Navy sonar and cetaceans: just how much does the gun need to smoke before we act?

Cetacean mass stranding events associated with naval mid-frequency sonar use have raised considerable conservation concerns. These strandings have mostly involved beaked whales, with common pathologies, including "bubble lesions" similar to decompression sickness symptoms and acoustic traumas. However, other cetacean species have also stranded coincident with naval exercises. Possible mechanisms for the strandings include a behavioral response that causes deep divers to alter their diving behavior, which then results in decompression sickness-like impacts. Current mitigation measures during military exercises are focused on preventing auditory damage (hearing loss), but there are significant flaws with this approach. Behavioral responses, which occur at lower sound levels than those that cause hearing loss, may be more critical. Thus, mitigation measures should be revised. A growing number of international bodies recognize this issue and have urged increasing scrutiny of sound-producing activities, but many national jurisdictions have resisted calls for increased protection.     

On North Pacific circulation and associated marine debris concentration

Marine debris in the oceanic realm is an ecological concern, and many forms of marine debris negatively affect marine life. Previous observations and modeling results suggest that marine debris occurs in greater concentrations within specific regions in the North Pacific Ocean, such as the Subtropical Convergence Zone and eastern and western "Garbage Patches". Here we review the major circulation patterns and oceanographic convergence zones in the North Pacific, and discuss logical mechanisms for regional marine debris concentration, transport, and retention. We also present examples of meso- and large-scale spatial variability in the North Pacific, and discuss their relationship to marine debris concentration. These include mesoscale features such as eddy fields in the Subtropical Frontal Zone and the Kuroshio Extension Recirculation Gyre, and interannual to decadal climate events such as El Ni?o and the Pacific Decadal Oscillation/North Pacific Gyre Oscillation.     

青海省纳日贡玛斑岩型铜钼矿床成矿岩体的物质来源及成矿背景分析

纳日贡玛斑岩型铜钼矿床是西南三江地区继玉龙特大型斑岩铜矿之后发现的又一大型矿床。在总结矿床地质特征的基础上,对该矿床的含矿斑岩体开展了详细的岩石学,地球化学及S、Ｏ、Pb、Sr同位素等特征的研究,并探讨了成矿意义。结果表明:纳日贡玛成矿斑岩体大部分为高钾钙碱性花岗岩,部分为钾玄岩系花岗岩,Ti、Ta、Yb、Ba等元素亏损,富集Zr,Hf、Rb和轻稀土元素,中低初始锶比值结合铅同位素分析结果表明它们主要来源于青藏高原加厚的下部地壳熔融,具有幔源成分的混染。      

Response of estuarine meio- and macrofauna to in situ bioremediation of oil-contaminated sediment

Numerous studies have demonstrated the efficacy of bioremediation for enhancing oil removal but the ecological effect on shoreline biota is unclear. Therefore, a field experiment was designed at an intertidal sandflat in SW England to assess the effects of nutrient addition to oiled sediments on meio- and macrofauna for a period of up to 45 weeks. Natural assemblages were exposed to different types of experimental treatments (no oil, oil alone, oil treated with slow-release fertiliser or liquid fertiliser). Bioremediation stimulated the microbial population and increased oil biodegradation. This, however, did not result in faster recolonisation rates of fertilised versus non-fertilised oiled sediments. Mild effects of oil and bioremediation treatments on benthic fauna were observed, including short-term shifts in dominance patterns. Decreased abundance of dominant species in the oiled compared to unoiled sediments resulted in significantly higher evenness of benthic assemblages within the first 11 weeks of the experiment.     

Toxicity of 1,4-dichlorobenzene in sediments to juvenile polychaete worms

Investigation of sediment contamination associated with a marine sewage outfall in Victoria (BC, Canada) found elevated concentrations of 1,4-dichlorobenzene (1,4-DCB). Juvenile polychaete worm (Neanthes) growth was significantly reduced at or near the outfall, roughly corresponding to elevated 1,4-DCB concentrations. There are few data on 1,4-DCB toxicity to marine organisms and no published literature on its toxicity to benthic marine organisms. To determine whether reduced polychaete growth (measured as dry weight) was due to 1,4-DCB exposure, a laboratory investigation was conducted. Uncontaminated marine sediment was spiked with 1,4-DCB and juvenile Neanthes were exposed in 20-d sublethal toxicity tests. There were no adverse effects on survival at any test concentration; mean survival was 80–100%. Statistically significant decreases in average dry weight only occurred at the highest 1,4-DCB concentration (19,900 μg/kg, dry weight); this represented a 1,4-DCB concentration more than 10 times higher than previously measured at the outfall (1710 μg/kg, dry weight). There were no adverse effects on survival or dry weight at the range of concentrations previously measured in sediments from the vicinity of the outfall.     

