Bulk Phosphorus Research Articles

A benchmark comparison of AI-based modeling of soil infiltration rates

ABSTRACT Infiltration is crucial in the hydrological cycle, serving as the primary process that increases soil moisture. This study investigates the estimation of soil infiltration rate (IR) using various techniques, including the group method of data handling, Gaussian process, support vector machine, artificial neural network (ANN), and multivariate adaptive regression splines. A total of 190 field observations were collected from Alashtar sub-watersheds in Lorestan, Iran. About 70% of the observations were used for model preparation, while 30% were used for validation. The input variables for the study are time, sand, clay, silt, pH, electrical conductivity, moisture content, soil bulk density, porosity, calcium carbonate, phosphorus, organic carbon, organic matter, nitrogen, and temperature, while IR is the output variable. Obtained results indicate that the ANN has a higher accuracy with coefficient of correlation values of 0.9366, 0.8624, mean absolute error values as 0.0607, 0.1000, Nash–Sutcliffe model efficiency values of 0.8732, 0.7350, the scattering index values of 0.3108, 0.5003, and the Legates and McCabe's index values of 0.6585, 0.5654 by using training and testing datasets, respectively. A sensitivity analysis highlighted that time is the parameter that most influences estimating the IR. The study underscores the precision of ANN in predicting soil IRs and the need for soft computing models in hydrological models to improve accuracy and reliability in IR prediction.

Phosphorus transport modeling in soils treated with nano-phosphorus fertilizers

Nanofertilizers play a promising role in crop production by reducing the application amount and increasing the application efficiency. Understanding the transport of plant nutrients in the soil is crucial for effectively managing nanofertilizer applications and minimizing their impact on the environment. This study investigated phosphorus transport in agricultural soil using 15-day and 30-day soil column experiment data from 2017 and 2018. Two soil column experiments were conducted using nano-rock phosphate, nano-hydroxyapatite fertilizers, and a commercial fertilizer (single super phosphate). The Hydrus 1D model was used to understand the transport mechanism of nano and bulk phosphorus fertilizers. Water and dissolved phosphorus fluxes were simulated using leachate data, and key phosphorus transport parameters, including longitudinal dispersivity and the diffusion coefficient, were determined. The Hydrus-1D model accurately captured leachate dynamics (R² = 0.82–0.99 and MAE = 0.38–0.56 cm/days). Phosphorus transport performed well for bulk fertilizer treatments (R² = 0.86–0.90, MAE = 0.08–0.19 ppm, and RMSE = 0.14–0.36 ppm). However, mixed results were obtained while validating nano fertilizer treatments (R² = 0.31–0.98, MAE = 0.046–0.41 ppm, and RMSE = 0.084–0.35 ppm). For nanofertilizers, the longitudinal dispersivity and distribution coefficient were reduced by 80.71 % and 19.20 %, respectively, compared to commercial fertilizers. The lower longitudinal dispersivity indicates that nano fertilizers release nutrients more slowly than bulk fertilizers. Similarly, a smaller distribution coefficient suggests that nano-phosphorus fertilizers are more concentrated in specific areas within the soil, leading to slower and more controlled nutrient distribution. Additionally, the leachate's observed total phosphorus concentration and the soil profile's phosphorus concentration support the study findings. The results indicate that the transport mechanism of nano and bulk fertilizers in soil is distinct and should be treated separately. This study's findings will contribute to developing optimal fertilizer application strategies for nano-phosphorus fertilizers.

