Search

Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydrofracking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydrofracking fluids, which return to the surface during hydrofracking, are common causes of environmental contamination. Since the chemistry of hydrofracking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequently injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While

The alkaline volcanic rocks of the 1.8-0.9 Ma Auca Mahuida and post-mid-Pliocene Rio Colorado backarc volcanic fields east of the Andean Southern Volcanic Zone at ~37°-38°S have pronounced intraplate-like chemical signatures with some striking similarities to oceanic DM-EM1-like lavas of the south Atlantic Tristan da Cunha type. These backarc lavas are considered to have formed as a series of mantle batches typified by 4-7 % melting, with decompression melting initiating in a garnet-bearing mantle above a steepening subduction zone, and final equilibration occurring near the base of a ~65- to 70-km-thick lithosphere at temperatures of ~1,350-1,380°C. Evolved Auca Mahuida mugearite to trachytic samples are best explained by crystal fractionation with limited mixing of partial melts of recently underplated basalts, in line with isotopic signatures that preclude significant radiogenic contamination in a preexisting refractory crust. Higher Ba/La and subtly higher La/Ta ratios than in nearby ~24-20 Ma primitive basalts or oceanic (OIB) lavas are attributed to the residual effects of slab fluids introduced during a shallow subduction episode recorded in the arc-like chemistry of the adjacent 7-4 Ma Chachahuen volcanic complex. Positive Sr, K and Ba spikes on mantle-normalized patterns of both primitive Auca Mahuida and ~24-20 Ma basalts, like those in EM-like OIB basalts, are attributed to mixing of continental lithosphere into the asthenosphere. In Patagonia, this mixing is suggested to have peaked as the South America continent accommodated to major late Oligocene plate convergence changes, as similar Sr, K and Ba spikes and DM-EM1 signatures are absent in ~50-30 Ma backarc lavas north of 51°S, and all of those south of 51°S. Introduction of an EM1-like component associated with lateral mantle flow of a Tristan da Cunha source is largely precluded by its Cretaceous age and distance to Patagonia. Keywords Patagonia plateau lavas * Auca Mahuida volcanic center * Andean Southern Volcanic Zone backarc * EM-like continental and oceanic basalts * Trace element and isotope geochemistry, Introduction One of the world's major Tertiary to Recent mafic backarc magmatic provinces is in the Patagonian backarc, east of the Andean arc under which the Nazca and Antarctic plates [...]

Additive manufacturing, an umbrella term for a number of different manufacturing techniques, has attracted increasing interest recently for a number of reasons, such as the facile customisation of parts, reduced time to manufacture from initial design, and possibilities in distributed manufacturing and structural electronics. Inkjet printing is an additive manufacturing technique that is readily integrated with other manufacturing processes, eminently scalable and used extensively in printed electronics. It therefore presents itself as a good candidate for integration with other additive manufacturing techniques to enable the creation of parts with embedded electronics in a timely and cost effective manner. This review introduces some of the fundamental principles of inkjet printing; such as droplet generation, deposition, phase change and post-deposition processing. Particular focus is given to materials most relevant to incorporating structural electronics and how post-processing of these materials has been able to maintain compatibility with temperature sensitive substrates. Specific obstacles likely to be encountered in such an integration and potential strategies to address them will also be discussed.

