石墨烯/聚苯胺修饰阴极对反硝化MFC性能影响

反硝化生物阴极微生物燃料电池（MFC）以电极为电子供体,在自养条件下完成硝酸盐去除过程.本研究以碳布（CC）为基底材料,分别制备获得还原氧化石墨烯修饰（rGO-CC）,聚苯胺修饰（PANI-CC）及二者复合修饰的CC电极（rGO/PANI-CC）,并考察其作为阴极材料对反硝化生物阴极MFC产电脱氮性能的影响.扫描电镜结果显示,rGO-CC和PANI-CC的碳纤维分别被片层状rGO和网状PANI覆盖,而rGO/PANI-CC表面呈现PANI在附着rGO的碳纤维上团聚的形貌,均增大了碳布的比表面积.循环伏安测试显示,rGO/PANI-CC具有最高的电化学活性.以rGO-CC,PANI-CC和rGO/PANI-CC为阴极构建MFC的产电能力分别提高了82%,24%和41%,其阴极对NO₃^--N的去除能力增强了23%,9%和13%.16S rDNA测序结果揭示修饰后电极表面微生物的多样性下降,Stappia和Pacacoccus属微生物的丰度增加.     

基于Stacking的地面PM2.5浓度估算

为了解决地面PM_2.5监测网络在空间和时间覆盖受限的问题,提出了基于宽时空覆盖的卫星气溶胶光学厚度AOD,利用Stacking方法建立地面PM_2.5浓度估算模型,将AOD、PM_2.5和各气象参数以及与PM_2.5排放有关的数据进行训练,使用改进网格搜索对模型超参数进行优化,通过对多重共线性分析,建立基于Stacking的最优PM_2.5浓度估算模型。选取2016-01-01-2016-12-31的数据作为实验对象,结果表明:相比于随机森林、GBRT和XGBoost 3种模型,使用岭回归作为元学习器的Stacking模型性能更优,可见Stacking适用于大范围地理区域的大气污染监测。     

排水管道沉积物微生物群落及环境因子分析

选取北京市某区的排水管道沉积物进行取样,采用高通量测序手段分析,结果表明变形菌门、广古菌门、拟杆菌门、厚壁菌门是排水管道沉积物微生物中的优势门类;在纲水平上,δ-变形菌纲、甲烷微菌纲、梭菌纲、拟杆菌纲占相对优势;在属水平上,功能性微生物硫酸盐还原菌（SRB）和产甲烷古菌（MA）普遍存在于各处管道.在所选的6段管段中,管段S3、S4处MA的相对丰度分别为20.6%、40.8%,高于其他管段,厌氧产甲烷的潜能较大,有发生可燃气积累的风险;管段S5、S6处的SRB相对丰度分别为9.14%、8.19%,高于其他管段,硫酸盐还原为硫化物的潜能较大,存在管道腐蚀的风险.RDA分析表明污水的DO、水温、硫酸根、TN与管道沉积物中微生物群落存在相关性.     

建筑垃圾堆放点样本集构建与优化研究

为更好地解决手工制作的建筑垃圾堆放点样本集效率低、数据量少,难以支撑基于深度学习的遥感图像目标检测算法训练需求的问题,采用基于像素的遥感分类方法构建建筑垃圾堆放点样本集,在此基础上结合直方图均衡化,CS-LBP算子约束以及迁移学习的方法对Wasserstein生成对抗模型（WGAN）进行优化,实现了样本集扩充。研究结果表明:相对于纯手工制作的样本集,基于像素的遥感分类方法可以显著提升样本集制作的效率;同时,经过WGAN优化后,生成样本模拟了原始数据的颜色与纹理特征分布规律,增加了原始数据的多样性,满足了扩充样本集的需求。     

Performance of different macrophytes in the decontamination of and electricity generation from swine wastewater via an integrated constructed wetland-microbial fuel cell process