Influence of cover crops on soil aggregate stability, size distribution and related factors in a no-till field

Soil aggregation plays an essential role in maintaining soil structure. A three-year field experiment was undertaken to explore the effects of cover crops on soil aggregate stability indices (mean weight diameter, water-stable aggregates greater than 0.25 mm, and soil erodibility factor), size distribution and their correlations with nine soil physical and chemical properties (soil bulk density, pH, organic carbon, total nitrogen, C/N, calcium, phosphorus, potassium, and cation exchange capacity) at 0–5 and 5–10 cm depths in a Marietta silt loam soil in a no-till field, Northeastern Mississippi. The cover crop treatments included elbon rye (Secale cereale L.), daikon radish (Raphanus sativus ssp. acanthiformis), Austrian winter field peas (Lathyrus hirsutus), and their mixture. The samples were wet-sieved to five size classes of aggregates (> 2, 2–1, 1–0.5, 0.5–0.25, and < 0.25 mm). Results showed that the < 0.25 mm aggregates dominated (50.95–78.02 %) soil aggregate size distribution at 0–5 and 5–10 cm depths. The rye plot soil displayed the greatest values for mean weight diameter (0.58 mm) in the two soil depths. Soil water-stable aggregates greater than 0.25 mm value under peas was significantly higher by 68.61 % compared to the no cover crop treatment at 0–5 cm depth, while soil erodibility factor did not change significantly. Mean weight diameter, water-stable aggregates greater than 0.25 mm, soil erodibility factor, 1–0.5 mm aggregates, and < 0.25 mm aggregates were significantly correlated with soil organic carbon, pH, bulk density, phosphorus, and potassium. The dominant factors driving changes in three aggregate stability indices and size fractions (excluding 2–1 mm aggregates) were bulk density and pH. Furthermore, high pH restricted soil aggregate stability and size distribution. This study demonstrated the positive impact of cover crops, specifically peas and rye, on soil aggregate stability and size distribution. This study will provide valuable information for future research on soil stabilization in crop production management systems.

Different microbial functional traits drive bulk and rhizosphere soil phosphorus mobilization in an alpine meadow after nitrogen input

Enhanced nitrogen (N) input is expected to influence the soil phosphorus (P) cycling through biotic and abiotic factors. Among these factors, soil microorganisms play a vital role in regulating soil P availability. However, the divergent contribution of functional microorganisms to soil P availability in the rhizosphere and bulk soil under N addition remains unclear. We conducted an N addition experiment with four N input rates (0, 5, 10, and 15 g N m−2 year−1) in an alpine meadow over three years. Metagenomics was employed to investigate the functional microbial traits in the rhizosphere and bulk soil. We showed that N addition had positive effects on microbial functional traits related to P-cycling in the bulk and rhizosphere soil. Specifically, high N addition significantly increased the abundance of most microbial genes in the bulk soil but only enhanced the abundance of five genes in the rhizosphere soil. The soil compartment, rather than the N addition treatment, was the dominant factor explaining the changes in the diversity and network of functional microorganisms. Furthermore, the abundance of functional microbial genes had a profound effect on soil available P, particularly in bulk soil P availability driven by the ppa and ppx genes, as well as rhizosphere soil P availability driven by the ugpE gene. Our results highlight that N addition stimulates the microbial potential for soil P mobilization in alpine meadows. Distinct microbial genes play vital roles in soil P availability in bulk and rhizosphere soil respectively. This indicates the necessity for models to further our knowledge of P mobilization processes from the bulk soil to the rhizosphere soil, allowing for more precise predictions of the effects of N enrichment on soil P cycling.

The role of calcium phosphates and silicates in the storage and transport of phosphorus at the upper-to-lower mantle transition: An experimental study to 25 GPa in a model peridotitic bulk composition

