Isolation,identification and desulfurization mechanism of a sulfur-oxidizing bacterium with salt tolerance北大核心CSCD

Micro-organism with efficient desulfurization performance is a key factor in the biological desulfurization technology. This study aimed to seek such a sulfur-oxidizing strain and understand its desulfurization mechanism. Wastewater in a sewage station of natural gas purification plant was used to screen the sulfide-oxidizing strain, and to identify it based on sequence similarity analysis of 16S rDNA and the morphological characteristics. Thiosulfate was used as substrate for investigating the sulfur oxidation performance and salinity tolerance; the OD600, content change of thiosulfate, sulfate, sulfur, pH and total alkalinity in the cultural system were also investigated. The strain DS-B was found to share the highest sequence similarity with Thioalkalivibrio thiocyanoxidans ARh2, therefore determined as Thioalkalivibrio. At the optimum temperature of 35 °C for growth and degradation, the removal efficiency of thiosulfate could reach 98.7% after 7 days. Strain DS-B had strong resistance to thiosulfate, and the optimal concentration of S2O32- was 2 × 104 mg/L. The analysis for sulfur oxides showed that it could oxidize thiosulfate by the pathway of S2O32-→SO42- / S2O32- → S → SO42-. Therefore the strain DS-B is a sulfur-oxidizing bacterium with great application prospect for its strong salt tolerance and conspicuous removal capability for thiosulfate.     

Toward rational design of amines for CO2 capture: Substituent effect on kinetic process for the reaction of monoethanolamine with CO2

Amines have been considered as promising candidates for post-combustion CO₂ capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO₂ is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products (carbamates, carbamic acids and bicarbonate) from amines + CO₂ were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO₂ based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies (E_a) for the reactions of a range of substituted monoethanolamines with CO₂ covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the E_a values for all pathways linearly correlate with pK_a of amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with pK_a of the amines, i.e. stronger basicity results in less difference in E_a. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.     

Genomic analyses of metal resistance genes in three plant growth promoting bacteria of legume plants in Northwest mine tailings, China

To better understand the diversity of metal resistance genetic determinant from microbes that survived atmetal tailings in northwest of China, a highly elevated level of heavymetal containing region, genomic analyses was conducted using genome sequence of three native metal-resistant plant growth promoting bacteria (PGPB). It shows that: Mesorhizobium amorphae CCNWGS0123 contains metal transporters from P-type ATPase, CDF (Cation Diffusion Facilitator), HupE/UreJ and CHR (chromate ion transporter) family involved in copper, zinc, nickel as well as chromate resistance and homeostasis. Meanwhile, the putative CopA/CueO system is expected to mediate copper resistance in Sinorhizobium meliloti CCNWSX0020 while ZntA transporter, assisted with putative CzcD, determines zinc tolerance in Agrobacterium tumefaciens CCNWGS0286. The greenhouse experiment provides the consistent evidence of the plant growth promoting effects of these microbes on their hosts by nitrogen fixation and/or indoleacetic acid (IAA) secretion, indicating a potential in-site phytoremediation usage in themining tailing regions of China.     

Design and demonstration of a next-generation air quality attainment assessment system for PM2.5 and O3

Due to the increasingly stringent standards, it is important to assess whether the proposed emission reduction will result in ambient concentrations that meet the standards. The Software for Model Attainment Test—Community Edition (SMAT-CE) is developed for demonstrating attainment of air quality standards of O₃ and PM_2.5. SMAT-CE improves computational efficiency and provides a number of advanced visualization and analytical functionalities on an integrated GIS platform. SMAT-CE incorporates historical measurements of air quality parameters and simulated air pollutant concentrations under a number of emission inventory scenarios to project the level of compliance to air quality standards in a targeted future year. An application case study of the software based on the U.S. National Ambient Air Quality Standards (NAAQS) shows that SMAT-CE is capable of demonstrating the air quality attainment of annual PM_2.5 and 8-hour O₃ for a proposed emission control policy.     

Development and case study of a science-based software platform to support policy making on air quality

This article describes the development and implementations of a novel software platform that supports real-time, science-based policy making on air quality through a user-friendly interface. The software, RSM-VAT, uses a response surface modeling (RSM) methodology and serves as a visualization and analysis tool (VAT) for three-dimensional air quality data obtained by atmospheric models. The software features a number of powerful and intuitive data visualization functions for illustrating the complex nonlinear relationship between emission reductions and air quality benefits. The case study of contiguous U.S. demonstrates that the enhanced RSM-VAT is capable of reproducing the air quality model results with Normalized Mean Bias < 2% and assisting in air quality policy making in near real time.     

Activated carbon enhanced ozonation of oxalate attributed to HO. oxidation in bulk solution and surface oxidation： Effect of activated carbon dosage and pH

Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.     

沈阳辉山水库水质污染现状分析及评价

根据《地表水环境质量评价办法》中规定的方法,对沈阳辉山水库进行了水质和富营养化状态评价,并对污染源和水质污染特性进行了分析。结果显示:水库水质类别为劣Ⅴ类,水质状况为重度污染。富营养化综合营养状态指数为34.44,辉山水库水质为中营养化水平,水库没有藻类水华的产生。水库主要污染指标为总磷、总氮和悬浮物,分别超出国家地表水Ⅲ类标准的14.2倍、5.85倍和2.72倍。整个库区水质变化不均匀,水质变化受库区沿岸污染物排放影响较大,辉山明渠上游和某工厂暗渠排污口输入是水库主要污染源,库区周围动迁后的荒地和蚯蚓养殖,是辉山水库地面径流和农业污染污染源。     

PX项目环境风险分析

系统分析了PX项目的环境风险,结果表明:PX项目装置各单元均不是危险化工工艺单元,安全设施和污染治理水平相较于其它石油化工装置更高,但是基于装置物料的危险性和生产企业的高环境敏感度,PX项目的环境保护工作面临较大挑战。在此基础上,剖析了目前国内PX项目存在的主要环境风险问题,并提出相应的对策建议。     

原子荧光光谱法测定环境水体中痕量锡研究

在对环境水进行检测时,一个非常重要的项目就是对锡含量进行检测,所以,运用准确、灵敏的测定方法对环境水体中痕量锡进行检测具有非常重要的意义。文章将结合实验,在对环境水体中的痕量锡进行测定时,运用原子荧光光谱法,对测定环境水体中痕量锡的方法进行了一定的研究。采用原子荧光光谱法测定环境水体中的痕量锡,方法检出限是0.10μg/L,相对标准偏差0.20%~0.90%,实际样品加标回收率为98%~102%,满足环境监测实验室分析测定要求,值得推广。     

Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B

Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria （Microcystis sp.） were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible- light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B （RhB） degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions.