基于QAR数据的发动机LTO阶段氮氧化物排放量计算与分析

氮氧化物是发动机运行过程中产生的一种主要污染物,对于航空器氮氧化物排放量的准确计算是控制排放和评估其环境影响的基础.本文依据BM2流量修正方法对机载快速存取记录器(QAR)数据中的燃油流量值进行标准化修正,并根据低压转子转速、空地传感器指示、油门杆解算器角度、飞行高度,对起飞着陆循环(LTO)进行更精确的阶段划分.同时,参考国际民航组织公布的特定发动机机型的分阶段排放指数,对PW-4077D发动机某次LTO阶段的氮氧化物排放量进行计算.结果表明,通过精准飞行阶段划分,结合QAR实测数据估算的LTO分阶段(起飞、爬升、进近、慢车)氮氧化物排放量分别达到3415.87、7574.57、3019.98、1721.33 g,与标准LTO估算方法相比,相差30%以上.这种发动机LTO阶段实际排放量的计算方法,可为近地面航空器乃至不同地区整个机场氮氧化物污染评估提供更加准确的依据.     

Effects and mechanism of freeze-thawing cycles on the soil N2O fluxes in the temperate semi-arid steppe

High nitrous oxide(N2O) emissions during freeze-thawing period(FTP) have been observed in many different ecosystems. However, the knowledge about the dynamic of soil N_2O emissions and its main driving mechanism during the freeze-thawing processes in grassland ecosystem is still limited. An in-situ experiment was conducted during the FTP on the sites with 0 and 15% surplus of the average rainfall and two levels of N addition(0,10 g N/(m~2·year)) during growing season(marked as W0N0, W15N0, W0N10, W15N10, respectively) to explore the effects of water and N background on soil N_2O emissions during FTPs and the relationship between soil N_2O emissions and environmental factors. The results indicated that water and N treatments conducted during growing season did not show significant effect on the N_2O effluxes of FTP, but the soil mineral N contents of W0N10 treatment were significantly higher than those of W0N0, W15N0, W15N10treatments(p 0.05). The soil PLFA concentrations of microbial groups monitored during 2015 spring freeze-thawing period(2015S-FTP) were lower than those during winter freeze-thawing period of 2014(2014W-FTP), while cumulative soil N_2O emissions of 2015S-FTP were higher than those of 2014W-FTP. The correlations between soil N_2O effluxes and most of the measured environmental factors were insignificant, multiple stepwise regression analysis indicated that the soil temperature, soil NH_4~+-N content and air temperature were the major environmental factors which significantly influenced the N_2O effluxes during 2014W-FTP, and air temperature and soil water content were the significant influencing factors during 2015S-FTP.     

氧化铜纳米颗粒对水稻幼苗根系代谢毒性的研究

为阐明氧化铜纳米颗粒(CuO NPs)暴露对植物生长的影响,分别用CuO NPs悬浮液、氧化铜大颗粒(CuO BPs)悬浮液和硫酸铜(CuSO4·5H2O)溶液进行处理,以蒸馏水(d H2O)作为对照,水培水稻幼苗,研究了CuO NPs对水稻幼苗根系相关生理生化行为的影响.结果表明,不同处理对水稻幼苗根系的影响有很大差异,经CuO NPs悬浮液处理后,水稻幼根受损较严重,根系活力明显降低,根内丙二醛(MDA)含量和过氧化氢(H2O2)含量显著升高,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性明显增强.不同处理对水稻幼苗根的影响依次为:CuO NPs>CuSO4·5H2O>CuO BPs>d H2O.说明氧化铜纳米颗粒对水稻根的毒害作用不仅是由于释放离子引起的,纳米颗粒本身也起着重要作用,氧化损伤可能是CuO NPs的主要致毒机制之一.     