Plants constitute a major element of constructed wetlands(CWs).In this study,a coupled system comprising an integrated vertical flow CW(IVCW) and a microbial fuel cell(MFC) for swine wastewater tre atment was developed to research the effects of macrophytes commonly employed in CWs,Canna indica,Acorus calamus,and Ipomoea aquatica,on decontamination and electricity production in the system.Because of the different root types and amounts of oxygen released by the roots,the rates of chemical oxygen demand(COD) and ammonium nitrogen(NH_4~+-N) removal from the swine wastewater differed as well.In the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,the COD removal rates were 80.20%,88.07%,84.70%,and 82.20%,respectively,and the NH_4~+-N removal rates were 49.96%,75.02%,70.25%,and 68.47%,respectively.The decontamination capability of the Canna indica system was better than those of the other systems.The average output voltages were 520±42,715±20,660±27,and 752±26 mV for the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,respectively,and the maximum power densities were 0.2230,0.4136,0.3614,and0.4964 W/m~3,respectively.Ipomoea aquatica had the largest effect on bioelectricity generation promotion.In addition,electrochemically active bacteria,Geobacter and Desulfuromonas,were detected in the anodic biofilm by high-throughput sequencing analysis,and Comamonas(Proteobacteria),which is widely found in MFCs,was also detected in the anodic biofilm.These results confirmed the important role of plants in IVCW-MFCs.     

Development of a static test apparatus for evaluating the performance of three PM2.5 separators commonly used in China

PM_(2.5) separator directly affects the accuracy of PM_(2.5) sampling.The specification testing and evaluation for PM_(2.5) separator is particularly important,especially under China's wide variation of terrain and climate.In this study,first a static test apparatus based on polydisperse aerosol was established and calibrated to evaluate the performance of the PM_(2.5) separators.A uniform mixing chamber was developed to make particles mix completely.The aerosol concentration relative standard deviations of three test points at the same horizontal chamber position were less than 0.57%,and the particle size distribution obeyed logarithmic normal distribution with an R~2 of 0.996.The flow rate deviation between the measurement and the set point flow rate agreed to within ± 1.0% in the range of -40 to 50℃.Secondly,the separation,flow and loading characteristics of three cyclone separators(VSCC-A,SCC-A and SCC112) were evaluated using this system.The results showed that the 50% cutoff sizes(D_(50)) of the three cyclones were 2.48,2.47 and 2.44 μm when worked at the manufacturer's recommended flow rates,respectively.The geometric standard deviation(GSD) of the capture efficiency of VSCCA was 1.23,showed a slightly sharper than SCC-A(GSD = 1.27),while the SCC112 did not meet the relevant indicator(GSD = 1.2 ± 0.1) with a GSD = 1.44.The flow rate and loading test had a great effect on D_(50),while the GSD remained almost the same as before.In addition,the maintenance frequency under different air pollution conditions of the cyclones was summarized according to the loading test.     

Density functional theory (DFT) studies of vanadium-titanium based selective catalytic reduction (SCR) catalysts

Based on density functional theory (DFT) and basic structure models, the chemical reactions on the surface of vanadium-titanium based selective catalytic reduction (SCR) denitrification catalysts were summarized. Reasonable structural models (non-periodic and periodic structural models) are the basis of density functional calculations. A periodic structure model was more appropriate to represent the catalyst surface, and its theoretical calculation results were more comparable with the experimental results than a non-periodic model. It is generally believed that the SCR mechanism where NH₃ and NO react to produce N₂ and H₂O follows an Eley-Rideal type mechanism. NH₂NO was found to be an important intermediate in the SCR reaction, with multiple production routes. Simultaneously, the effects of H₂O, SO₂ and metal on SCR catalysts were also summarized.     

