复合人工湿地中反硝化除磷作用的发生及其稳定性

将2套潮汐流人工湿地(T-A和T-B)构建为复合人工湿地(HCW),研究了HCW中反硝化除磷作用的发生及其稳定性.结果表明,当HCW按照两段进水潮汐流方式连续运行时,T-A的反硝化除磷性能和T-B的硝化性能均可得以强化,HCW随之具有理想的同步脱氮除磷效果;周期性补充碳源的磷移除操作可缓解T-A中磷素的过量积累,同时可提高反硝化聚磷菌(DPAOs)胞内聚β-羟基丁酸(PHB)的合成量,有助于HCW反硝化除磷效果的高效与稳定;当磷移除周期为30 d时,T-A在反硝化除磷过程中对TP与NOx--N的去除率分别为(97. 86±0. 70)%和(98. 29±2. 62)%,在磷移除过程中的磷素释放量、PHB合成量(以C/填料计)及补充碳源利用率分别为(1 486. 29±123. 25) mg、(4. 43±0. 57) mmol·g~(-1)和(94. 65±2. 66)%,HCW的磷素回收效率则为63. 97%.本研究为人工湿地同步脱氮除磷提供了新的思路,又进一步拓展了磷回收技术的研发和应用范围.     

N2流量比对AlCrMoSiN涂层组织结构和性能的影响

目的 减少硬质合金刀具在干式切削时产生的切削热,降低切削温度,从而提高刀具使用寿命。向AlCrSiN涂层中掺杂Mo元素,在涂层服役过程中易生成层状MoO_(3)润滑膜,降低刀面与切屑和工件间的摩擦,实现涂层刀具的自润滑功能。方法 利用高功率脉冲磁控溅射和脉冲直流磁控溅射复合技术制备AlCrMoSiN涂层,改变反应气体N_(2)流量,调节涂层的成分和结构。采用X射线衍射仪、扫描电子显微镜分析AlCrMoSiN涂层的物相成分和微观结构,利用纳米压痕仪、划痕仪和摩擦试验机分别测试涂层的力学性能和摩擦学行为。结果 当N_(2)流量比增大,AlCrMoSiN涂层沿(111)晶面择优生长,衍射峰变得尖锐,(111)和(200)晶面衍射峰向小角度偏移。当N_(2)流量比为16%时,涂层的硬度和弹性模量最大,分别为17.56 GPa和292.31 GPa。当N_(2)流量比为18%时,涂层的临界载荷最高,约为70.6 N,摩擦系数最低达0.54,磨损率为1.3×10^(–3)μm^(3)/(N·μm),此时涂层最耐磨。结论 N_(2)流量比对涂层组织结构有重要影响,随着N_(2)流量比增大,涂层的力学性能与摩擦磨损性能逐渐改善。     

铀胁迫对大豆与玉米幼苗细胞DNA损伤的彗星试验研究

以铀浓度为1000 μmol·L-1、800 μmol·L-1、600 μmol·L-1、400 μmol·L-1、200μmol·L-1和100μmol·L-1的6组铀溶液和对照组(0μmol·L-1)培养大豆和玉米幼苗,采用彗星试验研究铀胁迫对大豆和玉米幼苗细胞DNA的损伤情况.试验结果表明,铀浓度为1 000 μ...     

