Heavy Sands Research Articles

Determination and calculation of gamma and neutron shielding characteristics of UHPC with high titanium heavy slag sand

The primary aim of this work was to investigate the effects of HS contents on the mechanical properties, shielding performance, and impact properties of UHPC. The shielding performance against gamma rays was calculated and measured using the XCom program and radiation equipment with a 60Co source. Furthermore, other shielding parameters such as buildup factors and the effective fast neutron removal cross-sections were also calculated. The results displayed that the shielding performance against gamma rays of UHPC increased with increasing HS proportions, while the fast neutron removal cross-section reached the maximum value at 50 % HS content. Specifically, compared with S0, μ increased by about 10.81 % and 10.56 % at the energy of 0.662 MeV and 1.25 MeV, respectively, whereas the values of HVL and TVL all decreased by 10.66 % in the selected energies. Additionally, the results demonstrated that the mechanical property and impact properties increased with the increase of HS content.

Synergistic solidification of heavy metal tailings by polyethylene glycol (PEG) and microorganisms

A significant amount of tailings rich in heavy metals is left behind after mining, causing environmental pollution due to long-term storage. In recent years, microbial-induced carbonate precipitation (MICP) has shown potential to solidify and stabilize heavy metal-contaminated soils. However, high concentrations and complex mixtures of heavy metals have toxic effects on microorganisms, resulting in decreased carbonate yield. Additionally, tailings sand often has a small particle size and poor permeability, which significantly reduces the solidification uniformity when using traditional grouting methods. To address these challenges, a low pH treatment method using PEG-MICP was proposed. This method increased the unconfined compressive strength (UCS) of tailings sand by 2.5 times and significantly improved soil uniformity while substantially reducing exchangeable heavy metal ions. Microscopic analysis showed that the introduction of PEG modifies the morphology of calcium carbonate, transforming calcite from a mineral to sheet-like and faceted forms, thus enhancing solidification efficiency. This study suggests that PEG-MICP has broad application prospects for solidifying heavy metal-contaminated tailings sand.

Stability of THAI in situ combustion process in reservoirs with layers of grading permeabilities and porosities: Detailed qualitative investigations

The world-wide reserves of heavy oil, tar sand, and bitumen, etc., outweigh those of conventional oil by a factor of 7/3. Given that the conventional reserves are being rapidly depleted, the need to develop and produce the unconventional resources has never been so critical. However, the proven most efficient and environmentally-friendly technology, namely the THAI process, still requires further study, and it has no documented design procedures that factor in the non-ideal geological features of heavy oil and bitumen reservoirs. Throughout the literature, there is little reported on the effects of gradations in reservoir petro-physical parameters on the performance of the THAI process. Consequently, this work reports the results of numerical simulations for four different kinds of reservoirs, each having progressive gradations in permeabilities and porosities. The major findings from this in depth study include.(i) In terms of the temperature distribution, regardless of the permeability and porosity gradations, the high temperature zone is always skewed towards the highest permeabilities and porosities zone. Furthermore, it is found that, in any model in which the shoes of the VI wells have no direct communication pathway with the highest permeabilities and porosities zones of the reservoirs, the high temperature zones occur in two chambers, otherwise, there is one high temperature zone.(ii) It is found that generally, the combustion front tends to be lopsided in favour of the most permeable and porous zone. In the case of a bottom-up progressive increase in permeabilities and porosities (model L1), the single combustion front has greatest advance horizontally at the top and axially in the middle of the reservoir, while in model L2 (the converse of model L1), the combustion fronts propagated in two chambers before the chambers overlapped in the toe region of the HP well where it advanced fastest. Therefore, the combustion zone in model L1 was far more stable than in model L2.(iii) It is found that the combustion fronts in model L3, with the lowest permeabilities and porosities at the centre in the longitudinal direction, propagated in two chambers that overlapped each other around the toe region of the HP well and advanced greatest in the HP well and on either lateral edge of the reservoir. In model L4, which has lateral gradation in permeabilities and porosities, however, the thinner edge of the wedge-shape combustion front had advanced fastest along the vertical mid-plane where the HP well was located. Thus, the combustion zone in model L3 was far more stable than that in model L4.(iv) It is found that in all the models except model L4, there exist rich oil saturation zones in the most permeable and porous regions located ahead of the mobile oil zone (MOZ) of each reservoir. These are formed due to restrictions in the pathways via which the mobilised oil can drain into the HP well. In model L4, the HP well is already in the most permeable zone and consequently, the fluids that favourably reach there are rapidly gravity-drained into the HP well.

