内蒙古乌梁素海湖泊沉积物元素地球化学特征及其影响因素

在210Pb同位素测年的基础上,通过对乌梁素海沉积物元素含量的分析,研究了沉积物中元素的变化规律,探讨了沉积物中元素变化的影响因素,结果表明沉积物中Ca、Sr、Cu、Mn、P等元素随深度加深含量下降,其余元素含量随深度加深呈增加的趋势。通过对元素富集系数的变化规律进行研究后,发现Ca、Sr、Cu、Mn、P等元素的富集系数与其含量变化趋势基本相同,反映了该组元素主要受沉积通量的影响;Al、K、Be、Ba、Mg等富集系数与其含量的变化趋势具明显差异,与黏土含量变化一致;而Cr、Fe、Ni、V、Co、Pb、Zn等重金属元素可能受到黏土吸附作用影响。最后,应用有序样品聚类分析方法,对元素这一环境代用指标在研究湖泊历史演化中的作用进行了探讨,研究表明:在湖泊演化过程中,湖泊的形成、20世纪70年代入湖水量的急剧改变以及近年来河套灌区化肥用量逐年加大、大量生活污水和工业废水排入等人类活动的增强等事件,均在湖泊沉积物元素的变化中有所体现。     

乌干达Albert湖凹陷陡坡带成藏模式

乌干达Albert湖凹陷是世界上最年轻的生烃凹陷,至今仍处于断陷伸展阶段,特殊的地质背景使其具有独特油气富集特征。为了预测Albert湖西部陡坡带的勘探潜力,利用地震、钻井等资料开展了凹陷构造特征研究,系统分析了陡坡带石油地质条件和成藏模式。研究表明,板式陡坡带油气侧向运移,成藏条件优越;台阶式陡坡带以垂向运移为主,侧向运移为辅,成藏条件一般。运移和保存是Albert湖陡坡带油气富集的主控因素,西部陡坡带一台阶是有利勘探区带,资源潜力较大。此研究对非洲陆内裂谷油气勘探具有重要的指导作用。     

Geochemical characteristics of the Paleogene shales in the Dongying depression,eastern China

Fluctuations in lacustrine sedimentary environments significantly affect distributions of organic matter (OM), uranium, and other elements in shales. In this study a high-resolution geochemical record of fluctuations in the paleo-depositional environment of a terrestrial lake basin is provided on the basis of extensive samples collected from the Member 3 of the Paleogene Shahejie Formation (Es₃) of the Niu-38 well in the Dongying Depression, Eastern China. These samples were tested for total organic carbon (TOC), element concentrations, and biomarkers to study the evolution and fluctuation in the depositional environments of an ancient lake basin and associated geochemical response. The evolution and fluctuation of the sedimentary environment from a deep lake to a semi-deep lake and then to a shallow lake delta were indicated by geochemical response. During this evolution, the values of TOC, S₁, S₂, Sr, and Ts/(Ts + Tm) remarkably decreased, whereas those of Co, Ni, Rb, Na, Fe/Mn, Fe/(Ca + Mg), and C₂₉ mortane/C₂₉ hopane significantly increased. The deep lake basin shows depositional fluctuations, as indicated by rock lithofacies and their geochemical parameters. A close interrelationship was observed among U concentration, TOC content, and inorganic element content. Uranium concentrations are positively correlated with TOC contents, Ca and Sr concentrations, and Sr/Ba and Ca/Mg ratios but negatively with K, Na, Ba, and Rb contents and Fe/(Ca + Mg) and Fe/Mn ratios. The observed increase in U concentration in the lower Es₃ section is closely related to surface adsorption by clay minerals and OM, together with some replacements of Ca and Sr by U in the shales.     

Microbial diversity in Huguangyan Maar Lake of China revealed by high-throughput sequencing

Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.     

