<p>Increasingly variable rainfall patterns expose soils to more frequent waterlogging in humid climates. Yet, the effects of waterlogging on soil organic matter decomposition in mineral soils remain uncertain. We studied the impact of off-season waterlogging on carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) production and dissolved carbon dynamics in controlled greenhouse conditions using 32 monolithic soil columns (hereafter monoliths) (<span class="inline-formula"><i>h</i>=63 cm</span>, <span class="inline-formula"><i>d</i>=15.2 cm)</span> sampled from two agricultural fields (silty clay, sandy loam) in southern Finland. The 1.5 year study comprised three growth cycles with alternating growing and off-seasons. Spring barley (<i>Hordeum vulgare</i>) was grown in all monoliths during the growing seasons. In turn, during all three off-seasons, half of the monoliths were subjected to waterlogging lasting seven weeks, while in the other half soil moisture was maintained at <span class="inline-formula">∼70 <i>%</i></span> field capacity. Within these water treatment groups (waterlogged and control), the monoliths were further divided into two plant treatment groups: in half of the monoliths, an overwintering cover crop (<i>Festuca arundinacea</i>) was grown, while in the other half soil was left bare for the off-seasons. Soil temperature and moisture were continuously monitored, dissolved organic (DOC) and inorganic carbon (DIC) concentrations in pore water were analyzed at three depths and <span class="inline-formula">CO<sub>2</sub></span> fluxes were measured at the surface. Contrary to our hypothesis, waterlogging did not increase soil DOC content. Instead, on-going microbial/rhizospheric activity promoted an increase in DIC content while <span class="inline-formula">CO<sub>2</sub></span> fluxes declined, indicating an accumulation of respired <span class="inline-formula">CO<sub>2</sub></span> in soil pore water. The sustained <span class="inline-formula">CO<sub>2</sub></span> production could not be explained solely by mobilization of Fe-associated C, as initially hypothesized. After the onset of drainage of the waterlogged monoliths, <span class="inline-formula">CO<sub>2</sub></span> fluxes from both soils increased more than predicted based on changes in soil moisture and temperature, likely due to the release of previously accumulated <span class="inline-formula">CO<sub>2</sub></span>. These post-waterlogging increases in <span class="inline-formula">CO<sub>2</sub></span> fluxes roughly equaled the earlier decreases during waterlogging. Thus, although off-season waterlogging strongly influenced the temporal dynamics of <span class="inline-formula">CO<sub>2</sub></span> fluxes, it did not alter total cumulative <span class="inline-formula">CO<sub>2</sub></span> emissions from the studied agricultural soils.</p>
Abstract The Siwalik Group is a key laboratory for the study of the Neogene environment. The lower unit of the Siwalik Group was deposited in a meandering river system (between ~ 16 and 10 Ma) that changed to braided during the deposition of the Middle Siwalik (at ~ 10 Ma). The vegetation shifted from C3 to C4 in the central Himalaya, Nepal at ~ 7.4 Ma (Surai Khola) and ~ 6.6–5.9 Ma (Bakiya Khola), in contrast to that in the western Himalaya at ~ 8.8–8.6 Ma (Potwar Basin, Pakistan). Additionally, the Indian Summer Monsoon (ISM) was active in the central Himalaya as early as ~ 10.7 Ma, remaining steady until 9.5 Ma, and then decreased by 7.5 Ma, i.e., 0.5 million years later than in the western Himalaya. Not only the uplift of the Himalaya due to the activation of the Main Boundary Thrust, but the rise of the proto-Tibetan Plateau could be a possible reason behind the intensification of the Asian Summer Monsoon (ASM) at ~ 10 Ma. There was an enrichment of δ18O, and a decrease in thickness of the leaching zones, which is most likely associated with the intensification of the monsoon. The rate of weathering and erosion was also higher during 10–8 Ma, coinciding with the rapid sedimentation rate in the Ganga Basin at ~ 10 Ma. Furthermore, geochronological studies indicate that the Tethyan Himalayan and Greater Himalayan sediments were a prominent source of sediments till ~ 10 Ma, while subsequent detritus was sourced from the Lesser Himalaya. However, in the eastern Himalaya, the presence of dominant numbers of the Cretaceous and younger detritus highlights the uneven pattern of Himalayan exhumation. The condition and formation of paleosols in Lower Siwalik in the central Himalaya indicate a decrease in ASM. The present study compares and summarizes the climatic conditions in the western and eastern Himalaya during the Neogene.
