•High concentrations of Cd in soils of a rural area in the Three Gorges region, China, are reported.•Lognormal distribution plots and enrichment factors were applied to identify Cd ...sources.•Sedimentary rocks are main source of Cd in the Cd-enriched soils.•Results of sequential extractions show that a considerable fraction of the Cd in soils is in a labile form.
This study investigated the distribution and sources of Cd in soils from a Cd-rich area in the Three Gorges region, China. The results showed that in the study area arable soils contain 0.42–42mgkg−1 Cd with 0.12–8.5mgkg−1 in the natural soils, corresponding to high amounts of Cd (0.22–42mgkg−1) in outcropping sedimentary rocks in the area. Both lognormal distribution and enrichment factor (EF) plots were applied in an attempt to distinguish between geogenic and anthropogenic origins of Cd in the local soils. The lognormal distribution plots illustrated that geogenic sources dominated in soils with low and moderate Cd concentrations (<8.5mgkg−1), whereas anthropogenic sources (agricultural activities, coal mining) significantly elevated Cd contents in some arable soils (>8.5mgkg−1). The enrichment factor plots illustrated that the majority of the soil samples had EF values of <5, pointing to a geogenic origin of Cd in the soils, whereas some arable soils had EF values >5, pointing to an additional anthropogenic input of Cd to the soils. Sequential extraction results showed that Cd soluble in water and weak acid (water-soluble, exchangeable and carbonate fraction of the soil) accounts for an average of 31% of the total soil Cd, which indicates high potential for Cd mobility and bioavailability. The findings point to a potential health risk from Cd in areas with high geogenic background concentrations of this metal.
A novel magnesium-doped hydroxyapatite/chitosan nanomaterial (MHAP@CS) was prepared as soil passivator for treatment of copper and cadmium contaminated soil. The mechanism of the immobilization ...performance improvement was proposed. According to the characterization, magnesium ions were successfully incorporated into hydroxyapatite (HAP), and chitosan (CS) was also supported on HAP. Toxicity characteristic leaching procedure (TCLP) and Tessier sequential extraction method were conducted to evaluate the immobilization efficiency of MHAP@CS, and MHAP@CS showed higher efficiency in the reduction of the mobility of Cu and Cd than HAP. Meanwhile, adsorption experiments and XPS characterization were used to investigate the passivation mechanism. The maximum removal amount of MHAP@CS for Cu(II) and Cd(II) was 133.49 mg g
−1
and 131.84 mg g
−1
respectively. According to XPS and Zeta potential, the stabilization of Cu(II) and Cd(II) by MHAP@CS involved ion exchange, electrostatic adsorption and surface complexation. After magnesium doping and CS modification, the electronegativity and ion exchange capacity of HAP were significantly improved. The excellent immobilization performance suggested that MHAP@CS is an effective, green and facile soil passivator.
In this work, a compact sub-wavelength-pitch silicon waveguide array with low crosstalk is proposed and analyzed. The crosstalk is suppressed by periodic silicon nano-blocks symmetrically arranged ...along the silicon strip waveguides. The silicon nano-blocks are properly designed to work in the resonant region as a high-reflection boundary so that the evanescent fields of the silicon waveguide, which directly contribute to the coupling between waveguides, can be truncated. Meanwhile, the nano-blocks periodically perturb the evanescent fields to form a weak-radiating grating, leading to a millimeter-long effective radiation length required for highly directive optical phased arrays. Simulation results show that the crosstalk between the waveguides in the proposed design is at least 10 dB lower than traditional waveguide array with identical sizes within the 1500-1590 nm bandwidth. Furthermore, the proposed design achieves an effective radiation length up to 1.47 mm, resulting in a theoretical narrow beam width of 0.052°. Combining both the low crosstalk and the long effective radiating length, our design offers a promising platform for high-performance two-dimensional scanning optical phased array with a large field of view and a narrow beam width.