间种高粱及施用大颗粒尿素对茶园N2O排放的影响

茶园施肥量大、氧化亚氮(N_2O)排放系数高,且近年来我国茶园面积不断扩大,使茶园成为重要的农业N_2O排放源,亟需有效的茶园N_2O减排措施.本研究在我国中亚热带典型丘陵茶园,通过设置间种高粱、施用大颗粒尿素和常规施肥3种管理措施,观测不同管理措施下茶园土壤N_2O及相关环境因子动态,旨在解析茶园土壤N_2O排放的主控因子和明确提出的减排措施的有效性. 2 a的田间试验结果表明:①茶园土壤N_2O排放通量与土壤化学性质、温度及降雨有显著的相关性,土壤物理性质和土壤化学性质的交互作用对N_2O排放影响最大,土壤化学性质中的NO~-_3-N含量是决定N_2O排放量大小的最主要因素,茶园土壤N_2O减排研究的工作重点在于如何减小土壤中的NO~-_3-N含量;②间种高粱在未影响茶叶产量的前提下减少了51.2%的N_2O排放,从缓解全球气候变暖角度看,间种高粱是本研究中最佳的茶园管理措施;③施用大颗粒尿素在提高29.5%的茶叶产量同时减少了34.7%的N_2O排放,从兼顾经济效益及缓解全球气候变暖的角度看,茶园中施用大颗粒尿素则是本研究中最佳的施肥措施.     

氧化锰改性活性炭的优化制备及其对Cd(Ⅱ)的吸附研究

采用浸渍焙烧法制备了活性炭负载氧化锰的除镉(Cd(Ⅱ))吸附剂,通过L_9(3~4)正交试验确定最优制备条件如下:浸渍时间7 h,KMnO_4质量分数2.7%,焙烧温度470℃,焙烧时间2.5 h。通过BET、SEM、FTIR、XRD对改性活性炭(MOAC)进行表征,研究了pH值、吸附时间、初始浓度、吸附温度等对Cd(Ⅱ)吸附效果的影响。结果表明:MOAC表面烃基含氧官能团增多,氧化锰以MnO_2的形式负载到其表面;当MOAC的投加量为0.5 g/L,Cd(Ⅱ)的初始浓度为50 mg/L,溶液pH值为6.0,温度为298 K,吸附时间为12 h时,MOAC对Cd(Ⅱ)的吸附量高达84.15 mg/g,吸附过程符合准二级动力学方程和Langmuir等温吸附方程,热力学参数表明该吸附过程为放热、自发的过程。     

V-W/TiO_2/γ-Al_2O_3催化剂催化还原NO的研究

掺杂15%TiO2对γ-Al2O3改性制备了TiO2/γ-Al2O3复合氧化物载体,以此复合氧化物及TiO2、γ-Al2O3为载体用浸渍法负载钒钨制备了一系列催化剂,采用比表面积和孔结构分析、X射线衍射(XRD)、高分辨电镜(HRTEM)、原位红外(in situ FT-IR)等技术对载体和催化剂进行宏观-微观表征,同时在模拟氨气选择性催化还原NO(NH3-SCR)的反应条件下对催化剂的脱硝反应活性进行考察,比较研究TiO2掺杂对V2O5-WO3/TiO2和V2O5-WO3/γ-Al2O3催化剂的改性作用。结果发现,少量TiO2掺杂制得的TiO2/γ-Al2O3复合载体中,TiO2和γ-Al2O3之间的协同作用使得V2O5-WO3/TiO2/γ-Al2O3催化剂的选择性催化还原脱硝效率及活性窗口明显优于单一载体制备的催化剂,并表现出了良好的热稳定性;各种表征结果表明,TiO2/γ-Al2O3复合载体中TiO2高度分散在γ-Al2O3上,复合载体具有较大的比表面积,载体表面存在大量的Br?nsted酸位和较多的活性中间产物,这些可能是TiO2/γ-Al2O3复合载体催化剂具有较好SCR活性的原因。     