Contamination and sediment quality evaluation of toxic metals enrichment in heavy mineral-rich beach sands of Arish City, Northeastern Egypt

Contamination and sediment quality evaluation of toxic metals enrichment in heavy mineral-rich beach sands of Arish City, Northeastern Egypt

Mechanical composition and physical properties of irrigated soils of the gijduvan district of Bukhara region

The mechanical composition and physical properties of soils in irrigated agriculture in the Gijduvan district of Bukhara region were studied. In the Hamid Olimjon district (Sarmijon) area, Omad farm soil pits (sections) were dug on the contour 576. In the Gulistan district, the contours of the Shukur Tokhta farm 282-283 and the contour 648 of the Hasan Rajabi farm of the Gijduvan region, and the mechanical composition and physical properties of the soil were analyzed from the samples taken. made the mechanical composition of the soil is light, medium and heavy sand, porosity is considered unsatisfactory.

Primary source of titanomagnetite ores at the Orokolo Bay placer deposit: Implications for petrogenesis

AbstractCoastal and river sand sequences of Holocene age at Orokolo Bay in Papua New Guinea are host to secondary titanomagnetite ore deposits. The resource developer (Mayur Resources) declares a measured orebody of 139 million tons at grades of 11.35% Fe, 1.94% Ti, and 712 ppm Zr. Orokolo Bay is located near the boundary between the Papuan Thrust and Fold Belt and the Aure Fold Belt. This region is characterized by sedimentary rocks of the Papuan Basin, which are intruded and overlain by a diverse array of magmatic intrusive and volcanic rocks, ranging from mafic alkaline to felsic calc‐alkaline types related to arc–continent collisions in the Cenozoic. The Vailala and Purari rivers located to the east and west of Orokolo Bay, respectively, are the main sediment pathways. Earlier provenance studies have suggested that the deposited sediments mainly come from the erosion of volcanic rocks found within the catchments of these two rivers. However, these studies did not specifically identify the primary source of the Fe‐Ti ores within this region. Here, we report on a potential primary source of the Fe‐Ti ores by examining the occurrence and chemical compositions for detrital titanomagnetites, and associated pyroxene and amphibole minerals. The purpose of this was to discern specific attributes of the primary source for its identification. Lithic sediments comprised of magnesio‐hornblende (Mhbl), tschermakaite (Tsr) and magnesio‐hastingsite (Mhst) amphiboles, clinopyroxene (Cpx), and Fe‐Ti oxide minerals dominate the heavy sands. Feldspar is more abundant than quartz, and Cr‐spinel is rare. Two primary titanomagnetite types were categorized based on their homogeneous grain textures and TiO2 content, Tmt1 (average 28 wt% TiO2) and Tmt2 (average 7 wt% TiO2). Pleonaste exsolutions and zircon inclusions distinguish Tmt1 from Tmt2, while apatite and quenched glass inclusions occur in both. A portion of both primary titanomagnetites exhibits hydrothermal overprinting, this subset was categorized as Tmt3 (average 12.5 wt% TiO2). Fe‐Ti oxides are associated with Cpx and amphiboles as inclusions, and as pseudomorphs in opacitic amphiboles. Tmt1 coexists predominantly with Mhst‐Tsr but also appears less frequently with Mhbl and Cpx. Tmt2 occurs almost exclusively with Mhbl and Cpx. Titanomagnetite chemistry is low in Cr, Mg, and V content suggesting crystallization from evolved melts. Tmt3 is shows enriched Si, Ca, Al, and Mg concentrations that are characteristic of late‐stage fluids derived from calcareous rocks. Amphibole and Cpx chemistry indicate they were derived from a subalkaline source magma of arc affinity. Fe‐Ti thermobarometry reveals Tmt1 (990 to 967°C, −0.51 to −0.18 ΔNNO) formed at higher temperatures and in less oxidized conditions than Tmt2 (834 to 689°C, 0.33 to 3.2 ΔNNO). Amphibole thermobarometry reveals Mhst‐Tsr and Mhbl formed under similar conditions as Tmt1 and Tmt2, respectively. The lack of Cr‐spinel, olivine, and the abundant occurrence of zircon and Mhbl indicate an evolved subalkaline source characterized by felsic rocks related to arc magmatism. The only volcanic source which aligns with these characteristics is Mount Yelia within the Vailala River catchment. Compositional variation between Tmt1 and Tmt2 titanomagnetites and associated silicate minerals is attributed to heterogeneous temperature and ƒO2 conditions within the melt during crystallization. The provenance of Ti‐rich titanomagnetite ores from sources related to arc magmatism indicates the potential of other areas associated with arc activity in Papua New Guinea to host secondary deposits rich in Fe‐Ti ores.

