Search

There are few studies on denitrification related to the nitrogen cycle in Ebinur Lake wetland. This study aimed to explore the response of the diversity and composition of denitrifying bacteria to the environmental factors in wetland, so as to obtain more information about the community structure of denitrifying bacteria driven by environmental factors. Using the genes encoding nitrite reductase (nirS and nirK) as molecular markers, we analysed the seasonal changes in the diversity of denitrifying bacteria in halophyte soils by high-throughput sequencing technology. The results showed that the diversity of denitrifying bacteria was higher in July and lower in April, showing seasonal changes. The diversity index of denitrifying bacteria in rhizosphere soil was higher than that in non-rhizosphere soil. The diversity of denitrifying bacteria in the Phragmites australis rhizosphere soil was the highest. The diversity of nirK denitrifying bacteria was higher than that of nirS denitrifying bacteria, but the relative abundance was lower than that of nirS denitrifying bacteria. Three-way ANOVA showed that soil types, vegetation types and season had significant effects on the diversity of denitrifying bacteria. Furthermore, redundancy analysis indicated that nitrate was the environmental factor that significantly affected the community structure of nirS denitrifying bacteria in wetland, and electric conductivity, total nitrogen, ammonium and nitrate were the environmental factors that significantly affected the community structure of nirK denitrifying bacteria. These results provide data basis and theoretical support for the dynamic change of diversity of denitrifying bacteria in wetland. [ABSTRACT FROM AUTHOR]

Asphalt in damp-heat and saline-alkali areas is prone to damage, which resulting in fatigue failure of the mixture. However, the aging damage of asphalt in these areas has not been paid enough attention, and there is a lack of effective evaluation method for asphalt's fatigue performance. In this paper, the base asphalt and SBS-modified asphalt were immersed in several solutions (water, NaCl and Na2CO3) to simulate aging conditions and the frequency sweep test was employed to determine the viscoelasticity properties of the asphalt. And the fatigue properties of the asphalt were analysed by the simplified viscoelastic continuum damage model. The microstructural and chemical evolution of asphalt was investigated by SEM, FTIR, the pH value and total organic carbon tests. After being immersed, the anti-deformation properties of two asphalts were strengthened. The solution erosion led to an increased loss rate of the integrity factor C*, and resulting in weakened fatigue properties of asphalt. The oxygen-containing functional group gradually increased with the extension of immersion. There were chemical interactions in addition to physical interface disruption during the immersion process. Moreover, the influence of Na2CO3 solution on asphalt ranked first due to the highest molar concentration of Na+ and the OH− produced by hydrolysis of ${\rm CO}_3^{2-}$ C O 3 2 − . [ABSTRACT FROM AUTHOR]

In the present study, the effect of elastomer ratios in solution-based mixtures on the formation of the phase structure and properties of compositions based on butyl rubber, chlorobutyl rubber, and ethylene-propylene-diene rubber was investigated. This work determined the influence of the elastomer ratios in uncured blends and their impact on the patterns of phase structure formation in multicomponent polymer systems, alterations in molecular mobility, and their influence on ozone resistance. Attenuated total reflectance – Fourier transform infrared spectroscopy was employed to analyze the chemical structure of the polymer surfaces. The influence of blend ratio (mass percentage ratios of 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) on the phase structure and surface ozone oxidation was studied. The green strengths of the blends of ethylene-propylene-diene rubber and butyl/chlorobutyl rubbers were studied over a wide range of blend ratios. [ABSTRACT FROM AUTHOR]

High-temperature rutting is one of the common forms of pavement damage. To further improve the high temperature performance of crumb rubber modified asphalt (CRMA) pavement, heavy calcium carbonate (HCC) modified by sodium pyrophosphate was combined with crumb rubber to prepare composite modified asphalt binder. Their physical properties, viscoelastic properties and chemical composition were investigated through conventional physical tests, DSR, FTIR and fluorescence microscopes. The results show that with the increase of HCC content, the mixing and compaction temperatures of composite modified asphalt binders continued to increase. Further, the high temperature performance and fatigue resistance of binders were better than the original CRMA, due to the enhanced lipophilicity of HCC after modification. It can be found from the FTIR spectrum that the addition of HCC only existed in physical action. However, excessive HCC would cause agglomeration of the asphalt matrix, so the optimum dosage of HCC was determined to be 4%. [ABSTRACT FROM AUTHOR]