2001-2002年天目湖(沙河水库)浮游植物的生态学研究

2001年6月~2002年5月,对天目湖进行的浮游植物周年调查表明,天目湖共有浮游植物7门75属,其中年平均丰度为5026.20×104个/L,以蓝藻为主,占总丰度的54.45%;而年平均生物量为(15.364±9.103)mg/L,其中硅藻居首位,为6.634 mg/L,占浮游植物年平均生物量的43.18%;其周年变化是丰度和生物量最高值均出现在5月,丰度在5月和9月出现2个峰值,而生物量则在5、7、10月出现3个峰值。浮游植物丰度从大坝处1#点到河流入湖口的9#、10#点变化不明显但略有增加,而生物量则呈明显增加。通过对水温、透明度、营养盐与浮游植物丰度和生物量的线性回归分析发现,浮游植物丰度、生物量与水温、TP存在显著的正相关,而与N/P比、透明度存在显著性负相关,与TN相关性不是很明显。     

Breeding in the freshwater crayfish paranephrops planifrons white

The breeding cycle of female Paranephrops planifrons is described. The incubation of eggs and young takes place between April and December and covers about 25–26 weeks. The winter population contains some apparently adult females which do not breed. The number of eggs laid increases with the size of the parent, and in the population studied varied from some 20 to 30 eggs at 17 mm carapace length to 150 eggs at 30 mm carapace length. After hatching the young pass through two moults while still attached to the parent.     

Larval life span of the echinoid evechinus chloroticus (val.)

Newly metamorphosed Evechinus chloroticus (Val.) were observed in three larval cultures 36, 30, and 28 days after fertilisation, indicating that the free swimming larval life may last about 1 month.     

Distribution and ecology of Nectocarcinus antarcticus and N. bennetti (Brachyura: Portunidae) in the New Zealand region

The distributions of two swimming crabs endemic to the New Zealand region are described, mostly from material obtained at 118 of 2544 New Zealand Oceanographic Institute benthic stations sampled.

Nectocarcinus antarcticus (Jacquinot) was found within the geographic limits 34°S‐51°S and 166° E‐176° W, with concentrations around Cook Strait, the Chatham Rise, Foveaux Strait, and the Auckland Is. N. bennetti (Takeda & Miyake) occurred between 44° S and 53° S, and 165° E and 180°, most frequently in the south and west, on the ‘highs’ of the Campbell Plateau. Although the distributions overlap between 44° S and 51° S, and this overlap zone produced most of the available material, only one joint occurrence of the two species was noted. This apparent separation was not satisfactorily explained by any of the ecological factors recorded. The depth ranges of both species were broadly similar (0–550 m for TV. antarcticus, 20–474 m for JV. bennetti); both were most frequently obtained at depths less than 200 m. Both occurred primarily on the coarser sediment grades, though N. antarcticus occupied a broader range of grades than N. bennetti.

The size ranges of the two species were similar; carapace lengths were 8.0–62.0 mm for N. antarcticus and 5.8–68.0 mm for N. bennetti. The larger specimens of both species were found towards the southern limits of distribution. Larger specimens of N. antarcticus were absent from depths greater than 120 m; smaller N. antarcticus and all N. bennetti occurred throughout their respective depth ranges. Ovigerous N. antarcticus (smallest, 8.8 mm carapace length) were obtained at depths of 17–263 m from May to October; ovigerous N. bennetti (smallest 36.1 mm) were from depths of 150–183 m in May only.     

Role of mean circulation,tides, and waves in the transport of bottom sediment on the New Zealand continental shelf

Evaluation of velocity data on water movements over the New Zealand continental shelf has revealed that the mean circulation by itself is too slow to induce transport of bottom sediments. Tides generally have higher velocities, but are still not the main transporting agent except in the tide‐dominated Cook and Foveaux. Straits. Waves have the potential to stir sediments on the inner and middle shelf (less than about 70 m deep) during annual storms, and probably down to 130 m depth during the maximum 25‐y storm.

For sediment transport to take place, energies of at least two of the major water movements would have to complement one another. Optimum conditions for transport probably occur during storm periods when wave‐suspended sediment is readily moved by tides and the mean circulation.

The direction of transport is mainly along the continental shelf and is largely in response to prevailing weather patterns coincident with the direction of the mean circulation and strongly reinforced by the appropriate phase of the tide.