The Influence of Curing System on the Macroscopic Performance and Microstructure of Anti-Abrasive UHPC

In a previous study, we utilized saturated prewet high titanium heavy slag sand to produce UHPC (ST-UHPC). ST-UHPC has high impact and abrasion resistance. For better ST-UHPC applications, we investigate the mechanism of ST-UHPC under different curing systems from the microstructure and macroscopic perspective in this paper. We prepared ST-UHPC under four maintenance conditions: 20 °C standard curing, 90 °C steam curing, 90 °C dry curing and 210 °C 2 MPa pressure steam curing. Then, we analyzed the hydration product composition, the degree of cement hydration, the C-A-S-H gel microstructure and the substitution of Al3+ for Si4+ in relation to these prepared ST-UHPCs. Compared with standard curing, dry curing at 90 °C accelerated the water evaporation and reduced the hydration degree of ST-UHPC cementite. However, pressure steam curing significantly improved the hydration degree of ST-UHPC cementing material, and increased the MCL and Al[4]/Si of C-A-S-H gel. In addition, pressure steam curing reduced the Ca/Si and promoted the conversion of C-A-S-H cementing to tobermorite. Compared with dry curing at 90 °C, pressure steam curing significantly improved the macroscopic properties of ST-UHPC. The macro-performance difference of ST-UHPC under standard curing and 90 °C steam curing is small. The reason is that steam curing caused the water to be rapidly released in the internal aggregate of ST-UHPC. This resulted in the increase of the interface between the internal aggregate of ST-UHPC and the ST-UHPC cementate. The harmful pores in the ST-UHPC matrix under steam curing were also increased. To sum up, compared with standard curing, dry curing at 90 °C weakened the mechanical properties and microstructure of ST-UHPC, but steam pressure curing increased them. The single steam curing had no significant effect on the mechanical properties and microstructure of the ST-UHPC. Therefore, non-steam and room-temperature moisturizing maintenance should be adopted for anti-abrasive UHPC.

Spatial Distribution of some of the Common Minerals in Saad River Project, Maysan Province, Iraq

The aim of study was to diagnose and study the minerals that present in some of the soils of the Saad River project. The study included choosing a pilot area and taking three movement paths (Transect) in a vertical direction across the Saad River. Each of them passes through the largest number of soil units with the largest area and the most frequent. Nine sites of soil were selected as peduncles for each of the selected paths, with three soil peduncles for each strip path (the first was the shoulder of the river, the second was the river basin, and the third was the depressions). Soil peduncles were described in a fundamental morphological description according to the Soil Science Division Staff Manual (2017). Soil samples were also obtained from each horizon of the peduncles for the purpose of performing some required laboratory analysis. The results of the mineral analysis indicated that the light sand minerals are common, as their percentage ranged 95.80%-98.80%. The predominance was in the carbonate rock fragments in the first place, followed by the quartz minerals in all horizons of the study pedons. Quartz, both monocrystalline and polycrystalline quartz were found. Monocrystalline quartz was dominant in all study pedons, due to its resistance to weathering due to the nature of its chemical bonds, hardness, and lack of cracks, as well as its light weight. For the heavy sand minerals, their percentage was 1.20%-4.20% of the total sand minerals. The opaque minerals prevailed in all the horizons of the soil pedons of the study. The vertical distribution of the opaque minerals in the horizons of the soil pedons showed a heterogeneous distribution. The difference in their percentages may be due to the effect of sedimentation processes, which is a reflection of the state of variation in the physiographic sites and its impact on the mineral content of the sediments and the lack of activity of weathering processes.