生物炭与硅酸钠复合施加抑制水稻对土壤铅吸收富集的机制研究

将水稻秸秆生物炭（RB）、玉米秸秆生物炭（MB）分别与硅酸钠（G）复合施加到从矿区周边采集的铅（Pb）污染农田土壤,通过盆栽试验,比较分析了Pb在土壤-水稻系统各部位中的迁移和累积情况,探讨了生物炭与硅酸钠复合施加抑制水稻对Pb吸收转运的机制.结果表明,与对照组相比,生物炭与硅酸钠复合施加（RBG和MBG）使糙米Pb含量显著降低71.0%~75.6%,且比生物炭或硅酸钠单一施加时的降幅更大.其主要机制为：①生物炭与硅酸钠复合施加提高了土壤pH和有机质含量,促进了土壤对Pb的固定,从而使土壤Pb从弱酸提取态向可氧化态Pb转化,在成熟期RBG和MBG处理分别使CaCl₂溶液浸提的土壤有效Pb含量降低54.3%和60.0%.②生物炭与硅酸钠复合施加降低了DTPA溶液浸提的土壤有效态Fe含量,减少了根表铁膜的数量（DCB-Fe）,而且根系Pb含量与DCB-Fe含量之间呈显著正相关关系,推测生物炭与硅酸钠复合施加使根表用于存储Pb的铁膜减少,从而降低Pb进入根系的几率.③生物炭与硅酸钠复合施加显著降低了分蘖期TF_根-叶和成熟期TF_土-根、TF_茎-糙米、TF_叶-糙米（p<0.05）,阻碍Pb在糙米中累积.此外,生物炭与硅酸钠复合施加显著提高了稻谷质量（p<0.05）.因此,生物炭与硅酸钠复合施加可用于修复铅污染稻田土壤.     

基于混合生命周期评价的不同坝型温室气体排放对比分析

为了研究不同坝型对环境造成的影响,采用混合生命周期评价方法定量分析并比较同规模的重力坝和堆石坝水电枢纽布置在全生命周期内的温室气体排放.研究基于糯扎渡工程实例,生命周期考虑材料设备生产阶段、运输阶段、施工阶段和运行维护阶段.结果表明:重力坝方案和堆石坝方案生命周期温室气体排放量分别为1145.49×104和815.85×104t(以CO2当量计),重力坝比堆石坝多排放40.4%.其中,重力坝在生产、运输和运行阶段的碳足迹比堆石坝大,但堆石坝在施工阶段的碳足迹比重力坝大.运行阶段的温室气体排放量占全生命周期碳足迹的比例最大,其次是材料设备生产阶段、施工阶段和运输阶段.糯扎渡水电工程的碳排放因子明显低于火电碳排放因子,合理开展水电建设,是实现我国"十二五"规划碳减排目标的有效途径.     

基于受体和化学传输的综合模型解析重庆PM2.5来源

为进一步提高PM_2.5污染源解析的准确性,研究提出一种基于受体和化学传输的综合源解析模型（CTM-RM）,并以重庆冬季一次典型PM_2.5污染过程为例（2019年1月21～27日）开展模型评估与应用.结果表明,观测期间基于CTM-RM获得的模拟误差平方值较CAMx/PSAT低84.58%,PM_2.5及其化学组分浓度的模拟相对误差值较CAMx/PSAT下降15.69%～92.86%;此外,CTM-RM还可以获取重庆市PM_2.5污染源贡献的时空分布特征.观测期间,主城区PM_2.5农业源、工业源、电力源、民用源、交通源和其他源的调整因子R值分别为1.39±0.38、 1.54±0.48、 1.01±0.13、 1.02±0.58、 0.86±0.59和0.58±0.67,各污染源R值的累积分布函数差异明显.民用源和工业源是主城区PM_2.5的主要污染源（46.23%和28.23%）.与其他源不同,污染日交通源贡献率（8.62%）同比清洁日显著上升（P<0.00...     

基于改进型萤火虫群优化算法泄漏源源强及位置反算研究*

针对标准萤火虫群优化算法（GSO）在危化品泄漏源源强及位置反算中存在精度不高,容易陷入局部最优等局限,提出混合萤火虫-Nelder Mead单纯形算法（GSO-NM）,并与基于步长的改进萤火虫群优化算法（MGSO）以及单纯形搜索混合协同进化萤火虫群优化算法（HCGSOSSM）进行比较分析,将3种改进型萤火虫群优化算法应用于泄漏源源强及位置反算中进行比较分析。研究结果表明:GSO-NM算法可以有效提高定位精度和稳定性,能较为精确地反算出泄漏源源强及位置,为泄漏源源强及位置反算研究提供1种新思路。     

