外源8''-炔基脱落酸强化东南景天吸收重金属的研究

为探究脱落酸类似物8''-炔基脱落酸[8''-（C₂H）ABA]强化东南景天富集重金属的效应,通过水培的方法研究了外源8''-（C₂H）ABA分别对Cd（20 mg·L^-1）、Zn（160 mg·L^-1）单一胁迫下东南景天Cd/Zn积累和生理特性的影响,以及初步探讨了8''-（C₂H）ABA在植物重金属胁迫响应中的作用.实验结果表明：与天然ABA相比,外源8''-（C₂H）ABA能达到与ABA类似的作用效果,且对Cd胁迫下东南景天促进效果好于Zn;在Cd胁迫下,与对照相比,外源8''-（C₂H）ABA能显著增加东南景天根、叶中的Cd含量（44.2%、27.5%）,以及光合色素（10.7%）和叶中过氧化物酶（SOD）活性（52.9%）、超氧化物歧化酶（POD）（24.7%）和过氧化氢酶（CAT）活性（27.9%）抗氧化酶活性,使可溶性糖（SS）（13%）和游离脯氨酸（Pro）（37.4%）含量增加,而叶中丙二醛（MDA）（40%）含量明显降低.上述结果表明,一定浓度的8''-（C₂H）ABA可以提高东南景天抗氧化酶活性来增强其对重金属Cd的抗性及吸收和转运能力,在强化东南景天修复重金属污染方面具有应用潜力.     

粤港澳大湾区NO2污染的时空特征及影响因素分析

利用Aura卫星搭载的臭氧观测仪（OMI）反演的对流层NO₂柱密度数据,分析了自2005年以来粤港澳大湾区（GBA）对流层NO₂柱密度的空间分布特征、时间变化趋势及其影响因素.研究结果表明GBA对流层NO₂柱密度从2005~2018年呈减少的趋势,每年递减约为2.8%.小波系数显示时间演化过程中存在9个月的主振荡周期,冬季浓度较高,夏季较低.人为排放和各种自然因素,导致了GBA对流层NO₂柱浓度月变化在时间和空间上存在明显差异,最小值和最大值分别出现在6和12月,多年平均值分别为3.9665×10¹⁵和12.3423×10¹⁵molec/cm².NO₂在空间分布上呈现明显的空间分异特征,冬季12月最明显.NO₂污染严重的高值区主要出现在中部地区,如广州市、佛山市和中山市,最大的对流层NO₂柱密度可达18.8306×10¹⁵molec/cm²,大约是周边地区的3 倍,且高污染区域向四周逐渐扩散,连成一片.低值区主要在北部的肇庆市和东部的惠州市,多年平均的对流层NO₂柱密度约为7.1400×10¹⁵molec/cm².对流层NO₂柱密度的增长率在不同区域的变化趋势呈现明显的差异,变化范围为-15×10¹⁵~6×10¹⁵molec/cm²,增长率百分比范围为-65%~65%.出现增长的地区主要是肇庆市北部和惠州市东部的低值区;对流层NO₂出现明显减少的区域集中在中部的高值区,减少量最大的地区为广州市、佛山市和中山市交界处.     

电场与MnxCey催化剂在苯氧化反应中的协同效应及机理探究

挥发性有机物（VOCs）大量排放已成为日益严重的环境问题,为了实现VOCs的高效去除,本文采用自蔓延燃烧合成法制备了一系列锰铈复合氧化物催化剂,将稳恒直流电场引入典型VOCs气体苯的催化氧化过程,并基于不同电场条件下催化剂的理化性质表征结果进行机理分析.实验结果表明,Mn_xCe_y催化剂对含苯废气的去除有良好的效果,稳恒直流电场显著促进了催化剂的活性,其中Mn₁Ce₃的催化性能最佳,电流为5 mA时,Mn₁Ce₃催化剂在155℃可达到50%的苯转化率,在202.4℃可达到90%的苯转化率,对应的转化温度T₅₀和T₉₀比传统方法分别降低了62.4℃和48.3℃,且电场中的反应活化能由52.32 kJ·mol^-1降低至32.31 kJ·mol^-1.根据实验现象及表征结果,发现协同效应与活性位点的快速持续再生及活性氧物种的转化有关,由此提出苯在Mn_xCe_y催化剂上的氧化机理及电场协同催化的反应模型.     

