Shaping effects of rice,wheat, maize,and soybean seedlings on their rhizosphere microbial community

The rhizosphere microbiome plays critical roles in plant growth and is an important interface for resource exchange between plants and the soil environment. Crops at various growing stages, especially the seedling stage, have strong shaping effects on the rhizosphere microbial community, and such community reconstruction will positively feed back to the plant growth. In the present study, we analyzed the variations of bacterial and fungal communities in the rhizosphere of four crop species: rice, soybean, maize, and wheat during successive cultivations (three repeats for the seedling stages) using 16S rRNA gene and internal transcribed spacer (ITS) high-throughput sequencing. We found that the relative abundances of specific microorganisms decreased after different cultivation times, e.g., Sphingomonas, Pseudomonas, Rhodanobacter, and Caulobacter, which have been reported as plant-growth beneficial bacteria. The relative abundances of potential plant pathogenic fungi Myrothecium and Ascochyta increased with the successive cultivation times. The co-occurrence network analysis showed that the bacterial and fungal communities under maize were much more stable than those under rice, soybean, and wheat. The present study explored the characteristics of bacteria and fungi in crop seedling rhizosphere and indicated that the characteristics of indigenous soil flora might determine the plant growth status. Further study will focus on the use of the critical microorganisms to control the growth and yield of specific crops.

     

絮凝-电解氧化联合处理氰化提金废水

采用絮凝-电解氧化联合技术处理氰化废水,主要研究了聚硅酸铝铁 (PSAF) 添加量、絮凝时间、pH、电压、电解时间、极板间距对总氰(CN_T)、游离氰(CN⁻)、Cu、Zn离子去除率的影响,并对其反应机制做了分析。研究表明,当PSAF添加量为2 g·L⁻¹,絮凝时间为30 min,pH为9条件下,CN_T、CN⁻、Zn、Cu离子的去除率分别可达42.97%、100%、84.40%、34.88%。Zn(CN)₄²⁻、Cu(CN)₃²⁻、CN⁻的吸附量分别为567.88、89.76、439.74 mg·L⁻¹。以钛板为阴极,石墨板为阳极,采用一阴两阳体系对絮凝后液进行电解氧化实验,在电压为3 V、电解时间为2 h、极板间距为10 mm条件下,CN_T、CN⁻、Zn、Cu离子的去除率可达91.70%、100%、99.15%、94.49%。絮凝过程中Zn(CN)₄²⁻、Cu(CN)₃²⁻、CN⁻的去除是由电荷中和和化学吸附共同作用的,其中电荷中和起主要作用。Zn(CN)₄²⁻、Cu(CN)₃²⁻、CN^-的化学吸附主要归因于其与PSAF水解产生的羟基阳离子发生交换反应。XRD分析表明,加入酸性絮凝剂PSAF的瞬间,部分Zn(CN)₄^2-反应为Zn(CN)₂沉淀。电解氧化过程中Zn(CN)₄²⁻、Cu(CN)₃²⁻破络释放的氰根会被阳极表面产生的O₂、·OH完全氧化为N₂和CO₂,Zn、Cu离子在阴极板电沉积而被去除。     

Solid phase extraction with pyrenebutyric acid-bonded silica for analysis of polychlorinated biphenyls in sewage water by gas chromatography-mass spectrometry

A solid phase extraction (SPE) method using pyrenebutyric acid-bonded silica (PYB) as sorbent was developed to determine 23 polychlorinated biphenyls (PCBs) in sewage water by gas chromatography-mass spectrometry (GC-MS). Factors were optimized in SPE procedures including elution solvent, pH, and cartridge burden. The recoveries of 23 PCB congeners were 69.44-111.91% under optimized conditions. Comparisons were also conducted among PYB-SPE, C(18)-SPE and United States Environmental Protection Agency 608 (USEPA608) methods in the analysis of PCBs in sewage water samples. The results showed that the performance of PYB-SPE method was similar with USEPA608 method and better than C(18)-SPE method. Both PYB-SPE and USEPA608 methods were then employed to analyze PCBs in real spiked sewage water samples. The recoveries of PCB congeners determined by PYB-SPE method ranged from 70.6% to 92.4% in real spiked sewage water samples which were identified to be in accordance with USEPA608 method. Limits of detection (LOD) were in the range of 0.06-0.22ngL(-1) for PCB congeners. The optimized PYB-SPE method was successfully applied to the determination of PCBs in sewage water samples.     

