Analytical study of water infiltration and contaminant transport in barrier systems.

An analytical model was developed to assess the service time of the barrier system consisting of a two-layer cover system and a cut-off wall. The recursive method is used to evaluate the influence of the variable head loss boundary condition caused by the water infiltration. The impact of the types of cover systems and cut-off walls on the barrier system performance is assessed. The results show that cover system types are more likely to influence the long-time performance of barrier systems. Contaminant concentrations with H1* = 0.5 m and H2* = 0.3 m when t = 40 and 100 years are 1.17 and 1.42 times larger than those with H1* = H2* = 0.5 m, respectively. The decrease in hydraulic conductivity of cut-off wall and the increase in the thicknesses and retardation factors of it can also significantly improve the performance of barrier systems. Among all of the parameters, the cut-off wall thickness poses the most significant influence on the contaminant cumulative concentrations, followed by the retardation factor of the cut-off wall, the thickness and hydraulic conductivity of the lower cover layer, the hydraulic conductivity of the cut-off wall, and the thickness and hydraulic conductivity of the upper cover layer. Additionally, the proposed solution is used for the barrier system design of a mine legacy site. The minimum design thicknesses of the cut-off walls for three different cover system types and service times are obtained.

Source and risk assessment of heavy metals in mining-affected areas in Jiangxi Province, China, based on Monte Carlo simulation.

In recent years, heavy metal contamination of soils has become a major concern in China due to the potential risks involved. To assess environmental pollution and human health risks in a typical heavy metal polluted site in Jiangxi Province, a thorough evaluation of the distribution, pollution levels, and sources of heavy metals in soils of the Yangmeijiang River watershed was conducted in this study. Positive matrix factorization and Monte Carlo simulation were used to evaluate the ecological and human health risks of heavy metals. The research findings indicate that heavy metal pollution was the most severe at the depth of 20-40 cm in soils, with local heavy metal pollution resulting from mining and sewage irrigation. The high-risk area accounted for 91.11% of the total area. However, the pollution level decreased with time due to sampling effects, rainfall, and control measures. Leaf-vegetables and rice were primarily polluted by Cd and Pb. The main four sources of heavy metals in soils were traffic emission, metal smelting, agricultural activities and natural sources, mining extraction, and electroplating industries. Heavy metals with the highest ecological risk and health risk are Cd and As, respectively. The non-carcinogenic and carcinogenic risks of children were 7.0 and 1.7 times higher than those of adults, respectively. Therefore, children are more likely to be influenced by heavy metals compared to adults. The results obtained by the risk assessments may contribute to the identification of specific sources of heavy metals (e.g., traffic emissions, metal smelting, mining excavation, and electroplating industries). Additionally, the environmental impacts and biotoxicity associated with various heavy metals (e.g., Cd and As) can also be reflected. These outcomes may serve as a scientific basis for the pollution monitoring and remediation in the mining-affected areas.

Analytical model for organic contaminant transport in a cut-off wall and aquifer dual-domain system considering barrier arrangements.

This paper presents an analytical study of organic contaminants transport in a cut-off wall and aquifer dual-domain system, considering the effects of the inlet boundary conditions and cut-off structural arrangements. The comprehensive sensitivity analysis of parameters focusing on the breakthrough time, attenuation time and cumulative concentration are presented using the Monte Carlo simulation and Sobol global method. The simplified constant inlet boundary condition can lead to an excessively conservative prediction of the contaminant breakthrough compared to the 'finite mass' and 'decaying source' boundary conditions. The cut-off wall hydraulic performance can be enhanced by reducing the contaminant's head loss, shape factor, half-life and cut-off wall hydraulic conductivity while increasing the retardation factor. The contaminant's half-life can largely influence the maximum contaminant concentration, attenuation time and breakthrough time. For example, the maximum contaminant concentrations for T1/2 = 1.4 years and T1/2 = 100 years are 13 and 123 times greater than that for T1/2 = 0.1 year, respectively. The influence of the variation of shape factor on the breakthrough curve should be taken into consideration. Altering the structural arrangement of the cut-off wall to accommodate a smaller shape factor increases the contaminant breakthrough time. The proposed solution allows the analysis of a cut-off wall and aquifer system with different inlet boundary conditions and structural arrangements of the cut-off wall.

