Numerical investigation of the partial oxidation in a two-stage downdraft gasifyer

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Meta-analysis of global livestock urine-derived nitrous oxide emissions from agricultural soils

Nitrous oxide (N2O) is an air pollutant of major environmental concern, with agriculture representing 60% of anthropogenic global N2O emissions. Much of the N2O emissions from livestock production systems result from transformation of N deposited to soil within animal excreta. There exists a substantial body of literature on urine patch N2O dynamics, we aimed to identify key controlling factors influencing N2O emissions and to aid understanding of knowledge gaps to improve GHG reporting and prioritise future research. We conducted an extensive literature review and random effect meta-analysis (using REML) of results to identify key relationships between multiple potential independent factors and global N2O emissions factors (EFs) from urine patches. Mean air temperature, soil pH and ruminant animal species (sheep or cow) were significant factors influencing the EFs reviewed. However, several factors that are known to influence N2O emissions, such as animal diet and urine composition, could not be considered due to the lack of reported data. The review highlighted a widespread tendency for inadequate metadata and uncertainty reporting in the published studies, as well as the limited geographical extent of investigations, which are more often conducted in temperate regions thus far. Therefore, here we give recommendations for factors that are likely to affect the EFs and should be included in all future studies, these include: soil pH and texture; experimental set-up; direct measurement of soil moisture and temperature during the study period; amount and composition of urine applied; animal type and diet; N2O emissions with a measure of uncertainty; data from a control with zero-N application and meteorological data

Optimising storage conditions and processing of sheep urine for nitrogen cycle and gaseous emission measurements from urine patches

Abstract In grazing systems, urine patches deposited by livestock are hotspots of nutrient cycling and the most important source of nitrous oxide (N2O) emissions. Studies of the effects of urine deposition, including, for example, the determination of country-specific N2O emission factors, require natural urine for use in experiments and face challenges obtaining urine of the same composition, but of differing concentrations. Yet, few studies have explored the importance of storage conditions and processing of ruminant urine for use in subsequent gaseous emission experiments. We conducted three experiments with sheep urine to determine optimal storage conditions and whether partial freeze-drying could be used to concentrate the urine, while maintaining the constituent profile and the subsequent urine-derived gaseous emission response once applied to soil. We concluded that filtering of urine prior to storage, and storage at − 20 °C best maintains the nitrogen-containing constituent profile of sheep urine samples. In addition, based on the 14 urine chemical components determined in this study, partial lyophilisation of sheep urine to a concentrate represents a suitable approach to maintain the constituent profile at a higher overall concentration and does not alter sheep urine-derived soil gaseous emissions

Observed Effect of Magnetic Fields on the Propagation of Magnetoacoustic Waves in the Lower Solar Atmosphere

We study Hinode/SOT-FG observations of intensity fluctuations in Ca II H-line and G-band image sequences and their relation to simultaneous and co-spatial magnetic field measurements. We explore the G-band and H-line intensity oscillation spectra both separately and comparatively via their relative phase differences, time delays and cross-coherences. In the non-magnetic situations, both sets of fluctuations show strong oscillatory power in the 3 - 7 mHz band centered at 4.5 mHz, but this is suppressed as magnetic field increases. A relative phase analysis gives a time delay of H-line after G-band of 20\pm1 s in non-magnetic situations implying a mean effective height difference of 140 km. The maximum coherence is at 4 - 7 mHz. Under strong magnetic influence the measured delay time shrinks to 11 s with the peak coherence near 4 mHz. A second coherence maximum appears between 7.5 - 10 mHz. Investigation of the locations of this doubled-frequency coherence locates it in diffuse rings outside photospheric magnetic structures. Some possible interpretations of these results are offered.Comment: 19 pages, 6 figure

Quiet-Sun imaging asymmetries in NaI D1 compared with other strong Fraunhofer lines

Imaging spectroscopy of the solar atmosphere using the NaI D1 line yields marked asymmetry between the blue and red line wings: sampling a quiet-Sun area in the blue wing displays reversed granulation, whereas sampling in the red wing displays normal granulation. The MgI b2 line of comparable strength does not show this asymmetry, nor does the stronger CaII 8542 line. We demonstrate the phenomenon with near-simultaneous spectral images in NaI D1, MgI b2, and CaII 8542 from the Swedish 1-m Solar Telescope. We then explain it with line-formation insights from classical 1D modeling and with a 3D magnetohydrodynamical simulation combined with NLTE spectral line synthesis that permits detailed comparison with the observations in a common format. The cause of the imaging asymmetry is the combination of correlations between intensity and Dopplershift modulation in granular overshoot and the sensitivity to these of the steep profile flanks of the NaI D1 line. The MgI b2 line has similar core formation but much wider wings due to larger opacity buildup and damping in the photosphere. Both lines obtain marked core asymmetry from photospheric shocks in or near strong magnetic concentrations, less from higher-up internetwork shocks that produce similar asymmetry in the spatially averaged CaII 8542 profile.Comment: Accepted by Astron & Astrophys. In each in-text citation the year links to the corresponding ADS abstract pag