不同共代谢基质下四氯乙烯厌氧生物降解研究

分别用葡萄糖、乳酸盐和醋酸盐作为驯化好的厌氧污泥的共代谢基质 ,对四氯乙烯 ( PCE)的降解进行研究。结果表明 ,PCE是通过还原脱氯发生生物降解的。实验的回归结果表明 ,反应均符合一级动力学方程 ;反应速率常数的大小依次为 k乳酸盐 >k葡萄糖 >k醋酸盐 ;以乳酸盐作为共代谢基质时 ,PCE的降解速率较快 ,在实验条件下乳酸盐是最合适的共代谢基质     

氯化汞对小鼠睾丸生殖细胞的DNA损伤作用

探索氯化汞对雄性小鼠生殖细胞毒性的分子遗传机制。分别以 0 .0 1、0 .10、1.0 0 mmol/L的氯化汞体外处理小鼠睾丸细胞和以 0 .5、1.0、5 .0 μmol/kg的氯化汞体内暴露小鼠 ,应用单细胞凝胶电泳技术检测生殖细胞 DNA的损伤。体外处理 3种剂量组小鼠睾丸生殖细胞 DNA损伤率显著高于阴性对照组 ( 0 mmol/L组 ,P<0 .0 0 1) ;0 .1、1.0 mmol/L剂量组慧星细胞迁移率显著高于阴性对照组 ( P<0 .0 0 1,P<0 .0 5 )。体内暴露 3种浓度氯化汞组小鼠睾丸生殖细胞 DNA损伤率显著高于阴性对照组 ( 0μmol/kg,P<0 .0 0 1) ,5 .0 μmol/kg组慧星迁移率显著高于阴性对照组 ( P<0 .0 5 )。一定剂量的氯化汞处理引起生殖细胞 DNA损伤作用可能是氯化汞细胞毒性的机制之一。     

饮用水中硝酸根的催化还原研究进展

由于化肥的过度使用 ,造成地下水中硝酸盐的污染日益严重。饮用水中高浓度的硝酸盐对人类健康会产生极大的威胁。本文综述了催化还原脱除水中硝酸根的研究进展和现状 ,并对其发展趋势进行了简单的论述。     

红色非硫光合细菌的生长特性研究

红色非硫光合细菌菌种从城市污水处理厂活性污泥中分离得到,对红色非硫光合细菌的生长规律及其影响因素进行研究,试验表明在进行污水处理时所用的红色非硫光合细菌的最佳培养条件为接种量2%,pH7～8,光照强度为1500lx,光照厌氧条件下培养3～5d。这为红色非硫光合细菌应用于染料有机化工废水处理的进一步研究提供了理论依据。     

氧化锰共生矿烟气脱硫的机理及影响因素

利用南非的氧化锰共生矿进行烟气脱硫,研究了共生锰矿烟气脱硫性能及其机理,并考察了锰矿粒径、反应温度、液固比、进气流量、进口SO2浓度等因素对脱硫率的影响。结果表明,氧化锰共生矿中主要的锰化合物是MnO2、Mn2O3和MnCO3,烟气脱硫过程主要存在4种方式：MnO2与SO2发生氧化还原反应生成硫酸锰;液相中Mn2+催化氧化SO2产生硫酸;MnCO3与硫酸反应生成硫酸锰;Mn2O3与硫酸反应后生成的MnO2可以继续与SO2进行脱硫反应,但是Mn2O3与SO2直接反应的活性较差。氧化锰共生矿烟气脱硫的最佳工艺参数为：锰矿粒径200目、反应温度80 ℃、液固比10:1以及进气流量600 mL?min-1     

直接利用葡萄糖的液流催化燃料电池改进

液相催化燃料电池（LCFC）可直接处理生物质并产电,而电池结构等因素对电池性能有明显影响,但目前还缺乏上述方面的研究。通过系列产电实验考察了温度和酸化条件对Nafion115膜性能的影响、不同氧化条件下石墨毡的改性效果以及电池内部导流槽在不同葡萄糖浓度条件下的影响。结果表明：质子交换膜适宜以80 ℃酸化处理,该条件下电池功率密度达到5.39 mW·cm-2;石墨毡改性适宜以50 mL·min-1干空气流速在420 ℃条件下对其进行煅烧,该条件下电池功率密度进一步提升至6.21 mW·cm-2;葡萄糖浓度显著影响电池性能,当浓度为2.0 mol·L-1时,导流槽结构会降低电池性能,当浓度为1.0 mol·L-1和0.50 mol·L-1时,导流槽结构使电池性能更优,并且也更加稳定。     

海洋红球菌SY095产生物表面活性剂发酵培养基的优化

为提高海洋红球菌SY095发酵产生物表面活性剂的能力,研究发酵培养基中碳源及氮源的影响,并通过响应面分析法优化培养基各组分的含量。首先通过单因素实验,确定培养基最佳碳源、氮源分别为大豆油和尿素,在此基础上,利用Plackett-Burman实验设计筛选出2个对表面活性剂产量有显著影响的因子为尿素和K2HPO4,通过最陡爬坡实验和响应面分析法对显著影响因子进行优化,获得海洋红球菌产表面活性剂的最佳培养基配方为：大豆油2%（体积分数）,尿素2.35 g·L-1,K2HPO40.69 g·L-1,KH2PO4 1.0 g·L-1,MgSO4 0.5 g·L-1。使用该优化培养基配方,海洋红球菌发酵液的表面张力为29.254 mN·m-1,与预测值接近,表面张力活性比优化前提高了12.9%。