marine environment in the area. Differences in PAH composition and various PAH ratios indicate a natural, mostly petrogenic origin of PAH in sediments from the open sea locations, while the fjord locations show higher pyrogenic PAH contents with an increase towards upper sediment layers, indicating low inputs from human activities. Petrogenic PAH levels increase in deeper sediments at open sea locations, also when normalised to total organic carbon (TOC) contents, suggesting natural leakages of oil-related hydrocarbons in the area.