非正规垃圾填埋场包气带介质的污染物阻滞能力研究

非正规垃圾填埋场已成为地下水的潜在污染源,给城市供水安全带来了极大风险。以北京某非正规垃圾填埋场的3种典型包气带介质为研究对象,以Br-为示踪剂,采取土柱实验和数值模拟相结合的方法,通过对场区3种典型包气带介质饱和与非饱和状态下的Br-迁移速率的比较,探讨包气带介质对污染物的阻滞能力。结果表明,Br-在不同包气带介质饱和状态下的迁移速率为中砂>细砂>砂质粉土,这可能与不同介质中粉粒和粘粒的含量有关,同时介质的有机质含量也会影响Br-的迁移速率,但前者因素占了主导作用;在Br-迁移过程中,不同包气带介质的含水量是影响其迁移速率的主要因素,若能合理控制场区的地下水位,使得包气带介质长期处于非饱和状态,将会大大延缓垃圾渗滤液中污染物向地下水迁移;针对特定的非正规垃圾填埋场,可采取抽水等措施,控制场区的细砂和砂质粉土层处于非饱和状态,充分利用包气带介质在非饱和状态时较强的污染物阻滞能力,阻隔或延缓垃圾渗滤液中的污染物进入地下水中。     

生物膜氧化沟污水处理性能的研究

生物膜氧化沟是在普通氧化沟内放置合适填料，使之成为活性污泥法与生物膜法相结合的混合污水处理工艺。本研究通过清水试验，选择出了生物膜氧人诉合适填料及其安装方式，并同时比较了生物膜氧化沟和普通氧化沟的传质效果，水流阻力、水力混合特性。通过污水试验，确定了生物膜氧化沟的填料最佳填充率。并比较了生物膜氧化沟和普通氧化沟的去除ＣＯＤ、ＳＳ、ＴＮ效率及两者的污泥性能。     

社交媒体的环境关注能改善空气质量吗？

随着移动互联网的快速发展,社交媒体日益成为公众表达对重污染天气等环境问题关注的工具。本研究以微博为例,探讨了社交媒体反映的环境关注对城市PM_2.5浓度水平的影响以及内在机制。研究发现,微博上环境关注的空间分布显示出向高等级和高污染城市聚集的倾向,PM_2.5浓度水平高的地区集中在煤炭资源或重工业集聚的地区。空间回归模型的结果证实了社交媒体的环境关注能显著降低PM_2.5浓度水平,层级较高的城市及创新能力较强的城市能够更好地回应社交媒体的环境关注,并有效降低城市的PM_2.5浓度水平。本研究表明,社交媒体的环境关注已经成为环境治理中的一种重要力量,在分析环境问题时应该充分考虑新兴社交媒体平台的影响。     

Transport of a non-volatile contaminant in unsaturated porous media in the presence of colloids

Stable colloidal particles can travel long distances in subsurface environments and carry particle-reactive contaminants with them to locations further than predicted by the conventional advective-dispersive transport equation. When such carriers exist in a saturated porous medium, the system can be idealized as consisting of three phases: an aqueous phase, a carrier phase, and a stationary solid matrix phase. However, when colloids are present in an unsaturated porous medium, the system representation should include one more phase, i.e. the air phase. In the work reported, a mathematical model was developed to describe the transport and fate of the colloidal particles and a non-volatile contaminant in unsaturated porous media. The model is based on mass balance equations in a four-phase porous medium. Colloid mass transfer mechanisms among aqueous, solid matrix, and air phases, and contaminant mass transfer between aqueous and colloid phases are represented by kinetic expressions. Governing equations are non-dimensionalized and solved to investigate colloid and contaminant transport in an unsaturated porous medium. A sensitivity analysis of the transport model was utilized to assess the effects of several parameters on model behavior. The colloid transport model matches successfully with experimental data of Wan and Wilson. The presence of air-water interface retards the colloid transport significantly counterbalancing the facilitating effect of colloids. However, the retardation of contaminant transport by colloids is highly dependent on the properties of the contaminant and the colloidal surface.     