核壳结构KNbO3@Co(OH)2的制备及其活化过一硫酸盐降解帕珠沙星的研究

制备了以KNbO₃为载体材料的Co（OH）₂复合材料并对其进行了详细的表征,分析了材料的组成成分、组成形态进而确定了其为核壳结构形貌的KNbO₃@Co（OH）₂.利用合成的样品作为催化剂活化过一硫酸盐（peroxymonosulfate,PMS）来降解帕珠沙星（pazufloxacin,PZF）,结果表明制备的催化剂对PZF的去除效率显著增加.讨论了不同初始PMS剂量对降解效率的影响,发现随着PMS增加可活化生成更多的硫酸根自由基（sulfate radicals,SO₄^·-）和羟基自由基（hydroxyl radicals,HO^·）来降解PZF,但继续增大PMS用量降解效率未见明显提升.酸性和中性pH值条件下利于反应活化PMS降解PZF,而碱性体系减缓反应,甚至强碱体系更易形成Co（OH）₂沉淀不利于反应体系中活性组分CoOH⁺的形成,大大抑制了催化性能.此外,在体系中加入淬灭剂叔丁醇（tert-Butanol,TBA）或者乙醇（ethanol,ETOH）进行自由基的淬灭实验,结果表明SO₄^·-自由基为体系降解PZF过程中主要贡献的自由基,而HO^·自由基的贡献较少.催化剂具有较好的稳定性5次循环之后仍能在10 min之内完全去除PZF.本研究提出了新的思路为制备其他载体的Co（OH）₂核壳结构提供参考依据,同时将该催化剂结合高级氧化技术应用到水体新兴有机污染物净化领域具有很好的应用前景.     

Fas/FasL途径在氟暴露致PC12细胞凋亡中的作用

为了探讨Fas/FasL途径在氟暴露致PC12细胞凋亡中的作用及其机制,采用含20、40、80、160mg/L NaF培养液处理PC12细胞.结果表明,所有剂量NaF处理12、24、36、48h,PC12细胞活性升高;上述不同剂量NaF处理24h后,与对照组比,PC12细胞的活性氧水平、细胞凋亡率、细胞内Fas/FasL信号转导通路Fas和FasL、Caspase8、FADD、Caspase3基因和蛋白表达水平均呈显著上升（P < 0.05）,而Bid基因和蛋白表达水平显著下降（P < 0.05）,且呈氟暴露剂量依赖性.结果提示Fas/FasL途径在氟暴露致PC12细胞凋亡中起重要作用,其中FADD可能是Fas/FasL凋亡途径中的重要靶分子.     

Density functional theory (DFT) studies of vanadium-titanium based selective catalytic reduction (SCR) catalysts

Based on density functional theory (DFT) and basic structure models, the chemical reactions on the surface of vanadium-titanium based selective catalytic reduction (SCR) denitrification catalysts were summarized. Reasonable structural models (non-periodic and periodic structural models) are the basis of density functional calculations. A periodic structure model was more appropriate to represent the catalyst surface, and its theoretical calculation results were more comparable with the experimental results than a non-periodic model. It is generally believed that the SCR mechanism where NH₃ and NO react to produce N₂ and H₂O follows an Eley-Rideal type mechanism. NH₂NO was found to be an important intermediate in the SCR reaction, with multiple production routes. Simultaneously, the effects of H₂O, SO₂ and metal on SCR catalysts were also summarized.     

Preparation of solar-enhanced AlZnO@carbon nano-substrates for remediation of textile wastewaters

Photoactive aluminum doped ZnO(AlZnO) was synthesized by sol-gel method.After that,AlZnO photocatalyst was deposited on five carbon-based materials(CBMs) using ultrasonic route followed by solid-state mixing using ball mill.The CBMs used were poly aniline(PANI),carbon nitride(CN),carbon nanotubes(CNT),graphene(G),and carbon nanofibers(CNF).The crystal phases,elemental compositions,morphological,and optical properties of the AlZnO@CBMs composites were investigated.Experimental results revealed that two of AlZnO@CBMs composites exhibited superior bleaching efficiency(100% removal) and photocatalytic stability(three cycles) for 50 μmol/L Methylene Blue(MB) contaminated water after 60 min irradiation in visible light at pH 6.5,0.7% H_2O_2,and 5 g/L inorganic salts.Under optimum conditions,AlZnO@CBMs nanocomposites were employed for the treatment of mixed dyestuffs composed of MB,Methyl Orange(MO),Astrazone Blue FRR(BB 69),and Rhodamine B(RhB) dyes under dark,ultraviolet,visible,and direct sunlight.For mixed dyestuffs,the AlZnO@G achieved the highest dye sorption capacity(60.91 μmol dye stuffs/g) with kinetic rate 8.22 × 10~(-3) min~(-1) in 90 min via multi-layer physisorption(Freundlich isotherm) on graphene sheet.In additions,AlZnO@CN offered the highest photo-kinetic rate(K_(photo)) of～54.1 × 10~(-3) min~(-1)(93.8% after 60 min) under direct sunlight.Furthermore,the selective radical trapping experiment confirmed that the holes and oxidative superoxide radicals are crucial on dyes photodegradation pathway.Owing to their superior performance,AlZnO@G and AlZnO@CN nanocomposites can offer an effective in-situ solar-assisted adsorption/photocatalytic remediation of textile wastewater effluents.     

