Two high resolution terrestrial records of atmospheric Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland

Environmental archives like peat deposits allow for the reconstruction of both naturally and anthropogenically forced changes in the biogeochemical cycle of Pb as well as the quantification of past and present atmospheric Pb pollution. However, records of atmospheric Pb deposition from pre-industrial times are lacking.In a publication by Weiss et al. [Weiss, D., Shotyk, W., Boyle, E.A., Kramers, J.D., Appleby, P.G., Cheburkin, A.K., Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs. Sci Total Environ 2002;292:7-18]. Pb isotopes data measured by Q-ICP-MS and TIMS, concentration and enrichment data was presented for sites in eastern Canada (PeW1) and northwestern Scotland (LL7c), dating to 1586 A.D and 715 A.D., respectively. Here these same cores are re-analysed for Pb isotopes by MC-ICP-MS thereby acquiring ²⁰⁴Pb data and improving on the original data in terms of resolution and temporal coverage. Significant differences were found between the Q-ICP-MS/TIMS and MC-ICP-MS measurements, particularly at PeW1. These discrepancies are attributed to the problematic presence of organic matter during sample preparation and analysis complicated by the heterogeneity of the organic compounds that survived sample preparation steps. The precision and accuracy of Pb isotopes in complex matrices like peat is not always well estimated by industrial standards like NIST-SRM 981 Pb.Lead pollution histories at each site were constructed using the MC-ICP-MS data. The entire LL7c record is likely subject to anthropogenic additions. Contributions from local mining were detected in Medieval times. Later, coal use and mining in Scotland, Wales and England became important. After industrialization (ca. 1885 A.D.) contributions from Broken Hill type ores and hence, leaded petrol, dominate atmospheric Pb signatures right up to modern times. At PeW1 anthropogenic impacts are first distinguishable in the late 17th century with the mining and use of local coal. After industrialization (ca. 1810 A.D.), coal and petrol are the main Pb sources. A comprehensive estimate of the natural atmospheric background ²⁰⁶Pb/²⁰⁷Pb signature in eastern Canadian aerosols is made with a value of ~ 1.19.     

无建筑 亦无景观

……既无建筑,亦无景观,就一个承诺,承诺有一个地方,能够令您穿越空间……德国Archimedialab建筑事务所如是描述着自己的设计。无建筑,无景观并不意味着空间的缺失,而是在设计元素的因势利导下完成了环境的共生设计,产生出别样的空间体验。在设计中运用独具匠心的构思,尝试将非常规     

Occurrence of methanogenesis during start-up of a full-scale synthesis gas-fed reactor treating sulfate and metal-rich wastewater

The start-up of a full-scale synthesis gas-fed gas-lift reactor treating metal and sulfate-rich wastewater was investigated. Sludge from a pilot-scale reactor was used to seed the full-scale reactor. The main difference in design between the pilot- and full-scale reactor was that metal precipitation and sulfate reduction occurred in the same reactor. After 7 weeks the full-scale reactor achieved the sulfate conversion design rate of 15 kg/m3day. Zinc sulfide precipitation inside the reactor did not interfere with obtaining a high rate of sulfate reduction. 16S rRNA gene analysis demonstrated that the bacterial communities in both reactors were dominated by the sulfate-reducing genus Desulfomicrobium. Archaeal communities of both reactors were dominated by the methanogenic genus Methanobacterium. Most Probable Number (MPN) counts confirmed that heterotrophic Sulfate-Reducing Bacteria (SRB) were dominant (10(11) -10(12) cells/g VSS) compared to homoacetogens (10(5) -10(6) cells/g VSS) and methanogens (10(8) -10(9) cells/g VSS). Methanogenesis was not suppressed during start-up of the full scale-reactor, despite the predominance of SRB, which have a lower hydrogen threshold. Due to the short sludge retention time (4-7 days) competition for hydrogen is determined by Monod kinetics, not hydrogen thresholds. As the kinetic parameters for SRB and methanogens are similar, methanogenesis may persist which results in a loss of hydrogen.     

Adsorption of Pb and Cd by amine-modified zeolite

Natural zeolites, known for their excellent sorption properties towards metal cations, are widely used for the purification of wastewaters. The selectivity of clinoptilolite, a common zeolite mineral, for Pb is known to be particularly high, whereas its selectivity for Cd is often lower. Extraordinarily high sorption capacities for soft metal cations were observed in the case of thiol-functionalized silica gels and clays. In order to enhance the zeolites' sorption capacity for Cd, we treated natural heteroionic and Na-clinoptilolite in aqueous suspensions with cysteamine and propylamine solutions and investigated the sorption of Cd and Pb to amine-modified zeolite by a series of batch experiments. Stability constants for amine sorption on all zeolite samples at room temperature and 50 degrees C were obtained. Partial dimerization of cysteamine explains the enhanced sorption of this compound. In contrast, amine treatment did not enhance the adsorption capacity or selectivity of the clinoptilolite towards Cd and Pb. Instead, the amounts of adsorbed heavy metals decreased stoichometrically with increasing sorption of cysteamine and propylamine. This reduction can be explained by the blockage of channels by amine molecules and revealed that the modification of zeolites with mercaptoamines does not enhance the sorption capacity of zeolite for Cd and Pb.     

