1.
Study on shear behavior of kaolinite contaminated by heavy metal Cu (II).
Zhang, Z, Chen, Y, Fang, J, Guo, F
Environmental science and pollution research international. 2019;(14):13906-13913
Abstract
Numerous studies have shown that the invasion of the chemicals plays an important role on the geomechanical properties of the soil. This article aims to investigate the shear behavior of contaminated soil by laboratory tests and develop an extended shear strength model on the basis of the experimental results. In order to explicitly evaluate the effect of solution concentration on the shear strength behavior of soil, the remolded samples of kaolinite mixed with different concentrations of CuCl2 solutions were prepared to carry out a series of consolidated-undrained triaxial shear strength tests. The results indicate that different CuCl2 solution concentrations have significant influence on the shear strength property of kaolinite. With the increase of CuCl2 solution concentration, the shear strength of soil displays a declining tendency, and the strength properties including cohesion and internal friction angle are also reduced, which indicates the Cu (II) that existed in the soil samples has deteriorated the soil strength strongly. Based on the experimental results, an extended Mohr-Coulomb strength model for contaminated soils has been proposed by introducing osmotic suction as a macro variable parameter. The conclusions in this study can provide reference for pollution prevention of existing and future foundations.
2.
Transcriptomic analysis of Chlorimuron-ethyl degrading bacterial strain Klebsiella jilinsis 2N3.
Zhang, C, Hao, Q, Zhang, S, Zhang, Z, Zhang, X, Sun, P, Pan, H, Zhang, H, Sun, F
Ecotoxicology and environmental safety. 2019;:109581
Abstract
Chlorimuron-ethyl is a sulfonylurea herbicide with a long residual period in the field and is toxic to rotational crops. Klebsiella jilinsis 2N3 is a gram-negative bacterium that can rapidly degrade Chlorimuron-ethyl. In this study, the gene expression changes in strain 2N3 during degradation of Chlorimuron-ethyl was analyzed by RNA-Seq. Results showed that 386 genes were up-regulated and 453 genes were down-regulated. KEGG pathway enrichment analysis revealed the highest enrichment ratio in the pathway of sulfur metabolism. On the basis of the functional annotation and gene expression, we predicted that carboxylesterase, monooxygenase, glycosyltransferase, and cytochrome P450 were involved in the metabolism of Chlorimuron-ethyl biodegradation. Results of qRT-PCR showed that the relative mRNA expression levels of these genes were higher in treatment group than those in control group. The cytochrome P450 encoded by Kj-CysJ and the alkanesulfonate monooxygenase encoded by Kj-SsuD were predicted and further experimentally confirmed by gene knockout as the key enzymes in the biodegradation process. Cultured in basal medium containing Chlorimuron-ethyl (5 mg L-1) in 36 h, the strains of ΔKj-CysJ, ΔKj-SsuD, and WT reached the highest OD600 values of 0.308, 0.873, and 1.085, and the highest degradation rates of Chlorimuron-ethyl of 11.83%, 96.21%, and 95.62%, respectively.
3.
Enantioselective determination of the chiral pesticide isofenphos-methyl in vegetables, fruits, and soil and its enantioselective degradation in pak choi using HPLC with UV detection.
Gao, B, Zhang, Q, Tian, M, Zhang, Z, Wang, M
Analytical and bioanalytical chemistry. 2016;(24):6719-27
Abstract
An enantioselective method for the simultaneous determination of the chiral pesticide isofenphos-methyl in vegetables, fruits, and soil has been established using high-performance liquid chromatography with UV detection. The complete enantioseparation was conducted by reversed-phase liquid chromatography with a cellulose-tris-(4-methylbenzoate) chiral stationary phase (CSP) (Lux Cellulose-3). The effects of different mobile phase compositions, temperatures, and flow rates on enantioseparation were also investigated. The experimental and calculated electronic circular dichroism spectra indicate that the first peak is (S)-(+)-isofenphos-methyl and the second peak is (R)-(-)-isofenphos-methyl. Alumina-A and Florisil solid-phase extraction (SPE) columns were used to clean up for vegetable, fruit, and soil samples. The mean recoveries of the two enantiomers ranged from 83.2 to 110.9 % with intra-day relative standard deviations (RSDs) from 3.2 to 10.8 % and inter-day RSDs from 3.6 to 10 %. Good linearity (≥0.9992) was obtained for the two enantiomers in all matrix-matched calibration curves in the range of 0.25 to 20 mg L(-1). The limit of detection for two enantiomers in six matrices was in the range of 0.008 to 0.011 mg kg(-1), and the limit of quantification was estimated to range from 0.027 to 0.037 mg kg(-1). The results indicated that this method was a convenient and dependable approach for the simultaneous determination of isofenphos-methyl enantiomers in food and environmental samples. The stereoselective degradation of isofenphos-methyl in pak choi has shown that the (R)-(-)-isofenphos-methyl isomer (half-life t 1/2 = 2.2 days) degraded faster than the (S)-(+)-isomer (t 1/2 = 1.9 days). Graphical Abstract The enantioselective determination and enantioselective degradation of the chiral pesticide isofenphos-methyl.