Exposure of CuO nanoparticles and their metal counterpart leads to change in the gut microbiota and resistome of collembolans.

The widespread use of copper oxide nanoparticles (CuONPs) has dramatically increased their concentrations in soils and severely affected the health of soil organisms. The gut microbiota critically contributes to the metabolism and immune system of its host and is sensitive to environmental pollution. The toxic effect of CuONPs on the gut microbiota, especially in soil fauna, still needs further research. In the present study, a comprehensive toxicological test was performed to reveal the effects of CuONPs and their metal counterpart on the gut microbiota of soil collembolans using Illumina high throughput sequencing. Furthermore, the concomitant changes in the collembolans gut-associated antibiotic resistance genes (ARGs) and metabolism were investigated using high-throughput quantitative PCR and carbon and nitrogen stable isotope compositions. Both CuONPs and ionic copper (Cu) exposure disturbed the collembolan gut microbial community structure while only CuONPs reduced the gut microbial diversity. A total of 66 ARGs were detected in the collembolan guts, and CuONPs exposure induced a reduction in both diversity and abundance of ARGs. Additionally, CuONPs and ionic Cu exposure altered the C and N stable isotope compositions of the collembolans, indicating a change in their metabolism. Moreover, structural equation modeling indicated that 85.5% of the carbon stable isotope variations and 73.3% of the nitrogen stable isotope variations were explained by changes in Cu bioaccumulation and the gut microbiota. The results of the present study extend our knowledge regarding the comprehensive toxicity of metal oxide NPs on soil fauna.

[Application of uniform design in optimizing the condition of arsenic determination by atomic fluorescence spectrometry].

In the present paper, uniform design U10* (10(8)) was used to optimize the condition of arsenic determination in vegetable samples by hydride generation-atomic fluorescence spectrometry. Mathematical model was established and regression analysis was done, and the optimized solutions to those equations were obtained by making use of the UD3.0 software. Combining the life-span of hollow cathode filament, noise of negative voltage and other factors, the optimal condition was obtained as follows: negative voltage was 280-360 V; lamp current was 50-70 mA; carrier gas flow rate was 500-700 mL x min(-1); KBH4 concentration was 15.0-20.0 g x L(-1); HCL concentration was 0.6-1.2 mol x L(-1); sample size was 0.5-1.0 mL. Two samples of vegetable were analyzed under the optimized condition. The results showed that the relative standard deviation was less than 3.6%, and the recovery was within 94.1%-101.3%, with their detection limits of 0.42 microg x L(-1). In this paper, as an effective method of experiment design, uniform design was introduced to hydride generation-atomic fluorescence spectrometry analysis with multifactors, which offered a good idea for the optimization of experiment conditions.