Isolation and characterization of a cold-tolerant heterotrophic nitrification-aerobic denitrification bacterium and evaluation of its nitrogen-removal efficiency.

With a view toward addressing the poor efficiency with which nitrogen is removed from wastewater below 10 °C, in this study, we isolated a novel cold-tolerant heterotrophic nitrification-aerobic denitrification (HN-AD) bacterium from a wetland and characterized its nitrogen removal performance and nitrogen metabolic pathway. On the basis of 16S rRNA gene sequencing, this strain was identified as a species of Janthinobacterium, designated J1-1. At 8 °C, strain J1-1 showed excellent removal efficiencies of 89.18% and 68.18% for single-source NH4+-N and NO3--N, respectively, and removal efficiencies of 96.23% and 79.64% for NH4+-N and NO3--N, respectively, when supplied with mixed-source nitrogen. Whole-genome sequence analysis and successful amplification of the amoA, napA, and nirK functional genes related to nitrogen metabolism provided further evidence in support of the HN-AD capacity of strain J1-1. The deduced HN-AD metabolic pathway of the strain was NH4+-N→NH2OH→NO2--N→NO3--N→NO2--N→NO→N2O. In addition, assessments of NH4+-N removal under different conditions revealed the following conditions to be optimal for efficient removal: a temperature of 20 °C, pH of 7, shaking speed of 150 rpm, sodium succinate as a carbon source, and a C/N mass ratio of 16. Given its efficient nitrogen removal capacity at 8 °C, the J1-1 strain characterized in this study has considerable application potential in the treatment of low-temperature wastewater.

Diversity of soil faunal community as influenced by crop straw combined with different synthetic fertilizers in upland purple soil.

Soil fauna play a crucial role in sustaining agro-ecosystem functions. Crop straw is recommended for application to agricultural fields to improve soil quality. However, the effects of crop straw combined with different synthetic fertilizers on the soil faunal community remain unclear, and knowledge regarding purple soil is limited. Using the conserved cytochrome c oxidase I (COI) gene as markers, we examined the responses of the soil faunal community to different fertilization in upland purple soil of southwestern China. The accuracy of the morphological and molecular methods in characterizing soil nematodes was compared. Our results showed that different fertilization treatments significantly changed the soil faunal community structure (Adonis test, R2 = 0.43, P = 0.011). Sixteen biomarkers were identified according to LEfSe (linear discriminant analysis effect size). The diversity and species number of soil fauna were closely related to soil organic matter (SOM) and total phosphorus (TP) (P < 0.05). This study indicates that crop straw return can improve the soil fertility and diversity of soil fauna in purple soil. Additionally, the morphological approach and molecular method based on the COI gene can be considered as complementary approaches in characterizing soil nematode community.

Novel BiOBr by compositing low-cost biochar for efficient ciprofloxacin removal: the synergy of adsorption and photocatalysis on the degradation kinetics and mechanism insight.

C/BiOBr composite materials were synthesized via a simple one-step solvothermal method, with C derived from biochar, which was prepared from the low-cost straw. The samples were characterized by SEM, XRD, XPS and PL. The 2% C/BiOBr composite material showed a noticeable adsorption and photocatalysis synergistic effect to remove CIP. The adsorption rate and degradation rate were 1.45 times and 1.8 times that of BiOBr. The adsorption kinetics and isotherms of CIP on C/BiOBr were analyzed with the pseudo-second-order kinetic and Langmuir models. The degradation efficiency was 96.8% after 60 min of irradiation. High stability and degradability were still maintained after four cycles. The Bi-O-C bond accelerated electron transition and inhibited the rapid photogenerated electron pair recombination. In the degradation process of CIP, ˙O2 - and h+ played a significant role. Experiments proved that C/BiOBr is practical and feasible for the degradation of CIP under the synergistic effect of adsorption and photocatalysis.

[Structural characteristics of humic acids from a long-term petroleum contaminated soil].

Petroleum contamination in soil decreases with the increase in the distance of soil to the drilling well. Accordingly, an abandoned petroleum well which had been exploited for about twenty years in Songyuan city of Jilin Province, China, was selected to investigate the structural characteristics of soil humic acids (HAs) under different petroleum contamination levels. Surface (0-20 cm) soil samples were collected at 0.5, 1.5, 3.5, 5.5 and 7.5 m deep from well head, and the petroleum contents were respectively 153.3, 148.4, 129.2, 50.5 and 5.62 g x kg(-1). HAs were extracted with 0.1 mol x L(-) NaOH and 0.1 mol x L(-1) Na4 P2O7 and were characterized with elemental analysis, Fourier transformed infrared (FTIR) spectroscopy and solid-state 13C cross polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy. Results showed that the atomic C/H, O/C and (N+O) /C ratios of HAs increased from 0.74, 0.41 and 0.45 for 7.5 m to 0.80, 0.83 and 0.88 for 0.5 m, respectively. The relative intensity of the peaks assigned to aliphatic carbon (2 921, 2 851 and 1 454 cm(-1)) in the FTIR spectra gradually decreased with increasing contamination levels, while that of the peak assigned to aromatic C(1 600 cm(-1)) increased, and the calculated absorption intensity ratio of 2 921 to 1 600 cm(-1) (2 921/1 600) declined from 0.22 for 7.5 m to 0.11 for 0.5 m. The solid-state 13C NMR data suggested that the relative content of alkyl C(0-50 ppm ) decreased from 49.9% for 7.5m to 30.9% for 0.5 m, while that of O-alkyl C(50-110 ppm), aromatic C(110-160 ppm) and carboxyl C(160-190 ppm) increased respectively from 20.1%, 13.1% and 14.3% to 28.0%, 18.8% and 19.3%. These results showed substantial chemical, structural, and molecular differences among these HAs. The aliphaticity and hydrophobicity of HAs decreased while aromaticity and polarity increased with the increase in petroleum content. Namely, HAs tended to become aged in molecular structure. Therefore, it is imperative to renew and activate the aged HAs by adopting appropriate measures for the remediation of petroleum contaminated soil.

Facile construction of hollow carbon nanosphere-interconnected network for advanced sodium-ion battery anode.

Sodium-ion batteries are promising next-generation electrical-energy-storage devices due to the relative low cost, and the natural abundance of sodium resources. Yet developmental anodes in sodium-ion batteries such as carbonaceous materials have adagio sodium ion diffusion kinetics, huge volume expansion, poor rate performance and cycle stability. Herein, we report a high-performance sodium ion storage anode material, i.e., a unique nanonetwork-structured carbon (NNSC) with a valuable hollow nanosphere as network unit by developing a facile, efficient and post-treatment-free strategy. The as-constructed NNSC exhibits a three-dimensional interconnected hierarchical porous network and a luxuriant accessible surface area, which greatly enhance sodium ion transport and storage. Thus, the obtained NNSC demonstrates excellent sodium ion storage performance, including a high capacity of 250 mA h g-1, good rate capability, and ultra-long-term cycle life up to 9000 cycles. Such attractive capabilities could accelerate the application of sodium-ion batteries in large-scale energy storage.