黄土高原苹果园土壤N_2O排放研究

从2007年5月1日到2009年4月30日对黄土高原苹果园氧化亚氮(N2O)排放采用静态箱气相色谱法进行了为期两年的监测.分别在距果树2.5m(D2.5)、1.5m(D1.5)、0.5m(D0.5)的位置采样.研究结果表明,苹果园N2O排放量年际变化较大,2008年5月到2009年4月的N2O排放量(2.74kg·hm-·2a-1)比2007年5月到2008年4月(2.27kg·hm-·2a-1)高20.7%,主要原因是2008年夏季降雨量是2007年夏季降雨量的1.92倍,使得2008年夏季N2O排放量是2007年夏季的2.81倍.2008年5月到2009年4月的排放系数(0.082%)是2007年5月到2008年4月排放系数(0.035%)的2.34倍.施肥后、冻融交替期、苹果树落叶的前期、降雨后苹果园都有高的N2O排放峰,N2O的季节变化受到这些短期事件的显著影响.而这些短期事件对N2O排放的激发效应又受到降雨量、土壤孔隙充水率(WFPS)和地温的调控.D2.5和D0.5两个处理的N2O排放与气温(p≤0.01)和地温(p≤0.01或p≤0.05)显著相关.D1.5处理N2O排放与气温(p≤0.05)显著相关.     

单级和多级A/O工艺中氮的去除效果及N2O的产生特性

利用SBR反应器模拟单级和多级A/O工艺,在进水水质、水力停留时间(HRT)、泥龄(SRT)、温度、缺氧好氧时间比(A/O比)均相同的条件下,考察了两种脱氮系统中氮的去除效果及N_2O的释放情况.结果表明,对于与城市污水水质相当的进水水质,单级A/O工艺和多级A/O工艺对COD、氨氮的去除率均在95%以上,二者无明显区别,但是前者对TN的去除效率高于后者,二者的总氮去除率分别为72.1%和52.2%.在氮素的转化过程中,典型周期内(3 h)单级A/O工艺和多级A/O工艺中N_2O的产生量分别为16.95 mg和3.59 mg,其转化率(即N_2O的产量与TN的去除量之比)分别为11.47%和4.11%,且N_2O的产生和释放主要发生在好氧段(硝化阶段),缺氧段(反硝化阶段)基本无N_2O释放.单级A/O工艺比多级A/O工艺更有利于硝化细菌(AOB、NOB)的生长,在相同的运行条件下,两工艺中AOB的优势菌种皆为Nitrosomonas,但前者的相对丰度高于后者;单级A/O工艺中NOB的种类和相对丰度也明显多于多级A/O工艺.在实际运行中采用合适的A/O分区或供氧方式既可以较好地去除污水中氮素污染,又可以减少N_2O的释放对大气造成二次污染.     

Antibiotic contamination control mediated by manganese oxidizing bacteria in a lab-scale biofilter

Antibiotic micro-pollution is usually found at the ng/L–level in drinking water sources or discharge water of wastewater treatment plants. In this study, a novel approach mediated by manganese oxidizing bacteria (MnOB) in a biofilter was developed to control the pollution. The results indicated that the biogenic manganese oxide (MnO_x) produced during the oxidation of the feeding manganese ions could coat the surface of the filtering sand effecting the simultaneous removal of antibiotics. It was found that the removal of antibiotics is insured as long as the feeding manganese was well removed and was not influenced by the hydraulic loading. The growth rate of the MnOB group revealed that the antibiotic concentration at 50 and 100 ng/L promoted their activity, but it was inhibited at 500 and 1000 ng/L. The structure of the bacterial community was stable in the presence of antibiotics (50 ng/L), but their extracellular processes changed. The removal performance of the feeding manganese seemed to relate to the extracellular processes of the dominant bacterial genus. Moreover, the freshly formed MnO_x was a buserite-like material that was rich in Mn(III) and Mn(IV) (94.1%), favoring the degradation. The biofilter did not generate additional antibiotic resistant genes in the presence of antibiotics.     

高炉瓦斯灰(泥)中锌的萃取利用

我国南方数家钢铁厂瓦斯灰(泥)中含有具有利用价值ZnO。本法以瓦斯灰(泥)为原料,不需前期加工,用NH4Cl作萃取剂提取Zn制取活性ZnO。本法条件温和,较传统的酸法消耗少,腐蚀小,萃取剂可回用,所以成本低廉,加之国家有关优惠政策,使用本法利用瓦斯灰(泥)有较大的优势。