The homeodomain-leucine zipper (HD-ZIP) gene family, as one of the plant-specific transcription factor families, plays an important role in regulating plant growth and development as well as in ...response to diverse stresses. Although it has been extensively characterized in many plants, the HD-ZIP family is not well-studied in
, a valuable ornamental and traditional Chinese medicinal herb. In this study, 37 HD-ZIP genes were identified in
(
) through the
genome search method, and they were classified into four subfamilies based on phylogenetic analysis. Exon-intron structure and conserved protein domain analyses further supported the prediction with the same group sharing similar gene and protein structures. Furthermore, their expression patterns were investigated in nine various tissues and under cold stress based on RNA-seq datasets to obtain the tissue-specific and cold-responsive candidates. Finally,
,
, and
were selected to validate their expression through qRT-PCR analysis, and they displayed significantly differential expression under sudden chilling stress, suggesting they might be the key candidates underlying cold stress response. These findings will contribute to better understanding of the regulatory roles of the HD-ZIP family playing in cold stress and also will provide the vital targets for further functional studies of HD-ZIP genes in
.
The NAC (NAM, ATAF1/2 and CUC2) gene family is one of the largest plant-specific transcription factor families, functioning as crucial regulators in diverse biological processes such as plant growth ...and development as well as biotic and abiotic stress responses. Although it has been widely characterized in many plants, the significance of the NAC family in Dendrobium officinale remained elusive up to now. In this study, a genome-wide search method was conducted to identify NAC genes in Dendrobium officinale (DoNACs) and a total of 110 putative DoNACs were obtained. Phylogenetic analysis classified them into 15 subfamilies according to the nomenclature in Arabidopsis and rice. The members in the subfamilies shared more similar gene structures and conversed protein domain compositions. Furthermore, the expression profiles of these DoNACs were investigated in diverse tissues and under cold stress by RNA-seq data. Then, a total of five up-regulated and five down-regulated, cold-responsive DoNACs were validated through QRT-PCR analysis, demonstrating they were involved in regulating cold stress response. Additionally, the subcellular localization of two down-regulated candidates (DoNAC39 and DoNAC58) was demonstrated to be localized in the nuclei. This study reported the genomic organization, protein domain compositions and expression patterns of the NAC family in Dendrobium officinale, which provided targets for further functional studies of DoNACs and also contributed to the dissection of the role of NAC in regulating cold tolerance in Dendrobium officinale.
Hydrocarbons are ubiquitous in marine environments and might fuel hydrocarbon-metabolizing microbes in the ocean. Numerous studies have documented microbial hydrocarbon degradation in water columns ...and deep-sea surface sediment. However, the degradation potential and biogeochemical cycling of hydrocarbons in subsurface sediments remain largely unknown. In this study, we used two different hydrocarbons, n-hexadecane (HEX) and methylcyclohexane (MCH), to investigate the distribution and diversity of hydrocarbon-consuming bacteria in a core sediment sample from the Central Indian Ridge (CIR), which is adjacent to mid-ridge hydrothermal vents in the Indian Ocean. We observed different vertical profiles of HEX- and MCH-degrading bacteria in the core sediments. Specifically, HEX-degrading bacteria were universally distributed, while MCH-degrading bacteria were found only in the intermediate layers of the core sediments. Changing factors including dissolved oxygen might affect the natural distribution of different hydrocarbon consumers. We found that a novel species of the genus
C1-B045
might play a pivotal role in metabolizing MCH in the CIR deep biosphere. Through amino acid identity comparison with published sequences, we determined that
C1-B045
harbors two novel classes of cyclohexanone monooxygenases involved in MCH metabolism. This study sheds light on the structure and function of hydrocarbon-consuming microbes in deep biospheres.