Calcium (Ca) phosphates are major hosts for phosphorus, halogens and incompatible trace elements in the Earth’s crust and mantle and, by supplying almost all phosphorus to the biosphere, are indispensable for sustaining life on Earth. To better understand the role of Ca-phosphates in the deep silicate Earth portion of the global phosphorus cycle at depths of the transition zone, we performed experiments in the P-T range of 15–25 GPa and 1600–2000 °C using a moderately fertile peridotite doped with 3 % synthetic β-Ca3(PO4)2 and 1 % of a trace element mix containing a range of HFSE, LILE, REEs, Cl and Br. Tuite is stable to at least 25 GPa at which pressure its upper T-stability limit is between 1700 and 1750 °C. At 15 GPa, by comparison, the upper T-stability limit is located between 1750 and 1800 °C, indicating a negative slope of the tuite-out reaction(s). Thus, tuite is stable to at least 700-km depth with a maximum T-stability close to or slightly above the average current mantle adiabat (ACMA) at 20–25 GPa and significantly above the ACMA at 15 GPa. Beyond the P-T stability limit of majoritic garnet, tuite is the principal subsolidus phosphorus carrier in the uppermost lower mantle. Beyond the P-T stability limit of tuite, phosphorus is likely to either (i) enter a Ca3(PO4)2 polymorph with an even higher density, (ii) form an entirely new phosphate phase or (iii) be accommodated in lower mantle silicates in six-fold coordination. Within the P-T range of our experiments, the phases encountered show the following trend of phosphorus contents:Pmelt>Pmajoritic garnet > Polivine ≅ Pringwoodite > Pdavemaoite ≅ Pwadsleyite > Pclinoenstatite ≅ Pbridgmanite ≅ Pferropericlase. Even when coexisting with tuite, bridgmanite and ferropericlase show phosphorus contents < 100 µg/g, and davemaoite has phosphorus contents that do not exceed 390 µg/g, testifying to the very limited phosphorus storage capacity of the lower mantle. Model calculations based on the phosphorus contents of ocean island basalts (OIBs) compared with those of mid ocean ridge basalts (MORBs) indicate that the OIB source is significantly richer in phosphorus than the MORB source and, for a wide range of OIB phosphorus contents, is likely to contain modal apatite. The relative importance of Ca-phosphates and silicates as phosphorus carriers in the peridotitic upper and uppermost lower mantle is strongly dependent upon pressure and the bulk phosphorus content. With increasing P, phosphorus is progressively transferred from Ca-phosphates to silicates with an ensuing decrease in the modal amount of the Ca-phosphates. Dependent upon the bulk phosphorus content, this may cause the Ca-phosphates to disappear before the upper-to-lower mantle boundary is reached, leaving majoritic garnet as the major phosphorus host. Breakdown of garnet will subsequently cause tuite to re-appear in the uppermost lower mantle and to resume its role of the principal subsolidus phosphorus carrier. For sufficiently high bulk phosphorus contents, tuite will remain stable throughout the transition zone, thereby maintaining phosphorus saturation in the coexisting silicates, and will eventually be joined by the tuite newly generated by garnet breakdown.

Electronic, Elastic, Piezoelectric, and Infrared Properties of 2D Phosphorus Oxynitride by First Principles

Bulk phosphorus oxynitride (PON), isoelectronic with SiO2, is confirmed to have many polymorphs as the latter. However, its 2D counterparts have not been studied. In this work, crystal structure exploration and property study are performed on 2D PON with the help of first‐principle calculation. Three 2D PON sheets are found with thermal, dynamical, and mechanical stability and all of them can be viewed as oxygen‐doped known 2D γ phosphorus nitride (γ‐PN). In the studies, it is indicated that they are indirect bandgap materials with gap values larger than 3 eV. The situations of orbital hybridization are discussed and their bonding properties are analyzed. Infrared vibrational spectra of these 2D materials are simulated and the vibrational modes at the Brillouin center are assigned by the factor group analysis. The reasons for the disappearance of some infrared peaks in the simulated spectra are revealed based on the calculated Born effective charges and vibrational eigenvectors. Their piezoelectric stress tensors are computed via density‐functional perturbation method and the piezoelectric strain tensors are also deduced via the calculated elastic constants. In the results, it is uncovered that these 2D PON sheets have considerably greater piezoelectric coefficients than the primitive 2D γ‐PN, which make them promising for nanopiezoelectric use.

