Abstract Semi-permeable membrane covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semi-permeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced the bacterial richness and increased the bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting.
With continuous improvement of people's living standards, great efforts have been paid to environmental protection. Among those environmental issues, soil contamination by petroleum hydrocarbons has received widespread concerns due to the persistence and the degradation difficulty of the pollutants. Among the various remediation technologies, in-situ microbial remediation enhancement technologies have become the current hotspot because of its low cost, environmental friendliness, and in-situ availability. This review summarizes several in-situ microbial remediation technologies such as bioaugmentation, biostimulation, and integrated remediation, as well as their engineering applications, providing references for the selection of in-situ bioremediation technologies in engineering applications. Moreover, this review discusses future research directions in this area.
Among 50 CLE gene family members in the Populus trichocarpa genome, three and six PtCLE genes encode a CLE motif sequence highly homologous to Arabidopsis CLV3 and TDIF peptides, respectively, which potentially make them functional equivalents. To test and compare their biological activity, we first chemically synthesized each dodecapeptide and analysed its in vitro bioactivity on Arabidopsis seedlings. Similarly, but to a different extent, three types of poplar CLV3-related peptides caused root meristem consumption, phyllotaxis disorder, anthocyanin accumulation and failure to enter the bolting stage. In comparison, application of two poplar TDIF-related peptides led to root length promotion in a dose-dependent manner with an even stronger effect observed for poplar TDIF-like peptide than TDIF. Next, we constructed CaMV35S:PtCLE transgenic plants for each of the nine PtCLE genes. Phenotypic abnormalities exemplified by arrested shoot apical meristem and abnormal flower structure were found to be more dominant and severe in 35S:PtCLV3 and 35S:PtCLV3-like2 lines than in the 35S:PtCLV3-like1 line. Disordered vasculature was detected in both stem and hypocotyl cross-sections in Arabidopsis plants over-expressing poplar TDIF-related genes with the most defective vascular patterning observed for TDIF2 and two TDIF-like genes. Phenotypic difference consistently observed in peptide application assay and transgenic analysis indicated the functional diversity of nine poplar PtCLE genes under investigation. This work represents the first report on the functional analysis of CLE genes in a tree species and constitutes a basis for further study of the CLE peptide signalling pathway in tree development.
Ammonia synthesis by hydrogen and nitrogen is an important pathway for ammonia production. However, design of an energy efficient and environmentally friendly route for ammonia synthesis is still a challenge and needs to be overcome. Performance and economic feasibility of ammonia synthesis loop processes significantly depend on not only configuration arrangement but also on operating conditions. Thus, a novel ammonia synthesis route with exergy recovery and heat integration was designed by process simulation in this work. The energy and material balance of the proposed process was investigated and compared with the conventional process. The heat integration performance and its influence on total energy consumption were also evaluated. The investigation results showed that the energy consumption of the proposed process was reduced to 16.72 MW, which equaled 38.18% of the conventional process with the feed natural gas of both processes set at 0.083 kmol/s. Approximately 57.9 MW could be recovered in the proposed ammonia synthesis process by heat exchanger networks.
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