Laser Ablation (U-Th-Sm)/He Dating of Zircons: Analytical Age Bias and its Consequence for Studying Detrital Zircon Populations

The in situ (U-Th-Sm)/He and U/Pb laser-ablation double-dating procedure is a valuable method that can provide a large dataset relatively efficiently in contrast with conventional bulk helium thermochronometry. In this study, we evaluate the potential age error associated with the double ablation procedure and report the in situ (U-Th-Sm)/He double-ablation dating of 249 zircons from the Fish Canyon Tuff locality. With LA-ICP-MS pseudo-depth profiling and 3D numerical modelling, we show that the concentric double-ablation procedure in minerals with U-Th-Sm zoning can generate a significant (U-Th-Sm)/He age error (positive or negative), resulting in over-scattering and/or an offset of the mean age. Pseudo-depth profiling is insufficient to predict the individual age error, partly because of the superimposed ablations. To evaluate the consequence of this inherent bias, we confront a synthetic age distribution to the error expected for U-Th-Sm zoned zircons analysed with double-ablation (U-Th-Sm)/He thermochronometry. As expected, a strong age bias causes the spreading of peak ages, downgrading the original signal. Yet, the throughput of the ablation-based method can allow intra- and inter-sample peak age identification and comparison, and the coupling of (U-Th-Sm)/He and U/Pb ages extends our ability to deconvolute a multimodal age spectrum.     

Mega-RTAs and LDCs: Trade is not for the poor

Various upcoming large regional trade agreements dealing with new generation trade issues and involving the developed, as well as several emerging market developing economies, exclude the Least Developed Countries (LDCs). The LDCs are not strategically important enough for the other players to figure in these agreements. Nonetheless, these have important implications for the LDCs, particularly in terms of loss of preferential market access. Such preferential access, the paper argues, is likely to get confined to the WTO’s multilateral framework in the longer-term leaving LDCs little strategic economic space outside the WTO.     

Changing power relations in the WTO – Why the India–U.S. trade agreement should make us worry more,rather than less,about global trade governance

This review offers a critical reading of the November 2014 India–U.S. trade deal that unblocked an impasse in the World Trade Organization’s (WTO) Doha round and considers what it means for the way we govern global trade. It argues that the agreement, rather than being a ‘victory’ for the developing world or a cause for celebration, may simply reinforce an unfair and problematic system of distributing trade opportunities among WTO members. It may also obscure further the need for a fundamental overhaul of the way global trade is governed. In so doing, the review speaks to broader debates about what happens when ‘rising’ powers replace established states in global institutions in the absence of wider processes of reform; and it adds to growing concerns about the increasing precariousness of least developed countries (LDCs) in international economic regimes.     

南海区多鱼种声学评估工作程序

总结了利用SimradEK50 0声学系统进行了南海区多鱼种资源评估经验 ,介绍了多鱼种声学评估的工作流程 ,包括调查方案制定、声学数据采集、映像分析、积分值分配、资源量的计算方法等关键过程 ,同时及在工作中应该注意的细节。     

Bioaccumulation of polychlorinated biphenyls in mullet fish in a former ship dismantling harbour, a contaminated estuary, and nearby coastal fish farms

This study investigated the bioaccumulation of polychlorinated biphenyls (PCBs) toward mullet fish (Liza macrolepis) living in former PCB contaminated areas, the Ann-Ping harbour and the Er-Jen estuary, and fish farms located near the above two areas in 2003. The PCB body burdens of collected fish samples are proportional to the contamination level of their locations with the following rank order (greatest to least) from the Er-Jen estuary, the Ann-Ping harbour to the fish farms. Concentration of PCBs of the estuarine mullet has been approximately decreased to one-half of the peak concentration of the 1990s. Although the concentration of PCBs in farmed fish inhabiting near the two contaminated areas was greater than the average of those of fish from local fish markets in Taiwan, no particularly great contamination level was observed in their bodies. Using the less chlorinated PCB fraction (triCB + tetraCB)/total PCBs as the indicator of the origins of PCBs, fish near former contaminated areas had greater body burdens of the more chlorinated PCB congeners, while the farmed fish exhibited a PCB pattern more like that known to originate from air–water exchange with less chlorinated PCBs predominating. Although the PCB contamination has been stopped for a decade, the residual contaminants, supposedly existing in soil and sediments, still contribute to the body burden of fish residing in the estuary and the harbour.     