Laser constructed bulk oxygen vacancy caused high P doping for boosting the sodium‐storage capability

AbstractDefect‐assisted heteroatom doping can effectively enhance the intrinsic transfer characteristics of carriers in the crystal structure, which advantages over fast and efficient charge storage. In this work, a three‐dimensional self‐supporting titanium dioxide nanoparticle rich in bulk vacancies (L‐TiOx) on titanium substrate is synthesized by pulsed laser. Different from the surface vacancies, the bulk oxygen defects of L‐TiOx cause a uniform and bulk phosphorus (P) doping with a high concentration of ~5.71 at %, which endows the elevated electronic conductivity, and accelerates the transport of Na+. The obtained P‐doped L‐TiOx (LP‐TiOx) as an anode material in sodium‐ion batteries (SIBs) provides a reversible capacity of 400 mAh g−1 at 200 mA g−1, outstanding rate capability of 196 mAh g−1 at 10,000 mA g−1, and maintains stable performance over 1000 cycles. In situ X‐ray diffraction and ex situ high‐resolution transmission electron microscopy show that LP‐TiOx exhibits robust mechanical behavior with almost no lattice change under (de)sodiation. This work supplies a novel idea for high‐concentration bulk heteroatoms doping to enhance the electrochemical performance of SIBs.

Spatiotemporal distributions of poorly-bound heavy metals in surface sediments of a typical subtropical eutrophic estuary and adjacent bay

The toxicity of heavy metals is dependent on their bioavailability. This study explored the relationship existing among sedimentary nutrients such as bulk nitrogen (TN) and phosphorus (TP), organic carbon (OC), water column chlorophyll-a (Chl-a) and the poorly-bound fraction of sedimentary heavy metals (Cd, Ni, Zn, Cu, Pb and Cr) in the Dafengjiang River Estuary and adjacent Sanniang bay in 2017 and 2018. Results showed that the texture of the surface sediments was dominated by coarse sand, while sedimentary organic matter was dominated by marine phytoplankton and mariculture biodeposits. Surprisingly, concentrations of poorly-bound heavy metals in sediments were relatively high. The average contents of Cd and Ni did not vary both spatially and temporally, Cu and Pb only varied spatially, Cr varied both spatially and temporally, while Zn only varied temporally. Significant positive correlations occurred between sedimentary TN, TP, and OC, including water column Chl-a and poorly-bound heavy metals in sediments. As sediments are important sources of nutrients for primary productivity, the results of this study suggest that the remobilization of sequestered poorly-bound heavy metals in surface sediments deposited in shallow eutrophic estuaries and coastal waters enriched by labile organic matter can enhance by nutrients. The relationship between the poorly-bound heavy metals and nutrients in surface sediments and water column Chl-a is concerning and requires further in-depth investigation. This is because estuaries are economically important ecosystems rich in bioresources, characterized by dynamic biogeochemical conditions.

Effects of long-term vegetation restoration on soil physicochemical properties mainly achieved by the coupling contributions of biological synusiae to the Loess Plateau

Large-scale vegetation restoration has been performed to improve the fragile ecological environment of the Loess Plateau in the last decades. At present, the effects and mechanism of long-term vegetation restoration on soil properties in ecosystems require further exploration to provide a reference for rational ecological construction. Hence, we investigated the differences in vegetation attributes and soil properties between three typical vegetation types (Pinus tabulaeformis plantation forest, PTPF; Robinia pseudoacacia plantation forest, RPPF; natural secondary forest, NSF) after long-term (30–40 years) vegetation restoration in the western Loess Region, China. Our results showed that (1) the arborous synusia biomass of the plantation forests was twice that of NSF, whereas NSF had almost 50% higher near-surface synusia biomass than the plantation forests; (2) the soil nutrient contents of the plantation forests were lower (30%) than those of NSF; (3) the soil bulk density, organic matter, total nitrogen, and phosphorus were positively related to arborous and shrub synusia biomass; (4) the coupling effects of four biological synusiae (with the contribution of 47.67%) were the dominant factors affecting soil physicochemical properties. Natural forests have the better vegetation attributes and soil properties than plantation forests, indicating that the close-to-nature restoration should be considered in ecological restoration. These findings can provide scientific support and theoretical basis for reforestation and ecological restoration in the Loess Plateau region and similar areas in the future.

