Chunyun Jia

Investigation on the photocatalytic degradation of pyrene on soil surfaces using nanometer anatase TiO2 under UV irradiation

Photocatalytic degradation of pyrene on soil surfaces was investigated in the presence of nanometer anatase TiO(2) under a variety of conditions. After being spiked with pyrene, soil samples loaded with different amounts of TiO(2) (0%, 1%, 2%, 3%, and 4%, w/w) were exposed to UV irradiation for 25h. The results indicated that the photocatalytic degradation of pyrene followed pseudo-first-order kinetics. TiO(2) accelerated the degradation of pyrene generally as indicated by the half-life reduction from 45.90 to 31.36h, corresponding to the TiO(2) amounts from 0% to 4%, respectively. The effects of H(2)O(2), light intensity and humic acids on the degradation of pyrene were also investigated. The degradation of pyrene increased along with increasing the concentration of H(2)O(2), light intensity and the concentration of humic acids. All results indicated that the photocatalytic method in the presence of nanometer anatase TiO(2) was an advisable choice for the treatments of PAHs polluted soil in the future.

Variations in the bioavailability of polycyclic aromatic hydrocarbons in industrial and agricultural soils after bioremediation

The aim of this study was to demonstrate the variations in bioavailability remaining in industrial and agricultural soils contaminated by polycyclic aromatic hydrocarbons (PAHs) after bioremediation. After inoculation of Mycobacterium sp. and Mucor sp., PAH biodegradation was tested on a manufactured gas plant (MGP) soil and an agricultural soil. PAH bioavailability was assessed before and after biodegradation using solid-phase extraction (Tenax-TA extraction) and solid-phase micro-extraction (SPME) to represent bioaccessibility and chemical activity of PAHs, respectively. Only 3- and 4-ring PAHs were noticeably biodegradable in the MGP soil. PAH biodegradation in the agricultural soil was different from that in the MGP soil. The rapidly desorbing fractions (F(rap)) extracted by Tenax-TA and the freely dissolved concentrations of 3- and 4-ring PAHs determined by SPME from the MGP soil decreased after 30 days biodegradation; those values of the 5- and 6-ring PAHs changed to a lesser degree. For the agricultural soil, the F(rap) values of the 3- and 4-ring PAHs also decreased after the biodegradation experiment. The Tenax-TA extraction and the SPME have the potential to assess variations in the bioavailability of PAHs and the degree of biodegradation in contaminated MGP soils. In addition, Tenax-TA extraction is more sensitive than SPME when used in the agricultural soil.

Beneficiation of low-grade diasporic bauxite with hydrocyclone

Low-grade diasporic bauxite was treated with hydrocyclone of small cone-angle. The effects of apex diameter, feed pressure and feed concentration on separation indexes were tested, and then the separation process was discussed by hydrokinetics tentatively. The results show that the increase of apex diameter changes the spacial locality of the envelope of zero vertical velocity, resulting in decrease of the ratio of Al2O3/SiO2 in overflow and increase of the recovery of Al2O3 in underflow, while feed pressure and feed concentration have no remarkable effect on the spacial locality of the envelope of zero vertical velocity, however, the separation indexes are improved by the increase of feed pressure, but are worsened by the increase of feed concentration.

Cadmium-induced genomic instability in Arabidopsis: Molecular toxicological biomarkers for early diagnosis of cadmium stress.

Microsatellite instability (MSI) analysis, random-amplified polymorphic DNA (RAPD), and methylation-sensitive arbitrarily primed PCR (MSAP-PCR) are methods to evaluate the toxicity of environmental pollutants in stress-treated plants and human cancer cells. Here, we evaluate these techniques to screen for genetic and epigenetic alterations of Arabidopsis plantlets exposed to 0-5.0 mg L(-1) cadmium (Cd) for 15 d. There was a substantial increase in RAPD polymorphism of 24.5, and in genomic methylation polymorphism of 30.5-34.5 at CpG and of 14.5-20 at CHG sites under Cd stress of 5.0 mg L(-1) by RAPD and of 0.25-5.0 mg L(-1) by MSAP-PCR, respectively. However, only a tiny increase of 1.5 loci by RAPD occurred under Cd stress of 4.0 mg L(-1), and an additional high dose (8.0 mg L(-1)) resulted in one repeat by MSI analysis. MSAP-PCR detected the most significant epigenetic modifications in plantlets exposed to Cd stress, and the patterns of hypermethylation and polymorphisms were consistent with inverted U-shaped dose responses. The presence of genomic methylation polymorphism in Cd-treated seedlings, prior to the onset of RAPD polymorphism, MSI and obvious growth effects, suggests that these altered DNA methylation loci are the most sensitive biomarkers for early diagnosis and risk assessment of genotoxic effects of Cd pollution in ecotoxicology.

Removing cadmium from electroplating wastewater by waste saccharomyces cerevisiae

The appropriate condition and scheme of removing cadmium from electroplating wastewater were investigated by adsorption-precipitation method using waste saccharomyces cerevisiae(WSC) as sorbent. Effect factors on biosorption of cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae and precipitation process of waste saccharomyces cerevisiae after adsorbing cadmium were studied. The results show that removal rate of cadmium is over 88% after 30 min adsorbing under the condition of cadmium concentration 26 mg/L, the dosage of waste saccharomyces cerevisiae 16.25 g/L, temperature 18 ℃, pH 6.0 and precipitation time 4 h. Biosorption-precipitation method is effective to remove cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae. The SEM, infrared spectroscopy and Zeta-potential of the cells show that chemical chelating is the main adsorption form; electrostatic attraction, hydrogen bonding and van der Waals force all function in adsorption process; and ―NH2―,―C=O―,―C=O―NH―,―CH3, ―OH are the main adsorption groups.

