污泥浓度对微孔曝气氧传质过程的影响

污泥浓度是影响微孔曝气氧传质过程的重要因素之一。在小试及中试规模上,研究了不同污泥浓度对微孔曝气氧传质过程的影响,得出曝气性能随污泥浓度的变化规律。结果表明,当污泥浓度低于2000mg／L时,曝气性能随浓度的增大而增强,在2000～3000mg／L时,KLa达到最大值;当污泥浓度大于2000～3000mg／L时,曝气性能随污泥浓度增大而降低,当污泥浓度大于5000mg／L时,曝气性能急剧降低。这一规律对于在设计和运行中合理确定污水处理中的污泥浓度,在达到处理效果的前提下,尽量降低电耗具有重要意义。     

中国生态环境补偿费的理论与实践

在分析、总结国内外有关环境价值理论研究和生态补偿费征收工作实践经验的基础上,对生态环境补偿机制和生态环境补偿费政策的基本框架进行了较为深入的探讨。结果表明,自然要素所固有的生态环境价值是生态环境补偿的理论依据,征收生态环境补偿费是对环境破坏导致的生态环境价值损失的一种补偿。但是,在我国,生态环境补偿费的征收标准应当建立在我国国情所容许的基础之上,既要为保护和改善生态环境积累一定的的资金,又不能对国民经济发展和人民生活造成大的影响。同时,在资金的征收和管理上,应当与国家现有的生态环境管理体制相适应,与加强生态环境保护的统一监督管理机制有机地结合起来。     

Anaerobic degradation of xenobiotic organic contaminants (XOCs): The role of electron flow and potential enhancing strategies

In groundwater, deep soil layer, sediment, the widespread of xenobiotic organic contaminants (XOCs) have been leading to the concern of human health and eco-environment safety, which calls for a better understanding on the fate and remediation of XOCs in anoxic matrices. In the absence of oxygen, bacteria utilize various oxidized substances, e.g. nitrate, sulphate, metallic (hydr)oxides, humic substance, as terminal electron acceptors (TEAs) to fuel anaerobic XOCs degradation. Although there have been increasing anaerobic biodegradation studies focusing on species identification, degrading pathways, community dynamics, systematic reviews on the underlying mechanism of anaerobic contaminants removal from the perspective of electron flow are limited. In this review, we provide the insight on anaerobic biodegradation from electrons aspect — electron production, transport, and consumption. The mechanism of the coupling between TEAs reduction and pollutants degradation is deconstructed in the level of community, pure culture, and cellular biochemistry. Hereby, relevant strategies to promote anaerobic biodegradation are proposed for guiding to an efficient XOCs bioremediation.     

Reactive transport of uranium(VI) and phosphate in a goethite-coated sand column: an experimental study

The migration of uranium(VI) in subsurface environments is strongly influenced by its adsorption/desorption reactions at the solid/solution interface. Phosphate is often present in subsurface systems and was shown to significantly affect U(VI) adsorption in previous batch experiments. In this study, column experiments were conducted to investigate the effects of phosphate on U(VI) adsorption and transport under flow conditions. The adsorption of U(VI) and phosphate was very low on pure quartz sand with negligible effects on U(VI) and phosphate transport. However, U(VI) and phosphate transport was retarded in a column packed with goethite-coated sand. The presence of phosphate, either as a co-solute with U(VI) or pre-adsorbed, greatly increased U(VI) adsorption and retardation. U(VI) and phosphate adsorption in our column experiments were rate-limited, and the adsorption of U(VI) and phosphate was not reversible, with kinetic limitations more pronounced for desorption than for adsorption. This study demonstrated the importance of phosphate in controlling U(VI) mobility in subsurface environments and helped illustrate some phenomena potentially applicable to U(VI) adsorption and transport in natural systems, especially where U(VI) adsorption is rate-limited.     

Trace metals in surface sediments of the Taiwan Strait: geochemical characteristics and environmental indication

The concentration and geochemical fractionation of six trace metals related with environmental quality assessment, namely Cd, Cr, Cu, Ni, Pb, and Zn, in 30 surface sediments from both inshore and offshore areas of the Taiwan Strait were measured to investigate their distribution characteristics, evaluate their potential mobility, and assess their pollution status. The geoaccumulation index results indicated that, on average, the studied metals presented an order of Cd?>?Pb?>?Ni?>?Zn?>?Cu?>?Cr and were practically in uncontaminated status except Cd. The results of the sequential extraction analysis indicated that, on average, the studied metals were mostly accumulated in residual fraction except Cd whose concentration was the highest in the acid soluble fraction presenting a high risk to the environment, and their mobility decreased in the sequence of Cd?>?Pb?>?Ni?>?Cu?>?Zn?>?Cr. Based on the mean probable effect level quotients, the combination of the studied metals had an 8 % probability of being toxic at two sampling sites and had a 21 % probability of being toxic at the rest of sites. The spatial distribution of the studied metals in total concentrations and different geochemical fractions corroborated the previous findings about the possible sediment transportation routes in and around the Taiwan Strait.     

