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241.
Sina Maghami Nick Nadim K. Copty Selen Deviren Saygın Hasan Sabri Öztürk Burak Demirel S. Mehdi Emadian Günay Erpul Majid Sedighi Masoud Babaei 《水文研究》2024,38(3):e15135
Soil salt accumulation is a widespread problem leading to diminished crop yield and threatening food security in many regions of the world. The soil salinization problem is particularly acute in areas that lack adequate soil water drainage and where a saline shallow water table (WT) is present. In this study, we present laboratory-scale column experiments, extending over a period of more than 400 days that focus on the processes contributing to soil salinization. We specifically examine the combined impact of soil compaction, surface water application model and water quality on salt dynamics in the presence of a saline shallow WT. The soil columns (60 cm height and 16 cm diameter) were packed with an agricultural soil with bulk densities of 1.15 and 1.34 g/cm−3 for uncompacted and compacted layers, respectively, and automatically monitored for water content, salinity and pressure. Two surface water compositions are considered: fresh (deionized, DI) and saline water (~3.4 mS/cm). To assess the sensitivity of compaction on salt dynamics, the experiments were numerically modelled with the HYDRUS-1D computer program. The results show that the saline WT led to rapid salinization of the soil column due to capillarity, with the salinity reaching levels much higher than that at the WT. However, compaction layer provided a barrier that limited the downwards moisture percolation and solute transport. Furthermore, the numerical simulations showed that the application of freshwater can temporarily reverse the accumulation of salts in agricultural soils. This irrigation strategy can help, in the short-term, alleviate soil salinization problem. The soil hydraulic properties, WT depth, water quality, evaporation demand and the availability of freshwater all play a role in the practicability of such short-term solutions. The presence of a saline shallow WT would, however, rapidly reverse these temporary measures, leading to the recurrence of topsoil salinization. 相似文献
242.
Sarah McMullan Denis Vida Hadrien A. R. Devillepoix Jim Rowe Luke Daly Ashley J. King Martin Cupák Robert M. Howie Eleanor K. Sansom Patrick Shober Martin C. Towner Seamus Anderson Luke McFadden Jana Horák Andrew R. D. Smedley Katherine H. Joy Alan Shuttleworth Francois Colas Brigitte Zanda Áine C. O'Brien Ian McMullan Clive Shaw Adam Suttle Martin D. Suttle John S. Young Peter Campbell-Burns Richard Kacerek Richard Bassom Steve Bosley Richard Fleet Dave Jones Mark McIntyre Nick James Derek Robson Paul Dickinson Philip A. Bland Gareth S. Collins 《Meteoritics & planetary science》2024,59(5):927-947
On February 28, 2021, a fireball dropped ∼0.6 kg of recovered CM2 carbonaceous chondrite meteorites in South-West England near the town of Winchcombe. We reconstruct the fireball's atmospheric trajectory, light curve, fragmentation behavior, and pre-atmospheric orbit from optical records contributed by five networks. The progenitor meteoroid was three orders of magnitude less massive (∼13 kg) than any previously observed carbonaceous fall. The Winchcombe meteorite survived entry because it was exposed to a very low peak atmospheric dynamic pressure (∼0.6 MPa) due to a fortuitous combination of entry parameters, notably low velocity (13.9 km s−1). A near-catastrophic fragmentation at ∼0.07 MPa points to the body's fragility. Low entry speeds which cause low peak dynamic pressures are likely necessary conditions for a small carbonaceous meteoroid to survive atmospheric entry, strongly constraining the radiant direction to the general antapex direction. Orbital integrations show that the meteoroid was injected into the near-Earth region ∼0.08 Myr ago and it never had a perihelion distance smaller than ∼0.7 AU, while other CM2 meteorites with known orbits approached the Sun closer (∼0.5 AU) and were heated to at least 100 K higher temperatures. 相似文献
243.
