Temporal dynamics of total and active prokaryotic communities in two Mediterranean orchard soils treated with solid anaerobic digestate or managed under no-tillage

AbstractA field experiment was carried out to investigate the impact of two improved tillage systems (conventional tillage combined with the incorporation of solid anaerobic digestate, no-tillage) on the prokaryotic community composition in two tree orchard (olive, citrus) soils with contrasting texture, carbonate content, and pH, located in Southern Italy. Soil samples were taken over a 5-month period to assess immediate (2 days) vs short-term (7 and 18 weeks) responses. Phylogenetic diversity and compositional shifts of both total and metabolically active soil prokaryotic communities were assessed by next-generation sequencing of 16S rRNA gene templates from soil-extracted DNA/RNA. In both digestate-treated soils, copiotrophic α-Proteobacteria and oligotrophic Acidobacteria, Gemmatimonadetes, and Verrucomicrobia showed an immediate (2 days) but short-lived (7 weeks) shift in their relative abundance similar in persistence but not in magnitude; whereas selective soil type-dependent responses were observed for Actinobacteria, Chloroflexi, Firmicutes, and Planctomycetes. The autochthonous soil microbiota demonstrated resilience to the addition of the anaerobic digestate, which was dominated by Firmicutes, Bacteroidetes, Deinococcus-Thermus, and Euryarchaeota (Methanomicrobia). Likewise, a temporary increase in the relative abundances of copiotrophic taxa (Firmicutes, Bacteroidetes, Thaumarchaeota) was observed under conventional tillage, especially in the sandy loam (citrus) soil. Conversely, no-tillage favored the establishment of oligotrophic Chloroflexi and Verrucomicrobia in both soils. The active and the total prokaryotic communities differed from each other only in physically disturbed soils. Soil management induced compositional shifts in the predominant microbial copiotrophic/oligotrophic community balance, whose persistence was linked to the tillage system, while magnitude depended on soil type

Evaluation of Electrospun Self-Supporting Paper-Like Fibrous Membranes as Oil Sorbents

Presently, adsorption/absorption is one of the most efficient and cost-effective methods to clean oil spill up. In this work, self-supporting paper-like fibrous membranes were prepared via electrospinning and carbonisation at different temperatures (500, 650 or 800 °C) by using polyacrylonitrile/polymethylmethacrylate blends with a different mass ratio of the two polymers (1:0, 6:1 or 2:1). After morphological and microstructural characterisation, the as-produced membranes were evaluated as sorbents by immersion in vegetable (sunflower seed or olive) and mineral (motor) oil or in 1:4 (v:v) oil/water mixture. Nitrogen-rich membrane carbonised at the lowest temperature behaves differently from the others, whose sorption capacity by immersion in oil, despite the great number of sorbent and oil properties involved, is mainly controlled by the fraction of micropores. The encapsulation of water nanodroplets by the oil occurring during the immersion in oil/water mixture causes the oil-from-water separation ability to show an opposite behaviour compared to the sorption capacity. Overall, among the investigated membranes, the support produced with 2:1 mass ratio of the polymers and carbonisation at 650 °C exhibits the best performance both in terms of sorption capacity (73.5, 54.8 and 12.5 g g−1 for olive, sunflower seed and motor oil, respectively) and oil-from-water separation ability (74, 69 and 16 for olive, sunflower seed and motor oil, respectively)

Photocatalytic Degradation of Methylene Blue Dye by Electrospun Binary and Ternary Zinc and Titanium Oxide Nanofibers

Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In this work, Ti and/or Zn oxide nanofibers (NFs) with engineered architecture and surface were produced via electrospinning followed by calcination. Calcination and subsequent cooling were operated at fast rates to generate porous NFs with capture centers to reduce the recombination rate of the photogenerated charges. After morphological and microstructural characterisation, the NFs were comparatively evaluated as photocatalysts for the removal of methylene blue from water under UV irradiation. The higher band gap and lower crystallinity were responsible for the lower photocatalytic activity of the ternary oxides (ZnTiO3 and Zn2TiO4) towards the degradation of the dye. The optimal loads of the highly performing binary oxides were determined. By using 0.66 mg mL−1 wurtzite ZnO for the discoloration of an aqueous solution with a dye concentration of 15 µM, a higher rate constant (7.94 × 10−2 min−1) than previously reported was obtained. The optimal load for anatase TiO2 was lower (0.33 mg mL−1). The corresponding rate constant (1.12 × 10−1 min−1) exceeds the values reported for the commonly used P25–TiO2 benchmark. The catalyst can be reused twice without any regeneration treatment, with 5.2% and 18.7% activity decrease after the second and third use, respectively