The evolution mechanism of anti-abrasive UHPC microstructure under impact and erosion

In the mudslide prone areas of western China, concrete piers were severely damaged by washing.In our previous research, the anti-abrasive UHPC prepared with saturated prewet high titanium heavy slag sand (ST-UHPC) is proposed to prevent such damage. And we studied the effect of grinding and erosion on the performance of ST-UHPC before, but the mechanism has not been studied in depth In order to study the microstructure evolution of ST-UHPC cement by the grinding and erosion, we use XRD, SEM, 27Al NMR, 29Si NMR test methods in this paper. By this way, we studied the effects of shock and salt erosion on hydration products composition, migration and transformation of Al-containing hydration products, hydration degree of cement and C-A-S-H gel microstructure. The results showed that the impact of bedload damaged the microstructure of UHPC. Then the damage of UHPC microstructure accelerates the transport of aggressive ions. Next, SO42- erodes from the site of damage and produces expansive erosion products such as gypsum and calcareous vanadite. The erosion of SO42- and Mg2+ resulted in the dealuminization and decalcification of C-A-S-H gel in UHPC cement and mechanical properties degradation. Thus, the expansion damage of UHPC and the impact damage of UHPC structure are aggravated. So the microstructure damage of UHPC was further aggravated. Under the action of impact, the water impacting material forms various chemical bonds with the C-A-S-H substrate. The chemical bonds results in the evolution of C-A-S-H microstructure. In conclusion, the structure of C-A-S-H substrate deteriorates obviously under the coupling effect of scouring and erosion. And the impact resistance of C-A-S-H substrate decreases significantly.

The development of concrete filled steel tube with enhanced performance via the use of expansive ultra high performance concrete

The combination of ultra high performance concrete (UHPC) and steel tube is expected to create a concrete filled steel tube (CFST) with improved performance, meeting the increasing demands of high-rise buildings and long-span structures. However, UHPC suffers from high autogenous shrinkage, limiting the synergistic effects. Herein, we firstly prepared expansive UHPC with the combined use of high titanium heavy slag sand (HTHSS) serving as internal curing agent and MgO-based expansive agent (EA). After that, we systematically evaluated the volume stability and strength development of the expansive UHPC, where the results indicated that the addition of HTHSS could not only reduce autogenous shrinkage via humidity compensation but also provide water for the expansion reaction and enhance the efficiency of the expansion agent (EA), thus improving the volume stability of UHPC. After that, CFST with the expansive UHPC has been developed and the axial load-displacement curves showed a notable enhancement. Specifically, the peak bearing capacity of expansive UHPC concrete filled steel tube contributed to a 19% strength boost compared to that of CFST with traditional UHPC. This improvement was also evident in the stress-strain curves, as the peak stress of the expansive UHPC concrete filled steel tube was approximately 170 MPa, about 21% higher than that of traditional UHPC filled steel tube. This study provides a superior construction material, offering a valuable material choice for the development of the construction industry.

Impact of Sedimentary Conditions and Relative Distribution of Sand Sedimentary Minerals in Iraqi Soils