Potential of urban green spaces for supporting horticultural production: a national scale analysis

As urban areas and land-use constraints grow, there is increasing interest in utilizing urban spaces for food production. Several studies have uncovered significant potential for urban growing to supplement production of fruit and vegetables, focusing on one or two cities as case studies, whilst others have assessed the global scale potential. Here, we provide a national-scale analysis of the horticultural production potential of urban green spaces, which is a relevant scale for agri-food and urban development policy making using Great Britain (GB) as a case study. Urban green spaces available for horticultural production across GB are identified and potential yields quantified based on three production options. The distribution of urban green spaces within 26 urban towns and cities across GB are then examined to understand the productive potential compared to their total extent and populations. Urban green spaces in GB, at their upper limit, have the capacity to support production that is 8× greater than current domestic production of fruit and vegetables. This amounts to 38% of current domestic production and imports combined, or >400% if exotic fruits and vegetables less suited to GB growing conditions are excluded. Most urban green spaces nationally are found to fall within a small number of categories, with private residential gardens and amenity spaces making up the majority of space. By examining towns and cities across GB in further detail, we find that the area of green space does not vary greatly between urban conurbations of different sizes, and all are found to have substantial potential to meet the dietary needs of the local urban population. This study highlights that national policies can be suitably developed to support urban agriculture and that making use of urban green spaces for food production could help to enhance the resilience of the national-scale food system to shocks in import pathways, or disruptions to domestic production and distribution.Biotechnology and Biological Sciences Research Council (BBSRC): BB/S01425X/1, ESRC and NERC Scottish Governmen

Soil compaction effects on litter decomposition in an arable field: implications for management of crop residues and headlands

Soil compaction is a major threat to agricultural soils. Heavy machinery is responsible for damaging soil chemical, physical and biological properties. Among these, organic matter decomposition, which is predominantly mediated by the soil biota, is a necessary process since it underpins nutrient cycling and the provision of plant nutrients. Understanding factors which impact the functionality of the biota is therefore necessary to improve agricultural practices. To better understand the effects of compaction on the soil system, we determined the effects of soil bulk density and soil penetration resistance on the decomposition rates of litter in three distinct field zones: a grass margin, sown at the edge of the field adjacent to the crop, tramlines in the crop:margin interface, and crop. Three litters of different quality (ryegrass, straw residues and mixed litter) were buried for 1, 2, 4 and 6 months in litter bags comprising two different mesh sizes (0.02 and 2 mm). Bulk density and soil penetration resistance were greater in the compacted tramline than in the margin or the crop. The greatest amount of litter remaining in the bags after 6 months was found in the tramline, and the least in the grass margin. Differences between treatments increased with burial time. No significant differences in mass loss between the two mesh sizes was detected before the fourth month, implying that microbial activities were the main processes involved in the early stages of decomposition. Decomposition in the tramline was clearly affected by the degradation of soil structure due to heavy compaction. This study shows that soil conditions at the edges of arable fields affect major soil processes such as decomposition. It also reveals the potential to mitigate soil degradation by managing the headland, the crop residues and the machinery traffic in the field

Depth-resolved multimodal imaging : wavelength modulated spatially offset Raman spectroscopy with optical coherence tomography

Funding: UK Engineering and Physical Sciences Research Council (EPSRC: EP/J01771X/1, EP/M000869/1), the European Union FAMOS project (FP7 ICT, 317744) and the RS MacDonald Charitable Trust for funding.A major challenge in biophotonics is multimodal imaging to obtain both morphological and molecular information at depth. We demonstrate a hybrid approach integrating optical coherence tomography (OCT) with wavelength modulated spatially offset Raman spectroscopy (WM-SORS). With depth co-localization obtained from the OCT, we can penetrate 1.2mm deep into the strong scattering media (lard) to acquire up to a 14-fold enhancement of a Raman signal from a hidden target (Polystyrene) with a spatial offset. Our approach is also capable of detecting both Raman and OCT signals for pharmaceutical particles embedded in turbid media and revealing the white matter within a brain tissue layer. This depth resolved label-free multimodal approach is a powerful route to analyze complex biomedical samples.PostprintPeer reviewe