A synchronous distributed cloud-based virtual reality meeting system for architectural and urban design

In the spatial design fields such as architectural design and urban design, a consensus-building process among a variety of stakeholders like project executors, architects, residents, users, and general citizens is required. New technological developments such as cloud computing and Virtual Design Studios (VDS) enable the creation of virtual meeting systems. This paper proposes an approach towards a synchronous distributed design meeting system. In this paper, in addition to sharing a 3D virtual space for a synchronous distributed type design meeting, we developed a prototype system that enables participants to sketch or make annotations and have discussions as well as add viewpoints to them. We applied these functions to evaluate an architectural design and urban landscape examination. In conclusion, the proposed method was evaluated as being effective and feasible. Yet, it shows a few shortcomings including the fact that simultaneous operation is limited to one client, and more arbitrary shapes should be supported in future versions of the application.     

Kugelfallrheometer zur Prüfung von Selbstverdichtendem Beton

Falling-Ball Rheometer to prove Self-Compacting Concrete Self-compacting concrete (SCC) is a high-performance concrete whose performance is predicated by the flow characteristics of the fresh concrete mix. In a fresh state, SCC may be viewed as a two-phase suspension containing coarse disperse aggregates as well as a viscous mortar that, when compared to conventional concrete, achieves its specific flow characteristics through a relatively high mortar content. The selection of appropriate raw materials – particularly for manufacture of plastic mortars – are essential factors in determining the rheological properties and thus performance of the concrete. By adding organic or inorganic admixtures, or a combination thereof, one may influence the flow characteristics of the mortar. Mix design for SCC is largely dictated by the rheological properties of the fresh concrete, such that the volumetric design approach, as used for conventional concrete with a given design compressive strength, is no longer applicable. This paper reviews the possibility to optimize the viscosity of mortar by replacing cement by rock powders with the objective to design SCC with normal strength. A research investigation has been conducted, investigating the effect of rock powders on flow characteristics of mortar matrices. Self-compacting concrete requires a careful control of its flow behaviour. Fresh concrete acts as a non-Newtonian fluid. It is insufficient to describe the rheological behaviour of non-Newtonian fluids with a conventional one-point workability test. Rheological measurements are essential, to determine the flow behaviour dependent on the shear rate and to modify the mixture with the aim to achieve self-compacting properties. In order to measure the flow behaviour of SCC, the authors developed a rheometer which can be used simply.     

Optimal parameters in variable‐velocity scanning luminescence lifetime microscopy

We determine the optimal parameters (scan velocities) for measuring the luminescence lifetime on the microsecond scale using the recently introduced method based on scanning the excitation beam across the sample. Using simulations, we evaluate the standard deviation and bias of the luminescence decay rate determined by scanning with two different velocities. The analysis is performed for Poisson‐ and normal‐distributed signals, representing different types of detection techniques. We also show that a weak uncorrected background induces a bias in the obtained decay rate, and take this effect into account when choosing optimal measurement parameters. For comparison, the analysis is additionally performed for two conventional gating schemes for lifetime measurement. The variable‐velocity scanning method is found to be more robust to the effect of the background signal than the gating schemes.     

The GIF Quantum,a next generation post-column imaging energy filter

We describe a new post-column imaging energy filter for (scanning) transmission electron microscopy from 60 to 300 kV operating voltage. The completely redesigned GIF quantum has a gradient magnetic prism, dodecapole optics, a 10-times faster 40 Mpixel/sec CCD camera, a 1 μs electrostatic shutter, and new user interface, control, and auto-alignment software. An 8 dodecapole lens system, performs full 2nd and 3rd, and partial 4th and 5th order aberration correction. The improved aberration correction has allowed the size of the entrance aperture to be nearly doubled to 9.0 mm compared to current generation post-column designs. The electrostatic shutter provides exposure control down to 1 μs, extending the exposure time range to over 7 orders of magnitude. Spectroscopy operation has been improved with a larger 2 keV field of view at 200 kV, and a maximum acquisition rate of 1000 spectra per second. A high-speed DualEELS mode simultaneously acquires core- and low-loss spectra up to 2 keV apart. A more intuitive user interface includes new capabilities such as automated exposure control and optimized full spectrum acquisition. The auto-alignment software has been significantly enhanced to use the full flexibility of the dodecapole lens system.