Identification of potential electrotrophic microbial community in paddy soils by enrichment of microbial electrolysis cell biocathodes

Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in paddy soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five paddy soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%–45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in paddy soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.     

Removal and desorption of chromium in synthetic effluent by a mixed culture in a bioreactor with a magnetic field

Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0.The objective was to remove Cr(Ⅵ) and total Cr from the effluent,this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(Ⅵ) in a bioreactor with neodymium magnets that applied a magnetic field(intensity85.4 mT) to the mixed culture.The removal of Cr(Ⅵ) was approximately 100.0% for the bioreactor with a magnetic field and 93,3% for the bioreactor without a magnetic field for9 hr of recirculation of the synthetic effluent by the bioreactor.The removal of total Cr was61.6% and 48.4%,with and without a magnetic field,respectively;for 24 hr.The desorption of Cr(VI) in the synthetic effluent was 0.05 mg/L,which is below the limit established by Brazilian legislation(0.1 mg/L) for the discharge of effluent containing Cr(Ⅵ) into bodies of water.The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture.The desorption of Cr(Ⅵ) in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.     

Recent advances in catalytic decomposition of ozone

Ozone (O₃), as a harmful air pollutant, has been of wide concern. Safe, efficient, and economical O₃ removal methods urgently need to be developed. Catalytic decomposition is the most promising method for O₃ removal, especially at room temperature or even subzero temperatures. Great efforts have been made to develop high-efficiency catalysts for O₃ decomposition that can operate at low temperatures, high space velocity and high humidity. First, this review describes the general reaction mechanism of O₃ decomposition on noble metal and transition metal oxide catalysts. Then, progress on the O₃ decomposition performance of various catalysts in the past 30 years is summarized in detail. The main focus is the O₃ decomposition performance of manganese oxides, which are divided into supported manganese oxides and non-supported manganese oxides. Methods to improve the activity, stability, and humidity resistance of manganese oxide catalysts for O₃ decomposition are also summarized. The deactivation mechanisms of manganese oxides under dry and humid conditions are discussed. The O₃ decomposition performance of monolithic catalysts is also summarized from the perspective of industrial applications. Finally, the future development directions and prospects of O₃ catalytic decomposition technology are put forward.     

Effect of struvite and organic acids on immobilization of copper and zinc in contaminated bio-retention filter media

Few studies have been carried out to connect nutrient recovery as struvite from wastewater and sustainable utilization of the recovered struvite for copper and zinc immobilization in contaminated soil. This study revealed the effect of struvite on Cu and Zn immobilization in contaminated bio-retention soil in the presence of commonly exuded plant organic acids. The research hypothesis was that the presence of both struvite and organic acids may influence the immobilization of Cu and Zn in soil. The outcome of this research confirmed that more than 99% of Cu and Zn was immobilized in bio-retention filter media by struvite application. Water-soluble Cu and Zn concentrations of struvite treated soil were less than 1.83 and 0.86 mg/kg respectively, and these concentrations were significantly lower compared to the total Cu and Zn content of 747.05 mg/kg in the contaminated soil. Application of struvite to Cu- and Zn-contaminated soil resulted in formation of compounds similar to zinc phosphate tetrahydrate (Zn₃(PO₄)₂?4H₂O) and amorphous Cu and Zn phases. Struvite was effective in heavy metal remediation in acidic soil regardless of the presence of Ca impurities in struvite and the presence of plant organic acids in soil. Overall, this study revealed that struvite recovered from wastewater treatment plants has potential for use as an amendment for heavy metal remediation in contaminated bio-retention soil.     