Selective adsorption of bacteria on sulfide minerals surface

Abstract The adsorption of bacteria on sulfide minerals surface was studied, and the selective adsorption mechanism of cells on the sulfide minerals was investigated by means of FTIR, UVS and XPS. The results show that the three strains of bacteria adsorbed more preferentially on pyrite than on other two sulfide minerals surface at neutral and alkaline pH conditions. FTIR and UVS of three strains of bacteria indicate that there are more functional groups on their surface, such as O—H, C=O, N—H, C—O, and the content of saccharide is more than that of protein. The state of every element on sulfide minerals surface was analyzed by XPS. The empty orbital number of electronic shell of metal ions on minerals surface is important in selective adsorption process, and some stable constants of metal coordinates can be used to explain the contribution of some groups in saccharide of cell wall to the selective adsorption.

Selective adsorption of Mycobacterium Phlei on pyrite and sphalerite

The adsorption of Mycobacterium Phlei cells on the surfaces of pyrite and sphalerite was studied as functions of time and pH. The results indicated that a higher amount of cells adsorbing onto pyrite compared with that onto sphalerite under neutral and alkaline conditions, and it was also observed from photographs of scanning electron micrograph. To gain a better insight into the mechanisms of differential adsorption, the functional groups on cell surfaces and the chemical states of each element on mineral surfaces before and after interaction with bacterial cells were investigated. The results showed that many groups presented on cells surface, such as C-O-H, C-O-C, C=O, C-N, N-H and P=O. The change in state of each element on pyrite and sphalerite surfaces after interaction with bacterial cells revealed that there were chemical reactions between metal ions and S on mineral surface and atoms like N, O, P, etc. on cell surface, and the shifts in binding energy of each element on pyrite surface is larger than that of sphalerite. Possible mechanisms for selective adsorption of bacterial cells onto pyrite and sphalerite were discussed in the latter part of this paper.

WITHDRAWN: Studies on the interaction between triphenyltin and bovine serum albumin by fluorescence and CD spectroscopy

The interaction between triphenyltin (TPT) and bovine serum albumin (BSA) in physiological buffer (pH=7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that TPT could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of TPT with BSA were (7.04±0.0057)×10(2) and (0.77±0.016) which were obtained by the fluorescence quenching method. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) were positive, which indicated that the interaction of TPT with BSA was driven mainly by hydrophobic forces. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance r between donor (BSA) and acceptor (TPT) was calculated to be 3.05nm based on Forsters non-radiative energy transfer theory. The results of synchronous fluorescence, three-dimensional fluorescence and Circular Dichroism (CD) spectra showed that the triphenyltin induced conformational changes of BSA.

Cell cycle arrest mediated by Cd-induced DNA damage in Arabidopsis root tips

Accumulating evidence demonstrates that the aberrant expression of cell cycle regulation and DNA repair genes can result in abnormal cell proliferation and genomic instability in eukaryotic cells under different stresses. Herein, Arabidopsis thaliana (Arabidopsis) seedlings were grown hydroponically on 0.5 × MS media containing cadmium (Cd) at 0-2.5mgL-1 for 5d of treatment. Real time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis revealed that expression of DNA damage repair and cell cycle regulation genes, including BRCA1, MRE11, WEE1, CDKA;1 and PCNA1, showed an inverted U-shaped dose-response. In contrast, notably reduced expression was observed for G1-to-S transition-related genes, Histone H4, E2Fa and PCNA2; DSB end processing, GR1; G2-to-M transition-related gene, CYCB1;1; and DNA mismatch repair, MSH2, MSH6 and MLH1 genes in root tips exposed to 0.125-2.5mg/L Cd for 5d. Flow cytometry (FCM) analysis revealed significant increases of cells with a 2C nuclear content and with a 4C and 8C nuclear content under Cd stresses of 0.125 and 1-2.5mgL-1, respectively. Our results suggest that 0.125mgL-1 Cd-induced DNA damage induced the marked G1/S arrest, leading to accelerated growth in root tips, while 1.0-2.5mgL-1 Cd-induced DNA damage caused a notable G2/M arrest in root tips, leading to reduced growth in root tips. This may be a protective mechanism that prevents cells with damaged DNA from dividing under Cd stress.

DNA damage and genetic methylation changes caused by Cd in Arabidopsis thaliana seedlings

Amplified fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MASP) techniques are sensitive to deoxyribonucleic acid (DNA) damage and genetic methylation, respectively. Using these 2 techniques, Arabidopsis thaliana cultured with 0 mg/L (control), 0.5 mg/L, 1.5 mg/L, and 5.0 mg/L Cd(2+) for 16 d was used to analyze the DNA damage and methylation changes as a result of cadmium (Cd). The DNA was amplified by 14 AFLP primer pairs and 13 MSAP primer combinations. In the AFLP experiment, 62 polymorphic sites were found in the patterns of 11 primer combinations and a total of 1116 fragments were obtained in these patterns. There were no polymorphic bands in the remaining 3 pairs. The proportions of polymorphic sites in the 0.5-mg/L Cd(2+) and 5.0-mg/L Cd(2+) treatments were significantly different. Seven polymorphic fragments were then separated and successfully sequenced, yielding 6 nucleobase substitutions and 1 nucleobase deletion. Similarly, in the MSAP experiment, the MSAP% and number of demethylated-type bands were unchanged after Cd treatment, but the number of methylated-type bands was increased significantly in the 5.0-mg/L Cd(2+) treatment group, a finding that may be associated with the AFLP results. The polymorphic bands were also sequenced and the functions of their homologous genes were determined. The DNA damage and methylation changes may be the primary cause of certain pathology changes as a result of Cd uptake in plants.