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Purpose: Vegetation restoration is an effective measure for improving soil fertility in areas prone to water and soil erosion. However, how soil bacterial communities respond to changes in soil fertility remains unclear. Methods: The 0–10 and 10–20 cm soil layers in a vegetation restoration site and a soil erosion site located in the same area were chosen as the focus of this research. Results: The results showed that vegetation restoration significantly improved the soil fertility index of the soil erosion area. The vegetation restoration measures not only increased the bacterial abundance in the soil erosion area but also improved the bacterial diversity of the 0–10 cm soil layer in the soil erosion area. Vegetation restoration increased the bacterial abundance and Shannon index in the soil erosion area by increasing the clay and alkaline nitrogen contents. After vegetation restoration, the bacterial community composition in the soil erosion area changed from being dominated by Chloroflexi to being dominated by Proteobacteria and Actinobacteria. We also found that alkali-hydrolyzable nitrogen in the soil was the dominant factor causing the transformation of the soil bacterial community composition during the vegetation restoration process at the soil erosion site. Proteobacteria, Planctomycetes, and Bacteroidetes can be used as indicators of soil fertility changes in the process of vegetation restoration in soil erosion areas. Conclusions: Therefore, vegetation restoration plays a role in restoring the stability of degraded soil ecosystems.

Core IdeasMore salts were distributed in liquid water than saline ice during the saline water freeze‐thaw process.Leaching with saline ice melt‐water was better than leaching with saline water at reducing soil EC and SAR.Gypsum application could improve the soil Kswhen leached by the saline ice melt‐water.The addition of gypsum could eliminate the soil alkalinity hazards post leaching. Saline‐alkali soils adversely affect both the construction of ecological landscapes and crop production in coastal areas. This study aimed to investigate the effects of freeze‐thaw process on purifying saline water, and evaluate the potential of combining saline ice melt‐water leaching and gypsum addition for remediating coastal saline‐alkali soil. Saline water with a salinity of 10 g L−1was tested in this study, and the leaching experiment included four treatments: saline water direct leaching (S), saline water direct leaching combined with gypsum application (SG), saline ice melt‐water leaching (SI), and saline ice melt‐water leaching combined with gypsum application (SIG). The results showed that more salts were concentrated in the bottom ice layer than in the other ice layers after the saline water was completely frozen. The salinity of the melt‐water decreased during the melting process, and the mean salinity of melt‐water during the second half of the melting process was significantly lower than the salinity of source water samples. During the leaching phase, the cumulative leachate losses of Na+, Ca2+and Mg2+were significantly greater for the SI treatment than that for the S treatment. After leaching, the soil electrical conductivity (EC) significantly decreased, and the SI treatment exhibited better performance than the S treatment in terms of reducing the soil EC and sodium adsorption ratio (SAR). The application of gypsum improved the soil saturated hydraulic conductivity (Ks) and decreased both the soil pH and alkalinity when the coastal saline soil was leached by the saline ice melt‐water.

Benzo[a]pyrene diol epoxides (BPDEs) are the ultimate carcinogenic species of benzo[a]pyrene, a prototype polycyclic aromatic hydrocarbon (PAH). BPDE-modified DNA duplexes can adopt multiple conformations depending on the nature of the modified bases, the stereochemistry at the location of the covalent linkage, and the sequence context surrounding the lesion site. In this paper, we describe the preparation of enantiomeric 2-fluoro-BPDEs, trans-(7R,8S)-dihydroxy-(9S,10R)- and trans-(7S,8R)-(9R,10S)-epoxy-7,8,9,10-tetrtahydro-2-fluorobenzo[a]pyrene (22 and 23, respectively), as models for probing the BPDE-induced conformational heterogeneity. The multistep synthesis of the target diol epoxides described herein entails regiospecific succinoylation of 2-fluoropyrene, followed by a ring closure, regio- and stereospecific construction of the 7,8-dihydrodiol functionality, and a subsequent meta-chloroperbenzoic acid-mediated epoxidation. Stereoselectivity was achieved by using Jacobsen chiral catalysts, which produced greater than ∼90% enantiomeric excess. Absolute configurations at the C7,8 carbons of the FBP derivatives were determined by comparison of the circular dichroism (CD) spectra with those reported for the BP analogues. Analysis of the 3J7,8 vicinal coupling constants, CD shape, and charge density calculations all indicated that the prepared anti-FBPDEs preferentially adopt the pseudo-diequatorial C7,8 diol conformation. Hydrolysis of anti-FBPDEs produced a 9:1 ratio of trans- to cis-opened tetraols. Reactions of each of the anti-FBPDEs with deoxyguanosine 5‘-monophosphate produced predominantly trans-anti-N2-dG as the major adducts. Analogous reactions with two 11-mer oligodeoxynucleotides (5‘-CCATXGCTACC-3‘ where X = dT, dC) gave FBP-modified oligodeoxynucleotides with structures that were characterized by enzyme digest/HPLC and electrospray ionization time-of-flight mass spectrometry data. The oligonucleotide adducts were annealed with the appropriate sequences to form fully complementary duplexes [(5‘-CCATXG*CTACC-3‘)(5‘-GGTAGCYATGG-3‘), G* = FBP-N2-dG adduct, X = dT, Y = dA in duplex I; X = dC, Y = dG in duplex II] for CD and UV melting studies. The results of the present study were consistent with those reported previously for BPDE-modified duplexes in the same sequence contexts and support the utility of FBPDEs as useful structural probes.

Summary.:  Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring α,β-unsaturated carbonyl compounds in alcoholic solvents or β-hydroxyl carbonyl compounds in tetrahydrofuran.

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