Summary This article examines the process of airfield re-use across rural England, highlighting the framework and realities of procedural planning control. In doing so, it illustrates how the re-use of. airfield sites in the countryside raises issues of more general concern and mirrors wider debates within the sphere of development planning. In short, we are concerned with both opportunities for land re-cycling on rural airfields and the debates which are likely to emerge as additional sites are re-developed. 相似文献
244.
Measurements and Observations in the XXI century (MOXXI): innovation and multi-disciplinarity to sense the hydrological cycle 总被引:2,自引:2,他引:0
Flavia Tauro John Selker Nick van de Giesen Tommaso Abrate Remko Uijlenhoet Maurizio Porfiri 《水文科学杂志》2018,63(2):169-196
To promote the advancement of novel observation techniques that may lead to new sources of information to help better understand the hydrological cycle, the International Association of Hydrological Sciences (IAHS) established the Measurements and Observations in the XXI century (MOXXI) Working Group in July 2013. The group comprises a growing community of tech-enthusiastic hydrologists that design and develop their own sensing systems, adopt a multi-disciplinary perspective in tackling complex observations, often use low-cost equipment intended for other applications to build innovative sensors, or perform opportunistic measurements. This paper states the objectives of the group and reviews major advances carried out by MOXXI members toward the advancement of hydrological sciences. Challenges and opportunities are outlined to provide strategic guidance for advancement of measurement, and thus discovery. 相似文献
245.
Shore platforms control wave energy transformation which, in turn, controls energy delivery to the cliff toe and nearshore sediment transport. Insight into shore platform erosion rates has conventionally been constrained at millimetre-scales using micro-erosion metres, and at metre-scales using cartographic data. On apparently slowly eroding coasts, such approaches are fundamentally reliant upon long-term observation to capture emergent erosion patterns. Where in practise timescales are short, and where change is either below the resolution or saturates the mode of measurement, the collection of data that enables the identification of the actual mechanisms of erosion is hindered. We developed a method to monitor shore platform erosion at millimetre resolution within metre-scale monitoring plots using Structure-from-Motion photogrammetry. We conducted monthly surveys at 15 0.25 m2 sites distributed across the Hartle Loup platform in North Yorkshire, UK, over one year. We derived topographic data at 0.001 m resolution, retaining a vertical precision of change detection of 0.001 m. We captured a mean erosion rate of 0.528 mm yr-1, but this varied considerably both across the platform and through the year. We characterized the volume and shape of eroded material. The detachment volume–frequency and shape distributions suggest that erosion happens primarily via removal of shale platelets. We identify that the at-a-point erosion rate can be predicted by the distance from the cliff and the tidal level, whereby erosion rates are higher closer to the cliff and at locations of higher tidal duration. The size of individual detachments is controlled by local micro-topography and rock structure, whereby larger detachments are observed on more rough sections of the platform. Faster erosion rates and larger detachments occur in summer months, rather than in more energetic winter conditions. These results have the potential to form the basis of improved models of how platforms erode over both short- and long-timescales. © 2019 John Wiley & Sons, Ltd. 相似文献
246.
247.
A spectral response approach for detecting dominant phytoplankton size class from satellite remote sensing 总被引:1,自引:0,他引:1
Robert J W Brewin Samantha J Lavender Nick J Hardman-Mountfor Takafumi Hirata 《海洋学报(英文版)》2010,29(2):14-32
An important goal in ocean colour remote sensing is to accurately detect different phytoplank- ton groups with the potential uses including the validation of multi-phytoplankton carbon cycle models; synoptically monitoring the health of our oceans, and improving our understanding of the bio-geochemical interactions between phytoplankton and their environment. In this paper a new algorithm is developed for detecting three dominant phytoplankton size classes based on distinct differences in their optical signatures. The technique is validated against an independent cou- pled satellite reflectance and in situ pigment dataset and run on the 10-year NASA Sea viewing Wide Field of view Sensor (SeaWiFS) data series. Results indicate that on average 3.6% of the global oceanic surface layer is dominated by microplankton, 18.0% by nanoplankton and 78.4% by picoplankton. Results, however, are seen to vary depending on season and ocean basin. 相似文献
248.
