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Microorganisms are essential components of underground life systems and drive elemental cycling between plants and soil. Yet, in the ecologically fragile Loess Plateau, scant attention has been paid to the response of microbial communities to organic carbon (C) chemistry of both leaves and soils under different revegetation conditions, as well as subsequent alternation in their C metabolic functions. Here, Fourier transform infrared (FTIR) spectrum, amplicon sequencing of 16S rRNA and ITS, and temporal incubation with Biolog-Eco 96 plates were combined to explore the vegetative heterogeneity of microbial community properties and metabolic functions, as well as their regulatory mechanisms in three typical revegetation types including Robinia pseudoacacia L. (RF), Caragana korshinskii KOM. (SL), and abandoned grassland (AG). We observed higher bacterial-to-fungal ratios (B: F = 270.18) and richer copiotrophic bacteria (Proteobacteria = 33.08%) in RF soil than those in AG soil, suggesting that microbes were dominated by r-strategists in soil under RF treatment, which is mainly related to long-term priming of highly bioavailable leaf C (higher proportion of aromatic and hydrophilic functional groups and lower hydrophobicity). Conversely, microbial taxa in AG soil, which was characterized by higher leaf organic C hydrophobicity (1.39), were dominated by relatively more abundant fungi (lower B: F ratio = 149.49) and oligotrophic bacteria (Actinobacteria = 29.30%). The co-occurrence network analysis showed that microbial interactive associations in RF and AG soil were more complex and connective than in SL soil. Furthermore, Biolog-Eco plate experiments revealed that microorganisms tended to utilize labile C compounds (carbohydrates and amino acids) in RF soil and resistant C compounds (polymers) in AG soil, which were consistent with the substrate adaptation strategies of predominant microbial trophic groups in different revegetation environments. Meanwhile, we observed greater microbial metabolic activity and diversity advantages in RF vegetation. Collectively, we suggest that besides the nutrient variables in the leaf-soil system, the long-term regulation of the microbial community by the C chemistry of the leaf sequentially alters the microbial metabolic profiles in a domino-like manner. RF afforestation is more conducive to restoring soil microbial fertility (including microbial abundance, diversity, interactive association, and metabolic capacity). Our study potentially paves the way for achieving well-managed soil health and accurate prediction of C pool dynamics in areas undergoing ecological restoration of the Loess Plateau. [Display omitted] • The effects of leaf organic carbon chemistry on soil microbial composition and diversity are conspicuous. • Microbes dominated by r-strategists preferred to metabolize labile carbon in Robinia pseudoacacia L vegetation. • Microbes dominated by K-strategists maintained the highest metabolic superiority for chemically resistant carbon in abandoned grassland. • Readily degradable carbohydrates were metabolized with the highest priority in three revegetation soils with different microbial community profiles. [ABSTRACT FROM AUTHOR]

Lead (Pb) isotopic composition analysis is a useful tool to accurately identify the origin of Pb in environmental media. The existing calculation method of the contribution of Pb sources from Pb isotope ratios greatly restricted the development of Pb contamination source apportionment. In the present study, a new distance model for calculating the mass proportion of Pb sources, which is based on the distance between the samples and the possible Pb sources in the Pb isotope ratios plot, was presented. The inverse distance model was applied to calculate the contribution proportion of two Pb sources in three previous studies. The average absolute differences between the proportions calculated by the conventional binary mixing equation and the inverse distance model were 0.21%, 1% and 1.9%, respectively, indicating that the new model agreeably calculated the contribution of two Pb sources. The anthropogenic sources proportion (52%) calculated by the inverse distance model of three Pb sources to park soil Pb in Shanghai was comparable to the result that was calculated by the conventional ternary mixing equation (53%), which showed the validity of the new model in calculating the contribution proportion of three Pb sources. Rational results were obtained by the inverse distance model in calculating the contribution of four Pb sources, illustrating that the new model has potential use in calculating the apportionment of four or more Pb sources. These results suggest that the inverse distance model is a simple and efficient approach for calculating the contribution proportion of various Pb contamination sources, and provides a prospective in the study of this field. • A simple distance model to calculate the contribution of Pb sources was presented. • This new model computed rationally the contribution of four or more Pb sources. • Previous studies verified the precise performance of the inverse distance model. [ABSTRACT FROM AUTHOR]