Through compositional inclusion or exclusion, the photograph can assert and communicate what belongs in a picture, in a landscape, in an ecosystem. It can illuminate what we deem conservation-worthy, or, on a larger scale, which extinctions are attention-worthy. Photographic practice helps to illuminate the active nature of extinction, and our choices as actors and witnesses within that process. Here, researchers from the University of Leeds’ Extinction Studies Doctoral Training Programme present individual reflections on interdisciplinary practice-led research in the Scottish Small Isles. We consider how photography, as a form of praxis, can generate new forms of knowledge surrounding extinction: its meanings, representations, and legacies, particularly through visual representation. We offer seven perspectives on contemporary image-making, from disciplines including philosophy, conservation biology, literature, sociology, geology, cultural anthropology, and palaeontology. Researchers gathered experiential, ethical, even biological meanings from considering what to include or exclude in images: from the micro to the macro, the visible to the invisible, the aesthetic to the ecological. We draw conclusions around meaning-making through the process of photography itself, and the tensions encountered through framing and decision-making in a time of mass ecological decline.
Quang-Huy Dang, Philippe Reiffsteck, Minh-Ngoc Vu
et al.
This study aims to investigate the effect of plastic fine content on the undrained monotonic behavior of sandy soils (mixtures of host sand and various plastic fine content from 0 to 25%), and in particular, their static liquefaction resistance (undrained shear strength). Illite Arvel is considered as a plastic fine to add to the host sand, the Fontainebleau sand. Binary mixture samples are reconstituted by using the moist tamping technique. A series of undrained triaxial tests were carried out to study the influence of different parameters, such as the fine content, the initial density index, the confining pressure, and the over-consolidation ratio (OCR) on the behavior of sandy soil mixture. Based on the results acquired from these tests, the liquefaction susceptibility of the sandy soil is discussed by using Chinese criteria.
BACKGROUNDDolomite is a common carbonate mineral in sedimentary rocks, and dolomite rock serves as an important reservoir rock for oil and gas. However, the production of synthetic dolomite under normal temperature and pressure is not yet possible, the genesis of dolomite and dolomite reservoirs has been a difficult problem to understand in geological research. Fe ion is a prevalent impurity element in natural dolomite, and the Fe content in dolomite can serve as an indicator of the diagenetic environment, which provides valuable insights into the genesis of dolomite. The technology of Raman spectroscopy has evolved from qualitative analysis to quantitative analysis. Therefore, the quantitative characterization of carbonate mineral chemical composition can be accomplished using Raman spectroscopy. Previous studies have shown that the Raman spectra of calcite group minerals shift regularly with the change of cation composition. However, there is no systematic study on the relationship between Fe content and Raman spectrum in dolomite.OBJECTIVESTo discuss the influence of Fe content on the Raman spectrum of dolomite, and establish a test method for the determination of Fe content in dolomite by Raman spectroscopy.METHODSSeven dolomite samples from the Maokou Formation were collected from a well in the Sichuan Basin. Based on the petrography observation under a microscope, different types of dolomite with relatively clean grains were selected for EPMA to obtain the chemical composition of dolomite, then microscopic confocal laser Raman spectroscopy was conducted in the same area to acquire the corresponding dolomite Raman spectra. In addition, Raman spectra and corresponding chemical composition data of 14 typical dolomite samples were obtained from the RRUFF database for this study. The effect of Fe content on Raman spectroscopy of dolomite was studied by analyzing the correlation between the characteristic parameters of dolomite Raman spectroscopy and Fe content.RESULTS(1) Raman peaks for two lattice vibration (T and L) and three [CO3]2− group internal vibration (v1, v3 and v4) were observed in the dolomite Raman spectrum. Compared with dolomite, each Raman peak position of ankerite moves to a lower frequency. Moreover, the Raman shifts of T and L peaks of ankerite are reduced by 5cm−1 and 13cm−1 on average, and the Raman shifts of v1, v3 and v4 peaks are reduced by 3cm−1, 2cm−1 and 2cm−1 on average, respectively. (2) There is an obvious linear relationship between the Raman shift and their Fe content of dolomite minerals. The measured Raman shift decreases with the increase of Fe content in dolomite. Notably, the movement of the peak position of the lattice vibration mode is more obvious, with the change of Fe content in dolomite, compared with the internal vibration peak. (3) Because the ionic radius of Fe2+ is larger than that of Mg2+, when Fe2+ replaced Mg2+ in the dolomite lattice, the average length of the metal-oxygen bond in minerals becomes longer, and the bond energy becomes weaker. Thus, with the changing of the Raman active vibration mode, Raman shifts of each peak in the dolomite Raman spectrum decreases.CONCLUSIONSBased on the different influences of Fe content in dolomite on the Raman shift of lattice vibration peaks and internal vibration peaks in Raman spectroscopy, a testing method for determining Fe content in dolomite is preliminarily established based on the distance between L peak and v1 peak in Raman spectroscopy. Compared with traditional methods for testing the Fe content in dolomite, this method has lower requirements for samples and can be used for non-destructive testing, and is suitable for artificial synthesis experiments of dolomite.
