Elements content in tree rings from Xi'an, China and environmental variations in the past 30 years

Using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), the characteristics of chemical elements were analyzed in white poplar (Populus bonatii Levl.) and ailanthus (Ailanthus altissima (Mill.) Swingle) from three sites in the town of Xi'an, China. The results indicated that the concentration variations of Pb and Cd in tree rings were consistent with that of the environment where the trees were growing. P and Zn were translocated within tree rings to a certain degree, which led to an inaccurate pollution reconstruction. We also found that white poplar had a stronger absorptive capacity of Cd and Zn than ailanthus, which could make white poplar better as a species in environmental remediation. From this research we can see the great potential of tree rings for studying the history of different element pollution in the environment, showing that dendrochemical methods could be used as a powerful component in environmental monitoring programmes, to reconstruct past pollution history at the time when monitoring systems were not yet installed. (c) 2017 Elsevier B.V. All rights reserved

Tree-ring stable carbon isotope-based April-June relative humidity reconstruction since AD 1648 in Mt. Tianmu, China

Based on accurate dating, we have determined the stable carbon isotope ratios (delta C-13) of five Cryptomeria fortunei specimens from Mt. Tianmu, a subtropical area in southern China. The five delta C-13 time series records are combined into a single representative delta C-13 time series using a "numerical mix method." These are normalized to remove temporal variations of delta(13) C in atmospheric CO2 to obtain a carbon isotopic discrimination (Delta C-13) time series, in which we observe a distinct correlation between Delta C-13 and local April to June mean relative humidity (RH (AMJ) ) (n = 64, r = 0.858, p < 0.0001). We use this relationship to reconstruct RH (AMJ) variations from ad 1648 to 2014 at Mt. Tianmu. The reconstructed sequence show that over the past 367 years, Mt. Tianmu area was relatively wet, but in the latter part of the twentieth century, under the influence of increasing global warming, it has experienced a sharp reduction in relative humidity. Spatial correlation analysis reveals a significant negative correlation between RH (AMJ) at Mt. Tianmu and Sea Surface Temperature (SSTs) in the western equatorial Pacific and Indian Ocean. In other words, there is a positive correlation between tree-ring delta C-13 in Mt. Tianmu and SSTs. Both observed and reconstructed RH (AMJ) show significant positive correlations with East Asian and South Asian monsoons from 1951 to 2014, which indicate that RH (AMJ) from Mt. Tianmu reflects the variability of the Asian summer monsoon intensity to a great extent. The summer monsoon has weakened since 1960. However, an increase in relative humidity since 2003 implies a recent enhancement in the summer monsoon

Influence of frozen soil on the seismic responses of bridge structures considering the effect of temperature

Objective Recently, the seismic damage of an actual bridge structure in a frozen soil area has shown that the presence of frozen soil will increase the lateral stiffness of the bridge foundation, which may cause more serious seismic damage to the bridge structure, but there is a lack of research on the frozen soil-pile interaction effect of frozen soil bridge structures under seismic loadings and the corresponding seismic responses. Methods The present paper proposed efficient nonlinear numerical models to consider the effect of the frozen soil-pile interaction on the seismic responses of structures. First, the relationship between the depth of frozen soil and surface temperature was constructed. Then, the p-y spring modelling approach was presented to simulate the seismic behavior of frozen soil. Several as-recorded ground motions were selected as the seismic input. The seismic responses of piers and bearings of regular bridges with different depths of frozen soil under seismic loadings were investigated. Results The results show that the proposed efficient nonlinear numerical model can be adopted to model the seismic behavior of bridges considering frozen soil. And the proposed p-y curves for frozen soil can accurately predict the p-y relationship from the existing tests. When the PGA is relatively small, the pier curvature increases slightly; by contrast, in the case of large PGA, frozen soil can significantly increase the curvature demands, which can make the pier enter into the inelastic behavior. When the depth of frozen soil is small (the temperature is -5℃), the bearing displacement increases significantly, which increases the probability of unseating under seismic loadings. Moreover, frozen soil can transfer to the adverse locations of structural systems under seismic loadings. Conclusion Therefore, the conclusions of this paper can provide the necessary theoretical basis and data support for studying the seismic performance and corresponding seismic design methods of frozen soil bridge structures in China, which is of great significance for promoting the development and engineering application of disaster prevention and mitigation of bridge engineering in frozen soil areas in China

