Brine evolution in two inland evaporative environments: influence of microbial mats in mineral precipitation

This paper gives new insight into the precipitation sequences in six playa basins that host microbial mats. The study basins are distributed across two evaporitic endorheic drainage systems located in the Central part of Spain with markedly different hydrochemistry and mineralogy. One group, in the north, consists of highly alkaline, brackish to saline lakes containing a high concentration of chloride with dominant carbonate over sulphates. A second group of lakes are mesosaline to hypersaline, with sulphate the dominant anion over chloride. Mineral assemblages identified in both contain several phases that provide evidence for mixed carbonate-sulphate precipitation pathways, in the north, and sulphate-dominated pathways in the south. Regardless of their ionic composition, saline lakes support thin veneers of microbial mats which, by integrating several lines of evidence (hydrochemical and physical analyses, statistical analyses of ions, mineralogical assemblages, textural relationships among mineral phases and microbial mats) are shown to modify the chemical behavior of the evaporitic sediment and promote the formation of carbonates and sulphates from Ca-poor waters with high Mg/Ca ratios. Geochemical changes induced in the environment surrounding the microorganism favor the nucleation of hydrated Mg-carbonates (hydromagnesite and nesquehonite), calcite and dolomite. Simultaneously, the microbial mats provide nucleation sites for gypsum crystals, where they are subjected to episodic stages of growth and dissolution due to saturation indices close to zero. In addition, the bubbles produced by the metabolic activities of microorganisms are shown to promote the precipitation of hydrated Mg-sulphates, despite permanent subsaturation levels. Although common in the studied playa basins, this effect has not been previously reported and is key to understanding sulphate behavior and distribution. Modern and natural evaporitic microbial environments are important analogs for understanding brine evolution and mineral precipitation pathways in shallow water settings that have existed since the Archean on Earth and perhaps on Mars.     

Maritime network dynamics before and after international events

Investigating the influence of international events on global maritime networks is a challenging task that must comprehensively incorporate geographical, political, and maritime sciences. Understanding global maritime network dynamics is an initial and critical step in this investigation. This study proposes an automatic identification system (AIS)-based approach to understanding maritime network dynamics before and after international events. In this approach, a spatiotemporal modeling method is introduced to measure the similarity in shipping trends before and after international events. Then, a spatiotemporal analytic framework is proposed to understand the maritime network dynamics by grouping similar situation, and assessing possible indirect effects within a network. Finally, three case studies of international events, military conflict, lifted economic sanctions, and government elections, were used to investigate the observed network dynamics possibly affected by international events. The results indicate that container, tanker, and bulk shipping between India and its connected countries all declined more than 69% after military conflicts between India and Pakistan in August 2015. Tanker shipping between Iran and the United Arab Emirates increased 51% after economic sanctions on Iran were lifted. Container shipping between Sri Lanka and Singapore, Malaysia, and India increased more than 74% after the general election in Sri Lanka. These investigations demonstrate the feasibility of the proposed approach in assessing the possible effects of international events on maritime network dynamics.     

Regional differentiation of ecological conservation and its zonal suitability at the county level in China

China’s investments, financial incentives and deductions in terms of ecological conservation are based at the county level. Therefore, the monitoring and assessment of the effects of ecological conservation at the county level is important to provide a scientific basis for the assessment of the ecological and environmental quality at the county scale. This paper quantitatively estimated the dynamics of high-quality ecosystems and vegetation coverage over the past 15 years, and their relationships with the number of ecological conservation programs at the county level were analyzed. Then, the effects of ecological conservation measures on ecological changes at the county level and their regional suitability were assessed and discussed. The results showed that counties with a percentage of high-quality ecosystems greater than 50% were primarily distributed in northeastern China, southern subtropical China and the southeastern Qinghai-Tibet Plateau, and those with a percentage lower than 20% were mostly distributed in northwestern China, the southwestern karst region and the North China Plain. In recent decades, ecological conservation has focused on ecologically fragile regions; more than five ecological conservation programs have been implemented in most counties of the Three River Source Region in Qinghai Province, southeastern Tibet, western Sichuan, the Qilian Mountains, southern Xinjiang and other western regions, while only one or zero have been implemented in the eastern coastal area of China. Over the past 15 years, the proportional area of high-quality ecosystems has increased in approximately 53% of counties. The vegetation coverage of counties in the Loess Plateau, Huang-Huai-Hai Plain, Beijing-Tianjin-Hebei (Jing-Jin-Ji), Sichuan-Guizhou-Chongqing, and Guangdong-Guangxi provincial-level areas has increased significantly. However, it decreased in northern Xinjiang, central Tibet, central and eastern Inner Mongolia, the Yangtze River Delta and other regions. The relationships between the numbers of ecological conservation programs and the indicators of ecosystem restoration response, such as high-quality ecosystem and vegetation coverage, do not show positive correlations. These results suggest that ecological conservation programs should be planned and implemented according to the distribution patterns of high-quality ecosystems and that restoration measures such as afforestation should follow natural principles and regional differentiation under the background of climate change.     

