[Adsorptive Remediation of Cr(â ¥) Contaminated Groundwater with Chemically Synthesized Schwertmannite].

Schwertmannite is usually naturally found in acidic mining wastewater and frequently used in the adsorption of heavy metal anions from water and wastewater. Schwertmannite was synthesized through a facile chemical method and utilized to remove Cr(Ⅵ) from contaminated groundwater. The kinetics, thermodynamics and isotherms, as well as the effects of environmental factors on the Schwertmannite adsorption processes were investigated. The experimental results showed that the synthesized Schwertmannite had a strong adsorption capability of Cr(Ⅵ) from aqueous solution. At the pre-set initial concentrations of Cr(Ⅵ), the Schwertmannite adsorption of Cr(Ⅵ) achieved equilibrium within 24 h, and the Lagergren's second-order model fitted the adsorption process better compared to Lagergren's first-order model and intraparticle diffusion model. Langmiur equation fitted the adsorption isotherms better than Freundlich equation. The Cr(Ⅵ) adsorption on Schwertmannite mainly involved ion exchange reaction between Cr(Ⅵ) and anions such as OH- and SO42- and surface complexation reactions. The ΔHθ and ΔGθ were 6.368 kJ·mol-1 and -1.215 kJ·mol-1, respectively, therefore the adsorption of Cr(Ⅵ) was a spontaneous and endothermic process. The removal of Cr(Ⅵ) from aqueous solution increased with increasing Schwertmannite dosage at pH=4.5. Acidic pH in the range of 4.5-6 favored Cr(Ⅵ) removal with Schwertmannite compared to that under basic conditions. Under the conditions of 5 mg·L-1of initial Cr(Ⅵ) concentration, 0.5 g·L-1 of Schwertmannite dosage, pH=6, maximum Cr(Ⅵ) removal of 93.1% was achieved and the adsorption capacity of Cr(Ⅵ) with Schwertmannite reached up to 40.4 mg·g-1. Batch tests showed that the presence of HCO3- and SO42- inhibited the adsorption of Cr(Ⅵ) while Cl- had no significant impact. Cations and natural organic matter had a pH-dependent impact on Cr(Ⅵ) removal:at pH=8 natural organic matter and cations would significantly inhibit the Cr(Ⅵ) sorption, while the impact could be neglected at weak acidic conditions (pH=6).

[Acidophilic methanogens and their applications in anaerobic digestion].

Methanogens play an important role in global carbon cycle. There exists a range of unknown methanogenic archaea in acidic peat lands, among which, acidophilic methanogens have attracted increasing research interests because of their special metabolic characteristics. To introduce acidophilic methanogens in the anaerobic digestion process of high concentration organic wastes or waste water could essentially overcome the inhibition of acid accumulation on the methanogens and help reduce the operation cost, broadening the industrial application of anaerobic bio-treatment technology. In this paper, we reviewed the recent researches on acidophilic methanogens, with the focus on enrichment and isolation methods, physiological and biochemical characters, metabolic characteristics, and application of molecular biology. The potential applications of acidophilic methanogens in anaerobic digestion process were analyzed and proposed, and the directions for further researches were suggested.

[Ammonia-oxidizing archaea and their important roles in nitrogen biogeochemical cycling: a review].

As the first step of nitrification, ammonia oxidation is the key process in global nitrogen biogeochemical cycling. So far, the autotrophic ammonia-oxidizing bacteria (AOB) in the beta- and gamma-subgroups of proteobacteria have been considered as the most important contributors to ammonia oxidation, but the recent researches indicated that ammonia-oxidizing archaea (AOA) are widely distributed in various kinds of ecosystems and quantitatively predominant, playing important roles in the global nitrogen biogeochemical cycling. This paper reviewed the morphological, physiological, and ecological characteristics and the molecular phylogenies of AOA, and compared and analyzed the differences and similarities of the ammonia monooxygenase (AMO) and its encoding genes between AOA and AOB. In addition, the potential significant roles of AOA in nitrogen biogeochemical cycling in aquatic and terrestrial ecosystems were summarized, and the future research directions of AOA in applied ecology and environmental protection were put forward.

[Nitrogen loss and its control during livestock manure composting].

Composting is an effective way to realize livestock manure treatment and recycling. However, the nitrogen loss during manure composting is relatively serious. Studies on this nitrogen loss and its control could provide theoretic basis and practical reference for efficient nitrogen loss control. This paper described the nitrogen transformation and the main nitrogen loss ways during the composting, and summarized the main factors (including raw material characteristics, environment factors, and technological conditions) affecting the nitrogen loss in the composting. In addition, the research progress in the nitrogen loss control, including adjusting carbon and nitrogen metabolism, changing nitrogen form, adding ammonia adsorbent, and controlling pile aeration and temperature, was reviewed, and the prospects for future research were presented.

Effects of bamboo charcoal and bamboo vinegar on nitrogen conservation and heavy metals immobility during pig manure composting.