某垃圾焚烧厂投产前后周边土壤二英类化合物的分布

为研究垃圾焚烧厂运行对周边土壤二英类化合物（PCDD/Fs）含量的影响,采集了珠三角地区某垃圾焚烧厂投产前和投产后周边土壤样品,分析研究了该垃圾焚烧厂运行对周边土壤中PCDD/Fs含量和组分的变化.结果表明:①2012年（投产前）珠三角地区某垃圾焚烧厂周边土壤PCDD/Fs含量较低,范围为163~591 ng/kg（毒性当量范围为0.198~0.863 ng I-TEQ/kg,I-TEQ为国际毒性当量因子折算的毒性当量值）;2017—2019年（投产后）周边土壤PCDD/Fs含量范围为151~1.75×103 ng/kg（毒性当量范围为0.812~3.88 ng I-TEQ/kg）,与其他研究相比处于较低的水平.②投产后,距该垃圾焚烧厂较近（1.5 km）的采样点（S1）土壤PCDD/Fs含量逐年增长,在较远（5.2 km）但人口较密集的采样点（S3）土壤PCDD/Fs含量整体较高,但呈逐年下降趋势.③投产后,土壤中的17种PCDD/Fs单体组分中,毒性当量贡献率最高的单体为八氯二苯并二英（OCDD）和2,3,4,7,8-五氯二苯并呋喃（2,3,4,7,8-PeCDF）,二者毒性当量贡献率范围为15.7%~45.4%.④在同一采样点土壤PCDD/Fs单体组分年间差异不明显,但同一年份不同采样点差异明显.研究显示,目前该垃圾焚烧厂周边土壤PCDD/Fs含量较低,但仍需要长期监测其可能带来的风险.      

基于野外原位抽注试验和同位素技术的含水层反硝化速率研究

反硝化作用是地下水硝酸盐污染去除最重要的过程.由于水文地质条件和水文地球化学环境的复杂性和不确定性,精准测定含水层反硝化速率是反硝化过程的研究难点.选取潮白河冲洪积扇中部中国环境科学研究院地下水创新野外基地作为研究区,基于野外原位试验和15N同位素示踪法提出一种含水层反硝化速率的测定方法.该方法综合体现了研究区实际水文地质条件和水文地球化学环境对反硝化作用的影响,并充分考虑了硝酸盐在含水层中稀释弥散作用对计算结果的影响.结果表明:①潮白河冲洪积扇中部某地地下26~28 m处于还原环境,含水介质以粉细砂为主,ρ（NO₃-N）平均值为2.77 mg/L.②地下26~28 m反硝化速率在349.52~562.99 μg/（kg·d）（以N计,下同）之间,平均值为450.31 μg/（kg·d）.通过与研究区含水介质、采样深度和硝酸盐背景值相似的国内外案例对比研究,初步评估结果处于合理区间.③测试结果具有一定不确定性,主要来自忽略中间产物NO₂-和NO的计算方法、扰动采样方法、N₂O的操作规范程度及采样频率等方面.研究方法为测定含水层硝酸盐速率研究提供了新的思路,研究结果可为地下水中硝酸盐转化过程机理研究、地下水硝酸盐污染修复及风险管控提供关键的理论支撑数据.      

废塑料再生过程废水中微塑料去除模拟试验

微塑料是一种存在于不同环境介质中的新兴污染物,主要来源于废弃塑料制品,其存在污染范围广、潜在环境污染大的问题.废塑料再生企业生产废水中微塑料浓度远高于其他类型废水,对其生产废水中的微塑料进行处理具有重要的环境意义.模拟废塑料再生过程的生产废水并进行微塑料去除的絮凝沉淀试验,研究絮凝剂投加量、pH、水力快速搅拌条件的单因素和正交试验对废水中微塑料去除率及其各因素作用的影响.结果表明:①当PAC (聚合氯化铝)投加量为10 mL,PAM (聚丙烯酰胺)投加量为7 mL,pH为9,水力快速搅拌条件为100 r/min下维持40 s再200 r/min下维持40 s时,微塑料的总去除率最高,达91%.②PAC投加量是影响微塑料去除效果的主要因素,其次是pH.③微塑料的去除率与其本身的密度有关,密度大的ABS (acrylonitrile butadiene styrene,丙烯腈-丁二烯-苯乙烯)去除率最高,密度小的PE (polyethylene,聚乙烯)去除率最低.④不同粒径区间的微塑料去除率区别较大,粒径小(0.1~0.25 mm)的微塑料去除效果最好.研究显示,通过控制PAC和PAM的投加量、pH和水力搅拌速率等条件,能够有效将废水中的微塑料通过絮凝沉淀的方法去除,从而达到净化含微塑料生产废水的目的.      

