A computational
fluid dynamics (CFD) model was used to predict
the hydraulics and flow patterns of flow-guided sieve tray, which
combined common sieve holes with flow-guided holes. The model considered
the three-dimensional two-phase flow of gas and liquid, and each phase
was treated as interpenetrating continua that had separate transport
equations. Interaction between the two phases was considered via an
interphase momentum transfer term, which was incorporated into the
CFD model. On the basis of experimental measurement, the new correlations
of clear liquid height and gas holdup were developed. The velocity
distribution, clear liquid height, and foam height were predicted
and found to be in good agreement with the experimental data. Distribution
of clear liquid height and liquid holdup proved that flow-guided holes
can promote the liquid flow and decrease the clear liquid height.
The CFD method is a useful tool for optimizing the novel flow-guided
sieve tray.
Atrazine has been extensively used in China’s agricultural production for a long time and the potential risks to the environment have received widespread attention. The purpose of this study was to examine the effect of the continuous application of atrazine on soil herbicide residues, soil enzyme activity, and microbial community structure, as well as to provide a theoretical reference for the appropriate application of atrazine and the improvement of soil. Previous studies have focused on the effects of atrazine on soil microorganisms, but the experiments used higher doses than recommended. To reveal the actual effects of atrazine on soil microorganisms, the recommended dose of atrazine was used for 0, 1, and 2 years. We studied atrazine residues and enzyme activity in the soil, and phospholipid fatty acids (PLFA) were measured to study the structure of the soil microbiome. The results show that the rate of atrazine degradation occurred rapidly after the initial administration, and with the increase in continuous administration, its half-life decreased from 24.6 d in the first year to 14.1 d in the second year. The application of atrazine significantly affected soil urease activity and cellulase activity, but it had no significant effect on saccharase activity. The continuous application of atrazine had a significant effect on the biomass of cultured bacteria in soil, but not on the biomass of culturable fungi and actinomycetes in the soil. Furthermore, the results of PLFA analysis show that the application of atrazine had a significant effect on the microbial structure of the soil. These results indicate that the significant increase in the degradation rate of atrazine during continuous application is related to the high adaptability of the soil microbiome.
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