三峡库区消落带4种典型植物根际土壤养分与氮素赋存形态

三峡水库消落带土壤N循环受到植被覆盖和季节性淹水的影响,对三峡水库水质具有潜在的不利影响,进行消落带植被恢复和提高土壤N保持能力成为保护库区水环境的重要措施.选择三峡库区一级支流澎溪河消落带为研究对象,分别在冲积潮土、紫色土和水稻土分布区采集狗牙根、香附子、苍耳以及玉米这4种典型植物根际、非根际土壤,分析了根际与非根际土壤理化性质与N赋存形态特征,并比较了不同植物类型根际富集效果,初步探究不同植物根际效应对消落带土壤N循环的影响.结果表明,所有植物根际土壤p H均低于非根际,有机质、全氮、全磷、速效氮均高于非根际,且根际富集率表现为香附子狗牙根玉米苍耳;不同植物根际对土壤全钾、有效磷、速效钾影响作用不一致;植物根际土壤中可转化态氮TF-N及其不同赋存形态离子交换态氮(IEF-N)、碳酸盐结合态氮(CF-N)、铁锰氧化态氮(IMOF-N)和有机态和硫化物结合态氮(OSF-N)均高于非根际土壤,植物根际效应能够改变土壤N赋存形态及其对N循环的贡献率,但狗牙根和香附子根际土壤中TF-N占TN的比率低于非根际,而玉米和苍耳相反,表明消落带玉米和苍耳覆盖加快了N素向TF-N转化,不利于土壤N素保持;消落带土壤有机质、总磷和有效磷含量与可转化态N形态显著相关,是土壤N形态转化的主要因素.研究表明,消落带狗牙根和香附子覆盖对土壤N素的保持优于玉米和苍耳,植物根际效应对消落带土壤N循环的影响为消落带植被恢复中植物选择提供了参考.     

High aspect ratio micromachining of glass by electrochemical discharge machining (ECDM)

Micromachining of glass is essential for several microfluidic components, micro-pumps, micro-accelerometers, micro-reactors, micro-fuel cells and several biomedical devices. Unique properties such as high chemical resistance, thermal stability and transparency give glass scope for additional applications. However, poor machinability of glass is a major constraint, especially in high aspect ratio applications of glass in microsystem technology. Micro electrochemical discharge machining (micro ECDM) is an emerging nontraditional fabrication method capable of micromachining ceramic materials like glass. While surface features less than 100 μm have been successfully machined on glass, machining high aspect features is a challenge. Machining accuracy at high depths is severely affected due to overcut and tool wear. In this paper, high aspect ratio microtools fabricated in-house have been used for deep microhole drilling on glass using low electrolyte concentration. An aspect ratio of 11 has been achieved. The results show that lower electrolyte concentration reduced overcut by 22%, thus increasing the aspect ratio of the micro holes. Lowering the electrolyte concentration also reduced the tool wear and hole taper by 39% and 18% respectively.     

曝气生物滤池处理性能影响因素实验研究

采用上向流曝气生物滤池处理生活污水,考察了气水比、水力负荷、有机负荷、滤料层高度等因素对曝气生物滤池处理性能的影响。结果表明,气水比为5：1时,COD和NH3-N的去除率分别为87．6％和60．1％;水力负荷在0．21—0．86m^3／（m^2·h）的条件下,COD的去除率随水力负荷的增加降幅较小,NH3-N的去除率下降明显;有机负荷在1．15～2．96kg／（m^3·d）的条件下,BAF表现出很好的抗有机负荷冲击能力。BAF对有机物的去除主要发生在滤料层0～70cm段,对NH3-N的硝化主要发生在滤料层40—100cm段。     

进水比例对水解反应器出水水质的影响研究

针对城镇污水处理厂进水SS/BOD偏高、C/N比偏低的问题,通过对现有水解池结构进行改造,设置两层布水器,两层布水器之间形成污泥水解区,以强化污泥水解,改善出水水质.试验通过改变上下层布水器进水比例,力求最佳进水比例,使水解反应器起到初沉池作用的同时要提高废水的可生化性,以指导此类水解反应器的大规模应用.结果表明,4种进水比例均对COD和SS去除有不同的去除效果,但进水比例为1∶1较其他3种进水比例能够大幅提高出水中SCOD/COD比值和挥发性脂肪酸(VFA)浓度.以改善出水可生化性为原则,进水比例为1∶1时为最佳进水比例,即底部布水器进水50%,上层布水器处进水50%,既能为后续处理减少COD和SS的处理负担,又能提高出水的可生化性.     

不同降雨条件下侵蚀泥沙黏粒含量的变化规律

以2种典型黄土为研究对象,在模拟降雨条件下,研究了不同雨强和坡度条件下侵蚀过程中黏粒含量的变化规律,比较了泥沙侵蚀颗粒(未分散)和泥沙原始颗粒(分散后)大小分布特征,分析了团聚率和富集率.结果表明,泥沙侵蚀黏粒含量随着坡长和雨强的增大而增加,黄绵土变化明显,增加了8.77%和2.43%;而塿土只增加了2.76%和0.4%.随坡度的增大而减小,分别减少了4.91%和3.93%.黏粒团聚率<1,富集率>1,在侵蚀搬运过程中作为黏粒团被搬运,导致黏粒的富集.研究结果有助于深入了解泥沙颗粒在坡面侵蚀过程中的变化规律,深入理解土壤侵蚀机制,也能为面源污染模型的建立提供重要基础.     

