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  • 1
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (12). pp. 7036-7046.
    Publikationsdatum: 2020-07-31
    Beschreibung: Microplastic fibers make up a large proportion of microplastics found in the environment, especially in urban areas. There is good reason to consider synthetic textiles a major source of microplastic fibers, and it will not diminish since the use of synthetic fabrics, especially polyester, continues to increase. In this study we provide quantitative data regarding the size and mass of microplastic fibers released from synthetic (polyester) textiles during simulated home washing under controlled laboratory conditions. Consideration of fabric structure and washing conditions (use of detergents, temperature, wash duration, and sequential washings) allowed us to study the propensity of fiber shedding in a mechanistic way. Thousands of individual fibers were measured (number, length) from each wash solution to provide a robust data set on which to draw conclusions. Among all the variables tested, the use of detergent appeared to affect the total mass of fibers released the most, yet the detergent composition (liquid or powder) or overdosing of detergent did not significantly influence microplastic release. Despite different release quantities due to the addition of a surfactant (approximately 0.025 and 0.1 mg fibers/g textile washed, without and with detergent, respectively), the overall microplastic fiber length profile remained similar regardless of wash condition or fabric structure, with the vast majority of fibers ranging between 100 and 800 μm in length irrespective of wash cycle number. This indicates that the fiber staple length and/ or debris encapsulated inside the fabric from the yarn spinning could be directly responsible for releasing stray fibers. This study serves as a first look toward understanding the physical properties of the textile itself to better understand the mechanisms of fiber shedding in the context of microplastic fiber release into laundry wash water.
    Materialart: Article , PeerReviewed
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  • 2
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (21). pp. 12246-12253.
    Publikationsdatum: 2020-07-31
    Beschreibung: A substantial fraction of marine plastic debris originates from land-based sources and rivers potentially act as a major transport pathway for all sizes of plastic debris. We analyzed a global compilation of data on plastic debris in the water column across a wide range of river sizes. Plastic debris loads, both microplastic (particles 〈5 mm) and macroplastic (particles 〉5 mm) are positively related to the mismanaged plastic waste (MMPW) generated in the river catchments. This relationship is nonlinear where large rivers with population-rich catchments delivering a disproportionately higher fraction of MMPW into the sea. The 10 top-ranked rivers transport 88-95% of the global load into the sea. Using MMPW as a predictor we calculate the global plastic debris inputs form rivers into the sea to range between 0.41 and 4 X 106 t/y. Due to the limited amount of data high uncertainties were expected and ultimately confirmed. The empirical analysis to quantify plastic loads in rivers can be extended easily by additional potential predictors other than MMPW, for example, hydrological conditions.
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  • 3
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (14). pp. 7963-7971.
    Publikationsdatum: 2020-07-31
    Beschreibung: Recent studies suggest size-selective removal of small plastic particles from the ocean surface, an observation that remains unexplained. We studied one of the hypotheses regarding this size-selective removal: the formation of a biofilm on the microplastics (biofouling). We developed the first theoretical model that is capable of simulating the effect of biofouling on the fate of microplastic. The model is based on settling, biofilm growth, and ocean depth profiles for light, water density, temperature, salinity, and viscosity. Using realistic parameters, the model simulates the vertical transport of small microplastic particles over time, and predicts that the particles either float, sink to the ocean floor, or oscillate vertically, depending on the size and density of the particle. The predicted size-dependent vertical movement of microplastic particles results in a maximum concentration at intermediate depths. Consequently, relatively low abundances of small particles are predicted at the ocean surface, while at the same time these small particles may never reach the ocean floor. Our results hint at the fate of “lost” plastic in the ocean, and provide a start for predicting risks of exposure to microplastics for potentially vulnerable species living at these depths.
    Materialart: Article , PeerReviewed
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  • 4
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (8). pp. 4368-4376.
