Winter wheat fertilized with biogas residue and mining waste: yielding and the quality of grain

Metagenomics and network analysis decipher profiles and co-occurrence patterns of bacterial taxa in soils amended with biogas slurry

Microbial community and interaction play crucial roles in ecological functions of soil including nutrient cycling carbon storage, and water maintenance etc. Numerous studies have shown that the application of fertilizers alters bacterial diversity; However, it remains unknown whether and how the continuous application of biogas slurry from anaerobic digestion affects the spatiotemporal heterogeneity of soil layers, complexity and stability of microbial networks, and functions related to C and N cycling. Here, we investigated the bacterial taxa of purple soils treated with swine biogas slurry for four different periods (0, 1, 3 and 8 years) and five different soil depths (20, 40, 60, 80 and 100 cm). The results showed that the application period of biogas slurry and soil depth were two powerful drivers of bacterial diversity and communities. Biogas slurry input resulted in marked changes in the bacterial diversity and composition at the soil depths of 0-60 cm. The relative abundances of Acidobacteriota, Myxococcot, and Nitrospirota decreased, while Actinobacteria, Chloroflexi, and Gemmatimonadota increased with repeated biogas slurry input. The decreasing complexity and stability of the bacterial network with decreasing nodes, links, robustness, and cohesions were found with increasing years of biogas slurry application, suggesting that the bacterial network of soils treated by the biogas slurry became more vulnerability compared with the control. Also, the linkages between the keystone taxa and soil properties were weakened after biogas slurry input, leading to the cooccurrence patterns being less affected by the keystones in the high level of nutrients. Metagenomic analysis confirmed that biogas slurry input increased the relative abundance of liable-C degradation and denitrification genes, which could highly impact the network properties. Overall, our study could give comprehensive understandings on the impacts of biogas slurry amendment on soils, which could be useful for maintaining sustainable agriculture and soil health with liquid fertilization.

Parameters affecting LED photoreactor efficiency in a heterogeneous photo-Fenton process using iron mining residue as catalyst

In this article, a light-emitting diode (LED)-based photoreactor was designed and evaluated for degradation of the antibiotic sulfathiazole (STZ), using heterogeneous photo-Fenton process with an iron ore residue as catalyst. The effects of the type of magnetic stirrer bar, use of baffles, rotation speed, and type and intensity of irradiation source were evaluated. The results showed that the degradation of STZ was strongly influenced by rotation speed (1100 rpm) and that the use of an octagonal stirrer bar favoured high dispersion and greater contact of the catalyst with the reaction medium. Although the presence of baffles had little influence on STZ degradation, their use enabled good dispersion of the catalyst (due to axial flow) and eliminated the vortex formed at high stirring speeds. It was found that the iron mining residue could be activated by UV LEDs, visible light LEDs, and black light irradiation, with similar degradation efficiencies achieved. Using the LEDs, STZ concentrations below the detection limit were obtained after 40 min, with power consumption 38-fold (UV LEDs) and 22-fold (visible light LEDs) lower than required for black light irradiation. The results demonstrated the advantages of the use of LED devices as irradiation systems in heterogeneous photo-Fenton processes.

Impact of direct application of biogas slurry and residue in fields: In situ analysis of antibiotic resistance genes from pig manure to fields

Biogas slurry and residue contaminated with antibiotics are widely used as fertilizers in vegetable crop planting. However, their impact on the spreading of antibiotic resistance genes (ARGs) in vegetable fields is still largely unknown. In the present study, antibiotic resistant bacteria (ARB), ARGs and bacterial communities from pig manure to fields were monitored by using viable plate counts, high-throughput fluorescent quantitative PCR (HT-qPCR) and Illumina MiSeq sequencing. Eighty-three ARGs and 3 transposons genes were detected. Anaerobic digestion reduced relative abundance of tetracycline and Macrolide-Lincosamide-Streptogramin (MLSB) resistance genes. However, the number of ARB and the relative abundance of sulfa, aminoglycoside and florfenicol, chloramphenicol, and amphenicol (FCA) resistance genes, respectively, enriched up to 270 times and 52 times in biogas residue. Long-term application of biogas slurry and residue contaminated with antibiotics in fields increased the rate of ARB as well as relative abundance of ARGs and transposons genes. Additionally, bacterial communities significantly differed between the soil treated with biogas slurry and residue and the control sample, especially the phyla Bacteroidetes and Actinobacteria. Based on network analysis, 19 genera were identified as possible hosts of the detected ARGs. Our results provide an important significance for reasonable application of biogas slurry and residue.