北部湾南流江流域土地覆盖及生物多样性模拟

以北部湾独流入海河流南流江流域为研究对象,基于研究区2000年和2015年遥感数据解译的土地利用数据以及社会经济等数据,采用CLUE-S模型对未来2030年生态保护情景、自然增长情景以及粮食安全情景的土地利用格局进行了模拟预测,在此基础上采用InVEST模型对流域过去和未来不同情景的生物多样性进行了评估,探讨了流域生物多样性的生境质量和生境退化程度.结果表明：2000~2015年南流江流域建设用地、园地、水域和未利用地呈现出增加趋势,其中建设用地的增幅最大,而耕地和林地减幅最大.流域土地系统中共存在着34种土地网络转移流关系,上游存在24种,中游20种,下游28种,耕地与建设用地、耕地与林地以及林地与园地之间的转换占到流域总土地利用变化的70.74%.CLUE-S模型模拟未来土地利用的Kappa系数达到0.86,表明模型模拟未来情景的土地利用精度满足要求.2000年、2015年、2030年生态保护情景、2030年自然增长情景以及2030年粮食安全情景流域生境质量总得分和平均得分分别为866630,900357,921055,876231,865370和0.7457,0.7747,0.7925,0.7539,0.7466.2030年3种情景的中上游和下游地区生物多样性都呈现出不同程度的改善趋势,而中游地区则表现出退化趋势.     

Pt-Sn/Al2O3蜂窝催化剂催化氧化C6烃

采用等体积分浸法制备Pt-Sn/Al₂O₃蜂窝催化剂（Pt含量仅为0.06wt%）.运用X射线衍射（XRD）、透射电镜（TEM）等技术对催化剂理化性质进行表征,并选取4种代表性C₆烃（苯、环己酮、环己烷和正己烷）对催化剂性能进行评价.活性评价试验中,Pt/Sn比为3/1催化效果最佳.此时4种C₆烃转化率达到90%的温度（T₉₀）较Pt催化剂均降低约20℃,其原因在于Sn可将Pt分割为较小的团簇提高Pt分散度.寿命评价试验以环己烷为例同Pt-Sn蜂窝催化剂连续运行720h,催化活性无明显变化,其原因在于,Sn可有效抑制其粒径增长;Pt₃Sn合金降低表面对C₆烃的吸附,减少催化剂表面积炭.     

稻壳与聚氯乙烯共热解的特性及动力学

在热重分析仪中进行了稻壳和聚氯乙烯（PVC）的共热解实验,结果显示:在共热解时稻壳开始剧烈热解的温度相比单独热解时大幅度降低,由350℃降至300℃,表明掺入PVC降低了稻壳的热解温度。在升温速率为20℃/min,稻壳和PVC比例为2∶1（质量比）时,混合热解协同效应最明显。3种动力学分析方法均证明共热解现象的存在。利用Coats-Redfern法进行动力学分析,发现共热解活化能普遍较单独热解时低,表明PVC与稻壳共热解有明显的相互作用。利用Ozawa法进行分析,发现转化率为20%~60%阶段下共热解平均活化能值为37.60 kJ/mol,低于稻壳单独热解的平均活化能41.45 kJ/mol。Friedman法分析结果显示对应转化率下共热解活化能均低于稻壳单独热解活化能。稻壳和PVC共热解倾向于反应动力学控制。     

污泥生物炭去除水中重金属的研究进展

重金属带来的环境风险日益严峻,利用污泥生物炭去除水中重金属污染方面的研究得到了广泛关注。结合当前国内外研究现状,归纳了不同条件下制备的污泥生物炭对水中重金属,如Cd、Pb、Cr、As等的吸附机理,污泥生物炭对大多数重金属的吸附满足物理吸附和化学吸附的多重作用,可通过增加生物炭表面有效基团及有效吸附位点提升吸附性能。同时,总结了影响吸附效率的各种因素,探究了污泥生物炭的再生问题,并对今后污泥生物炭去除水中重金属的研究方向做出了展望。     

Effects of SO2 and H2O on low-temperature NO conversion over F-V2O5-WO3/TiO2 catalysts

F-V_2 O_5-WO3/Ti02 catalysts were prepared by the impregnation method.As the content of F ions increased from 0.00 to 0.35 wt.%,the NO conversion of F-V_2 O_5-WO_3/TiO_2 catalysts initially increased and then decreased.The 0.2 F-V_2 O_5-WO_3/TiO_2 catalyst(0.2 wt.% F ion)exhibited the best denitration(De-NOx) performance,with more than 95% NO conversion in the temperature range 160-360℃,and 99.0% N2 selectivity between 110 and 280℃.The addition of an appropriate amount of F ions eroded the surface morphology of the catalyst and reduced its grain size,thus enhancing the NO conversion at low temperature as well as the sulfur and water resistance of the V_2 O_5-WO3/Ti02 catalyst.After selective catalytic reduction(SCR) reaction in a gas flow containing SO_2 and H_2 O,the number of NH3 adsorption sites,active component content,specific surface area and pore volume decreased to different degrees.Ammonium sulfate species deposited on the catalyst surface,which blocked part of the active sites and reduced the NO conversion performance of the catalyst.On-line thermal regeneration could not completely recover the catalyst activity,although it prolonged the cumulative life of the catalyst.In addition,a mechanism for the effects of S02 and H_2 O on catalyst NO conversion was proposed.     

