SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Tonne

261

Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025.

Concepts: Atlantic Ocean, Coast, Pacific Ocean, Sea, Ocean, Marine debris, Waste, Tonne

76

Coastal Indigenous peoples rely on ocean resources and are highly vulnerable to ecosystem and economic change. Their challenges have been observed and recognized at local and regional scales, yet there are no global-scale analyses to inform international policies. We compile available data for over 1,900 coastal Indigenous communities around the world representing 27 million people across 87 countries. Based on available data at local and regional levels, we estimate a total global yearly seafood consumption of 2.1 million (1.5 million-2.8 million) metric tonnes by coastal Indigenous peoples, equal to around 2% of global yearly commercial fisheries catch. Results reflect the crucial role of seafood for these communities; on average, consumption per capita is 15 times higher than non-Indigenous country populations. These findings contribute to an urgently needed sense of scale to coastal Indigenous issues, and will hopefully prompt increased recognition and directed research regarding the marine knowledge and resource needs of Indigenous peoples. Marine resources are crucial to the continued existence of coastal Indigenous peoples, and their needs must be explicitly incorporated into management policies.

Concepts: Ethnic group, Kilogram, Overfishing, Indigenous Australians, Tonne, Indigenous peoples, Transformation of culture, Metric system

28

Purussaurus brasiliensis thrived in the northwestern portion of South America during the Late Miocene. Although substantial material has been recovered since its early discovery, this fossil crocodilian can still be considered as very poorly understood. In the present work, we used regression equations based on modern crocodilians to present novel details about the morphometry, bite-force and paleobiology of this species. According to our results, an adult Purussaurus brasiliensis was estimated to reach around 12.5 m in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. It was capable of generating sustained bite forces of 69,000 N (around 7 metric tons-force). The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition. The evolution of a large body size granted P. brasiliensis many advantages, but it may also have led to its vulnerability. The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts.

Concepts: Predation, Ecology, Mass, Kilogram, Alligatoridae, Caimaninae, Tonne, Deinosuchus

26

An efficient production synthesis of the SGLT-2 inhibitor Empagliflozin (5) from acid 1 is described. The key tactical stage involves I/Mg exchange of aryl iodide 2 followed by addition to glucono lactone 3 in THF. Subsequent in situ treatment of the resulting lactol with HCl in MeOH produces β-anomeric methyl glycopyranoside 4 which is, without isolation, directly reduced with Et3SiH mediated by AlCl3 as a Lewis acid in CH2Cl2/MeCN to afford 5 in 50% overall yield. The process was implemented for production on a metric ton scale for commercial launch.

Concepts: Alcohol, Carbon dioxide, Hydrogen, Aluminium, Gilbert N. Lewis, The Key, Methane, Tonne

22

Tropospheric ozone and black carbon (BC) contribute to both degraded air quality and global warming. We considered ~400 emission control measures to reduce these pollutants by using current technology and experience. We identified 14 measures targeting methane and BC emissions that reduce projected global mean warming ~0.5°C by 2050. This strategy avoids 0.7 to 4.7 million annual premature deaths from outdoor air pollution and increases annual crop yields by 30 to 135 million metric tons due to ozone reductions in 2030 and beyond. Benefits of methane emissions reductions are valued at $700 to $5000 per metric ton, which is well above typical marginal abatement costs (less than $250). The selected controls target different sources and influence climate on shorter time scales than those of carbon dioxide-reduction measures. Implementing both substantially reduces the risks of crossing the 2°C threshold.

Concepts: Carbon dioxide, Agriculture, Smog, Air pollution, Greenhouse gas, Global warming, Tonne, Ton

7

We quantified the wholesale transformation of the boreal landscape by open-pit oil sands mining in Alberta, Canada to evaluate its effect on carbon storage and sequestration. Contrary to claims made in the media, peatland destroyed by open-pit mining will not be restored. Current plans dictate its replacement with upland forest and tailings storage lakes, amounting to the destruction of over 29,500 ha of peatland habitat. Landscape changes caused by currently approved mines will release between 11.4 and 47.3 million metric tons of stored carbon and will reduce carbon sequestration potential by 5,734-7,241 metric tons C/y. These losses have not previously been quantified, and should be included with the already high estimates of carbon emissions from oil sands mining and bitumen upgrading. A fair evaluation of the costs and benefits of oil sands mining requires a rigorous assessment of impacts on natural capital and ecosystem services.