Decontaminating soil organic pollutants with manufactured nanoparticles

Organic pollutants in soils might threaten the environmental and human health. Manufactured nanoparticles are capable to reduce this risk efficiently due to their relatively large capacity of sorption and degradation of organic pollutants. Stability, mobility, and reactivity of nanoparticles are prerequisites for their efficacy in soil remediation. On the basis of a brief introduction of these issues, this review provides a comprehensive summary of the application and effectiveness of various types of manufactured nanoparticles for removing organic pollutants from soil. The main categories of nanoparticles include iron (oxides), titanium dioxide, carbonaceous, palladium, and amphiphilic polymeric nanoparticles. Their advantages (e.g., unique properties and high sorption capacity) and disadvantages (e.g., high cost and low recovery) for soil remediation are discussed with respect to the characteristics of organic pollutants. The factors that influence the decontamination effects, such as properties, surfactants, solution chemistry, and soil organic matter, are addressed.     

Study of the ambient air metallic elements Cr,Cu, Zn,Cd and Pb at HAF sampling sites

This study characterized diurnal variations in the compositions of total suspended particulates (TSP) and dry deposits of particulates from ambient air, and the metallic elements that are contained in them at harbor, airport and farmland (HAF) sampling sites from August, 2013 to July, 2014. Two-way ANOVA of the amounts of metallic elements in the TSP and dry deposits was carried out in all four seasons at the HAF sampling sites. The metallic elements Cr and Cu originated in local emission sources at the airport. Metallic elements Zn and Pb originated in local emission sources at the harbor. Finally, metallic element Cd originated in local emissions form farmland. The following results were also obtained. (1) The metallic composition of the TSP differed significantly from that of the dry deposits in all four seasons at the harbor and farmland sampling sites, but not at the airport sampling site. (2) High correlations coefficients were found between the amounts of metallic elements Cr and Cu in the TSP and those in the dry deposits at the airport sampling site. (3) Pb was present in the TSP and the dry deposits at the harbor sampling site.     

Annual ambient atmospheric mercury speciation measurement from Longjing,a rural site in Taiwan

The main purpose of this study was to monitor ambient air particulates and mercury species [RGM, Hg(p), GEM and total mercury] concentrations and dry depositions over rural area at Longjing in central Taiwan during October 2014 to September 2015. In addition, passive air sampler and knife-edge surrogate surface samplers were used to collect the ambient air mercury species concentrations and dry depositions, respectively, in this study. Moreover, direct mercury analyzer was directly used to detect the mercury Hg(p) and RGM concentrations. The result indicated that: (1) The average highest RGM, Hg(p), GEM and total mercury concentrations, and dry depositions were observed in January, prevailing dust storm occurred in winter season was the possible major reason responsible for the above findings. (2) The highest average RGM, Hg(p), GEM and total mercury concentrations, dry depositions and velocities were occurred in winter. This is because that China is the largest atmospheric mercury (Hg) emitter in the world. Its Hg emissions and environmental impacts need to be evaluated. (3) The results indicated that the total mercury ratios of Kaohsiung to that of this study were 5.61. This is because that Kaohsiung has the largest industry density (~60 %) in Taiwan. (4) the USA showed average lower mercury species concentrations when compared to those of the other world countries. The average ratios of China/USA values were 89, 76 and 160 for total mercury, RGM and Hg(p), respectively, during the years of 2000–2012.     

机载设备温度试验摆放间距研究

目的 在多台产品进行温度试验时,确定高低温试验箱中产品合理的放置间距,以确保试验有效。方法 基于接触式测量,对机箱类产品的摆放间隔随温度变化进行测试,并对所有测试结果画出数据曲线,进行分析研究。结果 通过对高低温试验箱中1、5、10、15 cm放置间距的产品的温度变化情况进行测定,经过对比分析研究,最终确定了合理的放置间距。结论 经过分析研究,最终确定按照测试方案中制定的10 cm间距摆放,则整个试验过程可信度仍较高。     

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。