Dynamic nano-Ag colloids cytotoxicity to and accumulation by Escherichia coli: Effects of Fe3+, ionic strength and humic acid

Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials, and thus, the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag⁺ ratios. Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays, and shifts to both Ag particles and released Ag⁺ in 48 hr bioassays. Herein, as a continued study, the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically. The cytotoxicity and mechanisms of nano-Ag colloids are dynamic throughout exposure and are derived from both Ag ions and particles. Ag accumulation by E. coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure, and thereafter mainly from intracellular Ag ions. Fe³⁺ accelerates the oxidative dissolution of nano-Ag colloids, which results in decreasing amounts of Ag particles and particle-related toxicity. Na⁺ stabilizes nano-Ag colloids, thereby decreasing the bioavailability of Ag particles and particle-related toxicity. Humic acid (HA) binds Ag⁺ to form Ag⁺-HA, decreasing ion-related toxicity and binding to the E. coli surface, decreasing particle-related toxicity. HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na⁺ or Fe³⁺. The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors, and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.     

Metabolomic modulations in a freshwater microbial community exposed to the fungicide azoxystrobin

An effective broad-spectrum fungicide, azoxystrobin (AZ), has been widely detected in aquatic ecosystems, potentially affecting the growth of aquatic microorganisms. In the present study, the eukaryotic alga Monoraphidium sp. and the cyanobacterium Pseudanabaena sp. were exposed to AZ for 7 days. Our results showed that 0.2–0.5 mg/L concentrations of AZ slightly inhibited the growth of Monoraphidium sp. but stimulated Pseudanabaena sp. growth. Meanwhile, AZ treatment effectively increased the secretion of total organic carbon (TOC) in the culture media of the two species, and this phenomenon was also found in a freshwater microcosm experiment (containing the natural microbial community). We attempted to assess the effect of AZ on the function of aquatic microbial communities through metabolomic analysis and further explore the potential risks of this compound. The metabonomic profiles of the microcosm indicated that the most varied metabolites after AZ treatment were related to the citrate cycle (TCA), fatty acid biosynthesis and purine metabolism. We thereby inferred that the microbial community increased extracellular secretions by adjusting metabolic pathways, which might be a stress response to reduce AZ toxicity. Our results provide an important theoretical basis for further study of fungicide stress responses in aquatic microcosm microbial communities, as well as a good start for further explorations of AZ detoxification mechanisms, which will be valuable for the evaluation of AZ environmental risk.     

一株高效嗜碱反硝化菌的分离鉴定及其脱氮特性研究

为了应对日趋严苛的废水TN排放标准要求,试验采用溴百里酚蓝（BTB）培养基,从某煤化工废水处理厂反硝化缺氧池活性污泥中,经多次分离、纯化获得了一株高效兼性厌氧反硝化菌株HK13.通过形态观察及16S rRNA基因序列分析,菌株HK13被鉴定为施氏假单胞菌属（Pseudomonas stutzeri）.在此基础上,利用含硝酸盐模拟废水,探讨了碳源类型、C/N（碳氮比）、初始pH、溶解氧（以不同摇床转速表征不同浓度的溶解氧）和培养温度对菌株HK13反硝化脱氮能力的影响,确定了该菌株的最优生长条件和最大脱氮效率.结果表明:①菌株HK13最适反硝化脱氮条件为以柠檬酸钠碳源,C/N 8,培养温度35℃,初始pH 8~10,摇床转速100 r/min.②初始ρ（NO₃--N）为106.67 mg/L下,反应12 h后菌株HK13对TN的去除率可达92.62%;反应9~12 h时,该菌株的脱氮速率最高,可达20.03 mg/（L·h）,其16 h的脱氮率在98%以上,且无亚硝酸盐积累.③菌株HK13适宜生长的温度和pH范围广泛,分别为20~40℃和7~10.研究显示,菌株HK13具有快速高效的脱氮能力及嗜碱特性,拓宽了生物脱氮工艺对环境条件的适用范围,在废水脱氮领域具有广泛的应用前景.      

日本城市有机废弃物甲烷发酵资源化系统案例分析及最新研究进展

为建设可持续发展社会,日本近年来大力推动甲烷发酵以实现城市有机废弃物的减量化和资源化。首先介绍了日本城市有机废弃物资源化的2个实用案例,长冈市厨余垃圾沼气发电中心和丰桥市生物质资源利用中心的设计和运营状况。两者的长期稳定运行及产能效果验证了甲烷发酵技术在城市有机废弃物减量化和资源化上的可行性。其次,为了应对社会发展趋势和城市有机废弃物处理的技术需求,介绍了日本有关厨余垃圾、污泥以及废纸（城市有机废弃物的3大组分）的单独发酵及共发酵的部分研究成果。此外,简要介绍了应用厌氧膜生物反应器（AnMBR）进行相关高效甲烷发酵的最新研究成果。并根据实用案例调查和实验研究结果,以100万人口城市为例,对城市有机废弃物的各种甲烷发酵系统的产能效果进行了模拟概算。     

含油污泥处理技术进展

石油工业生产的特征固体废物——含油污泥,是一种由石油烃、水、固体颗粒物和其他物质（如重金属）组成的固态/半固态复合物,因毒性和易燃性被归入危险废物管理。我国含油污泥年产量高达500万t,其中含有15%~50%的石油烃。含油污泥的处理要兼顾无害化和资源化。基于其组成、性质和危害,介绍了含油污泥的油品资源化分离法（离心、溶剂萃取、热解）和无害化剩余含油残渣处理法（焚烧、固化、生物处理）等国内外常用的处理方法。大体上,含油污泥的处理思路为,首先预处理降低含水率、提高含油率,再经油品分离法回收含油污泥中的石油烃,最后无害化处理剩余含油残渣。讨论了各方法的特点以及国内外研究进展,提出了含油污泥处理技术的发展建议。