Metal-bonded perovskite lead hydride with phonon-mediated superconductivity up to 46 K under atmospheric pressure

In the search for high-temperature superconductivity in hydrides, a plethora of multi-hydrogen superconductors have been theoretically predicted, and some have been synthesized experimentally under ultrahigh pressures of several hundred GPa. However, the impracticality of these high-pressure methods has been a persistent issue. In response, we propose a new approach to achieve high-temperature superconductivity under atmospheric pressure by implanting hydrogen into lead to create a stable few-hydrogen metal-bonded perovskite, Pb$_4$H. This approach diverges from the popular design methodology of multi-hydrogen covalent high critical temperature ($T_c$) superconductors under ultrahigh pressure. By solving the anisotropic Migdal-Eliashberg (ME) equations, we demonstrate that perovskite Pb$_4$H is a typical phonon-mediated superconductor with a $T_c$ of 46 K, which is six times higher than that of bulk Pb (7.22 K) and higher than that of MgB$_2$ (39 K). The high $T_c$ can be attributed to the strong electron-phonon coupling (EPC) strength of 2.45, which arises from hydrogen implantation in lead that induces several high-frequency optical phonon modes with a relatively large phonon linewidth resulting from H atom vibration. The metallic-bonding in perovskite Pb$_4$H not only improves the structural stability but also guarantees better ductility than the widely investigated multi-hydrogen, iron-based, and cuprate superconductors. These results suggest that there is potential for the exploration of new high-temperature superconductors under atmospheric pressure and may reignite interest in their experimental synthesis soon.Comment: 6 pages, 4 figure

Charmless Bˉs→VV\bar{B}_s\to VV Decays in QCD Factorization

The two body charmless decays of $B_s$ meson to light vector mesons are analyzed within the framework of QCD factorization. This approach implies that the nonfactorizable corrections to different helicity amplitudes are not the same. The effective parameters $a_i^h$ for helicity $h=0,+,-$ states receive different nonfactorizable contributions and hence are helicity dependent, contrary to naive factorization approach where $a_i^h$ are universal and polarization independent. The branching ratios for $\bar{B}_s\to VV$ decays are calculated and we find that branching ratios of some channels are of order $10^{-5}$, which are measurable at future experiments. The transverse to total decay rate $\Gamma_T/\Gamma$ is also evaluated and found to be very small for most decay modes, so, in charmless $\bar{B}_s\to VV$ decays, both light vector mesons tend to have zero helicity.Comment: 16pages. Typos and mistakes fixed. Numerical results change

Sources, Influencing Factors, and Pollution Process of Inorganic Nitrogen in Shallow Groundwater of a Typical Agricultural Area in Northeast China

As one of the largest agricultural areas, the Sanjiang Plain of Northeast China has faced serious inorganic nitrogen pollution of groundwater, but the sources and the formation mechanism of pollution in the regional shallow groundwater remain unclear, which constrains the progress of pollution control and agricultural development planning. An investigation on potential nitrogen sources, groundwater inorganic nitrogen compounds (NH4+, NO3−, NO2−), and topsoil total nitrogen concentration (TN) was conducted in a typical paddy irrigation area of Sanjiang Plain. Multivariate statistical analysis combined with geospatial-based assessment was applied to identify the sources, determine the governing influencing factors, and analyze the formation process of inorganic nitrogen compounds in shallow groundwater. The results show that the land use type, oxidation-reduction potential (Eh), groundwater depth, NO2− concentration, and electrical conductivity (EC) are highly correlated with the NO3− pollution in groundwater, while DO and Eh affected the distribution of NH4+ most; the high concentrations of NO3− in sampling wells are most likely to be found in the residential land and are distributed mainly in densely populated areas, whereas the NH4+ compounds are most likely to accumulate in the paddy field or the lands surrounded by paddy field and reach the highest level in the northwest of the area, where the fields were cultivated intensively with higher fertilization rates and highest values of topsoil TN. From the results, it can be concluded that that the NO3− compounds in groundwater originated from manure and domestic waste and accumulated in the oxidizing environment, while the NH4+ compounds were derived from N fertilization and remained steady in the reducing environment. NO2− compounds in groundwater were the immediate products of nitrification as a result of microorganism activities

The Prediction Methods for Potential Suspended Solids Clogging Types during Managed Aquifer Recharge