Effects of calcination temperature on physicochemical property and activity of CuSO4/TiO2 ammonia-selective catalytic reduction catalysts

CuSO_4/TiO_2 catalysts with high catalytic activity and excellent resistant to SO_2 and H_2 O,were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH_3.The performance of catalysts is largely affected by calcination temperature.Here,effects of calcination temperature on physicochemical property and catalytic activity of CuSO_4/TiO_2 catalysts were investigated in depth.Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N2 adsorption-desorption,X-ray diffraction,thermogravimetric analysis,Raman spectra,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,temperature-pro grammed desorption of NH_3,temperature-programmed reduction of H_2 and in situ diffuse reflectance infrared Fourier transform spectroscopy.Results revealed that high calcination temperature had three main effects on the catalyst.First,sintering and anatase transform into rutile with increase of calcination temperature,causing a decrement of specific surface area.Second,decomposition of CuSO_4 under higher calcination temperature,resulting in disappears of Br(?)nsted acid sites(S-OH),which had an adverse effect on surface acidity.Third,CuO from the decomposition of CuSO_4 changed surface reducibility of the catalyst and favored the process of NH_3 oxidation to nitrogen oxides(NO_x).Thus,catalytic activity of the catalyst calcined under high temperatures(≥600℃) decreased largely.     

基于边介数的省域生态廊道构建方法优化

我国城市建设和生态保护工作均对土地资源有大量需求,二者之间的矛盾在经济优先发展区表现尤为明显.为了有效地改善生态环境,管控土地利用并引导其变化发展,需要建设具备不可替代特征的省域生态廊道.最小累积阻力模型（minimum cumulative resistance,MCR）是识别生态廊道最常用、有效的模型,但在应用于省域尺度时,MCR模型识别的潜在廊道路由存在冗余的问题.因此,通过引入网络科学中的边介数指数（edge-betweenness）对MCR模型进行优化,计算潜在廊道路由的边介数指数值,选取出其中最为重要和简明的结构来连通生态源地,即提取潜在路由中的骨干路由（backbone route）和关键战略点（key strategic point）作为不可替代的结构来指导省域生态廊道建设.将优化后的MCR模型应用于广东省,构建了全长5 493 km的省域生态廊道,其中包含生态源地20处,关键战略点11个,骨干生态廊道29条.骨干路由与关键战略点构成的不可替代省域生态廊道（irreplaceable provincial corridor）能够实现"廊道数量和占地面积最少、连通性基本不变"的目标.研究显示,边介数能够对潜在路由进行优化筛选,识别出维护省域生态安全的关键结构;不可替代生态廊道能够指导省域生态规划和土地空间的发展利用,并为更高水平的生态安全环境提供了演进的基础;同时也为土地资源紧张的地区提供了建设生态廊道的参考与依据.      

Chemical characteristics of road dust PM2.5 fraction in oasis cities at the margin of Tarim Basin

In order to understand the compositions characteristics of particulate matter with aerodynamic diameter less than 2.5 μm (PM_2.5) fraction in road dust (RD_2.5) of oasis cities on the edge of Tarim Basin, 30 road dust (RD) samples were collected in Kashi, Cele, and Yutian in the spring, 2018, and RD_2.5 was collected using the resuspension approach. Eight water-soluble ions, 39 trace elements and 8 fractions of carbon-containing species in PM_2.5 were analyzed. Ca²⁺ and Ca were the most abundant ions and elements in RD_2.5 (7.1% and 9.5%). Cl^- in RD_2.5 was affected not only by attributed to saline-alkali soils in oasis cities of the Tarim Basin and dust from Taklimakan Desert but also by human activities. Moreover, the organic carbon/elemental carbon (OC/EC) ratio indicated that carbon components in RD_2.5 in Cele town mainly come from fossil fuel combustion, while those in Yutian and Kashi mainly come from biomass combustion. It is noteworthy that high Ca in RD_2.5 was seriously affected by anthropogenic emissions, and high Na and K contents in RD_2.5 could be derived from soil and desert dust. It was estimated that Cd, Tl, Sn and Cr were emitted from anthropogenic emissions using the enrichment factor. The coefficients of divergence (COD) result indicated that the influence of local emission on road dust emission is greater than that of long-distance transmission. This study is the first time to comprehensively analyze the chemical characteristics of road dust in oasis cities, and the results provides the sources of road dust at the margin of Tarim Basin.