Composting is an effective methodology for the treatment of organic waste like pig manure (PM) before land application. However, nitrogen loss through NH(3) volatilization during the thermophilic phase is one of the major disadvantages of composting. The presence of Cu and Zn in compost arising from pig feed additives is also an issue. In this study the effects of bamboo charcoal (BC) and bamboo vinegar (BV) added to composting piles on nitrogen conservation and immobility of Cu and Zn during PM composting was investigated. Total Kjeldahl nitrogen (TKN) loss and mobility of Cu and Zn decreased with increased BC addition. TKN loss and mobility of Cu and Zn in the treatment with 9% BC at the end of composting significantly decreased by 65%, 35% and 39% respectively, as compared to the control. Addition of BV further decreased TKN loss. After composting, TKN loss in the treatment with 3% BC+0.4% BV was 23% lower than that in the treatment with 9% BC. The final results indicated that by adding BC or BC+BV into PM composting is an effective method to reduce TKN loss and control the mobility of Cu and Zn.

Pharmacokinetics and the bystander effect in CD::UPRT/5-FC bi-gene therapy of glioma.

BACKGROUND: Cytosine deaminase (CD) converts 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) in CD/5-FC gene therapy, 5-FU will be mostly converted into nontoxic beta-alanine without uracil phosphoribosyltransferase (UPRT). UPRT catalyzes the conversion of 5-FU to 5-fluorouridine monophosphate, which directly kills CD::UPRT-expressing cells and surrounding cells via the bystander effect. But the pharmacokinetics and the bystander effect of CD::UPRT/5-FC has not been verified in vivo and in vitro. Before the CD::UPRT/5-FC bi-gene therapy system is used in clinical trial, it is essential to monitor the transgene expression and function in vivo. Thus, we developed a preclinical tumor model to investigate the feasibility of using (19)F-magnetic resonance spectroscopy ((19)F-MRS) and optical imaging to measure non-invasive CD and UPRT expression and its bystander effect. METHODS: C6 and C6-CD::UPRT cells were cultured with 5-FC. The medium, cells and their mixture were analyzed by (19)F-MRS. Rats with intracranial xenografted encephalic C6-CD::UPRT glioma were injected intraperitoneally with 5-FC and their (19)F-MRS spectra recorded. Then the pharmacokinetics of 5-FC was proved. Mixtures of C6 and C6-CD::UPRT cells at different ratios were cultured with 5-FC and the cytotoxic efficacy and survival rate of cells recorded. To determine the mechanism of the bystander effect, the culture media from cell comprising 25% and 75% C6-CD::UPRT cells were examined by (19)F-MRS. A comparative study of mean was performed using analysis of variance (ANOVA). RESULTS: (19)F-MRS on samples from C6-CD::UPRT cells cultured with 5-FC showed three broad resonance signals corresponding to 5-FC, 5-FU and fluorinated nucleotides (F-Nuctd). For the C6 mixture, only the 5-FC peak was detected. In vivo serial (19)F-MRS spectra showed a strong 5-FC peak and a weak 5-FU peak at 20 minutes after 5-FC injection. The 5-FU concentration reached a maximum at about 50 minutes. The F-Nuctd signal appeared after about 1 hour, reached a maximum at around 160 minutes, and was detectable for several hours. At a 10% ratio of C6-CD::UPRT cells, the survival rate was (79.55 +/- 0.88)% (P < 0.01). As the C6-CD::UPRT ratio increased, the survival rate of the cells decreased. (19)F-MRS showed that the signals for 5-FU and F-Nuctd in the culture medium increased as the ratio of C6-CD::UPRT in the mixture increased. CONCLUSIONS: (19)F-MRS studies indicated that C6-CD::UPRT cells could effectively express CD and UPRT enzymes. The CD::UPRT/5-FC system showed an obvious bystander effect. This study demonstrated that CD::UPRT/5-FC gene therapy is suitable for 5-FC to F-Nuctd metabolism; and (19)F-MRS can monitor transferred CD::UPRT gene expression and catalysis of substrates noninvasively, dynamically and quantitatively.

Effect of MSW source-classified collection on the emission of PCDDs/Fs and heavy metals from incineration in China.

Municipal solid waste (MSW) source-classified collection represents a change in MSW management in China and other developing countries. Comparative experiments were performed to evaluate the effect of a newly established MSW source-classified collection system on the emission of PCDDs/Fs (polychlorinated dibenzo-p-dioxins and dibenzofurans) and heavy metals (HMs) from a full-scale incinerator in China. As a result of presorting and dewatering, the chlorine level, heavy metal and water content were lower, but heat value was higher in the source-classified MSW (classified MSW) as compared with the conventionally mixed collected MSW (mixed MSW). The generation of PCDDs/Fs in flue gas from the classified MSW incineration was 9.28 ng I-TEQ/Nm(3), only 69.4% of that from the mixed MSW incineration, and the final emission of PCDDs/Fs was only 0.12 ng I-TEQ/Nm(3), although activated carbon injection was reduced by 20%. The level of PCDDs/Fs in fly ash from the bag filter was 0.27 ng I-TEQ/g. These results indicated that the source-classified collection with pretreatment could improve the characteristics of MSW for incineration, and significantly decrease formation of PCDDs/Fs in MSW incineration. Furthermore, distributions of HMs such as Cd, Pb, Cu, Zn, Cr, As, Ni, Hg in bottom ash and fly ash were investigated to assess the need for treatment of residual ash.