U–Pb dating was conducted for zircons from a total of 14 samples from 13 granite bodies in southwestern Cambodia using LA-ICP-MS. The granitic rock samples were collected from southwestern Cambodia, southwest of the Mae Ping Fault extending from northwest Cambodia via Tonle Sap Lake to southern Vietnam. The studied rock bodies belong to the ilmenite-series, except for three granitic rock bodies. They were identified as I-or A-type. The analysis yielded three distinct age ranges: 295–309, 191–232, and 75–98 Ma. The 295–309 Ma ages are associated with the Paleo-Tethys Sea subduction beneath the Indochina Block. The ages of 191–232 Ma may correspond to the amalgamation period of the Sibumasu and Indochina Blocks during the Indosinian Orogeny. Granitic rocks with ages of 75–98 Ma occur near the southeastern Cambodia-southern Vietnam border. Formation of these granitic rocks was associated with the Paleo-Pacific Ocean Plate (the Izanagi Plate) subduction beneath the Indochina Block. The region in which these granitic rocks occur is part of the Dalat–Kratie Zone.
The objective of this study is to propose an artificial neural network (ANN) model to predict the excavation-induced tunnel horizontal displacement in soft soils. For this purpose, a series of finite element data sets from rigorously verified numerical models were collected to be utilized for the development of the ANN model. The excavation width, the excavation depth, the retaining wall thickness, the ratio of the average shear strength to the vertical effective stress, the ratio of the average unloading/reloading Young’s modulus to the vertical effective stress, the horizontal distance between the tunnel and retaining wall, and the ratio of the buried depth of the tunnel crown to the excavation depth were chosen as the input variables, while the excavation-induced tunnel horizontal displacement was considered as an output variable. The results demonstrated the feasibility of the developed ANN model to predict the excavation-induced tunnel horizontal displacement. The proposed ANN model in this study can be applied to predict the excavation-induced tunnel horizontal displacement in soft soils for practical risk assessment and mitigation decision.
Engineering geology. Rock mechanics. Soil mechanics. Underground construction
The Albertine Basin is an important rift basin in the East African Rift System, enriched in oil and gas resources. The upper Miocene to lower Pliocene hydrocarbon source rocks are important source rocks in the basin, but the research is relatively limited. In this work, we evaluate the source rocks of the upper Miocene and lower Pliocene in the Albertine Basin by integrations of geological, rock pyrolysis and elemental geochemistry data and analyses the paleoenvironmental evolutions of the late Miocene to early Pliocene. These results show that the two sets of source rocks are under the mature stage, but the abundance and type of organic matter are different. The lower Pliocene source rocks have higher organic matter abundance and belong to middle-good source rocks, yielding type Ⅱ1 -Ⅱ2 kerogen. The upper Miocene source rocks have lower organic matter abundance and belong to poor source rocks, yielding type Ⅱ2-Ⅲ kerogen. The sedimentary environment is an important controlling factor for the difference in source rocks. During the late Miocene to early Pliocene, the study area was a freshwater lake with strong reducibility, gradually increasing water depth, a warmer climate, flourishing bacteria and microorganisms, and better organic matter types. At the same time, lake productivity is elevated, the sedimentation rate is accelerated, and organic matter can be preserved more efficiently, so the abundance of organic matter in source rocks is higher.
Geology, Engineering geology. Rock mechanics. Soil mechanics. Underground construction
Small unmanned aerial systems (sUAS) are becoming increasingly popular due to their affordability and logistical ease for repeated surveys. While sUAS-based remote sensing has many applications in water resource management, their applicability and limitations in fluvial settings is not well defined. This study uses a combined thermal-optic sUAS to monitor the seasonal geothermal influence of a 1-km-long reach of the Yellowstone River, paired with in-situ streambed temperature profiles to evaluate geothermal seep interactions with Yellowstone River in Montana, USA. Accurate river water surface elevation along the shoreline was estimated using structure from motion (SfM) photogrammetry digital surface models (DSMs); however, water surface elevations were unreliable in the main river channel. Water temperature in thermal infrared (TIR) orthomosaics was accurate in temperature ranges of tens of degrees (>≈30 °C), but not as accurate in temperature ranges of several degrees (>≈15 °C) as compared to in-situ water temperature measurements. This allowed for identification of geothermal features but limited the ability to identify small-scale temperature changes due to river features, such as pools and riffles. The study concludes that rivers with an average width greater than or equal to 123% of the ground area covered by a TIR image will be difficult to study using structure from motion photogrammetry, given Federal Aviation Administration (FAA) altitude restrictions and sensor field of view. This study demonstrates the potential of combined thermal-optic sUAS systems to collect data over large river systems, and when combined with in-situ measurements, can further increase the sUAS utility in identifying river characteristics.