This study investigated the relative distribution of sand-separating minerals and the effect of sedimentary and climatic conditions on their distribution in some soils from northern and southern Iraq. The samples were collected from four Iraqi governorates: Erbil (included the soils from areas of Shaqlawa, Soran, and Juman), Sulaymaniyah (included the soils from Dokan, Sayed Sadeq, and Halabja), Maysan (included the soils of Al-Kahla, Ali Al-Sharqi, Awasha, Kumit, Ali Al-Gharbi, and Al-Tayyib), and Wasit Governorate (included the soils of Zurbatiya, Badra, Jassan, Al-Muwafiqiyah, Al-Numaniyah, and Zubaidiyah). The results indicated that the percentages of light sand minerals were higher than the percentages of heavy sand minerals in all the soils of the study sites. It is attributed to the nature of the mineral composition and the intensity of the weathering factor’s influence on the sedimentation sites or during transportation. The results also indicated the dominance of the quartz group, followed by the group of carbonate rock pieces and the group of feldspar minerals in terms of dominance within the light part of sand minerals in all soil samples in southern Iraq (Wasit and Maysan). The rock-cut minerals group was dominant, followed by the quartz and feldspar minerals group in all soil samples in northern Iraq (Erbil and Sulaymaniyah). The other light minerals of the group were found in varying proportions and distribution in all soil samples, which included (mudstone, lime, evaporites, igneous and metamorphic rocks, clay-coated grains, and other minerals). The results showed that the percentages of the opaque minerals were higher in all soil samples than the group of non-opaque minerals, which included minerals (zircon, tourmaline, rutile, strolite, epidote, and kyanite) with irregularity and a significant difference in the proportions as the large percentages indicate that they bear transportation over long distances and their resistance to weathering processes. These ratios were more evident in the northern regions of Erbil and Sulaymaniyah, which indicate the intensity of weathering processes (wet climate) compared to the soils of Wasit and Maysan in southern Iraq. The low percentages appeared in the soil samples due to the short transportation distance and the diversity of the source rocks.

Preparation and Properties of HUHPC with Low Shrinkage and High Impact Resistance

At present, nuclear energy is widely used to reduce pollution and clean energy. However, the radiation-proof concrete currently used to prepare nuclear shields cannot meet the protection requirements of nuclear safety. Therefore, there is an urgent need to develop radiation-proof concrete materials with high impact resistance and ultra-high strength. In this paper, the low-shrinkage, high-impact Heavy Ultra-High-Performance Concrete (HUHPC) was designed by the following innovative methods: Porous high titanium heavy slag sand (HTHS) (industrial solid waste) with “slow-water release” effect and expansion agent were synergistically used to improve volume stability; Irregular HTHS with “embedded lock” effect and steel fibers were synergistically utilized to enhance impact resistance; Heavy ilmenite sand was used to lift volume weight. The workability, mechanical properties, volume stability, impact resistance, and microstructure were studied. The results show that the designed HUHPC volume weight is more than 2,800 kg/m3 which can enhance the radiation protection performance greatly. The 180 d shrinkage of HUHPC is less than 400 µε, which volume stability is improved by more than 30%. The addition of lithium carbonate slightly decreased the 28 d strength of HUHPC, but the appropriate admixture amount (0.9%) could improve the impact resistance of HUHPC by 33%.

Study of the Variations in the Vertical and Horizontal Distribution of Heavy Sand Minerals in the Hilla River Sediments

Study of the Variations in the Vertical and Horizontal Distribution of Heavy Sand Minerals in the Hilla River Sediments

Assessing the Current Status and Proposing Solutions for Heavy Metal Management in the Saigon River Basin Sediments

The sediment is the final environment where heavy metals accumulate and directly impact the health of aquatic systems and humans.Therefore, the study was carried out to determine the total content and forms of heavy metals in the sediments at 13 locations in the Saigon River basin in rain and dry seasons of 2022. In addition, this research also assesses the pollution risk level and the correlation between heavy metals and physicochemical properties in the sediments. Chemical analysis was applied to determine the contributors of heavy metals while the geochemical calculation methods (hazard quotient (HQ), geo-accumulation index (Igeo), pollutant load index (PLI), individual contamination factors (ICF) and global contamination factors (GCF), risk assessment code (RAC)) were used to assess the pollution risk level in river sediments. The results show that Ag, Ba, Mn and Zn were metals with high pollution risks, especially in rain season. The results showed that the total concentration of heavy metals in sediments in rain season ranges from 109.92 to 4591.01 mg.kg–1 (Mn > Zn > Li > Ba > Ag > Cr > Cu > Pb) and in dry season from 0 to 3117.8 mg.kg–1 (Mn > Ag > Zn > Li > Ba > Cr > Cu > Pb). Applying the sequential extraction method, the metal forms of Ba, Cr, Cu and Li in the sediment samples are mainly residues (F5) (up to 76.53%), proving these elements dominated by natural sources. In contrast, the Mn extract composition was strongly influenced by human activity with exchange (F1) (>50%) and carbonate (F2) (>20%) components predominating. For Ag, Pb and Cu were mainly in organic form (F4). In dry season, the river sediments didn’t contain Pb because it didn’t carry away rainwater. In particular, Zn had a strong fluctuation between the extracted forms in rain and dry seasons, showing impacts from nature and humans sources. Besides, the statistical analysis results showed that pH affected Cu and Zn contents with a negative correlation, but did not detect the correlation between heavy metals and sand, clay, electrical conductivity (EC) in Saigon river sediments. The research results are foundational for the implementation and design of effective remediation strategies to prevent risks of river sediments degradation in the future.
 