Tectona grandisL.f. mediated restoration of marginal lands in Eastern Uttar Pradesh, North India

AbstractTectona grandisL.f. has considerable potential to restore marginal and degraded lands as it offers multiple co‐benefits during the restoration venture. It provides good quality wood for multipurpose use, including biomass for bioenergy and noninvasive traits. For this, aboveground biomass (AGB) was assessed along with testing the critical soil properties (soil physicochemical and biological properties) across different plantation sites during a 4‐year study period (2015–2018). The study suggested that the soil properties like bulk density, moisture content, pH, organic carbon, available nitrogen, phosphorus, and potassium have shown significant mean improvement in all planted sites collectively. These were improved by −0.21 g cm−3, 0.68%, −0.68, 0.27%, 13.69 mg kg−1, 11.77 mg kg−1, 95.20 mg kg−1, respectively, in an arid area (Mirzapur, i.e., M1, M2, M3, M4, M5, and M6 sites, representing a warm and tropical dry climate) from the unplanted control (CM1) during 2015–2018. Moreover, the microbial biomass carbon and dehydrogenase activity were significantly improved by 56.71 mg kg−1and 6.92 μg TPF g−1 hr−1, respectively, from CM1. Similar results were also observed in the semiarid areas of Varanasi, representing a humid subtropical climatic pattern (i.e., V4 and V5 sites) compared to the unplanted control in the (CV1). Furthermore, the AGB was found between 12.56 and 229.13 kg tree−1, representing 5 and 30 years of plantation, respectively, in 2018. Reference sites (V1, V2, and V3) were also considered that reflect a planted control, which helped assess the comparison between variable sites and the sites under restoration. Therefore, the study further suggested that this tree species has the tremendous potential to restore marginal and degraded lands in the arid and semiarid areas of North India with a significant biomass supply as an additional benefit.

Vegetation Composition, Forage Biomass and Soil Seed Bank of a Continuously Grazed Rangeland Site in Tropical Sub-Humid Environment, Tanzania

Most rangelands along the agro-pastoral villages of Tanzania are yearlong grazed and at various states of degradation. These rangelands contribute to over 60% of the meat and milk production in the country. An inventory was conducted to assess the status of grazing resources in a typical agro-pastoral village of Tanzania having communal rangelands. Systematic random sampling techniques were employed whereby line transects and quadrat frame were used following standard procedures to collect samples and undertake field measurements for both vegetation and soil parameters. The vegetation cover for desirable pasture species, undesirable pasture species and litter were 67.7%, 10.5% and 9.4%, respectively. The soil bare patches covered 12.3 % of the surveyed rangeland site. The most dominant grass species were Enteropogon macrostachyus, Bothriochloa insculpta and Heteropogon contortus. Forage dry matter (DM) yield was 806.8 kg DM/ha. Tree density was 1500 trees/ha and the total canopy cover was 63.49%. Combretum collinum was the most dominant tree species. Soil bulk density, pH, organic carbon, nitrogen, phosphorus and potassium were 1.4 g/cm3, 6.3%, 1.14%, 0.09%, 0.89 mg/kg and 0.33 g/kg, respectively. A total of 11 dicotyledonous species mainly forbs and 9 monocotyledonous species including two perennial grasses were revealed from the incubated soil samples. The findings of this study demonstrate that the communal grazing areas have low pasture productivity, poor soil seed-bank and high cover of woody plants mainly bushes. In order, to improve forage biomass at the study site and elsewhere with similar environments selective bush clearing and re-seeding should be considered.