Transmissivity variations in mudstones

Many people in sub-Saharan Africa have to rely on meager water resources within mudstones for their only water supply. Although mudstones have been extensively researched for their low permeability behavior, little research has been undertaken to examine their ability to provide sustainable water supplies. To investigate the factors controlling the occurrence of usable ground water in mudstone environments, an area of Cretaceous mudstones in southeastern Nigeria was studied over a 3 yr period. Transmissivity (T) variations in a range of mudstone environments were studied. The investigations demonstrate that within the top 40 m of mudstones, transmissivity can be sufficient to develop village water supplies (T > 1 m2/d). Transmissivity is controlled by two factors: low-grade metamorphism and the presence of other, subordinate, lithologies within the mudstones. Largely unaltered mudstones (early diagenetic zone), comprising mainly smectite clays, are mostly unfractured and have a low T of < 0.1 m2/d. Mudstones that have undergone limited metamorphism (late diagenetic zone) comprise mixed layered illite/smectite clays, and ground water is found in widely spaced fracture zones (T > 1 m2/d in large fracture zones; T < 0.1 m2/d away from fracture zones). Mudstones that have been further altered and approach the anchizone comprise illite clays, are pervasively fractured, and have the highest transmissivity values (T > 4 m2/d). Dolerite intrusions in unaltered, smectitic mudstones are highly fractured with transmissivity in the range of 1 < T < 60 m2/d. Thin limestone and sandstone layers can also enhance transmissivity sufficiently to provide community water supplies.     

Aliphatic and aromatic hydrocarbons in marine biota and coastal sediments from the Gulf and the Gulf of Oman

The composition and spatial distribution of aliphatic and polycyclic aromatic hydrocarbons (PAHs) were investigated in biota and coastal sediments from four countries surrounding the Gulf (Bahrain, Qatar, United Arab Emirates and Oman). The levels of total petroleum hydrocarbons (TPH), aliphatic unresolved mixture and PAHs in sediments and biota were relatively low compared to world-wide locations reported to be chronically contaminated by oil. Only in the case of the sediments collected near the BAPCO oil refinery in Bahrain, having concentrations of 779 μg g⁻¹ total petroleum hydrocarbon equivalents and 6.6 μg g⁻¹ ∑PAHs, can they be categorized as chronically contaminated. Some evidence of oil contamination was also apparent in sediments and bivalves around Akkah Head and Abu Dhabi in the UAE, and near Mirbat in Oman. Contaminant patterns in sediments and biota indicated that the PAHs were mainly from fossil sources, with the exception of the high PAH concentrations in sediments near the BAPCO refinery that contained substantial concentrations of carcinogenic PAH combustion products.     

地震辐射能对环境应力场的依赖性

用圆盘形位错模式,并认为位错是裂纹尖端的塑性位移,而不是整个断层面上的弹性位移,在时间域内计算了地震破裂释放的地震波总能量 E.结果表明能量正比于地震矩 M0和区域应力场0 的平方,并随破裂速度 vr的增加而增加,即 E M002f(vr).f 是 vr 的增函数.在频率域内,用我们导出的地震定标律公式对震源速度谱的平方进行积分,也同样得到了 EM002的结果.如果0=10MPa,则 E=4.79M0,这个结果与 Vassiliou 和 Kanamori 的结果一致.还计算了地震辐射效率 =5.26%.从地震波能量的分配上看,大部分能量在第一拐角频率 fc1和第三拐角频率 fc3之间,占92.3%.频率 fc1 的能量占3.85%,f>fc3的能量占3.85%.对于矩震级 Mw=6.0的地震,fc38Hz,所以这些地震的绝大部分能量的频率范围都<2Hz.这个现象已被 Vassiliou 和 Kanamori 所证实.上述结果表明,地震释放的能量对区域应力场有强烈的依赖性.      

祁连山与钨矿化有关的花岗岩类的基本特征

在对祁连成矿带与钨矿化有关花岗岩的时空分布、区域地质、地球化学、同位素及其成矿特征等综合分析基础上，初步总结了钨型，钨-钼型和铌-钽-钨型三类花岗岩的特征，侵入时期以加里东期为主，华力西期次之，以I-S为主的复式花岗岩体为钨矿床的形成提供最有利的物源和热源，为进一步寻找大型-超大型钨矿床提供找矿标志和特征提示。