The characterization of wear-causing particles and silica sand in particular

Erodants and abradants are two types of wear-causing particles (WCP). Despite their effects on the severity and rate of wear, WCP are inadequately characterized in a surprising number of publications, especially those involving impingement erosion and three-body abrasion. That shortfall makes it difficult to correlate features of WCP with the details of worn surfaces, or to develop wear models that account for those features. It is argued that the documentation of WCP should go beyond simply reporting their composition and mean particle size. In late 1985, ASTM Committee G2 on Wear and Erosion established a task group on the characterization of WCP. At that time, image analysis was slower and less sophisticated than it is today. While that ASTM task group failed to produce a consensus standard, computerized particle characterization methods were developing in fields other than tribology, fields like geoscience, heavy sand mining, materials processing, and pharmaceuticals. A notable exception to this is ferrography, which is a widely-used diagnostic for lubricated tribosystems. In the context of dry wear, it is useful to identify which features of WCP would be beneficial to document, and to identify some techniques and scales of detail appropriate to particular tribosystems. Examples are presented here for the morphological and mechanical characterization of silica sand grains, as prompted by a triboanalysis of the abrasive and erosive wear of biomass pre-processing equipment. The authors propose a minimum level of documentation for WCP, one that can enrich tribosystem analysis both in laboratory tests and field studies.

Soil evolution in basaltic parent materials under successive climate changes, Saudi Arabia

This study was designed to investigate the successive effects of the early Pleistocene subhumid and early to middle Holocene semi-arid paleoclimates and late Holocene to present day arid/hyperarid conditions on pedogenesis and evolution in Harrat Ithnayn volcano in the Arabian Shield, Saudi Arabia. The investigations were conducted using pedological macro and micro-features, physicochemical characteristics, elemental geochemistry, weathering indices and mineralogical analyses for light and heavy sand and clay fractions. The targeted soils developed in a subhumid paleoclimate and are classified as vitric Andisols, which are little to moderately weathered. Subhumid climate effects were evident through the presence of pedogenic Fe (crystalline oxides, Fed = 25 to 58 g kg─1), fairly high Feo/Fed (0.24 to 0.87), and the predominance of hydroxy-Al smectite and kaolinite. Residual primary minerals and modern arid conditions simultaneously led to accumulation of secondary salts and carbonates. Exchangeable Ca and Mg pools contributed 21–56 % of total Ca and Mg contents, while exchangeable K contributed only up to 4 %. Soil processes thus involved andisolization, salinization, and calcification. These processes were due to successive moist paleoclimates and the current arid conditions, thus revealing their formation under multiple climates.

Changes in the granulometric composition of Zarafshan river soils under irrigation and comparative analysis

According to the granulometric composition of all soil types (typical, light gray, gray-meadow and meadow-alluvial) located on terraces I - II - III of the Zarafshan oasis, it is mainly medium and heavy sand, physical clay (<0.01 mm) and large dust (0.05 – 0.01 mm), medium dust (0.01 – 0.005 mm), fine dust (0.005 – 0.001 mm) and silt particles due to irrigation for many years reduced sand particles and increased the amount of dust and silt particles in all layers of the soil . It is explained by the erosion of feldspar, mica-like substances in the sand particles, the increase of dust and silt particles in the upper layers of the soil as a result of irrigation, and the fact that certain parts are washed to the lower layers of the soil.