China’s Belt and Road Initiative in Support of the Resourcing Future Generations Program

The Resourcing Future Generations (RFG) program is a global strategy proposed by the International Union of Geological Sciences to meet global demand for natural resources. The Belt and Road (B&R) initiative of China provides a great opportunity for promoting the RFG across much of the Eurasian continent. The countries covered by the B&R initiative are mostly low-income economies. With rapid developments of economy and infrastructure construction, these countries are set to have huge demands for mineral resources in the future. However, the proven mineral reserves in this region are too limited, and the region’s overall level of metal recycling is far from optimistic. These countries are expected to have obstacles in meeting future demands. However, the regional Tethyan metallogenic domain and Central Asia metallogenic district are key areas for new discoveries of mineral resources, possessing a variety of mineral resources with a positive prospecting potential. The B&R initiative of China provides favorable opportunity for mutual beneficial cooperation to improve regional exploration and prospecting through geological mapping, inter-comparison study on Tethyan metallogenic domain, joint assessment of mineral resource potentials, joint training of geological engineers and workers and building information systems.     

Unresolved Complexity in Assessments of Mineral Resource Depletion and Availability

Considerations of mineral resource availability and depletion form part of a diverse array of sustainable development-oriented studies, across domains such as resource criticality, life cycle assessment and material flow analysis. Given the multidisciplinary nature of these studies, it is important that a common understanding of the complexity and nuances of mineral supply chains be developed. In this paper, we provide a brief overview of these assessment approaches and expand on several areas that are conceptually difficult to account for in these studies. These include the dynamic nature of relationships between reserves, resources, cut-off grades and ore grades; the ability to account for local economic, social and environmental factors when performing global assessments; and the role that technology improvements play in increasing the availability of economically extractable mineral resources. Advancing knowledge in these areas may further enhance the sophistication and interpretation of studies that assess mineral resource depletion or availability.     

Economics,Helium, and the U.S. Federal Helium Reserve: Summary and Outlook

In 2017, disruptions in the global supply of helium reminded consumers, distributors, and policy makers that the global helium supply chain lacks flexibility, and that attempts to increase production from the U.S. Federal Helium Reserve (the FHR) may not be able to compensate for the loss of one of the few major producers in the world. Issues with U.S. and global markets for helium include inelastic demand, economic availability of helium only as a byproduct, only 4–5 major producers, helium’s propensity to escape earth’s crust, an ongoing absence of storage facilities comparable to the FHR, and a lack of consequences for the venting of helium. The complex combination of these economic, physical, and regulatory issues is unique to helium, and determining helium’s practical availability goes far beyond estimating the technically accessible volume of underground resources. Although most of these issues have been analyzed since helium was recognized to be a valuable mineral commodity in the early 1900s, very few economic models have been developed that adequately consider the unique characteristics of helium and helium markets. In particular, there is a notable lack of recent empirical work to estimate the responsiveness of helium demand, supply, prices, and trade patterns to the ongoing drawdown and sale of helium reserves stored in the FHR. In general, existing models of helium either do not account for an oligopoly controlling supply, or they do not evaluate potential helium extraction and storage programs based on an intertemporal maximization of the value of the resource. Such models could be of very limited use to decision makers. This review found only one working paper with a helium market model that has incorporated both of these vital considerations. That and other economic studies along similar lines could be very useful in helping inform current helium policy discussions and decisions.     

The usability of climate information in sub-national planning in India,Kenya and Uganda: the role of social learning and intermediary organisations

Correctly estimating the effect of elevated CO₂ (eCO₂) on biomass production is paramount for accurately projecting agricultural productivity, global carbon balances and climate changes. Plant physiology suggests that eCO₂ should result in a strongly positive CO₂ fertilisation effect (CFE) via positive effects on photosynthesis and water use efficiency. However, the CFE in CO₂ experiments is often constrained because of other factors of which rainfall pattern is particularly important. Here, we apply a generally applicable, empirically derived relationship between the CFE and an index of seasonal rainfall balance (SRB), to identify how historical and projected future rainfall patterns modify the CFE using 25 native grassland sites in south-eastern (SE) Australia as a test case. We found that historical and projected rainfall produced SRBs that varied widely from year-to-year resulting in a CFE that was only positive in about 40% of years, with no or even negative biomass responses in the remainder of years; a finding that is in marked contrast to other studies that have not taken account of relationships between rainfall seasonality and plant responses to CO₂. The dependence of the CFE on SRB also means that using the CFE from a specific eCO₂ experiment can be misleading as the result will be heavily influenced by the SRB during the period of experimentation but this problem can be avoided by using a robust general relationship of the kind used in this study. Generalisations of grassland biomass responses to the rising CO₂ concentration are contextual in terms of the variability in precipitation seasonality; as such, this provides a new lens by which to view aboveground responses to the rising CO₂ concentration and fosters a novel approach for cross-site comparisons among experiments.