    Publikationsdatum: 2020-07-31
    Beschreibung: It is important to understand the fragmentation processes and mechanisms of plastic litter to predict microplastic production in the marine environment. In this study, accelerated weathering experiments were performed in the laboratory, with ultraviolet (UV) exposure for up to 12 months followed by mechanical abrasion (MA) with sand for 2 months. Fragmentation of low-density polyethylene (PE), polypropylene (PP), and expanded polystyrene (EPS) was evaluated under conditions that simulated a beach environment. PE and PP were minimally fragmented by MA without photooxidation by UV (8.7 ± 2.5 and 10.7 ± 0.7 particles/pellet, respectively). The rate of fragmentation by UV exposure duration increased more for PP than PE. A 12-month UV exposure and 2-month MA of PP and PE produced 6084 ± 1061 and 20 ± 8.3 particles/pellet, respectively. EPS pellets were susceptible to MA alone (4220 ± 33 particles/pellet), while the combination of 6 months of UV exposure followed by 2 months of MA produced 12,152 ± 3276 particles/pellet. The number of fragmented polymer particles produced by UV exposure and mechanical abrasion increased with decreasing size in all polymer types. The size-normalized abundance of the fragmented PE, PP, and EPS particles according to particle size after UV exposure and MA was predictable. Up to 76.5% of the initial EPS volume was unaccounted for in the final volume of pellet produced particle fragments, indicating that a large proportion of the particles had fragmented into undetectable submicron particles.
    Materialart: Article , PeerReviewed
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  • 5
    Publikationsdatum: 2020-02-06
    Beschreibung: Chemical investigation of the marine sponge Ircinia oros yielded four linear furanosesterterpenoids, including the known metabolites ircinin-1 (1) and ircinin-2 (2) and two new compounds, ircinialactam E (3) and ircinialactam F (4). Their chemical structures were elucidated by using a combination of [α]D, NMR, HRMS, and FT-IR spectroscopy. The absolute configuration of C-18 in compounds 1–3 was identified as R by electronic circular dichroism (ECD) spectroscopy coupled with time-dependent density functional theory calculations. Compounds 1–4 showed moderate leishmanicidal, trypanocidal, and antiplasmodial activities (IC50 values 28–130 μM). This is the second report of rare glycinyl lactam derivatives 3 and 4 from the genus Ircinia.
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  • 6
    Publikationsdatum: 2020-02-06
    Beschreibung: Shallow gas migration along hydrocarbon wells constitutes a potential methane emission pathway that currently is not recognized in any regulatory framework or greenhouse gas inventory. Recently, the first methane emission measurements at three abandoned offshore wells in the Central North Sea (CNS) were conducted showing that considerable amounts of biogenic methane originating from shallow gas accumulations in the overburden of deep reservoirs were released by the boreholes. Here, we identify numerous wells poking through shallow gas pockets in 3D seismic data of the CNS indicating that about one third of the wells may leak, potentially releasing a total of 3-17 kt of methane per year into the North Sea. This poses a significant contribution to the North Sea methane budget. A large fraction of this gas (~42 %) may reach the atmosphere via direct bubble transport (0-2 kt yr-1) and via diffusive exchange of methane dissolving in the surface mixed layer (1-5 kt yr-1), as indicated by numerical modeling. In the North Sea and in other hydrocarbon-prolific provinces of the world shallow gas pockets are frequently observed in the sedimentary overburden and aggregate leakages along the numerous wells drilled in those areas may be significant.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 7
    Publikationsdatum: 2020-12-04
    Beschreibung: Nanoscale ternary chalcogenides have attracted intense research interest due to their wealth of tunable properties and diverse applications in energy and environmental and biomedical fields. In this article, ultrasmall magnetic CuFeSe2 ternary nanocrystals (〈5.0 nm) were fabricated in the presence of thiol-functionalized poly(methacrylic acid) by an environmentally friendly aqueous method under ambient conditions. The small band gap and the existence of intermediate bands lead to a broad NIR absorbance in the range of 500-1100 nm and high photothermal conversion efficiency (82%) of CuFeSe2 nanocrystals. The resultant CuFeSe2 nanocrystals show superparamagnetism and effective attenuation for X-rays. In addition, they also exhibit excellent water solubility, colloidal stability, biocompatibility, and multifunctional groups. These properties enable them to be an ideal nanotheranostic agent for multimodal imaging [e.g., photoacoustic imaging (PAI), magnetic resonance imaging (MRI), computed tomography (CT) imaging] guided photothermal therapy of cancer.
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  • 8
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (5). pp. 3001-3011.
