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Context. The phosphorus (P) sorption capacity of biochar and the effects of biochar amendment on soil P sorption and availability remain uncertain. Aims. This study determined the specific contributions of the biochar inorganic component (mineral ash) and its carbon skeleton to the P sorption capacity of biochar. Methods. A woody biochar and its acid-washed counterpart were added to two types of paddy soils with two P-retention capacities: high P sorption (HPS) and low P sorption (LPS). Key results. Washing biochar with HCl solution drastically decreased the concentrations of calcium, magnesium, iron (Fe), and aluminium (Al) in the biochar. However, Fourier transform infrared and X-ray photoelectron spectroscopy spectra indicated that the washing procedure did not decrease the biochar organic carbon content and its surface functional groups. Acid-washed biochar showed nearly zero P sorption after 24 h of equilibration with P solution, and its incorporation had little effect on P sorption of the two paddy soils. Amendment with original alkaline woody biochar tended to increase P sorption capacity of LPS soils, but decreased that of HPS soils. The variations in Langmuir P sorption maxima, an indicator of soil P sorption capacity, among the soils and biochar treatments could be primarily explained by the amorphous Fe and Al concentrations, which indicates that the effect of biochar addition on soil P sorption was highly dependent on intrinsic soil P-retentive properties. Conclusion. These results demonstrate that the biochar carbon skeleton had a very limited contribution to biochar P-retention capacity. Implications. Our results suggest that the application of aged biochar with lower mineral contents to humid acidic highly weathered soils will have limited P retention capacity. Keywords: amorphous iron and aluminum, biochar, carbon skeleton, Langmuir adsorption equation, multiple linear regression, paddysoil, phosphate sorption, phosphorus availability., Introduction Biochar, which is the product of biomass (i.e. crop residues, manure, and biosolid) pyrolysis under limited air supply, has recently received considerable research attention for its potential role in [...]

In order to investigate physiological and molecular mechanisms underlying the impacts of organic selenium and nanoselenium on the drought stress of pak choi (Brassica chinensis var. pekinensis. cv. 'Suzhouqing'), we sprayed 20 mL of 0, 5, 10, 20 mg L−1 concentrations of organic selenium (DCK, DO5, DO10, DO20) and nanoselenium (DN5, DN10, DN20). We measured photosynthetic pigment, antioxidant and nutritional quality, performed transcriptome sequencing of leaves using RNA-seq technology, obtained 297,176,114 clean sequences, and identified differential expressed genes. Organic selenium and nanoselenium increased the photosynthetic capacity by upregulating light-trapping pigment proteins, regulated reactive oxygen species homeostasis by activating the antioxidant system through the upregulation of glutathione S-transferase, and maintained water homeostasis through glutathione oxidase activity, thus enhancing weight. They contributed to the elevated total selenium content by increasing expression levels of ABC transporter, adenylate kinase, and cysteine desulphurase. Additionally, hub genes related to these metabolic pathways were identified using a weighted gene coexpression network analysis. The consistent results with the upregulated genes identified in the Kyoto Encyclopedia of Genes and Genomes pathway confirmed the accuracy and reliability of the transcriptome sequencing data. This study provides scientific reference to further in-depth research on the molecular effect of selenium on crops under drought stress conditions. [ABSTRACT FROM AUTHOR]