Climate change and river flooding: Part 2 sensitivity characterisation for british catchments and example vulnerability assessments 总被引:4,自引:0,他引:4
This paper is the second of a series describing a scenario-neutral methodology to assess the sensitivity and vulnerability of British catchments to changes in flooding due to climate change. In paper one, nine flood sensitivity types were identified from response surfaces generated for 154 catchments. The response surfaces describe changes in 20-year return period flood peaks (RP20) in response to a large set of changes in precipitation, temperature and potential evapotranspiration. In this paper, a recursive partitioning algorithm is used to link families of sensitivity types to catchment properties, via a decision tree. The tree shows 85 % success characterising the four sensitivity families, using five properties and nine paths. Catchment annual average rainfall is the primary partitioning factor, with drier catchments having a more variable response to climate (precipitation) change than wetter catchments and higher catchment losses and permeability being aggravating factors. The full sensitivity-exposure-vulnerability methodology is illustrated for two catchments: sensitivity is estimated by using the decision tree to identify the sensitivity family (and its associated average response surface); exposure is defined from a set of climate model projections and combined with the response surface to estimate the resulting impacts (changes in RP20); vulnerability under a range of adaptive capacity thresholds is estimated from the set of impacts. Even though they are geographically close, the two catchments show differing vulnerability to climate change, due to their differing properties. This demonstrates that generalised response surfaces characterised by catchment properties are useful screening tools to quantify the vulnerability of catchments to climate change without the need to undertake a full climate change impact study. 相似文献
249.
新疆西天山吐拉苏火山盆地金矿的构造控矿规律 总被引:9,自引:6,他引:9
新疆西天山吐拉苏火山盆地金矿在不同尺度上受不同级别的构造控制。在大地构造尺度上,Ⅰ级控矿构造为与博罗科努丰生代岛弧带平行的NWW向基底断裂带,该断裂带控制与石炭纪火山岩有关的金矿带的展布,在区域尺度上,Ⅱ级控矿构造为NW向走滑断裂和NE向张笥断裂,控制金矿床的分布。在矿床尺度上,Ⅲ级控矿构造为陡倾的近SN向张性断裂和与破火山口有关的环状断裂,控制金矿体的定位和产状。 相似文献
250.
Marine-like potash evaporite formation on a continental playa: case study from Chott el Djerid, southern Tunisia 总被引:3,自引:0,他引:3
Robert G. Bryant Bruce W. Sellwood Andrew C. Millington Nick A. Drake 《Sedimentary Geology》1994,90(3-4):269-291
An exceptional flood in January 1990 led to the formation of a large ephemeral lake on the Chott el Djerid, a salt playa in southern Tunisia. Repeated observations made during 1990 show that the ephemeral lake underwent four evolutionary stages: (1) initial flooding, (2) evaporative concentration of lake waters, (3) the movement of concentrated brine pools over the playa surface as a result of wind action, and (4) total desiccation of the lake by September 1990. During all four stages the brine chemistry of the lake was monitored. Water inflow into the Chott el Djerid basin was found to have a consistent Ca-SO4-Cl-rich and HCO3-CO3-poor chemistry, reflecting the recycling of homogeneous assemblages of Cretaceous, Mio—Pliocene and Quaternary evaporites within the catchment. As the ephemeral lake shrank, these waters produced an Na-Mg-K-Cl-SO4 brine which was similar to modern sea water. Mineral saturation data show that, during the desiccation of the lake, saturation with respect to both gypsum and halite was achieved and that the most concentrated brines were ultimately saturated with respect to potash phases. After the desiccation of the lake the main mineral phases found on the Chott included gypsum and halite. In addition, ephemeral deposits of carnallite (observed as carnallitite,3KMgCl3·6H20 + NaCl) were found. This assemblage is that which would be expected to form if the waters had undergone salt norm evaporation at 1 bar pressure at 25°C (SNORM) in the evaporation model proposed by Jones and Bodine (1987). The nature of both the brine chemistry and evaporite mineralogy provides a new and rare example of marine-like potash-bearing evaporites being formed in a contemporary continental playa. 相似文献