    Publikationsdatum: 2020-11-25
    Beschreibung: The chemical parameters needed to explain and predict bioavailability, biodynamics, and baseline toxicity are not readily available for most nonpolar chemicals detected in the environment. Here, we demonstrate that comprehensive two-dimensional gas chromatography (GC × GC) retention times can be used to predict 26 relevant properties for nonpolar chemicals, specifically: partition coefficients for diverse biotic media and passive sampler phases; aquatic baseline toxicity; and relevant diffusion coefficients. The considered biotic and passive sampler phases include membrane and storage lipids, serum and muscle proteins, carbohydrates, algae, mussels, polydimethylsiloxane, polyethylene, polyoxymethylene, polyacrylate, polyurethane, and semipermeable membrane devices. GC × GC-based chemical property predictions are validated with a compilation of 1038 experimental property data collected from the literature. As an example application, we overlay a map of baseline toxicity to fathead minnows onto the separated analyte signal of a polychlorinated alkanes (chlorinated paraffins) technical mixture that contains 7820 congeners. In a second application, GC × GC-estimated properties are used to parametrize multiphase partitioning models for mammalian tissues and organs. In a third example, we estimate chemical depuration kinetics for mussels. Finally, we illustrate an approach to screen the GC × GC chromatogram for nonpolar chemicals of potentially high concern, defined based on their GC × GC-estimated biopartitioning properties, diffusion properties, and baseline toxicity.
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  • 9
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (17). pp. 9747-9755.
    Publikationsdatum: 2021-05-10
    Beschreibung: Previous studies report high and increasing iron (Fe) concentrations in boreal river mouths. This Fe has shown relatively high stability to salinity-induced aggregation in estuaries. The aim of this study was to understand how the speciation of Fe affects stability over salinity gradients. For Fe to remain in suspension interactions with organic matter (OM) are fundamental and these interactions can be divided in two dominant phases: organically complexed Fe, and colloidal Fe (oxy)hydroxides, stabilized by surface interactions with OM. The stability of these two Fe phases was tested using mixing experiments with river water and artificial seawater. Fe speciation of river waters and salinity-induced aggregates was determined by synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy. The relative contribution of the two Fe phases varied widely across the sampled rivers. Moreover, we found selective removal of Fe (oxy)hydroxides by aggregation at increasing salinity, while organically complexed Fe was less affected. However, Fe–OM complexes were also found in the aggregates, illustrating that the control of Fe stability is not explained by the prevalence of the respective Fe phases alone. Factors such as colloid size and the chemical composition of the OM may also impact the behavior of Fe species.
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  • 10
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    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (6). pp. 3214-3222.
    Publikationsdatum: 2021-05-10
    Beschreibung: Blanket bogs contain vast amounts of Sphagnum-derived organic substances which can act as powerful chelators for dissolved iron and thus enhance its export to the coastal ocean. To investigate the variations in quantity and quality of these exports, adsorptive cathodic stripping voltammetry (CSV) was used to characterize the metal binding properties of molecular weight-fractionated dissolved organic matter (MW-fractionated DOM) in the catchment and coastal plume of a small peat-draining river over a seasonal cycle. Within the plume, both iron- and copper-binding organic ligands showed a linear, conservative distribution with increasing salinity, illustrating the high stability of peatland-derived humic substances (HS). Within the catchment, humic colloids lost up to 50% of their copper-binding capacity, expressed as a molar ratio to organic carbon, after residing for 1 week or more in the main reservoir of the catchment. Immediately downstream of the reservoir, the molar ratio [L2]/[Corg], where L2 was the second strongest copper-binding ligand, was 0.75 × 10–4 when the reservoir residence time was 5 h but 0.34 × 10–4 when it was 25 days. Residence time did not affect the carbon specific iron-binding capacity of the humic substances which was [L]/[Corg] = (0.80 ± 0.20) × 10–2. Our results suggest that the loss of copper-binding capacity with increasing residence time is caused by intracolloidal interactions between iron and HS during transit from peat soil to river mouth.
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  • 11
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    ACS (American Chemical Society)
    In:  The Journal of Physical Chemistry C, 121 (33). pp. 17603-17616.
    Publikationsdatum: 2020-09-07
    Beschreibung: Guest exchange in clathrates is a complex activated phenomenon of the guest–host cage interaction on the molecular-scale level. To model this process, we develop a mathematical description for the nonequilibrium binary permeation of guest molecules during gas replacement based on the microscopic “hole-in-cage-wall” diffusive mechanism. The transport of gas molecules is envisaged as a series of jumps between occupied and empty neighboring cages without any significant lattice restructuring in the bulk. The gas exchange itself is seen as two-stage swapping initiated by almost instantaneous formation of a mixed hydrate layer on the hydrate surface followed by a much slower permeation-controlled process. The model is constrained by and validated with available time-resolved neutron diffraction data of the isostructural CH4 guest replacement by CO2 in methane hydrate, a process of possible importance for the sequestration of CO2 with concomitant recovery of CH4 in marine gas hydrates.
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