Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation

Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.     

两个四层钢框架结构缩尺模型侧倾倒塌的预测和验证

总结了数字化预测钢框架结构倒塌和预测精度通过两个4层标准抗弯框架的1∶8缩尺模型的地震模拟器试验得到证实的研究计划。文中论证了以下几点:(1)由于结构框架和地震地面运动的实际综合作用,可能发生侧倾倒塌;(2)P-Δ效应和构件损坏接近倒塌的结构框架的性能起主导作用;(3)只要构件的损坏在分析模型中有足够的代表性,那么就可以用相对简单的分析模型来合理地预测结构的倒塌;(4)接近倒塌的框架体系对于框架中每个重要构件所经历的受力过程非常敏感,意味着通常用于构件试验的对称循环加载过程并不能为模拟接近倒塌的损坏提供足够的信息。     

The effectiveness of double hulls in reducing vessel-accident oil spillage

While much work has been done in investigating determinants of oil spillage attributed to vessel accidents, little research has been conducted on the effectiveness of ship hull design in reducing marine pollution. This paper addresses whether the double-hull requirement reduces vessel-accident oil spillage. The volume of oil spillage due to oil-cargo vessel accidents was investigated using tobit regressions and an empirical data set of individual vessel accident pollution incidents investigated by the US Coast Guard from 2001 to 2008. The results indicate that the double hull design on average reduces the size of oil spills by 20% and 62% in tank barge and tanker ship accidents, respectively.     

利用变形河流阶地限定帕米尔北缘木什背斜的缩短、隆升和侧向扩展

位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发育数级开阔平坦的沿轴向展布的河流阶地,阶地可划分为4期。利用阶地堆积细颗粒石英光释光测年获得阶地面T2a、T3和T4的形成年龄分别为(15.8±2.40)ka、(55.1±10.3)ka、(131.4±23.9)ka。伴随背斜的生长扩展,河流阶地面发生了横向和纵向掀斜,并形成断层陡坎和褶皱陡坎。木什背斜晚第四纪的缩短和隆升主要是通过褶皱翼旋转机制进行的,估算其最小缩短速率为(1.6±0.3)mm/a,最小隆升速率为(1.9±0.3)mm/a。与此同时,沿轴向背斜发生了向东的侧向迁移和旋转。根据背斜垂直隆升与侧向扩展之间的关系,估算背斜在131～16ka期间向东的侧向迁移扩展速率较快,为 (14.6±3.6)mm/a; 自16ka至今,侧向迁移扩展速率迅速减小至(1.7±0.3)mm/a,背斜向东的迁移扩展可能已基本停止,而以侧向旋转为主。     

Physical Properties, Morphology and Petrological Characteristics of Pumices from the Central Indian Ocean Basin

About 400 pumice clasts collected from the Central Indian Ocean Basin(CIOB)were studied for their morphology and were classified based on their shape and size.A majority of the samples range between<1 cm and 36 cm and in the Zinggs shape diagram plot in the equant and oblate fields.The Corey Shape Factor for most of the samples is close to 0.7,which is common for volcaniclastic material. The physical properties such as density,specific gravity,void ratio,porosity,moisture content and degree of saturation...     

Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones,South Eastern Desert,Egypt