Characterization of atmospheric bulk phosphorus deposition in China

Atmospheric phosphorus (P) deposition is an important environmental nutrient which has significant implications for terrestrial and aquatic ecosystems due to regulating the ratio of nitrogen (N) and P. Here, P bulk deposition and its spatial and temporal variation characteristics were monitored in China from June 2019 to May 2021, and the concentrations and fluxes of different P species were further investigated. The annual mean concentrations in precipitation were 0.14 ± 0.02 mg L−1 for total P (TP), 0.06 ± 0.01 mg L−1 for dissolved inorganic P (DIP), 0.05 ± 0.007 mg L−1 for dissolved organic P (DOP), and 0.03 ± 0.003 mg L−1 for particulate P (PP). Annual bulk deposition fluxes of TP, DIP, DOP and PP were 1.08 ± 0.12, 0.46 ± 0.07, 0.36 ± 0.05, and 0.26 ± 0.03 kg ha−1 yr−1 on average, respectively. Atmospheric bulk P concentration showed a negative correlation with precipitation. PP, DIP and DOP contributed 24%, 43% and 33% of TP, respectively. DIP and DOP accounted for 56% and 44% of total dissolved P (TDP). According to analysis of PCA source identification, TP in the bulk deposition most likely originated from anthropogenic sources of combustion in China. The N:P ratios (by mass) in deposition (precipitation) were 32.1 ± 3.88 higher than the Redfield ratio (16.0), which may lead to P-limitation and eutrophication of the water body, and may affect the structure, diversity, and function of ecosystems.

Blue and black phosphorene on metal substrates: a density functional theory study

We have performed density functional theory calculations to study blue phosphorene and black phosphorene on metal substrates. The substrates considered are the (111) and (110) surfaces of Al, Cu, Ag, Ir, Pd, Pt and Au and the (0001) and (100) surfaces of Zr and Sc. The formation energy E F is negative (energetically favorable) for all 36 combinations of overlayer and substrate. By comparing values of ΔΩ, the change in free energy per unit area, as well as the overlayer-substrate binding energy E b, we identify that Ag(111), Al(110), Cu(111), Cu(110) and possibly Au(110) may be especially suitable substrates for the synthesis and subsequent exfoliation of blue phosphorene, and the Ag(110) and Al(111) substrates for the synthesis of black phosphorene. However, these conclusions are drawn assuming the source of P atoms is bulk phosphorus, and can alter upon changing synthesis conditions (chemical potential of phosphorus). Thus, when the source of phosphorus atoms is P4, blue phosphorene is favored only over Pt(111). We find that for all combinations of overlayer and substrate, the charge transfer per bond can be captured by the universal descriptor , where Δχ and are, respectively, the differences in electronegativity and atomic size between phosphorus and the substrate metal.

Photon avalanche in nanoluminophore obtained by REE silicate evaporation

A bulk phosphor composition Sr2Y6.8YbEr0.2Si6O26 was synthesized. A nanophosphorus in an amorphous state was obtained from this sample by the method of pulsed electron beam evaporation. The spectra of upconversion photoluminescence of bulk and nanosamples were studied. In the field of pumping power of nanosample with 78 mW laser radiation with a wavelength of 980 nm, there is a threshold population of energy levels Er3+. Laser radiation carries out resonant pumping of 4I13/2 → 4F9/2 transition. Then there is an intensive red radiation upon transition 4F9/2 → 4I15/2. A photon avalanche was found in the nanophosphore, at which the intensity of red radiation increases ∼80 times compared to the bulk phosphorus.

Environmental associations and effects of disturbances by common wombats in alpine Tasmania

AbstractThe common wombat (Vombatus ursinus) is the largest extant fossorial mammal in Tasmania. Fossorial mammals have substantial edaphic and geomorphic effects, which, in turn can affect vegetation. We asked whether wombat disturbances were associated with particular environments in an alpine environment in Tasmania, and whether, and to what degree, they altered topography, soil or vegetation. Soil analyses, vegetation surveys and topographic transects were used to test for the effects of wombat activity. We contrasted toilets and controls. We compared adjacent burrows, mounds and paths. We also mapped burrows and animal trails. Wombat burrowing created distinct topography and was linked to feeding areas by path systems. There was no difference in bulk density, pH or phosphorus among burrow mounds, paths and undisturbed areas. Burrow mounds, usually used as toilets, were higher in nitrogen (mg L−1) (9. 8 ± 6.3) than either paths (2.3 ± 2.0) or controls (1.08 mg L−1 ± 1.5). Herbs were favoured by wombat disturbance, having a mean percentage cover of 27.8 ± 4.1 on burrow mounds compared to 14 ± 2.69 on controls, and a mean percentage cover of 51.6 ± 7.8 in toilets compared to 25.6 ± 4.8 in control plots. In contrast, shrubs have greater percentage cover in controls than on mounds (47.2 ± 12.0 cf. 12.7 ± 5.0) and toilets (37.3 ± 10 cf. 17.8 ± 6.5). Overall, wombat activity and modification of the alpine environment were concentrated in grassy vegetation above the winter water table, although paths, burrows and toilets extended into less grassy alpine communities. Our results imply that common wombats have a major role in engineering topography and soils with subsequent effects on vegetation, directly affecting at least 1.2% of the study area. Their reduction, or loss, is likely to lead to substantial changes in patterns of geodiversity and biodiversity.