Quantifying the environmental impacts of artisanal fishing gear on Kenya's coral reef ecosystems

The environmental impacts of artisanal fishing gear on coral reef ecosystems were studied in the multi-gear fishery of southern Kenya to evaluate which types of gear have the greatest impact on coral reef biodiversity. The gear types studied were large and small traps, gill nets, beach seines, hand lines and spear guns. Levels of coral damage, proportion of juvenile fish and discards, size and maturity stage at first capture were quantified and compared amongst the gear types. Results indicate that fishers using beach seines, spears and gill nets cause the most direct physical damage to corals. Spear fishers showed the highest number of contacts to live corals per unit catch followed by fishers using gill nets (12.6 ± 1.8 and 5.9 ± 2.0 coral contacts per kg fish caught per trip respectively). Apart from discarding 6.5% of their daily catch in the sea, as it was too small, beach seine fishers also landed the highest percentage of juvenile fish (68.4 ± 15.7%), a proportion significantly higher (p < 0.001) than in any other gear. The size and maturity stage at first capture for 150 of 195 species caught by all gear types was well below the lengths at which they mature. For example, 100% of Lethrinus xanthochilus, 99% of Lethrinus nebulosus and 94% of Lethrinus harak caught were juveniles. Across all gear types, 50.1 ± 22.7% of the catch consisted of juvenile fish, indicating serious growth overfishing. Field assessment of levels of coral density showed that fishing grounds where beach seines were still in use had a significantly lower density than where beach seining was not used. This correlation is likely to arise in part because seines cannot be used in the most coral rich areas, and in part because coral loss is a consequence of seine use. On a per gear basis therefore, beach seines had the most impact on coral reef biodiversity. This study emphasizes the need to enforce restrictions on destructive gear and mesh sizes.     

Transnational linkages and the spillover of environment-efficiency into developing countries

Arguments about the “positive” influence of growing transnational linkages have typically focused on their role in diffusing environmentally superior innovations which help to raise countries’ environment-efficiency. The present article empirically tests these claims by examining whether developing countries’ linkages with more CO₂- and SO₂-efficient economies contribute to domestic improvements in CO₂- and SO₂-efficiency. Our large-N, statistical findings caution against some of the efficiency-oriented optimism voiced by supporters of globalization. Although imports ties with more pollution-efficient countries are found to spillover into improved domestic CO₂- and SO₂-efficiency, neither transnational linkages via exports, inward foreign direct investment (FDI) nor telephone calls appear to have any influence on domestic pollution-efficiency.     

Sediment provenance in a tropical fluvial and marine context by magnetic 'fingerprinting' of transportable sand fractions

The sources and fluxes of sediment to the Great Barrier Reef lagoon from north‐eastern Australian rivers have been the subject of much concern and study, with the large catchments of the Burdekin and Fitzroy Rivers thought to be the key sources at present. Here, the utility of newly developed magnetic ‘fingerprinting’ methods for identifying sediment provenance, both onshore and offshore, and in association with individual large flood events, is investigated. Within the Burdekin catchment, sediments are mobilized from different subcatchments by runoff generated by intense, localized rainfall events. Magnetic measurements were made on untreated and acid‐treated samples of river channel sediments within the Burdekin River subcatchments and from the estuarine and inner shelf depocentres of Burdekin River sediments. The acid treatment removes all discrete magnetic particles and coatings, and leaves magnetic inclusions (protected within host silicate grains) as the basis of the measured magnetic signature of a sample. The magnetic properties of the acid‐treated samples display statistically distinct sediment provenance groupings. Sand samples from the Upper Burdekin River appear magnetically distinct from samples from tributaries of the Burdekin (e.g. Hann Creek, Fanning River) and also from nearby coastal rivers, including the Haughton. Suspended sand samples from a Burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999. Comparisons of the terrestrial, acid‐treated sand fractions with the same, acid‐treated, sand‐size fractions from transects taken offshore suggest that the surface sediments in Upstart Bay and Bowling Green Bay have different sources. Some of these sources are as yet unidentified but may represent the unsampled, lower‐discharge south‐western Burdekin subcatchments, and/or along‐shore drift of sand from the south, perhaps even from the Fitzroy River, over millennial timescales of cyclone pumping. The magnetic inclusion method precludes any obfuscation or confounding of sediment source, which might arise from hydraulic sorting and/or post‐depositional magnetic diagenesis or authigenesis.     