N. W. Chaney, L. Torres-Rojas, N. Vergopolan
et al.
<p>Over the past decade, there has been appreciable progress
towards modeling the water, energy, and carbon cycles at field scales
(10–100 m) over continental to global extents in Earth system models
(ESMs). One such approach, named HydroBlocks, accomplishes this task while
maintaining computational efficiency via Hydrologic Response Units (HRUs),
more commonly known as “tiles” in ESMs. In HydroBlocks, these HRUs are
learned via a hierarchical clustering approach from available global
high-resolution environmental data. However, until now there has yet to be
a river routing approach that is able to leverage HydroBlocks' approach to
modeling field-scale heterogeneity; bridging this gap will make it possible
to more formally include riparian zone dynamics, irrigation from surface
water, and interactive floodplains in the model. This paper introduces a
novel dynamic river routing scheme in HydroBlocks that is intertwined with
the modeled field-scale land surface heterogeneity. Each macroscale polygon
(a generalization of the concept of macroscale grid cell) is assigned its
own fine-scale river network that is derived from very high resolution
(<span class="inline-formula">∼</span> 30 m) digital elevation models (DEMs); the inlet–outlet reaches of a domain's
macroscale polygons are then linked to assemble a full domain's river
network. The river dynamics are solved at the reach-level via the kinematic
wave assumption of the Saint-Venant equations. Finally, a two-way coupling
between each HRU and its corresponding fine-scale river reaches is
established. To implement and test the novel approach, a 1.0<span class="inline-formula"><sup>∘</sup></span> bounding
box surrounding the Atmospheric Radiation and Measurement (ARM) Southern
Great Plains (SGP) site in northern Oklahoma (United States) is used. The
results show (1) the implementation of the two-way coupling between the land
surface and the river network leads to appreciable differences in the
simulated spatial heterogeneity of the surface energy balance, (2) a limited
number of HRUs (<span class="inline-formula">∼</span> 300 per 0.25<span class="inline-formula"><sup>∘</sup></span> cell) are required to
approximate the fully distributed simulation adequately, and (3) the surface
energy balance partitioning is sensitive to the river routing model
parameters. The resulting routing scheme provides an effective and efficient
path forward to enable a two-way coupling between the high-resolution river
networks and state-of-the-art tiling schemes in ESMs.</p>
Organic-rich shales in between salt rock layers distribute widely in Qianjiang Sag, Jianghan Basin, central China. Due to the complexity of matrix mineral components and their distribution and tight pore structure, Archie’s law cannot be used directly to calculate oil saturation in those shale oil reservoirs. A new oil content model for shale oil reservoirs was introduced. By analyzing the logging and core experimental data from Qianjiang Sag, Jianghan Oilfield, we built the relationship between kerogen and the different well logging porosities including nuclear magnetic resonance (NMR) porosity, neutron porosity, and density porosity. And we used the dual-Vsh method to calculate the total organic carbon (TOC). After calculating the volume fraction of the solid organic matters and separating it from the TOC, we acquired the hydrocarbon fluid content in the formations. The calculated oil content results are coherent with the core experimental data, which indicates the efficiency of this model. This model is simple and can be quickly applied. However, this method also shows its weakness in calculation precision when the TOC is not calculated precisely or the quality of the porosity logs is low.
There is considerable interest in optimizing geothermal exploration techniques via the mapping of alteration and evaporate mineralisation, as well as of thermal emissions associated with geothermally active areas on the Earth’s surface. Optical and thermal satellite sensor technologies, improvements in processing algorithms and the means for large scale (e.g. 1:250,000) spatial data distribution are required for detecting both these attributes. The extensive visible, -near, -shortwave and thermal infrared (VNIR-SWIR-TIR) data archive acquired by the multi-spectral Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) provides a rich source of geoscience related imagery for geothermal exploration. Examples of generating large scale mosaicked ASTER imagery to provide province to continental mineral mapping have been undertaken in areas including such as Australia, western USA, Namibia and Zagros Mountains Iran. In addition, ASTER’s thermal infrared imagery also provides night time land surface temperature (LST) estimates relevant for detecting possible geothermal related anomalies.This study outlines existing methods for the application of ASTER data for geothermal exploration in East Africa. The study area encompasses a section of the East African Rift System across the Tanzanian and Kenyan border. The area includes rugged volcanic terrain which has had geological mapping of limited coverage at detailed scales, from various heritages and mapping agencies. This study summarizes the technology, the processing methodology and initial results in applying ASTER imagery for such compositional and thermal anomaly mapping related to geothermal activity. Fields observations have been used from the geothermal springs of Lake Natron, Tanzania, and compared with ASTER derived spectral composition and land surface temperature results. Published geothermal fields within the Kenyan portion of the study area have also been incorporated into this study.