The implementation and development of managed aquifer recharge (MAR) have been limited by the clogging attributed to physical, chemical, and biological reactions. In application field of MAR, physical clogging is usually the dominant type. Although numerous studies on the physical clogging mechanism during MAR are available, studies on the more detailed suspended clogging types and its prediction methods still remain few. In this study, a series of column experiments were inducted to show the process of suspended solids clogging process. The suspended solids clogging was divided into three types of surface clogging, inner clogging and mixed clogging based on the different clogging characteristics. Surface clogging indicates that the suspended solids are intercepted by the medium surface when suspended solids grain diameter is larger than pore diameter of infiltration medium. Inner clogging indicates that the suspended solids particles could transport through the infiltration medium. Mixed clogging refers to the comprehensive performance of surface clogging and inner clogging. Each suspended solids clogging type has the different clogging position, different changing laws of hydraulic conductivity and different deposition profile of suspended solids. Based on the experiment data, the ratio of effective medium pore diameter (Dp) and median grain size of suspended solids (d50) was proposed as the judgment index for suspended solids clogging types. Surface clogging occurred while Dp/d50 was less than 5.5, inner clogging occurred while Dp/d50 was greater than 180, and mixed clogging occurred while Dp/d50 was between 5.5 and 180. In order to improve the judgment accuracy and applicability, Bayesian method, which considered more ratios of medium pore diameter (Dp) and different level of grain diameter of suspended solids (di), were developed to predict the potential suspended solids types

Suitability Evaluation of River Bank Filtration along the Second Songhua River, China

The Second Songhua River is the biggest river system in Jilin Province, China. In recent years, the rapid economic development in this area has increased the prominence of water resources and water-related environmental problems; these include surface water pollution and the overexploitation of groundwater resources. Bank infiltration on the floodplains of the Second Songhua River is an important process of groundwater-surface water exchange under exploitation conditions. Understanding this process can help in the development of water resource management plans and strategies for the region. In this research, a multi-criteria evaluation index system was developed with which to evaluate the suitability of bank filtration along the Second Songhua River. The system was comprised of main suitability indexes for water quantity, water quality, the interaction intensity between surface water and groundwater, and the exploitation condition of groundwater resources. The index system was integrated into GIS (Geographic Information System) to complete the evaluation of the various indicators. According to the weighted sum of each index, the suitability of river bank filtration (RBF) in the study area was divided into five grades. Although the evaluation index system and evaluation method are applicable only to the Second Songhua River basin, the underlying principle and techniques it embodies can be applied elsewhere. For future generalization of the evaluation index system, the specific evaluation index and its scoring criteria should be modified appropriately based on local conditions

Laws and Mechanism of the Fe (III) Clogging of Porous Media in Managed Aquifer Recharge

The use of stormwater for managed aquifer recharge (MAR) has become one of the most important ways to deal with water shortages and the corresponding environmental geological problems, especially in the north of China. The Fe (III) clogging of porous media is a common and significant problem that influences the effect of the infiltration rate. This paper focuses on the migration characteristics and clogging mechanisms of iron hydroxides in sand columns. The results indicate that the permeability of porous media significantly decreased at the inlet of the fine sand column and inside the coarse sand column. We demonstrated that, when the Fe (III) concentration was higher, a smaller infiltration medium size was produced more rapidly, and there was more significant clogging. More than 80% of the injected Fe (III) remained in the sand column, and more than 50% was retained within 1 cm of the column inlet. The mass retention increased with the decrease in the size of the infiltration medium particles and with the increase in the injected Fe (III) concentration. The main material that caused Fe (III) clogging was iron hydroxide colloids, which were in the form of a granular or flocculent membrane coating the quartz sand. The mechanisms of clogging and retention were blocking filtration and deep bed filtration, adsorption, and deposition, which were strongly affected by the coagulation of Fe (III) colloidal particles

Imputation of Ammonium Nitrogen Concentration in Groundwater Based on a Machine Learning Method

Ammonium is one of the main inorganic pollutants in groundwater, mainly due to agricultural, industrial and domestic pollution. Excessive ammonium can cause human health risks and environmental consequences. Its temporal and spatial distribution is affected by factors such as meteorology, hydrology, hydrogeology and land use type. Thus, a groundwater ammonium analysis based on limited sampling points produces large uncertainties. In this study, organic matter content, groundwater depth, clay thickness, total nitrogen content (TN), cation exchange capacity (CEC), pH and land-use type were selected as potential contributing factors to establish a machine learning model for fitting the ammonium concentration. The Shapley Additive exPlanations (SHAP) method, which explains the machine learning model, was applied to identify the more significant influencing factors. Finally, the machine learning model established according to the more significant influencing factors was used to impute point data in the study area. From the results, the soil organic matter feature was found to have a substantial impact on the concentration of ammonium in the model, followed by soil pH, clay thickness and groundwater depth. The ammonium concentration generally decreased from northwest to southeast. The highest values were concentrated in the northwest and northeast. The lowest values were concentrated in the southeast, southwest and parts of the east and north. The spatial interpolation based on the machine learning imputation model established according to the influencing factors provides a reliable groundwater quality assessment and was not limited by the number and the geographical location of samplings

