There are limited data on polycyclic aromatic hydrocarbons (PAHs) in both the atmosphere and soil of the Tibetan Plateau (TP). Concentrations of PAHs were therefore measured in 13 XAD resin-based ...passive air samplers and 41 surface (0–5 cm) soil samples across the TP. The average concentration of atmospheric PAHs was 5.55 ng/m3, which was lower than that reported for other background areas, but higher than the Arctic. Concentrations in the soils fell in a wide range from 5.54 to 389 ng/g, with an average of 59.9 ng/g. Elevation was found to play an important role in determining the spatial distribution of soil PAHs. The air–soil exchange state showed that the soils of the TP will likely remain as a sink for high molecular weight PAHs, but may become a potential “secondary source” for low molecular weight PAHs.
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•The levels of PAHs in air and soil of the Tibetan Plateau were relatively lower than other background region of world.•The soil PAHs concentration decreased with the increase of elevation.•The Tibetan Plateau will likely remain as a sink for high molecular weight PAHs.•The Tibetan Plateau may become a potential “secondary source” for low molecular weight PAHs.
The Tibetan soil will likely remain as a sink for high molecular weight PAHs, but may become a potential “secondary source” for low molecular weight PAHs.
All-inorganic cesium lead halide perovskite nanocrystals have emerged as attractive optoelectronic nanomaterials owing to their stabilities and highly efficient photoluminescence. However, the ...inorganic perovskites of CsPbBr3 synthesized by the solution method often suffer from byproducts such as Cs4PbBr6 and CsPb2Br5. Herein, we have investigated thoroughly the solvent-related effect on the phase formation in CsBr–PbBr2 system through single crystal X-ray diffraction measurement. It is found that the prepared product is dominantly determined by the coordination number (CN) of Pb(II) and the ratio of precursors. By use of dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) as the solvent, Pb2+ is found to be surrounded by six-coordination sites, and the products can be tuned from CsPbBr3 to Cs4PbBr6 by increasing the precursor ratio of CsBr to PbBr2. On the contrary, in the solvent of water, only Pb2+ eight-coordinated crystal of CsPb2Br5 can be produced, regardless of the ratio of CsBr to PbBr2. More importantly, with the investigation of the extended X-ray absorption fine structure (EXAFS) for Pb L-II edge in precursor solutions, we identify that the CNs of Pb(II) of resultants are the same as those of the corresponding plumbite oligomers in precursor solutions. In addition, the phase transitions from Cs4PbBr6 to CsPbBr3, amorphous state, and CsPb2Br5 triggered by water vapor have also been observed clearly. This work not only enriches our understanding of the phase formation of CsBr–PbBr2 system but also provides the knowledge of the degradation of halide perovskites in the environment of humidity.
Snow is an efficient scavenger for the deposition of contaminants. Atmospheric transport and snow deposition jointly control the distribution of pollutants in remote mountain/polar regions. But can ...the contaminants contained within snow be used to reflect the interactions of air circulation patterns? The physicochemical properties of perfluoroalkyl substances (PFASs) are unique because of their high water solubilities. Taking advantage of this, 15 surface-snow and 3 snow-pit samples were collected across a vast area of western China (spanning 20° of latitude and 25° of longitude), to investigate the concentrations, composition profiles (fingerprints), and deposition fluxes of PFASs. Both a high concentration (3974 pg/L) and deposition flux (4.0 μg/m2/yr) for a total of 16 PFASs were found in the snow at Yulong, the most southern sample site, possibly because of its close proximity to source regions of pollutants in South Asia and high rate of snow deposition. Perfluorobutanoic acid was the most commonly found chemical in snow, but in general the PFAS composition in the snow of western China showed large spatial differences, with long-chain (C > 10) PFASs being relatively dominant in the north and west of the region and short-chain (C < 6) PFASs in the south and east. On the basis of the different compositions of PFASs in the snow of western China and the previously reported features of pollutant sources in Europe and India, we found that PFASs in snow can be used as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon. The belt along 33°N is a key location where both the Indian Monsoon and westerly winds can arrive/interact; however, the contribution of the monsoon was found to be above 70%, while that of the westerly winds can be lower than 30%. The western part of the 33°N belt was found to be more vulnerable to the Indian Monsoon, and could be grouped into the monsoon domain, while the influence of the westerly winds increased from west to east along the belt. This finding is opposite to previous results, which reported that the western part of the 33°N belt was mainly under the influence of the westerly winds, and for the first time quantifies the relative contribution of westerly winds and the Indian Monsoon to the atmospheric transport of chemicals.