Plasmonic silver/silver oxide nanoparticles anchored bismuth vanadate as a novel visible-light ternary photocatalyst for degrading pharmaceutical micropollutants

The degradation of pharmaceutical micropollutants is an intensifying environmental problem and synthesis of efficient photocatalysts for this purpose is one of the foremost challenges worldwide. Therefore, this study was conducted to develop novel plasmonic Ag/Ag₂O/BiVO₄ nanocomposite photocatalysts by simple precipitation and thermal decomposition methods, which could exhibit higher photocatalytic activity for mineralized pharmaceutical micropollutants. Among the different treatments, the best performance was observed for the Ag/Ag₂O/BiVO₄ nanocomposites (5 wt.%; 10 min's visible light irradiation) which exhibited 6.57 times higher photodegradation rate than the pure BiVO₄. Further, the effects of different influencing factors on the photodegradation system of tetracycline hydrochloride (TC-HCl) were investigated and the feasibility for its practical application was explored through the specific light sources, water source and cycle experiments. The mechanistic study demonstrated that the photogenerated holes (h⁺), superoxide radicals (?O₂^?) and hydroxyl radicals (?OH) participated in TC-HCl removal process, which is different from the pure BiVO₄ reaction system. Hence, the present work can provide a new approach for the formation of novel plasmonic photocatalysts with high photoactivity and can act as effective practical application for environmental remediation.     

Effects of calcination temperature on physicochemical property and activity of CuSO4/TiO2 ammonia-selective catalytic reduction catalysts

CuSO_4/TiO_2 catalysts with high catalytic activity and excellent resistant to SO_2 and H_2 O,were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH_3.The performance of catalysts is largely affected by calcination temperature.Here,effects of calcination temperature on physicochemical property and catalytic activity of CuSO_4/TiO_2 catalysts were investigated in depth.Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N2 adsorption-desorption,X-ray diffraction,thermogravimetric analysis,Raman spectra,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,temperature-pro grammed desorption of NH_3,temperature-programmed reduction of H_2 and in situ diffuse reflectance infrared Fourier transform spectroscopy.Results revealed that high calcination temperature had three main effects on the catalyst.First,sintering and anatase transform into rutile with increase of calcination temperature,causing a decrement of specific surface area.Second,decomposition of CuSO_4 under higher calcination temperature,resulting in disappears of Br(?)nsted acid sites(S-OH),which had an adverse effect on surface acidity.Third,CuO from the decomposition of CuSO_4 changed surface reducibility of the catalyst and favored the process of NH_3 oxidation to nitrogen oxides(NO_x).Thus,catalytic activity of the catalyst calcined under high temperatures(≥600℃) decreased largely.     

UV/H2O2 oxidation of tri(2-chloroethyl) phosphate: Intermediate products, degradation pathway and toxicity evaluation

Tri(2-chloroethyl) phosphate (TCEP) with the initial concentration of 5 mg/L was degraded by UV/H₂O₂ oxidation process. The removal rate of TCEP in the UV/H₂O₂ system was 89.1% with the production of Cl^? and PO₄^3? of 0.23 and 0.64 mg/L. The removal rate of total organic carbon of the reaction was 48.8% and the pH reached 3.3 after the reaction. The oxidative degradation process of TCEP in the UV/H₂O₂ system obeyed the first order kinetic reaction with the apparent rate constant of 0.0025 min^?1 (R²=0.9788). The intermediate products were isolated and identified by gas chromatography-mass spectrometer. The addition reaction of HO? and H₂O and the oxidation reaction with H₂O₂ were found during the degradation pathway of 5 mg/L TCEP in the UV/H₂O₂ system. For the first time, environment risk was estimated via the “ecological structure activity relationships” program and acute and chronic toxicity changes of intermediate products were pointed out. The luminescence inhibition rate of photobacterium was used to evaluate the acute toxicity of intermediate products. The results showed that the toxicity of the intermediate products increased with the increase of reaction time, which may be due to the production of chlorine compounds. Some measures should be introduced to the UV/H₂O₂ system to remove the highly toxic Cl-containing compounds, such as a nanofiltration or reverse osmosis unit.