人工智能技术对长江流域水污染治理的思考

随着经济的快速发展和城市化进程的不断加速,促使水污染严重的长江流域需从污染物去除过程的建模与优化、污水处理过程的优化控制、水污染监测系统的构建开展水污染治理研究.传统的水污染处理技术存在污染物去除效率预测精度较低、污水优化控制成本较高、水污染监测滞后效应严重的问题.人工智能技术能够有效克服上述问题,因此通过梳理国内外学者利用人工智能技术在污水污染物去除过程的建模与优化、污水处理过程的优化控制及水污染监测系统的构建等方面的研究成果,为全面加强长江流域水污染治理能力提供科学可靠的技术指导.结果表明:①利用人工神经网络技术（径向基神经网络、多层前馈网络-人工神经网络、多层感知器神经网络）对污水污染物去除过程进行建模与优化,为精确预测长江流域重金属（Cr、Cu）、营养盐（TN、TP）、持久性有机污染物〔PBDEs（多溴二苯醚）、HCH（六氯环己烷）〕的去除率提供重要参考价值.②采用污水处理的自动控制技术与人工智能技术（递归神经网络、支持向量机、模糊神经网络等）构建污水智能控制系统,为长江流域实现高效节能的污水优化控制提供重要的技术指导.③利用在线监测仪器和人工智能技术（小波神经网络、多元线性回归-人工神经网络、叠层去噪自动编码器等）建立水污染智能监测系统,为解决长江流域水污染监测响应滞后问题提供有力的技术支持.因此,人工智能技术对长江流域提高污水污染物去除率,降低污水优化控制成本,提升水污染监测时效性具有重要的推广价值.      

弹射起飞和拦阻着陆冲击试验方法探讨

目的研究舰载机机载装备弹射起飞和拦阻着陆冲击试验的工程实现方法。方法从GJB 150.18A—2009、MIL-STD-810F/G及其提供的实测数据出发,分析弹射起飞和拦阻着陆冲击载荷特征,对几种常用试验方法的工程实现进行探讨和比较。结果弹射起飞和拦阻着陆冲击具有瞬态、交变、低频、大位移、高速度等特征。阻尼正弦波方法的实施路径比较明确,复杂波形再现方法实施路径比较模糊且复杂,超长脉冲半正弦波方法具有多种局限性,前两种方法的速度、位移都较大。结论阻尼正弦波方法较复杂波形再现方法更容易实现,但两者都需要大位移、高速度的专用冲击试验设备和适当的波形处理技术,超长脉冲半正弦波方法在前面两种标准推荐方法能够实现时,不建议使用。     

新时代国土整治与生态修复转型思考

针对全球变化影响下的国土空间和生态系统,生态文明建设和国土空间规划是中国在新时代的积极响应,国土整治与生态修复的转型和提升成为必然要求。在介绍国土整治与生态修复概念内涵的基础上,指出中国国土空间生态环境问题的复杂性和生态文明建设的新理念要求决定了国土整治与生态修复的转型。从工作理念、理论基础、技术体系和制度建设等方面,分析了当前国土整治与生态修复工作中存在的不足,主要包括整体综合理念滞后、理论基础体系欠缺、技术支撑相对薄弱、体制机制不尽完善等方面。针对这些不足,提出了新时代国土整治与生态修复转型的路径和策略,主要策略包括强化系统思维、提升理论体系、加强技术支撑、完善机制建设等内容,以期为国土整治与生态修复推进美丽中国建设提供科学依据。