Synergic regulation of redox potential and oxygen uptake to enhance production of coenzyme Q10 in Rhodobacter sphaeroides.

The physiological role of Coenzyme Q10 (CoQ10) as an electron carrier suggests its association with redox potential. Overexpression of glyceraldehyde-3-phosphate dehydrogenase type I (gapA-1) in Rhodobacter sphaeroides elevated the NADH/NAD+ ratio and meanwhile enhanced the CoQ10 content by 58%, but at the sacrifice of biomass. On the other hand, Vitreoscilla hemoglobin was heterologously expressed to enhance the oxygen uptake ability of the cells, leading to 127% improvement of biomass. Subsequent coexpression of gapA-1 and vgb resulted in a CoQ10 titer of 83.24mg/L, representing 71% improvement as compared to the control strain RspMCS. When gapA-1 and vgb genes were co-expressed in a previously created strain RspMQd [1], 163.5mg/L of CoQ10 was produced. Finally, 600mg/L of CoQ10 production was achieved in fed-batch fermentation. These results demonstrated the synergic effect of redox potential regulation and oxygen uptake improvement on enhancing CoQ10 production in R. sphaeroides.

A DNA Binding Protein Is Required for Viral Replication and Transcription in Bombyx mori Nucleopolyhedrovirus.

A DNA-binding protein (DBP) [GenBank accession number: M63416] of Bombyx mori nuclear polyhedrosis virus (BmNPV) has been reported to be a regulatory factor in BmNPV, but its detailed functions remain unknown. In order to study the regulatory mechanism of DBP on viral proliferation, genome replication, and gene transcription, a BmNPV dbp gene knockout virus dbp-ko-Bacmid was generated by the means of Red recombination system. In addition, dbp-repaired virus dbp-re-Bacmid was constructed by the means of the Bac to Bac system. Then, the Bacmids were transfected into BmN cells. The results of this viral titer experiment revealed that the TCID50 of the dbp-ko-Bacmid was 0; however, the dbp-re-Bacmid was similar to the wtBacmid (p>0.05), indicating that the dbp-deficient would lead to failure in the assembly of virus particles. In the next step, Real-Time PCR was used to analyze the transcriptional phases of dbp gene in BmN cells, which had been infected with BmNPV. The results of the latter experiment revealed that the transcript of dbp gene was first detected at 3 h post-infection. Furthermore, the replication level of virus genome and the transcriptional level of virus early, late, and very late genes in BmN cells, which had been transfected with 3 kinds of Bacmids, were analyzed by Real-Time PCR. The demonstrating that the replication level of genome was lower than that of wtBacmid and dbp-re-Bacmid (p<0.01). The transcriptional level of dbp-ko-Bacmid early gene lef-3, ie-1, dnapol, late gene vp39 and very late gene p10 were statistically significantly lower than dbp-re-Bacmid and wtBacmid (p<0.01). The results presented are based on Western blot analysis, which indicated that the lack of dbp gene would lead to low expressions of lef3, vp39, and p10. In conclusion, dbp was not only essential for early viral replication, but also a viral gene that has a significant impact on transcription and expression during all periods of baculovirus life cycle.

[Effects of bm47 deletion on viral replication and transcription of Bombyx mori nucleopolyhedrovirus].

Bombyx mori nucleopolyhedrovirus (BmNPV) bm47 gene is found in all sequenced lepidopteran nucleopolyhedroviruses (NPVs). It is one of the core genes of NPVs. However, the role of bm47 in the biological cycle of NPV remains unknown. In this study, the Red recombination system was used to knock out bm47 from BmNPV to construct bm47-ko-Bacmid in E. coli BW25113 system. Then bm47 gene was introduced back to the viral genome using the Bac-to-Bac system to create the repair virus bm47-re-Bacmid. TCID50 assay and real-time PCR (qPCR) were used to evaluate the effects of bm47 deletion on viral DNA replication, gene transcription, and protein expression. qPCR results showed that bm47 knock-out had no significant effect on viral DNA replication. However, the qPCR results showed that bm47-ko-Bacmid significantly decreased the transcription levels of early gene lef-3, late gene vp39, and very late gene p10 at 48 h and 72 h after viral transfection of BmN cells (P < 0.05). This work will provide a foundation for further studies on the biological function of BmNPV bm47 in viral replication and transcription.