The Great Barrier Reef: a 700 000 year diagenetic history

A deep borehole through Ribbon Reef 5 in the Great Barrier Reef off north‐eastern Australia has identified a variety of cements, including epitaxial, radial prismatic and spherular aragonite, together with blocky, prismatic and fibrous calcite. These cements are discontinuously arranged within the sequence that consists predominantly of grainstones but locally includes clotted muddy and filamentous textures that may be of microbial origin. Calcite cements vary in morphology with groups of crystals that include acute scalenohedral, rhombohedral and flattened concordant terminations; these show varying densities of inclusions that locally define growth zones and in some terminations divide in the manner of ‘split crystals’ to form fibrous fringes. Morphological changes in calcite are inferred to reflect changes in water chemistry and crystal growth rates at the time of growth, allied to their relationship to the palaeo‐water table, and linked in turn to changes in sea‐level. Neomorphism and dissolution are widespread and variations in the severity of both imply response to the degree of undersaturation of pore waters that at times were probably balanced within very narrow limits. A total of 10 depositional units are identified. Those units at the base of the borehole reflect deposition and diagenesis within a marine environment. The influence of meteoric waters, indicated by stable isotopes, is first apparent at the top of Unit 1 and in Unit 2 (184 to 155 m below sea floor). Petrographic evidence of vadose conditions appears at the tops of Unit 3 (131 to 99 m below sea floor). Units 4 to 8, all deposited under marine conditions, provide isotopic evidence of meteoric or mixing‐zone waters and petrographic indicators of vadose conditions, typically at the top of the units. Evidence indicates that in Unit 5 the water table was mobile and Units 6a, 6b, 7 and 8, all characterized by ultraviolet fluorescent cements, are capped by sub‐aerial erosion surfaces. Unit 9 (the Holocene) reflects the recent re‐establishment of marine conditions. The extent of alteration of the entire sequence reflects the substantial and pervasive influence of meteoric waters. This effect is interpreted as a result of a greater rainfall and river flow from the mainland during early and late stages of interstadial periods. The study reflects progress in the ability to recognize the diagenetic signal generated by sea‐level change. However, whereas the isotopic results reflect the changing relationships between vadose and phreatic zones in groundwater systems beneath successive emergent surfaces, their correspondence with petrographic features is expressed only weakly and commonly lacks the systematic sequential overprinting implied by the distribution of cathodoluminescent zones of cements in many ancient limestones.     

Empty marine container logistics: facts,issues and management strategies

With the global container population exceeding 25 million TEU (Twenty-foot Equivalent Unit) and the annual production of new boxes exceeding 3 million TEU it is estimated that around 1.5 million TEU of empty containers are sitting in yards and depots around the world waiting for use. Although utilization rates have improved since 2004, container utilization depends on the very dynamic nature of container transportation, and the container building and leasing industries. Owing primarily to the chronic trend of increasing trade imbalances across the oceans, and despite recent trends along some trade routes, the empty container management problem has become a major issue for the container shipping industry during the last decade. This paper examines and analyzes empty container logistics at a global, interregional, regional and local level. Special consideration is given to key factors affecting the empty container logistics management and strategies implemented by ocean carriers and other stakeholders to better manage empty containers.