CO3O4/介孔分子筛催化剂对苯催化完全氧化的研究

分别以介孔分子筛MCM-41、MCM-48、SBA-15为载体,采用等体积浸渍法制备了氧化钴/介孔分子筛催化剂,利用N2吸附、X射线衍射、程序升温还原等技术对催化剂进行了表征,考察了Co3O4的负载量及载体的孔结构对催化剂完全催化氧化苯的性能的影响.结果表明,Co3O4的负载量为20%时,催化剂的催化活性最好;载体的孔径和催化剂的可还原性能是影响催化活性的主要因素,催化剂活性顺序为Co3O4/SBA-15>Co3O4/MCM-41>Co3O4/MCM-48.     

长期运行的不同序批式活性污泥工艺去除Cr(Ⅵ)的比较研究

对不同序批式(SBR)活性污泥工艺,即厌氧SBR、好氧SBR及厌氧好氧SBR去除废水中的Cr(Ⅵ) 进行了研究。结果表明,在反应器起始Cr(Ⅵ)浓度为0.5～2 mg/L时,好氧SBR的Cr(Ⅵ) 去除率低于20％,微生物量不断降低;厌氧和厌氧好氧SBR的Cr(Ⅵ)去除率都达到94％以上,但前者的微生物量持续减少、出水浊度高,而后者的微生物量稳定增加、出水浊度低。因此,厌氧好氧SBR更适合于去除废水中的Cr(Ⅵ)。对厌氧好氧SBR系统的进一步研究表明,该系统在厌氧阶段有明显的磷释放、聚羟基烷酸(PHA)合成和糖原降解,好氧阶段有明显的磷吸收、PHA降解和糖原合成。还对厌氧好氧SBR中Cr(Ⅵ) 的去除机理进行了讨论。     

pH对活性污泥表面特性和形态结构的影响

采用4个平行的序批式反应器,研究了不同pH下活性污泥絮体表面特性和形态结构的变化.结果表明:酸性条件下(pH=4.0,5.5)污泥产生的胞外聚合物总量较多,其中多糖和蛋白质的含量远大于中性(pH=7.0)和偏碱性条件(pH=9.0).污泥表面Zeta电位随pH的升岛而降低;pH对污泥相对疏水性的影响规律并不明显,EPS组成比例较EPS总量本身更易影响污泥表面相对疏水性;此外,在酸性条件下,丝状菌大量生长,导致污泥絮体的平均粒径增大,并且呈现双峰粒径分布,絮体分形维数较低,结构松散;在中性条件下,无明显丝状菌牛长,絮体平均粒径减小,分形维数较高,结构致密;偏碱性条件下,虽然没有出现大量丝状菌,但絮体平均粒径较中性条件略有增大,分形维数相应减小.     

Correcting climate model simulations in Heihe River using the multivariate bias correction package

The simulations from climate models require bias correction prior to use in impact assessments or when used as predictors in statistical or dynamic downscaling models. Recent works have sought to address each of these limitations and the results are the Multivariate Recursive Nesting Bias Correction (MRNBC) and Multivariate recursive Quantile-matching Nested Bias Correction (MRQNBC) methods. The model was applied to a mountain region of Heihe River. A comparison of the historical and generated statistics shows that the model preserves all the important characteristics of meteorological variables at daily, monthly, seasonally and annual time scales. This study has documented the performance of Multivariate Recursive Nesting Bias Correction to remove the discrepancy between the predictors in the simulated GCM and the reanalysis NCEP data and assess the projected future precipitation accuracy in the headwater region of Heihe River. A relatively high spatial resolution GCM outputs—ACCESS1-3—from the CMIP5 Earth System Models (ESMs) was employed to downscale for the historical 1960–2005 and the future period 2010–2100 under the scenarios of Representative Concentration Pathways RCP4.5 and RCP8.5. The MRNBC method can dramatically increase the performance of the simulated precipitation data. Verified by statistical score metrics applied for evaluation of the results, the developed method appears to be an important statistical tool in the correction of the bias between the GCM output and the reanalysis data, leading to significant improvements in the predictive performance accuracy of the precipitation projections. The projected precipitation under RCP8.5 appeared to exhibit the significant increasing trend relative to the RCP4.5 scenario in the headwater region of Heihe River. Future precipitation will increasing by 8% and 20% for near and long term period under RCP4.5 and increasing 14% and 37% for near and long term period, under RCP8.5, respectively.     