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•Perfluorobutanoic acid is the most commonly found chemical in snow from western China.•Long-chain PFASs are relatively dominant in north and short-chain PFASs in south.•PFASs in snow can be used as an atmospheric tracer.•The belt along 33–35°N is a key location where the Indian Monsoon interact with westerly winds.
The van der Waals heterojunctions of 2D materials offer tremendous opportunities in designing and investigating multifunctional and high‐performance electronic and optoelectronic devices. In this ...study, a vertical p–n diode is constructed by vertically stacking p‐type few‐layer black phosphorus (BP) on n‐type few‐layer indium selenide (InSe). The photodetector based on the heterojunction displays a broadband and gate‐modulated photoresponse under illumination. More importantly, by taking advantage of the strong linear dichroism of BP, the device demonstrates a highly polarization‐sensitive photocurrent with an anisotropy ratio as high as 0.83. Additionally, the device can function in a zero‐bias photovoltaic mode, enabling a fast photoresponse and low dark current. The external quantum efficiency can reach ≈3%, which is impressive for BP‐based devices. The results pave the way for the implementation of p‐BP/n‐InSe heterostructure as a promising candidate for future multifunctional optoelectronics and, especially, polarization‐sensitive applications.
A vertical van der Waals heterojunction between few‐layer p‐black phosphorus (BP) and n‐InSe is constructed. The photocurrent anisotropy ratio of the device can reach 0.83, substantially higher than those of reported BP‐based photodetectors. Moreover, this device features a wide‐range, fast, self‐powered, and gate‐modulated photoresponse. These results demonstrate the heterojunction as a promising candidate for multifunctional optoelectronics, especially, highly polarization‐sensitive applications.
The germination, growth, total phenolics, glucosinolate, myrosinase and antioxidant activity of radish sprouts germinated under 0 (control), 10, 50 and 100
mM of NaCl were investigated. The ...glucoraphasatin (4-methylthio-3-butenyl-glucosinolate), total glucosinolate and total phenolic contents of 5- and 7-day-old sprouts treated with 10 and 50
mM of NaCl were significantly decreased. However, the antioxidant activity of sprouts treated with 10 and 50
mM of NaCl was not affected. The glucoraphasatin and total glucosinolate contents of 5- and 7-day-old sprouts, total phenolic contents of 3- and 5-day-old sprouts were significantly increased and myrosinase activities of 3- and 5-day-old sprouts were inhibited, although the germination was dramatically inhibited by 100
mM of NaCl treatment. These results indicated that salt stress (100
mM of NaCl treatment) could improve the nutritional value of radish sprouts, and germination of sprouts under adequate salt stress could be one useful way to enhance health-promoting compounds of plant food.