Context: Heavy metal ion removal from wastewater has become a global concern due to its extensive negative effects on human health and the environment. The density functional theory is employed to investigate the possibility of removing Pb2+, Hg2+, and Cd2+ ions from wastewater using nano-graphene. Researchers have shown that NG can efficiently remove heavy metals from media. Additionally, it was shown that the adsorption of Pb2+, Hg2+, and Cd2+ ions might reduce the large pristine NG (HOMO–LUMO) gap. Methods: HSE06 may accurately represent NG electrical characteristics. The DFT-D3 method was also used to account for Van der Waals interactions in the present study. The results demonstrated that charge transfer and binding energy remained greater in cation-NG systems with greater electron transfer rates. Pb2+, Hg2+, and Cd2+ adsorption results indicated that Egap was significantly reduced by 68%, 15%, and 21%, respectively. The Pb2+@NG complex exhibited the strongest oscillator strength. This may be explained by the enormous occupation number difference between the 2px orbital of the C atoms and the 6 s orbital of the Pb2+ cations. The greater Ebin value of Pb2+@NG is consistent with the increased predicted redshifts (199 nm). DFT (hybrid functional HSE06) studies that rely on time showed that the relevant complexes have "ligand-to-metal charge transfer" excitations. In general, it was found that Pb2+@NG had the greatest k value, binding energy, redshifts, and charge transfer rate among the complexes. The theoretical insights of this study may influence experimental efforts to identify NG-based compounds that are effective and efficient at removing pollutants from wastewater. [ABSTRACT FROM AUTHOR]

Context: Hydrogen fluoride (HF) is extensively present in environmental and industrial pollutants. It may harm the health of humans and animals. This work evaluated the adsorption of an (HF)n linear chain (n = 1, 2, 3, and 4) onto an AlP nanocage through ab initio calculations for the evaluation of its performance in sensing and monitoring (HF)n within aqueous and gaseous media. Methods: The present work adopted density functional theory (DFT) at the 6–311 G (d, p) basis set to analyze (HF)n linear chain adsorption onto AlP nanocages with the B3LYP functional. This paper examined the adsorption energy, configuration optimization, work function, and charge transfer. In addition, the contributions of the HF linear chain size to electronic properties and adsorption energy were measured. The dimer form of HF on the surface of AlP nanocages was found to have the highest stability based on the adsorption energy values. Once (HF)n was adsorbed onto the nanocage, the HOMO-LUMO energy gap experienced a large reduction from 3.87 to 3.03 eV, enhancing electrical conductivity. In addition, AlP nanocages may serve in the sensing of (HF)n under multiple environmental pollutants. [ABSTRACT FROM AUTHOR]

The size of particles determines the adsorption reaction. In this study, three different particle sizes of biochar (0.25-1 mm, 0.075-0.25 mm, <0.075 mm) were produced from rapeseed straw (SBC) and chicken manure (MBC). The biochar was mixed with high phosphorus (P) soil and low P soil and then incubated for 30 days. We conducted isothermal P sorption and desorption experiments to evaluate the effects of biochar particle size on sorption-desorption characteristics of soil P, and analyzed soil properties associated with P sorption. The results showed that P sorption capacity of SBC and MBC in the water system was highest for the smallest particle size (<0.075 mm) (SBC: 43125 mg ⋅ kg-1, MBC: 20083 mg ⋅ kg-1), followed by the intermediate particle size (0.075-0.25 mm) (SBC: 37376 mg ⋅ kg-1, MBC: 13199 mg ⋅ kg-1) and the largest particle size (0.25-1 mm) (SBC: 27749 mg ⋅ kg-1, MBC: 12251 mg ⋅ kg-1). However, there was little difference in soil P sorption between the three particle sizes of the same biochar in the soil system. In comparison with no biochar treatment, the addition of SBC increased the Langmuir P sorption maximum (Smax) by 236.8%-755.7%, and decreased soil P desorption rate. The addition of MBC increased Smax, but the enhancement was less than that of SBC. Soil P desorption rate was increased by 7.2%-295.9%. Both SBC and MBC significantly increased the contents of soil total P, available P, and exchangeable calcium (Ca) and magnesium (Mg). The increases in Ca and Mg contents due to biochar addition was 64.0%-257.1% (SBC) and 39.1%-205.3% (MBC), respectively. The contents of soil exchangeable Ca and Mg were positively correlated with Smax. These results suggested that biochar particle size had little effect on soil P sorption, but the enrichment of Ca and Mg due to biochar addition played a critical role in regulating soil P sorption. The rapeseed straw biochar had a high adsorption capacity for soil P, making it suitable for improving the P fixation capacity of soil rich in P and reducing the loss of excess P. Chicken manure biochar could be used to improve the P availability of low P soils and increase the contents of available P. [ABSTRACT FROM AUTHOR]