Laws and Mechanism of the Fe (III) Clogging of Porous Media in Managed Aquifer Recharge

The use of stormwater for managed aquifer recharge (MAR) has become one of the most important ways to deal with water shortages and the corresponding environmental geological problems, especially in the north of China. The Fe (III) clogging of porous media is a common and significant problem that influences the effect of the infiltration rate. This paper focuses on the migration characteristics and clogging mechanisms of iron hydroxides in sand columns. The results indicate that the permeability of porous media significantly decreased at the inlet of the fine sand column and inside the coarse sand column. We demonstrated that, when the Fe (III) concentration was higher, a smaller infiltration medium size was produced more rapidly, and there was more significant clogging. More than 80% of the injected Fe (III) remained in the sand column, and more than 50% was retained within 1 cm of the column inlet. The mass retention increased with the decrease in the size of the infiltration medium particles and with the increase in the injected Fe (III) concentration. The main material that caused Fe (III) clogging was iron hydroxide colloids, which were in the form of a granular or flocculent membrane coating the quartz sand. The mechanisms of clogging and retention were blocking filtration and deep bed filtration, adsorption, and deposition, which were strongly affected by the coagulation of Fe (III) colloidal particles

Flow Velocity Effects on Fe(III) Clogging during Managed Aquifer Recharge Using Urban Storm Water

Storm water harvesting and storage has been employed for nearly a hundred years, and using storm water to recharge aquifers is one of the most important ways to relieve water scarcity in arid and semi-arid regions. However, it cannot be widely adopted because of clogging problems. The risk of chemical clogging is mostly associated with iron oxyhydroxide precipitation; anhydrous ferric oxide (HFO) clogging remains a problem in many wellfields. This paper investigates Fe(III) clogging levels at three flow velocities (Darcy velocities, 0.46, 1.62 and 4.55 m/d). The results indicate that clogging increases with flow velocity, and is mostly affected by the first 0–3 cm of the column. The highest water velocity caused full clogging in 35 h, whereas the lowest took 53 h to reach an stable 60% reduction in hydraulic conductivity. For the high flow velocity, over 90% of the HFO was deposited in the 0–1 cm section. In contrast, the lowest flow velocity deposited only 75% in this section. Fe(III) deposition was used as an approximation for Fe(OH)3. High flow velocity may promote Fe(OH)3 flocculent precipitate, thus increasing Fe(III) deposition. The main mechanism for a porous matrix interception of Fe(III) colloidal particles was surface filtration. Thus, the effects of deposition, clogging phenomena, and physicochemical mechanisms, are more significant at higher velocities

Hydrochemical Evolution and Quality Assessment of Groundwater in the Sanjiang Plain, China

Groundwater is subjected to contamination threats from human activities, such as agriculture, especially long-term farming in the Sanjiang Plain, China. Identifying the sources and distribution of pollution is essential for its reasonable prevention and control. In this study, we analysed the chemical characteristics of 389 samples at 60 shallow groundwater monitoring points from 2011 to 2015 in the Sanjiang Plain using traditional hydrochemical methods, water quality assessment, Pearson’s correlation, and principal component analysis (PCA). Although groundwater type in this area was predominantly HCO3-Ca·Mg, three forms of nitrogen pollution (ammonia, nitrate, and nitrite) were all detected in this area. The interaction of natural geochemical and anthropogenic factors during hydrochemical formation is confirmed by the high coefficients of variation and Gibbs plots of the main ions in the water. The overall shallow groundwater situation was described as good, with more than 40% and 90% of groundwater samples suitable for drinking and irrigation according to the quality assessment, respectively. The proportion of poor water quality in the wet season was higher than that in the dry season. NO3-N and NH3-N were identified as the major anthropogenic pollutants in the study area. Results from Pearson’s correlation and principal component analysis shows two main pollutants fall into two chemical controlling factors together with natural chemical parameters, which implies that the migration and transformation of pollutants may have affected the overall hydrochemical characteristics of the regional groundwater. Therefore, findings from this paper can provide insight into the chemical evolution of groundwater in response to long-term agricultural activities and can help contribute to better management of groundwater resources and agricultural sustainable development