Granite-hosted,Nb-,Ta-,Sn-,U-,Th-,and Zr(Hf)-bearing mineralization from the Abu Rusheid shear zones occurs about 97 km southwest of the town of Marsa Alam,South Eastern Desert,Egypt.The SSE-trending brittle-ductile Abu Rusheid shear zones crosscut the peralkalic granitic gneisses and cataclastic to mylonitic rocks(mylonite,protomlyonite,and ultramylonite).The northern shear zone varies in width from 1 to 3 m with a strike length of >500 m,and the southern shear zone is 0.5 to 8 m wide and >1 km long.These shear zones locally host less altered lamprophyre and locally sheared granitic aplite-pegmatite dykes.The rare-metal minerals,identified from the peralkalic granitic gneisses and cataclastic to mylonitic rocks are associated with muscovite,chlorite,quartz,fluorite,pyrite,magnetite,and rare biotite that are restricted to the Abu Rusheid shear zones;these are columbite-tantalite and pyrochlore(var.betafite) in the northern shear zone and ferrocolumbite in the southern shear zone.Cassiterite occurs as inclusions in the columbite-tantalite minerals.U-and Th-minerals(uraninite,thorite,uranothorite,ishikawaite,and cheralite) and Hf-rich zircon coexist.Magmatic(?) zircon contains numerous inclusions of rutile,fluorite,U-Th and REE minerals,such as uranothorite,cheralite,monazite,and xenotime.Compositional variations in Ta/(Ta+Nb) and Mn/(Mn+Fe) in columbite range from 0.07-0.42 and 0.04-0.33,respectively,and Hf contents in zircon from 1.92-6.46 of the two mineralized shear zones reflect the extreme degree of magmatic fractionation.Four samples of peralkalic granitic gneisses and cataclastic to mylonitic rocks from the southern shear zone have very low TiO2(0.02 wt%-0.04 wt%),Sr [(15-20)×10-6],and Ba [(47-78)×10-6],with high Fe2O3T(0.94 wt%-1.99 wt%),CaO(0.14 wt%-1.16 wt%),alkalis(9.2 wt%-10.1 wt%),Rb [(369-805)×10-6],Zr [(1033-2261)×10-6],Nb [(371-913)×10-6],U [(51-108)×10-6],Th [(36-110)×10-6],Ta [(38-108)×10-6],Pb [(39-364)×10-6],Zn [(21-424)×10-6],Y [(8-304)×10-6],Hf [(29-157)×10-6],and ∑REE [(64-304)×10-6],especially HREE [(46-167)×10-6].Three samples from the northern shear zone also have very low TiO2(0.03 wt%),Sr [(11-16)×10-6],and Ba [(38-47)×10-6],with high Fe2O3T(1.97 wt%-2.91 wt%),CaO(0.49 wt%-1.01 wt%),alkalis(7.2 wt%-8.3 wt%),Rb [(932-978)×10-6],Zr [(1707-1953)×10-6],Nb [(853-981)×10-6],Ta [(100-112)×10-6],U [(120-752)×10-6],Th [(121-164)×10-6],Pb [(260-2198)×10-6],Zn [(483-1140)×10-6],Y [(8-304)×10-6],Hf [(67-106)×10-6],and ∑REE [(110-231)×10-6],especially HREE [(91-177)×10-6].The very high Rb/Sr(57.5-88.9),and low Zr/Hf(16.9-25.6),Nb/Ta(7.7-9.8),and Th/U(0.21-1.01) are consistent with very frac-tionated fluorine-bearing granitic rocks that were altered and sheared.The field evidence,textural relations,and compositions of the ore minerals suggest that the main mineralizing event was magmatic(629+/-5 Ma,CHIME monazite),with later hydrothermal alteration and local remobilization of the high-field-strength elements.     

Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C

Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.     

Inhibition by polycyclic aromatic hydrocarbons of ATPase activities in Sebastiscus marmoratus larvae: relationship with the development of early life stages

Sebastiscus marmoratus larvae were exposed to waterborne polycyclic aromatic hydrocarbons (PAHs) containing 3-5 rings, benzo[a]pyrene (BaP), pyrene (Py) or phenanthrene (Phe), respectively at 0.01, 0.1 and 1 μg L?1. Cumulative mortality, frequency of dorsal curvature and rate of pericardial and yolk sac edema in larvae treated for 8 days were significantly increased in a dose-dependent manner. All three PAHs resulted in reduction of the lower jaw, and the extent of reduction increased with increasing concentrations of the PAHs. Na+/K+-ATPase and Ca2+-ATPase activity in larvae exposed to the three PAHs were all significantly inhibited in a dose-dependent manner. Analysis using the Pearson correlation coefficient indicated a significant correlation between the rate of the dorsal curvature and edema and the inhibition of Na+/K+-ATPase and Ca2+-ATPase activity, suggesting that the developmental defects caused by PAHs were related to their inhibition of Na+/K+-ATPase and Ca2+-ATPase activity.