Identifying conservation priorities for threatened Eastern Himalayan mammals

To augment mammal conservation in the Eastern Himalayan region, we assessed the resident 255 terrestrial mammal species and identified the 50 most threatened species based on conservation status, endemism, range size, and evolutionary distinctiveness. By using the spatial analysis package letsR and the complementarity core‐area method in the conservation planning software Zonation, we assessed the current efficacy of their protection and identified priority conservation areas by comparing protected areas (PAs), land cover, and global ecoregion 2017 maps at a 100 × 100 m spatial scale. The 50 species that were most threatened, geographically restricted, and evolutionarily distinct faced a greater extinction risk than globally nonthreatened and wide‐ranging species and species with several close relatives. Small, medium‐sized, and data‐deficient species faced extinction from inadequate protection in PAs relative to wide‐ranging charismatic species. There was a mismatch between current PA distribution and priority areas for conservation of the 50 most endangered species. To protect these species, the skewed regional PA distribution would require expansion. Where possible, new PAs and transboundary reserves in the 35 priority areas we identified should be established. There are adequate remaining natural areas in which to expand current Eastern Himalayan PAs. Consolidation and expansion of PAs in the EH requires strengthening national and regional transboundary collaboration, formulating comprehensive regional land‐use plans, diversifying conservation funding, and enhancing information sharing through a consolidated regional database.     

Knowledge-based Journalism in Science and Environmental Reporting: Opportunities and Obstacles

Recent calls for knowledge-based journalism advocate a new level of formal knowledge in news reporting to meet the professional challenges caused by rapid change in the news industry. Scientifically knowledgeable journalism has the potential to redefine the existing science–media relationship. However, the audience for such journalism is unclear, nor is it known how this new journalism would function within rapidly changing newsroom practices. Implementing knowledge-based journalism requires theory-based propositions to show the actual benefits of improved scientific understanding for news consumers and an understanding, from research into professional cultures, of why new practices in journalism are adopted or abandoned. This paper develops that theoretical basis by examining knowledge-based journalism’s potential and some of the intellectual and institutional barriers to it.     

Government to Citizens (G2C) communication and use of social media in the post-disaster reconstruction phase

Post-disaster reconstruction (PDR) poses specific and complex challenges that government agencies have to deal with. Existing crisis management and communication models as well as literature on social media adoption by public organisations tend to focus on the critical stage, neglecting the issues that arise when the social, physical and cultural environments affected by a disaster have to be rebuilt. Conversely, this paper presents some preliminary findings on the Government to Citizen (G2C) communications and social media usage in PDR settings. The PDR process that followed the earthquakes in Emilia-Romagna (Northern Italy) in 2012 was used as a case study. Data derived from field notes and multiple-choice questionnaires revealed that government agencies provided information mainly about housing and infrastructure and financing and that they addressed this information to all citizens, although information was sometimes targeted specifically to business people, homeowners and members of community-based groups. Government officers gave preference to face-to-face contacts, Web portals and printed material. Social media were used predominantly as additional means of communication of PDR-related information, thus underrating their potential for community engagement and G2C bidirectional communication. In the discussions, findings are integrated into and validated against literature and communication theories.     

水平流人工快速渗滤系统对岩源性磷拦截效果研究

选取沸石,陶粒,无烟煤及其组合作为水平流人工快速渗滤系统的填料,进行不同进水水质和水力负荷下对岩源性磷拦截效果的研究。结果表明:相同运行条件下,单一填料沸石对悬浮颗粒物和岩源性磷的去除效果最好,平均值分别达到了90.47%、39.91%;组合填料的运行稳定性更好,且水力负荷为0.2 cm/s时效果最好,最高可达82.85%和46.18%;长期的运行模拟中发现系统的堵塞现象,在实际应用中要充分考虑填料的更换和再生的可操作性,保证系统运行的稳定高效。     

Stabilization of nanoscale zero-valent iron in water with mesoporous carbon (nZVI@MC)

Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxidation. Herein, we report the nZVI incorporated into mesoporous carbon(MC) to enhance stability in aqueous solution and mobility in porous media. Meanwhile, the reactivity of nZVI is preserved thanks to high temperature treatment and confinement of carbon framework. Small-sized(～16 nm) nZVI nanoparticles are uniformly dispersed in the whole carbon frameworks. Importantly, the nanoparticles are partially trapped across the carbon walls with a portion exposed to the mesopore channels. This unique structure not only is conductive to hold the nZVI tightly to avoid aggregation during mobility but also provides accessible active sites for reactivity. This new type of nanomaterial contains ～10 wt% of iron. The nZVI@MC possesses a high surface area(～ 500 m~2/g) and uniform mesopores(～ 4.2 nm) for efficient pollutant diffusion and reactions. Also, high porosity of nZVI@MC contributes to the stability and mobility of nZVI. Laboratory column experiments further demonstrate that nZVI@MC suspension(～4 g Fe/L) can pass through sand columns much more efficiently than bare nZVI while the high reactivity of nZVI@MC is confirmed from reactions with Ni(II). It exhibits remarkably better performance in nickel(20 mg/L) extraction than mesoporous carbon, with 88.0% and 33.0%uptake in 5 min, respectively.