Soil moisture plays a fundamental role in eco-hydrological processes in the semi-arid Loess Plateau. Catchments on the Loess Plateau can be generally divided into the hillslope domain and gully ...domain. However, the soil moisture variations linked to topographic domains and land use types remain poorly understood. Therefore, in this study, differences in soil moisture among three typical land use types (forestland, native grassland, and farmland) were investigated and compared between the spatial domains of hillslope and gully in the Jiegou catchment on the semi-arid Loess Plateau of China. Additionally, the spatial variations in the soil moisture of the 0–100 cm layers were explored in both wet and dry periods to evaluate the seasonal effects of different spatial domains and land use types. The results showed that including gully soil moisture weakly increased the spatially averaged soil moisture in the catchment but obviously increased the variability during wet periods. In contrast, the spatial means decreased weakly while the variability obviously decreased during dry periods. Soil moisture in forestland was lower than that in native grassland and farmland at all spatial domains during both wet and dry periods. The results also indicated that surface soil moisture (0–10 cm) differs between spatial domains but not land use types, which mainly due to the differences of evapotranspiration on the two topographic domains. In contrast, deep soil moisture (80–100 cm) differs among land use types but not spatial domains, which because of the differences of root water uptake among land use types. In addition, slope aspect played a more important role than slope gradient and elevation in the distribution of soil moisture at the hillslope domain. This was because the slope aspect affected the ground temperature by receiving different solar radiation, and further affected the soil evaporation and vegetation transpiration. Therefore, the results of this study indicates that both topographic domains and land use types should be considered when attempting to characterize soil moisture variability or modelling surface hydrological processes at catchment scale in heavily gullied regions.
•The presence of gullies clearly changed soil moisture spatial variability, but had weak effects on spatial means.•Both spatial means and spatial variability of soil moisture related to spatial domains and land use types.•Variations in soil moisture were different between wet and dry periods in water-limited regions.•Slope aspect played a more important role than slope gradient and elevation in soil moisture distribution in gullied regions.
Zn‐ and Na‐modulated Fe catalysts were fabricated by a simple coprecipitation/washing method. Zn greatly changed the size of iron species, serving as the structural promoter, while the existence of ...Na on the surface of the Fe catalyst alters the electronic structure, making the catalyst very active for CO activation. Most importantly, the electronic structure of the catalyst surface suppresses the hydrogenation of double bonds and promotes desorption of products, which renders the catalyst unexpectedly reactive toward alkenes—especially C5+ alkenes (with more than 50% selectivity in hydrocarbons)—while lowering the selectivity for undesired products. This study enriches C1 chemistry and the design of highly selective new catalysts for high‐value chemicals.
Direct synthesis of olefins using Fe‐based catalysts is a component of the traditional Fischer–Tropsch process. Na‐doping of Fe catalysts alters the surface electronic structure, which promotes CO activation and desorption of products, while suppressing hydrogenation of double bonds. A Na‐modulated catalyst is especially selective for alkenes (particularly C5+).
Salidroside inhibited the proliferation of cancer cell. Nevertheless, the mechanism has not been completely clarified. The purpose of the study is to explore the mechanisms of salidroside against ...gastric cancer. To analyze the changes of microRNA (miRNA) in gastric cancer cells under the treatment of salidroside, the miRNA expression was analyzed by using RNA-seq in cancer cells for 24 h after salidroside treatment. The differentially expressed miRNAs were clustered and their target genes were analyzed. Selected miRNA and target mRNA genes were further verified by q-PCR. The expressions of target genes in cancer cells were detected by immunohistochemistry. Cancer cell apoptotic index was significantly increased after salidroside treatment. The proliferation of gastric cancer cells were blocked at S-phase cell cycle. The expression of 44 miRNAs changed differentially after salidroside treatment in cancer cells. Bioinformatic analysis showed that there were 1384 target mRNAs corresponding to the differentially expressed miRNAs. Surprisingly, salidroside significantly up-regulated the expression of tumor suppressor miR-1343-3p, and down-regulated the expression of MAP3K6, STAT3 and MMP24-related genes. Salidroside suppressed the growth of gastric cancer by inducing the cancer cell apoptosis, arresting the cancer cell cycle and down-regulating the related signal transduction pathways. miRNAs are expressed differentially in gastric cancer cells after salidroside treatment, playing important roles in regulating proliferation and metastasis. Salidroside may suppress the growth of gastric cancer by up-regulating the expression of the tumor suppressor miR-1343-3p and down-regulating the expression of MAP3K6 and MMP24 signal molecules.
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