Simulated Raman spectra of bulk and low-dimensional phosphorus allotropes.

We present a comprehensive theoretical and experimental Raman spectroscopic comparative study of bulk Phosphorus allotropes (white, black, Hittorf's, fibrous) and their monolayer equivalents, demonstrating that the application of the Placzek approximation to density functional theory calculated frequencies allows reliable and accurate reproduction of the bulk spectra at a relatively low computational cost. As well as accurate frequencies, peak intensities are also reproduced with reasonable accuracy. Having established the viability of the method we apply it to other less well characterised phosphorus forms such as isolated P4 cages and the planar blue-phosphorus phase. There are several speculative structural models in the literature for amorphous red phosphorus, and we predict Raman spectra for several of these. Via comparison with experiment this allows us to eliminate many of them such as the P2P2-zigzag chain and connected P4 models. The combination of Density functional theory (DFT) modelling, Placzek approximation for intensities with experimental Raman spectroscopy is demonstrated as a powerful combination for accurate characterisation of phosphorus species.

Numerical Analysis of Phosphorus Concentration Distribution in a Silicon Crystal during Directional Solidification Process

For bulk doping, boron and phosphorus are usually used as p-type and n-type dopants, respectively. The distribution of these dopant concentrations in a silicon crystal along the vertical direction is governed by the segregation phenomena. As the segregation coefficient of phosphorus is small, phosphorus concentration distribution in a silicon crystal becomes inhomogeneous; inhomogeneous phosphorus concentration distribution affects the distribution of resistivity in the crystal. Therefore, it is important to control the phosphorus concentration distribution in a silicon crystal and make it uniform. In this study, by numerical analysis, we investigated the effect of the evaporation flux at the melt surface on phosphorus concentration distribution during the directional solidification process. To obtain a homogeneous phosphorus concentration distribution in the silicon crystal, we had to control the phosphorous evaporation flux at the melt surface and maintain approximately the same phosphorus concentration in the melt during the entire solidification process even though the growth rate was always changing.

Lithium intercalation drives mechanical properties deterioration in bulk and single-layered black phosphorus: a first-principles study

It is of critical importance to understand the mechanical properties change of electrode materials during lithium intercalation in the mechanical design of Li-ion batteries (LIBs), for the purpose of the high reliability and safety in their applications. Here, we investigated the mechanical properties of both bulk and single-layered black phosphorus (BP) during the lithium intercalation process by using the first-principles calculations. Our results show that the Young’s modulus of bulk and single-layered phosphorus strongly depends on the lithium intercalation. The mechanical bearing capacities, such as critical strain and stress, are significantly reduced by several times after lithium intercalation in both bulk and single-layered BP, which may reduce the reliability of LIBs. Our findings suggest that this notable mechanical properties deterioration during lithium intercalation should be considered carefully in the mechanical design of LIBs, in order to keep the work reliable and safe in the charge-discharge process.

LATE PLEISTOCENE/HOLOCENE ENVIRONMENTAL HISTORY OF THE SOUTHERN BRAZILIAN PANTANAL WETLANDS

This study presents paleolimnological records from two lakes denominated locally as Lagoa Negra and Lagoa Castelo (Pantanal Brazilian Wetland), using sediment cores. The sediment core was dated using 14C geochronologies and samples were analyzed for bulk density, grain size, organic matter, carbonate, phosphorus, carbon and nitrogen elemental and isotopic composition (δ13C and δ15N), sedimentary pigments and sponge spicules. Pollen and diatoms remains were analyzed only in Lagoa Negra because they were scanty and poorly preserved in Lagoa Castelo core. Paleolimnological and palynological records were used with the objective to gain a better understanding of the environmental history of the Pantanal during the last 21,000 cal yrs BP (calibrated years Befor e Present). The different phases in the development of the lakes were based on the palynological analysis of Lagoa Negra core (CONISS analysis) used as a proxy key. The Lagoa Negra core indicates than the late Pleistocene (~21,000 to 12,200 cal yrs BP) was marked by strong river-lake connectivity (~21,000-19,000 cal yrs BP and ~13,000-12,200 cal yrs BP) and with regression of the Paraguay River between ~19,000-13,000 cal yrs BP. The emergence of the gallery forest in the early to mid-Holocene (~12,200 to 8500 cal yrs BP) indicates wetter conditions, similar to the present. In such conditions began the development of Lagoa Negra, from ~11,500 cal yrs BP, with the deposition of fine organic-rich sediments. In the mid to late Holocene (8500 cal yrs BP to present) the connectivity with the river was reduced or lost completely, between ~8200 and 6500 cal yrs BP (Lagoa Negra). The semi-closed Lagoa Castelo reduced connectivity with the Paraguay River only about 6500 cal yrs BP, when abruptly occurs the transition to deposition of organic sediments. A reactivation of the river-lakes interaction was detected after this period, although not as intense as in the early Holocene.

Marsh edge erosion and associated carbon dynamics in coastal Louisiana: A proxy for future wetland-dominated coastlines world-wide

Coastal wetland loss through marsh edge erosion is a serious problem in Louisiana. The majority of studies on coastal land loss use aerial and satellite photographic analysis while field and site-specific measurements are limited. The aim of this study was to spatially and temporally measure coastal marsh edge erosion and investigate factors responsible for differences in erosion including shoreline orientation, soil physio-chemical properties, and wind speed and duration. A total of 33 transects across six island sites in northern Barataria Basin, Louisiana were established. Transects on shorelines facing different compass directions were measured for erosion for up to 2 years. Soils were analyzed for physiochemical properties including bulk density, organic matter, total carbon, nitrogen, and phosphorus. Bathymetric surveys were conducted to determine the extent of the erosive bay bottom profile. In addition, 14C dating of the basal organic matter (1.5–1.6 m) was conducted. Erosion rates ranged from 49.27 to 324.85 cm y-1 with a mean value of 141.69 ± 22.45 cm y−1. As expected, erosion rates were significantly different (p < 0.001) between protected and unprotected sites. The erosion rate was not correlated with wind speed (r = -0.07), weakly correlated with compass direction of shoreline (r = 0.25) and water level (r = 0.25) but strongly correlated with duration of wind (r = 0.60). Erosion rate was negatively correlated (r = -0.45) with bulk density and positively correlated with organic matter content (r = 0.42) of the top 40 cm of the soil. Over time, the marsh is eroded down to a depth of 1.5 m, which correlates to annual loss of 1.82 ± 0.29 m3 volume of marsh per meter shoreline length including a loss of organic matter (141.5 ± 22.55 kg m−1) and carbon (63.32 ± 10.09 kg m−1) previously preserved for up to 850 years. As a consequence, annual CO2 emissions for Barataria Basin were estimated to be 1.56 ± 0.26 million tCO2e y−1. Results can inform coastal managers as to the most vulnerable marshes to target restoration efforts. Due to high relative sea level rise in coastal Louisiana, these results can also be used to inform the world's stable coastlines on the relative vulnerability of their coastal marshes in the near future, due to projected eustatic sea level. Consequently, the eroding coastlines across the globe may be a significant source of CO2 emissions in near future, as millennial age stored soil carbon is released in a relatively short time, potentially overwhelming human efforts to slow rising atmospheric CO2 levels.