Calc-alkaline plutons are the major crustal building blocks of continental margins, but are rarely exposed in oceanic island arcs. Two of the best examples are the ∼10 km wide Hidden Bay and Kagalaska plutons that intrude Eocene mafic volcanic–sedimentary rocks on Adak and Kagalaska islands in the central Aleutian arc. Twenty new Ar/Ar and U/Pb ages, coupled with published ages, show that the Hidden Bay pluton was intruded in multiple stages from ∼34·6 to 30·9 Ma, whereas the Kagalaska pluton was intruded at ∼14 Ma. The plutons largely consist of medium- to high-K2O hornblende-bearing cumulate diorite (53–55 wt % SiO2) and hornblende–biotite granodiorite (57–64 wt %), with lesser amounts of gabbro (50–52 wt % SiO2), leucogranodiorite (67–69 wt % SiO2) and aplite (76–77 wt % SiO2) that can generally be linked to each other by crystal fractionation. The compositions of these plutons are generally similar to those of continental plutons, except for more oceanic-like large ion lithophile element and isotopic signatures (87Sr/86Sr = 0·703–0·7033; ɛNd = 9·4–7·7) that reflect oceanic- rather than continental-type crustal contaminants. Chemical similarities between the Hidden Bay homogeneous gabbros and high-Al basalts in Adak Pleistocene-Holocene volcanoes indicate little temporal evolution in the general character of the mantle-derived basalts. Rather than a unique arc setting and distinctive magmas, formation of the Aleutian calc-alkaline plutons seems to require a sufficient crustal thickness (∼37 km) and a high enough water content to stabilize pargasitic hornblende amphibole in a relatively closed magma system that favors increasing K, Ti and H2O at the end of a magmatic cycle. This termination of magmatism coincides with a northward migration of the magmatic front that is inferred to be associated with fore-arc subduction erosion. In accord with Adak region crustal architecture based on seismic data, crystallization models for the plutons suggest that mantle-generated hydrous arc basalts fractionated olivine and clinopyroxene in the lower crust to form high-Al basaltic composition magmas that rose into the mid-crust, where gabbro and diorite crystallized to form the magmas that buoyantly rose into the upper crust and crystallized to form the volumetrically dominant granodiorite (58–63 wt % SiO2). The most important temporal changes in chemistry can be explained by fore-arc crust incorporated into the mantle wedge by fore-arc subduction erosion creating 'adakitic' signatures at times of northward arc migration and a change to a more continental subducted sediment component at the time of Plio-Pleistocene glaciation. [ABSTRACT FROM AUTHOR]

Abstract: Worldwide, soil erosion has greatly decreased agricultural productivity and continues unabatedly despite decades of developing sustainability and soil conservation strategies. Current strategies need integrated interdisciplinary perspectives to develop more effective measures, especially in degrading mountainous landscapes where rising sediment concentrations persist. By comparing spatio‐temporal field observations and community perceptions with the Geographic Information System (GIS)‐based universal soil loss equation (USLE), this study critically examined theorized erosion patterns (by USLE) in a degraded landscape (Shanko Bahir, Ethiopia) to improve soil conservation strategy development. Daily hydro‐sedimentological data (showing 792 mm of rainfall leading to 3·2 Mg ha−1 y−1 of sediment yield) revealed mild but variable erosion patterns in 2012. Overlooking hydrology hindered the USLE's suitability for conservation planning. For instance, the median infiltration rate (33 mm h−1) was rarely exceeded (3·5% of events), meaning runoff‐induced erosion risk were not well predicted spatio‐temporally by the USLE R‐factor. Conversely, heterogeneous local perspectives explicitly considered accumulated runoff, saturation (“the water at the top level rests on the bottom”), fertility, and gullies as drivers of erosion (“black soil breaks and forms gorges”). Additionally, they designated steeper mono‐cropped lands as at risk (incidentally also highlighted by USLE). Observational evidence showed steeper midslope areas decreasing in topsoil depth by 14 mm, flatter downslope areas by 0·8 mm, and the mild upslope areas increasing 2 mm. Operationalizing effective soil conservation strategies will require expanding beyond (USLE‐based) technical knowledge to incorporate local stakeholders and consider the main hydrological processes causing erosion in sub‐humid mountainous landscapes: saturated pathways, downslope saturation, subsurface flow, and gully formation. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a method for the rapid synthesis of metallic microtracks on polyetherimide is presented. The method relies on the photosynthesis of silver nanoparticles on the surface of the polymer substrates from photosensitive silver chloride (AgCl), which is synthesized directly on the polyetherimide surface. The study reveals that the use of AgCl as a photosensitive intermediate accelerates the reactions leading to the formation of silver nanoparticles by up to two orders of magnitude faster than other photodecomposition schemes. The patterning can be conducted under blue light, with notable advantages over UV exposure. Polymers of significant interest to the microelectronics and 3D printing industries can be directly patterned by light using this photography‐inspired technique at throughputs high enough to be commercially advantageous. Light exposures as short as a few seconds are sufficient to allow the direct metallization of the illuminated polyetherimide surface. The results show that the silver required for the seed layer is minimal, and the later copper electroless plating results in the selective growth of conductive tracks for circuitry on the light‐patterned areas, both on flexible films and 3D printed surfaces. [ABSTRACT FROM AUTHOR]