Water-Holding Properties of Clinoptilolite/Sodium Polyacrylate-Modified Compacted Clay Cover of Tailing Pond.

Clinoptilolite and sodium polyacrylate (Na-PAA) were used as water-retaining agents to improve the water-holding capacity of compacted clay cover (CCC). The optimum moisture content and Atterberg limits of the CCC modified by clinoptilolite and Na-PAA were studied. The soil-water characteristic curve (SWCC) of the CCC modified by clinoptilolite and Na-PAA was studied. The mesostructure of the CCC was analyzed by polarized light microscopy. The test results show that: (1) the optimum moisture content and liquid limit of the CCC modified by clinoptilolite and Na-PAA increased, while the maximum dry density decreased; (2) the SWCC of the CCC modified by clinoptilolite and Na-PAA shifts to the upper right, and the volume moisture content of modified CCC is higher than that of unmodified CCC under the same matrix suction; (3) compared with the unmodified CCC, the air-entry value (AEV) of the clinoptilolite-modified CCC increased by 65.18% at most, and the AEV of the further modified CCC with Na-PAA in-creased by about two times; and (4) the flocculation structure and porosity of modified CCC decreased, and the porosity was distributed uniformly.

Field Investigation of Effect of Plants on Cracks of Compacted Clay Covers at a Contaminated Site.

Compacted clay covers (CCCs) are effective in restricting the upward migration of volatile organic compound (VOC) and semi-volatile organic compound (SVOC) vapors released mainly from unsaturated contaminated soils and hence mitigate the risks to human health. Desiccation cracking of CCCs would result in numerous preferential channels. VOC or SVOC vapors can prefereially migrate through the cracks and emit into the atmosphere, exposing threats to human health and surrounding environmental acceptors. This study presented results of comprehensive field investigation of desiccation crack distribution in CCCs, where four herbaceous plants were covered at the industrial contaminated site in. The plants included Trefoil, Bermuda grass, Conyza Canadensis, and Paspalum, and the corresponding planting areas were labeled as S1, S2, S3, and S4, respectively. The quantity and geometry parameters of the cracks including crack width, depth, and length, were investigated. The results showed that the cracks of the CCCs were mainly distributed in the areas of S3 (Conyza Canadensis) and S4 (Paspalum), where more cracks were formed when the degree of compaction (DOC) of the CCCs was less than 87%. In addition, the results revealed that: (1) no cracks were found in the area S1 (Trefoil); (2) the quantity, average width, average depth, average length, and maximal length of the cracks in the investigated areas followed S4 (Paspalum) > S3 (Conyza Canadensis) > S2 (Bermuda grass); (3) the maximal crack length in the area S2 (Bermuda grass) was the shortest, which was approximately one-seventh and one-eighth of those in the areas S3 (Conyza Canadensis) and S4 (Paspalum), respectively; and (4) the maximal width and depth of the cracks followed S3 (Conyza Canadensis) > S4 (Paspalum) > S2 (Bermuda grass).

Microbial induced carbonate precipitation for immobilizing Pb contaminants: Toxic effects on bacterial activity and immobilization efficiency.

Microbial induced carbonate precipitation (MICP) is a natural bio-mediated process, which has been explored for soil stabilization and heavy metals immobilization in soil and groundwater. Previous studies have shown that MICP is capable of immobilizing various heavy metals including lead (Pb). However, most studies focus merely on the immobilization of heavy metals with relatively low concentration. This study: (1) presents results of an investigation into the toxic effects of Pb on bacterial activity and immobilization efficiency within a wide range of Pb concentrations; and (2) identifies controlling biotic and abiotic factors of Pb immobilization by MICP. In the first series of tests, bacterial strains (Sporosarcina pasteurii) are inoculated into nutrient solutions containing 0-50 mM Pb(NO3)2 and incubated at 30 °C. Biochemical parameters are measured over time, which include pH, electrical conductivity, urease activity, and viable cell number. In the second series of tests, grown bacterial strains are mixed with urea, calcium salts and Pb(NO3)2 in solution. Viable cell number, produced ammonium concentration, aqueous Pb concentration of the mixed solution, and total precipitation mass are measured. The results show that the presence of Pb has marginal effect on bacterial growth and associated urease activity at Pb concentration < 30 mM. The calcium source and initial bacteria concentration are found to remarkably influence Pb immobilization efficiency in terms of Pb removal percentage. Supplementary geochemical simulation results indicate that the Pb immobilization mechanisms includes abiotic precipitation, biotic precipitation and bio-sorption.

Effect of curcumin on JAK-STAT signaling pathway in hepatoma cell lines / 药学学报

The effect of curcumin on JAK-STAT signaling pathway was investigated in hepatoma cell lines Huh7 and Hep3B. Curcumin inhibited cell proliferation and induced apoptosis of both cell lines, but Huh7 cells were more sensitive to curcumin than Hep3B cells. Curcumin (50 micromol x L(-1)) significantly increased phosphorylations of p38 (T180/Y182) and STAT-1 (S727) in Huh7 and Hep3B cells, and caused relocalization of phosphorylated-STAT-1 (Y701) from cytoplasm to nucleus in Hep3B cells. In addition, curcumin (25 and 50 micromol x L(-1)) dramatically suppressed the phosphorylation level of STAT-1 (Y701) and resulted in a significant reduction of nuclear phosphorylated-STAT-1 (Y701) in Huh7 cells.

Effect of p21-targeted shRNA on curcumin-induced apoptosis of human hepatoma Huh7 cells / 药学学报

In the present study, shRNA plasmid of pSi-p21 targeting p21 mRNA was constructed and the effect of p21 shRNA on curcumin-induced apoptosis of human hepatoma Huh7 cells was investigated. The effect of curcumin on the expression of p21 mRNA and protein and the silence efficiency of pSi-p21 were detected with RT-PCR and Western blotting. The effect of pSi-p21 on curcumin-induced apoptosis of Huh7 cells was evaluated with DAPI staining. The results showed that curcumin significantly upregulated p21 mRNA and protein expression, which was knocked down by pSi-p21 of Huh7 cells. DAPI staining results showed that pSi-p21 significantly decreased curcumin-induced apoptosis of Huh7 cells. The data suggested that curcumin induced apoptosis of Huh7 cells via upregulation of p21 expression.