Concepts: Carbon dioxide, Ecology, Petroleum, Ecosystem, Mining, Tonne, Carbon capture and storage, Oil sands

6

Plastics contamination in the marine environment was first reported nearly 50 years ago, less than two decades after the rise of commercial plastics production, when less than 50 million metric tons were produced per year. In 2014, global plastics production surpassed 300 million metric tons per year. Plastic debris has been detected worldwide in all major marine habitats, in sizes from microns to meters. In response, concerns about risks to marine wildlife upon exposure to the varied forms of plastic debris have increased, stimulating new research into the extent and consequences of plastics contamination in the marine environment. Here, I present a framework to evaluate the current understanding of the sources, distribution, fate, and impacts of marine plastics. Despite remaining knowledge gaps in mass budgeting and challenges in investigating ecological impacts, the increasing evidence of the ubiquity of plastics contamination in the marine environment, the continued rapid growth in plastics production, and the evidence-albeit limited-of demonstrated impacts to marine wildlife support immediate implementation of source-reducing measures to decrease the potential risks of plastics in the marine ecosystem. Expected final online publication date for the Annual Review of Marine Science Volume 9 is January 03, 2017. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Concepts: Oceanography, Greek loanwords, Plastic, Ocean, Marine debris, Marine biology, Tonne, Metric system

3

Using a least-cost optimization framework, it is shown that unless emissions reductions beyond those already in place begin at the latest by 2025 (± 2 years) for the U.S. automotive sector, and by 2026 (- 3 years) for the U.S. electric sector, 2050 targets to achieve necessary within-sector preventative CO2 emissions reductions of 70% or more relative to 2010 will be infeasible. The analysis finds no evidence to justify delaying climate action in the name of reducing technological costs. Even without considering social and environmental damage costs, delaying aggressive climate action does not reduce CO2 abatement costs even under the most optimistic trajectories for improvements in fuel efficiencies, demand, and technology costs in the U.S. auto and electric sectors. In fact, the abatement cost for both sectors is found to increase sharply with every year of delay beyond 2020. When further considering reasonable limits to technology turnover, retirements, and new capacity additions, these costs would be higher, and the feasible timeframe for initiating successful climate action on the 70% by 2050 target would be shorter - perhaps having passed already. The analysis also reveals that optimistic business-as-usual scenarios in the U.S. will, conservatively, release 79 - 108 billion metric tons of CO2. This could represent up to 13% of humanity’s remaining carbon budget through 2050.

Concepts: Photosynthesis, Carbon dioxide, Carbon, Delay, Tom DeLay, Technology, Target Corporation, Tonne

3

A total of 2,514,346 metric tons (Mt) of asbestos were imported into Spain from 1906 until the ban on asbestos in 2002. Our objective was to study pleural cancer mortality trends as an indicator of mesothelioma mortality and update mortality predictions for the periods 2011–2015 and 2016–2020 in Spain.

Concepts: Cancer, Mesothelioma, Asbestos, Tonne, Windows Update, Metric system

2

A concise, efficient and scalable synthesis of thapsigargin and nortrilobolide from commercially available ®-(-)-carvone was developed. Our synthetic strategy is inspired by nature’s carbon-carbon bond formation sequence, which facilitates the construction of a highly functionalized sesquiterpene lactone skeleton in five steps via an enantioselective ketone alkylation and a diastereoselective pinacol cyclization. We envision that this strategy will permit the construction of other members of the family, structural analogs and provide a practical synthetic route to these important bioactive agents. In addition, we anticipate that the prodrug Mipsagargin, which is currently in late-stage clinical trials for the treatment of cancer, will also be accessible via this strategy. Hence, the limited availability from natural sources, coupled with an estimated demand of one metric ton per annum for the prodrug, provides a compelling mandate to develop practical total syntheses of these agents.

Concepts: Clinical trial, Total synthesis, Paclitaxel total synthesis, Chemical synthesis, Tonne