Modified ADM1 for modeling free ammonia inhibition in anaerobic acidogenic fermentation with high-solid sludge

Anaerobic acidogenic fermentation with high-solid sludge is a promising method for volatile fatty acid (VFA) production to realize resource recovery. In this study, to model inhibition by free ammonia in high-solid sludge fermentation, the anaerobic digestion model No. 1 (ADM1) was modified to simulate the VFA generation in batch, semi-continuous and full scale sludge. The ADM1 was operated on the platform AQUASIM 2.0. Three kinds of inhibition forms, e.g., simple inhibition, Monod and non-inhibition forms, were integrated into the ADM1 and tested with the real experimental data for batch and semi-continuous fermentation, respectively. The improved particle swarm optimization technique was used for kinetic parameter estimation using the software MATLAB 7.0. In the modified ADM1, the K_s of acetate is 0.025, the k_m,ac is 12.51, and the K_{I_NH3} is 0.02, respectively. The results showed that the simple inhibition model could simulate the VFA generation accurately while the Monod model was the better inhibition kinetics form in semi-continuous fermentation at pH 10.0. Finally, the modified ADM1 could successfully describe the VFA generation and ammonia accumulation in a 30 m³ full-scale sludge fermentation reactor, indicating that the developed model can be applicable in high-solid sludge anaerobic fermentation.     

Investigation of nuclear enzyme topoisomerase as a putative molecular target of monohaloacetonitrile disinfection by-products

Disinfection by-products occur widely as the unintended effect of water disinfection and are associated with toxicity and adverse human health effects. Yet the molecular mechanisms of their toxicity are not well understood. To investigate the molecular basis of hyperploidy induction by monohaloacetonitriles, the interaction of monohaloacetonitriles with topoisomerase Ⅱ in Chinese hamster ovary cells was examined. We showed a concentration-dependent inhibition of DNA decatenation activity of topoisomerase under acellular conditions while in vitro monohaloacetonitrile treatment expressed mixed results. The working hypothesis, that topoisomerase Ⅱ is a molecular target of monohaloacetonitriles, was only partially supported.Nevertheless, this research serves as a starting point toward molecular mechanisms of toxic action of monohaloacetonitriles.     

新疆某新建广播电视塔周边环境的辐射环境影响预测与分析研究

对新疆某地区新建广播电视塔周边环境20 m~500 m,离地高度0 m~200 m的电磁辐射影响进行预测,探寻此范围内电磁辐射最高值覆盖区域,说明广播电视塔周围电磁场的分布情况及变化趋势,得出距广播电视塔的水平安全距离及周围高层建筑物的限制高度,以期为电视发射塔电磁辐射防护措施的制定提出切实可行、针对性强的建议,从而为环保部门管理及日益增多的电磁辐射投诉提供依据.研究表明:电视塔周围的高层建筑物外的电磁场强度随着高度的提高而增大.     

基于ABR-MBR组合工艺优化反硝化除磷性能的研究

基于ABR-MBR一体化反应器,以低C/N比生活污水为研究对象,结合厌氧折流板反应器(ABR)微生物相分离的特性,通过优化与ABR优质供碳和脱氮除磷相耦合的膜生物反应器(MBR)硝化液回流比以实现高效反硝化除磷,并对ABR-MBR污泥回流比进行优化.结果表明,在ABR段有机负荷为2.0 kg·(m3·d)-1、系统的水力停留时间(HRT)为9 h、泥龄(SRT)为15 d,系统获得最优的处理效果时的硝化液回流比和污泥回流比分别为300%和100%.其中TN和溶解性PO3-4-P平均去除率分别达84%和94%,ABR中反硝化除磷量可达系统总去除量的87%,平均出水TN和溶解性PO3-4-P浓度分别为12.98 mg·L-1和0.43 mg·L-1.     

绿色屋面不同基质组分对降雨径流水质和水量的影响

通过模拟降雨强度50~80 mm的降雨实验,研究了3种常用基质(商业基质、火山岩基质和田园土基质)绿色屋面的径流滞留率和径流水质的特点.结果表明:商业基质的径流滞留率最高,达到48.6%,火山岩基质和田园土基质的滞留率分别为33.6%和30.4%;随着降雨历时的延长,3种基质屋面径流中各水质参数浓度呈现出逐渐降低的趋势,但是,随着降雨强度的加大,商业基质径流中TN浓度和COD呈现出逐渐升高的趋势,而火山岩和田园土基质径流水质参数未呈现出明显变化;田园土基质屋面径流EC、TN、COD、TP和TSS的浓度均值高达3973.54、36.96、503.67、2.64和92.02 mg·L~(-1),显著高于商业基质屋面和火山岩基质屋面;商业基质屋面能够有效地中和模拟降雨的pH,且径流中EC、TP和TSS浓度与火山岩基质屋面径流无明显差异.但是,这2种基质屋面径流中TN和COD的浓度(商业基质:17.47 mg·L~(-1)和87.99 mg·L~(-1),火山岩基质:10.95 mg·L~(-1)和157.85 mg·L~(-1))均超出国家地表水环境质量V类标准;通过综合分析3种屋面基质径流滞留率和径流水质,认为商业基质是我国北方地区较为适宜的绿色屋面基质.研究结果可为绿色屋面的科学构建和城市暴雨径流管理提供科学依据,并为我国海绵城市的建设提供重要的理论依据.