鄱阳湖大型底栖动物群落结构的空间分布及影响因子研究

由于受人类活动干扰的加强以及受与长江干流之间"江湖关系"变化的影响,近年来鄱阳湖水生生态系统的状况及变化受到较多关注。对底栖动物群落结构的研究将有助于了解鄱阳湖生态系统结构现状及影响因子,对鄱阳湖保护对策的制定形成有效支撑。2016年7月,对鄱阳湖湖区(分别于鄱阳湖保护区和南矶山保护区)的底栖动物群落结构及相关环境因子进行了调查。调查共发现大型底栖动物27种,隶属于5门8纲,平均密度为48.40 ind.·m-2,其中主要以软体动物门为主;平均生物量为28.12 g·m-2,亦主要由软体动物门贡献。湖区主要优势种为河蚬(Corbicula fluminea)(优势度y=0.0655)、铜锈环棱螺(Bellamya aeruginosa)(y=0.0336)、霍甫水丝蚓(Limnodrilus hoffmeisteri)(y=0.0268)。底栖动物密度、生物量及多样性指数均呈现出鄱阳湖保护区高于南矶山保护区的格局,且二者在群落组成上有明显差异,鄱阳湖自然保护区主要以腹足纲和寡毛纲为主,南矶山自然保护区主要以瓣鳃纲和腹足纲为主。典范对应分析的结果显示,鄱阳湖保护区主要受到高水深、低浊度及高溶氧的影响;南矶山保护区各样点之间群落相似性较差,分别受不同因子的影响,这表明在各区域内部,局域微生境在局域群落结构的塑造上起主要作用,因此该区域内生态系统的保护应适当考虑空间尺度。     

Synthesis of a three-dimensional network sodium alginate–poly(acrylic acid)/attapulgite hydrogel with good mechanic property and reusability for efficient adsorption of Cu2+ and Pb2+

Environmental Chemistry Letters - Water pollution caused by heavy metals has dramatically impacted ecosystems in recent years. For instance, 45.4% of lakes in China are in the category of moderate...     

Protoplast preparation and regeneration conditions of Bacillus subtilis ZGL14 producing alkaline pectinase北大核心CSCD

The protoplast fusion technique is one of the important microbial breeding methods. The main factors that affect protoplast preparation and regeneration were investigated using Bacillus subtilis ZGL14 as the starter strain. The optimal conditions for protoplast preparation and regeneration were determined in this study by optimizing the cell age, lysozyme concentration, enzymolysis time, enzymolysis temperature, pH values of the osmotic pressure stabilizer, regeneration medium types, and culture type. The results indicated that the optimal condition for protoplast preparation of B. subtilis ZGL14 was as follows: 9 h of cell age, 0.2 mg/mL of lysozyme concentration, 10 min of enzymolysis time, 32 °C of enzymolysis temperature, and 7.0 of osmotic pressure stabilizer pH value. Under this condition, the protoplast formation and regeneration rates were > 98% and > 30%, respectively. A good protoplast regeneration effect can be achieved using the regeneration medium with sodium succinate as osmotic pressure stabilizer in combination with Ca2+. The single-layer culture was better than double-layer for regeneration. The optimal condition for protoplast preparation and regeneration of B. subtilis ZGL14 was determined in this study, which provides technical support for protoplast fusion breeding of B. subtilis. © 2018 Science Press. All rights reserved.     

Isolation,identification, and the degradation characteristics of a thiobencarb-degrading bacterium Bacillus sp. T2北大核心CSCD

Thiobencarb, a thiocarbamate herbicide, is widely used to control weeds in rice paddies. Screening for highly efficient thiobencarb-degrading bacteria is important for the bioremediation of thiobencarb-contaminated environments. The aim of this study was to isolate and identify highly efficient thiobencarb-degrading bacteria and to identify the degradation pathway and the degrading properties. The thiobencarb-degrading strain was isolated using methods of microbiological acclimation and enrichment and was then identified using a 16S rRNA phylogenetic analysis. The degrading properties of the isolated bacterium were determined by single-factor experiments, and the degradation products were identified using gas chromatography-mass spectrometry (GC-MS). A thiobencarb-degrading strain T2, which can utilize thiobencarb as the sole source of carbon for energy and growth, was isolated from paddy soil. Strain T2 degraded more than 98.3% of 0.4 mmol/L of thiobencarb within 36 h. It was preliminarily identified as Bacillus sp. T2 according to the 16S rRNA gene analysis and from its morphological, physiological, and biochemical characteristics. The metabolic products of the thiobencarb degradation for strain T2 were identified as 4-chlorobenzyl mercaptan, 4-chlorobenzaldehyde, and 4-chlorobenzoic acid by the GC-MS. Based on metabolite identification, it was speculated that thiobencarb degradation in strain T2 was initiated by the hydrolysis of the thioester bond to produce 4-chlorobenzyl mercaptan, which was further oxidized to 4-chlorobenzaldehyde and 4-chlorobenzoic acid. The thiobencarb degradation that was initiated by the hydrolysis of the thioester bond by strain T2 is a new metabolic pathway, which provides valuable research material and reliable experimental data for revealing the metabolic process and mechanism of thiobencarb microbial degradation in soil. The strain Bacillus sp. T2 has a very high degradation efficiency, suggesting it is a good prospect for microbial remediation in thiobencarb-polluted environments. © 2018 Science Press. All rights reserved.     

Use of portable X-ray fluorescence spectrometry for environmental quality assessment of peri-urban agriculture

Urban expansion into traditional agricultural lands has augmented the potential for heavy metal contamination of soils. This study examined the utility of field portable X-ray fluorescence (PXRF) spectrometry for evaluating the environmental quality of sugarcane fields near two industrial complexes in Louisiana, USA. Results indicated that PXRF provided quality results of heavy metal levels comparable to traditional laboratory analysis. When coupled with global positioning system technology, the use of PXRF allows for on-site interpolation of heavy metal levels in a matter of minutes. Field portable XRF was shown to be an effective tool for rapid assessment of heavy metals in soils of peri-urban agricultural areas.