Separation of Rare Earths from the Transition Metals Using a Novel Ionic-Liquid-Based Aqueous Two-Phase System: Toward Green and Efficient Recycling of Rare Earths from the NdFeB Magnets

An ionic-liquid-based aqueous two-phase system (iL-ATPS) consisting of an ionic liquid, tributylmethylammonium nitrate (N4441NO(3)), and NaNO3 aqueous solutions was developed for the extraction and separation of rare-earth ions, for example Nd(III), from transition-metal ions. The excellent selectivity of a green nonfluorinated ionic liquid and the low-viscosity feature of an aqueous two-phase system were combined in our suggested iL-ATPS. The results indicated that efficient separation of Nd(III) from transition metal ions, Fe(III), Ni(II), and Co(II), could be obtained in our suggested iL-ATPS. Furthermore, different parameters of the separation process, including the concentrations of HNO3 and NaNO3 and the added amount of N4441NO(3), were optimized. Notably, the extraction kinetics of Nd(III) could be improved significantly in the present iL-ATPS compared with the conventional organic-solvent-based ionic-liquid extraction systems. The similar environment across the liquid liquid interface was revealed by the ultralow viscosity and interfacial tension of the ionic-liquid-rich phase in the iL-ATPS. This feature was responsible for the enhanced extraction kinetics of Nd(III). In addition, the structures of the extraction complexes were elucidated by using NMR spectroscopy and molecular simulations. It was demonstrated that NO3- ions were in the inner coordination shell of Nd(III) ions to interact with Nd(III) ions, while N4441(+) surrounded Nd(III) ions at the outer coordination shell of Nd(III) ions. Moreover, 2 mol/L HNO3 aqueous solutions could be used to effectively strip Nd(III) from the loaded ionic-liquid-rich phase. After 5 cycles, the extraction performance of the ionic liquid remained nearly unchanged. The present work highlights an environmental method to selectively separate rare-earth ions from the complicated solutions coexisting with other transition-metal impurity ions. It provides a basis for the future application in recycling of rare-earth elements from the spent NdFeB magnets.</p

Spatial Variation in Bacterioplankton Communities in the Pearl River, South China: Impacts of Land Use and Physicochemical Factors

River ecosystems are critical for human and environmental health, with bacterioplankton playing a vital role in biogeochemical cycles. Unveiling the spatial patterns of bacterioplankton communities in relation to environmental factors is important for understanding the processes of microbial variation and functional maintenance. However, our understanding of the correlations among bacterioplankton communities, physicochemical factors, and land use, especially in large rivers affected by intensive anthropogenic activities, remains relatively poor. Here, we investigated the bacterioplankton communities in July 2018 in three main tributaries of the Pearl River, i.e., Beijiang, Xijiang, and Pearl River Delta, based on 16S rRNA high-throughput sequencing. Results showed that the most dominant phyla, Proteobacteria, Actinobacteria, Cyanobacteria, and Planctomycetes accounted for 33.75%, 22.15%, 11.65%, and 10.48% of the total abundance, respectively. The bacterioplankton communities showed remarkable differences among the three tributaries in terms of composition, structure, diversity, and predictive functional profiles. Mantel and partial Mantel tests revealed that the bacterioplankton communities were affected by physicochemical variables (p &lt; 0.01) and land use (p &lt; 0.01). Redundancy analysis identified specific conductivity, dissolved oxygen, agricultural land, ammonium, urban land, and water transparency as the dominant environmental factors influencing the bacterioplankton communities in the Pearl River. Variation partitioning analysis indicated that both physicochemical factors and land use had direct effects on the bacterioplankton community, and that land use may also shape bacterioplankton communities through indirect effects of physicochemical factors on riverine ecosystems. This study provides fundamental information on the diversity, spatial patterns, and influencing factors of bacterioplankton communities in the Pearl River, which should enhance our understanding of how such communities change in response to environmental gradients and anthropogenic activities

Two-Step Hydrothermal Synthesis of Well-Dispersed (Na0.5Bi0.5)TiO3 Spherical Powders

(Na0.5Bi0.5)TiO3 (NBT) powders that have well-dispersed, uniform particle size and well-developed spherical shape were successfully prepared by a two-step hydrothermal synthesis method. Nanosized TiO2 powders were firstly synthesized by a hydrothermal method, and then the TiO2 particles are used as a raw material to synthesize NBT powders. It was found that by using the TiO2 nanoparticles as Ti source, the well-dispersed spherical NBT powders with about 200 nm in size could be obtained at 200°C for 4 h with a low mineralizer concentration of 6 mol/L NaOH in the second step. The formation of spherical NBT powders can be explained by first generating nuclei on the surface of TiO2 nanoparticles via in situ crystallization mechanism and then crystal growing and agglomerating by dissolution-recrystallization mechanism

Kinetics and the difference for extraction of praseodymium and neodymium from nitrate aqueous solution by [A336][NO3] using the single drop technique

The kinetics and the difference for Pr(III) and Nd(III) extraction front nitrate aqueous solution using trialkylmethylammonium nitrate ([A336][NO3) as extractant were investigated by the single drop technique. The dependence of the extraction rate of Pr(III) and Nd(III) on the concentrations of free Pr(III) and Nd(III) ions, the concentrations of NaNO3 and H+ in aqueous solutions, and the concentrations of [A336][NO3] in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(III) and Nd(III) were obtained. These equations demonstrated that the reaction rate constant of Pr(III) with [A336][NO3] was double than that of Nd(III). The effect of the addition of diethylenetriaminepentaacetic acid (DTPA) on the difference in the extraction rate of Pr(III) and Nd(III) by [A336][NO3] was also investigated. It was revealed that the difference in the complex formation rates of Pr(Iii) and Nd(III) with DTPA made a significant impact on the difference in the extraction rates of Pr(III) and Nd(III) with [A336][NO3], The ratio of extraction rates of Pr(lII) to Nd(III) with [A336][NO3] was in proportion to the ratio of complex formation rates of Pr(III) to Nd(III) with DTPA. The extraction rate difference for Pr(III) and Nd(III) with [A 336][NO3] increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(III) ions in the aqueous nitrate solution than that with Pr(III) ions. Therefore, the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(III) and Nd(III) in kinetics. The study on the extraction mechanism indicated that both the extraction of Pr(III) and Nd(III) by [A336][NO3] were diffusion controlled, and the reactions obeyed S(N)2 mechanism. The present work highlights a possible approach to strengthen the kinetic separation of Pr(III) and Nd(III). (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved

Separation of V from alkaline solution containing Cr using acidified primary amine N1923 with the addition of trisodium citrate

Extraction and separation of V(V) and Cr(VI) in the alkaline solution obtained from the Sub-molten Salt Method to treat the high chromium vanadium slags has been a thorny problem in the past decades. In this work, a new liquid-liquid solvent extraction strategy was proposed by using acidified primary amine N1923 (denoted as A-N1923) to separate V(V) from alkaline solution containing Cr(VI) and AI(III). It was indicated that co-extraction of Cr(VI) and Al(III) with V(V) can be avoided with the addition of trisodium citrate previously into the feed solutions. The influence from various factors, including the concentration of trisodium citrate, the initial aqueous pH value, concentration of A-N1923 in the organic phase, diluents in the organic phase, and the initial concentration ratio of V(V) to Cr(VI) in alkaline solutions, on the separation of V(V), Cr(VI) and Al(III) were investigated. The extraction loading capacity of V(V) in the organic phase could reach 6.67 g/L at 298 K. Al(III) in the organic phase can be stripped selectively using 0.18 mol/L trisodium citrate solution, and then V(V) can be recovered by 1.0 mol/L NaNO3 solutions. The regeneration and reusability of the organic phases after stripping were discussed. The present work highlights a novel approach to separate and recover V(V) from alkaline leaching solution containing Cr(VI) and Al(III), especially being applicable for those strongly alkaline solution produced by treating the high chromium vanadium slags using the Sub-molten Salt Method. (C) 2017 Elsevier B.V. All rights reserved.</p