Simulation planning of power supply capacity: an approach to optimal industrial microgrid operation with carbon emission permits

ABSTRACT

Microgrids integrated with distributed generation provide energy intensive enterprises (EIEs) with a solution to cut down their total system costs. However, unreasonable capacity allocation of power supply in industrial microgrid may result in capacity shortage or excess, thus leading to uneconomical solutions. Considering carbon emission permits and renewable energy access on demand side, this paper analyses and evaluates the long-term impacts of power supply capacity on economic benefits and carbon emission. The power suppliers consist of industrial self-generation, wind power generation and power grid. A HOMER software based industrial microgrid model is designed, and time series simulation of the model for a cycle of 10 years is performed to provide numerical analysis. The simulation results with sensitivity analysis show that optimal capacity planning of power supply can lead to considerable economical and ecological benefits under carbon emission permits; besides, it can also be conducive to peak load shedding for power grid.     

复合生物反应器低溶解氧同步脱氮除磷

利用复合生物反应器(HBR)中同时存在的活性污泥和悬浮生物膜混合生物体系,进行了同步脱氮除磷的试验研究.结果表明,溶解氧浓度和进水COD/TN对系统脱氮除磷效果有重要影响.当曝气量(Qair)控制在0.07m3/h时,系统的同步脱氮除磷效果较好,最大释磷率(释磷结束时溶液中PO3-4-P浓度与初始PO3-4-P浓度百分比)为249%,TN平均去除率为80.0%,PO3-4-P去除率为92.2%.曝气量升高或降低,TN、PO3-4-P去除率均降低.随着COD/TN的升高,系统TN、PO3-4-P去除率也逐渐升高,COD/TN从3.2升高至10.5,系统TN平均去除率从70.3%升高至84.9%,PO3-4-P平均去除率从82.2%高至96.0%.整个试验过程中污泥体积指数(SVI)均小于90 mL/g,污泥的沉降性能良好.实验采用复合反应器进水后未经过传统脱氮、除磷理论认为所必须的缺氧、厌氧段而直接曝气,仍然取得较高的TN、PO3-4-P去除率.     

Investigation of crashes at pedestrian hybrid beacons: Results of a large-scale study in Arizona

Introduction: The pedestrian hybrid beacon (PHB) is a traffic control device used at pedestrian crossings. A recent Arizona Department of Transportation research effort investigated changes in crashes for different severity levels and crash types (e.g., rear-end crashes) due to the PHB presence, as well as for crashes involving pedestrians and bicycles. Method: Two types of methodologies were used to evaluate the safety of PHBs: (a) an Empirical Bayes (EB) before-after study, and (b) a long-term cross-sectional observational study. For the EB before-after evaluation, the research team considered three reference groups: unsignalized intersections, signalized intersections, and both unsignalized and signalized intersections combined. Results: For the signalized and combined unsignalized and signalized intersection groups, all crash types considered showed statistically significant reductions in crashes (e.g., total crashes, fatal and injury crashes, rear-end crashes, fatal and injury rear-end crashes, angle crashes, fatal and injury angle crashes, pedestrian-related crashes, and fatal and injury pedestrian-related crashes). A cross-sectional study was conducted with a larger number of PHBs (186) to identify relationships between roadway characteristics and crashes at PHBs, especially with respect to the distance to an adjacent traffic control signal. The distance to an adjacent traffic signal was found to be significant only at the α = 0.1 level, and only for rear-end and fatal and injury rear-end crashes. Conclusions: This analysis represents the largest known study to date on the safety impacts of PHBs, along with a focus on how crossing and geometric characteristics affect crash patterns. The study showed the safety benefits of PHBs for both pedestrians and vehicles. Practical Applications: The findings from this study clearly support the installation of PHBs at midblock or intersection crossings, as well as at crossings on higher-speed roads.