Evaluation of fertility of irrigated soils in Uzbekistan

The article examines the current productivity status of irrigated soils, encompassing aspects such as mechanical composition, agrochemical properties, salinity levels, and soil quality evaluation. The study highlights that the prevailing condition of the researched irrigated soils primarily comprises heavy sand texture. These soils exhibit a deficiency in humus content, rendering them low in organic matter. Additionally, they are characterized by a notable scarcity of mobile phosphorus and a correspondingly low content of exchangeable potassium. The research further categorizes the soils under investigation into three distinct cadastral groups based on their quality attributes. Through this classification, a comprehensive assessment of the soils’ varying characteristics is achieved. Moreover, the study quantifies the average credit score of these soils, indicating their overall quality level, which was found to be 55 points on average. The findings underscore the significance of understanding the intricate interplay between soil characteristics and agricultural productivity. This analysis provides valuable insights for optimizing soil management practices, ultimately contributing to enhanced agricultural output within the studied area.

Effect of Rhizome Severing on Survival and Growth of Rhizomatous Herb Phragmites communis Is Regulated by Sand Burial Depth.

Rhizome fragmentation and sand burial are common phenomena in rhizomatous clonal plants. These traits serve as an adaptive strategy for survival in stressful environments. Thus far, some studies have been carried out on the effects of rhizome fragmentation and sand burial, but how the interaction between rhizome fragmentation and sand burial affects the growth and reproduction of rhizomatous clonal plants is unclear. We investigated the effect of the burial depth and rhizome fragment size on the survival and growth of the rhizomatous herb Phragmites communis using 288 clonal fragments (6 burial depths × 8 clonal fragment sizes × 6 replicates) in a field rhizome severing experiment. The ramet survival of the rhizomatous species significantly increased with the sand burial depth and clonal fragment size (p < 0.01), and the effects of the clonal fragment size on ramet survival depended on the sand burial depth. Sand burial enhanced both the vertical and horizontal biomass (p < 0.05), while the clonal fragment size affected the vertical biomass rather than the horizontal biomass. Sand burial facilitated the vertical growth of ramets (p < 0.05) while the number of newly produced ramets firstly increased and then decreased with the increasing clonal fragment size, and the maximal value appeared in four clonal fragments under a heavy sand burial depth. There is an interaction between the burial depth and rhizome fragment size in the growth of rhizome herbaceous plants. The population growth increases in the increase of sand burial depth, and reaches the maximum under severe sand burial and moderate rhizome fragmentation.

Determination of the concentration-dependent effective diffusivity of CO2 in unconsolidated porous media saturated with heavy oil by considering the swelling effect

Effective diffusivity of CO2 in the unconsolidated sandpack saturated with a Lloydminster heavy oil was determined in the form of an exponential function of CO2 concentration in the diluted and swollen liquid-phase. For such a purpose, two pressure-decay experiments were executed at different pressure ranges (i.e., 855–817 kPa and 1993–1905 kPa) and a temperature of 299.65 K. First, the sandpack saturated with heavy oil was prepared under an increased temperature of 348.15 K because the reduced heavy oil viscosity was required to saturate the sand column with heavy oil in a diffusion cell. Next, the diffusion cell containing the Lloydminster heavy oil-saturated sand column was integrated into a pressure-decay experimental system with pressure-monitoring devices. Then, pressure-history curves of both the diffusion experiments were continuously recorded to be compared with the theoretically calculated ones. The Fick's 2nd law incorporated with the volume-translated Peng-Robinson equation of state (PR-EOS) was implemented to determine the concentration-dependent effective diffusivity of CO2 in a sandpack saturated with heavy oil considering its swelling effect through minimizing the deviations between the theoretically computed pressure-history curves with the experimentally recorded ones. For the computation of the Fick's 2nd law, the Crank-Nicolson scheme finite difference method (FDM) was applied to take the local oil swelling into account for enhancing the accuracy of such a determined diffusivity. The excellent agreements between the theoretically computed and experimentally measured pressure-history curves at both the pressure ranges signify that such a determined effective diffusivity considering the CO2 concentration is accurate and reliable.