Remediation of COPR sites requires the key information including chromium oxidation, speciation and spatial distribution. Samples were gathered from a COPR site in Luliang County in Qujing, Yunnan ...Province of China. The total Cr, Cr（VI） and chromium species were investigated. Results indicated the concentration of total Cr was between 110.5 and 21,774 mg/kg, and the concentration of Cr（VI） was between 0.1 and 1075 mg/kg. The map of total-Cr and ratio of Cr（VI）/total-Cr（%） showed that the maximum of total-Cr and Cr（VI） appeared in the layers near the surface. In the horizontal direction, the pollution was more serious in the middle and southeast part than that in the west. Additionally, acid extractable chromium increased in the layers at depth from-0.3 to-2.0 m, and it decreased in the deeper layers. There was a trend that the movable Cr（VI） migrated to the deeper layers, and then it turned into Cr（III）. Water played an important role for the Cr distribution. Cr（VI） in COPR released to the soil solution after rainfall, and then gravity led the solution down to the deeper layers. After repeated rainfall and leaching,Cr（VI） moved to the deeper soil layers. Due to capillarity and evaporation, Cr（VI） migrated and was enriched at thesurface layer. Therefore, measures on controlling water movement should be taken in the remediation of the COPR site.
Adsorbent preparation of non-toxicity, low cost, large adsorption capacity and outstanding reusability is imperative in purifying Cd-contaminated water. In this work, novel environmental friendly ...shell-coated magnetic attapulgite, named as attapulgite/CoFe2O4@SiO2-chitosan/EDTA (ATPCFS-CSEs), was successfully prepared by solvothermal and sol-gel process. Chitosan and EDTA were selected to functionalize the magnetic attapulgite to provide abundant amino groups and carboxyl groups. Sodium tripolyphosphate was chosen as non-toxic cross-linker in surface deposition-crosslinking, and subsequently amidation reaction was taken for functionalization by chitosan and EDTA. The adsorbents were characterized by SEM, TEM, XRD, FTIR, VSM, BET and XPS, and the adsorption properties including adsorption isotherm, contact time, adsorbents dosage, pH value of initial solution, competitive ions, desorption experiment and recycling method for repeated use were evaluated. The nano-composite adsorbent exhibited well-defined architecture and paramagnetic behavior. The adsorption behavior agreed well with Langmuir model, and adsorption capacity was up to 127.79 mg/g. High concentration ionic competition experiments showed that the ATPCFS-CSEs has high selectivity. Removal efficiency was still above 88% after 5 cycles. The adsorption mechanism was also discussed. Functional groups complexed with cadmium ions with the formation of stable complexes. ATPCFS-CSEs is an excellent adsorbent for removal and separation of Cd2+ from contaminated water.
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•Attapulgite/CoFe2O4@SiO2-chitosan/EDTA was environmental-friendly synthesized.•The maximum cadmium adsorption capacity was 127.79 mg/g.•Attapulgite/CoFe2O4@SiO2-chitosan/EDTA could be recycled for five consecutive cycle.
Magnetic nano-composite materials have been attracting considerable attention due to their unique properties and versatile applications. In this study, a novel magnetic amino-functionalized conjugate ...adsorbent, named as bentonite/CoFe2O4@MnO2-NH2 (BCFMNs), was synthesized by combining APTES and MnO2 with magnetic bentonite. XRD, FT-IR, SEM, EDS, TEM, and VSM techniques were used to characterize its structure and magnetic properties. Results were in indicative of productive synthesis, well-defined architecture and satisfactory magnetism. BET examinations illustrated 84.97m2/g of specific surface area, 0.15cm3/g of pore volume and 7.02nm average pore size. The effect parameters such as adsorbent dosage, contact time, initial concentration and ion selectivity and recycling were evaluated and optimized systematically. Also, the metal concentrations were measured by ICP-MS spectrometer. The feasibility of the BCFMNs for removal of Cd2+ from aqueous solution was also evaluated by adsorption experiments with the maximal adsorption efficiency for Cd2+ up to 98.88%. Cd2+ adsorption could be interpreted by the Langmuir adsorption isotherm and the maximum adsorption capacity was 115.79mg/g. The results revealed that the adsorbent still had higher selectivity of Cd2+ removal even in the presence of high concentration coexisting cations. The as-prepared magnetic conjugate adsorbent could be recycled by taking advantage of its magnetic properties. The distinctive structure of BCFMNs and its excellent adsorption performance of cadmium reflects its prospective application in water treatment.
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•Solvothermally synthesized amino-functionalized magnetic bentonite/CoFe2O4@MnO2•Adsorbent has high sorption and kinetic performances for potential application.•Effectively adsorbed Cd2+ from solution with high amount of coexisting cations
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