Competing pathways of cresol formation in toluene photooxidation: OH-toluene adducts react with NO2 or with O2?

Methyl-hydroxy-cyclohexadienyl radicals (OTAs) are the key products of the photooxidation of toluene, with implications for the fate of toluene. Hence, we investigated the photooxidation mechanisms and kinetics of three main OTAs (o-OTA, m-OTA, and p-OTA) with NO₂ using quantum chemical calculations as well as the fate of OTAs under the different concentration ratios of NO₂ and O₂. The mechanism results show that the pathway of H-abstraction by NO₂ to anti-HONO (anti-H-abstraction) is more favorable than the syn-H-abstraction pathway, because the strong interaction between OTAs and NO₂ is formed in the transition states of the anti-H-abstraction pathways. The branching ratios of the anti-H-abstraction pathways are more than 99% in the temperature range of 216−298 K. The total rate constant of the OTA-NO₂ reaction is 9.9 × 10⁻¹² cm³/(molecule∙sec) at 298 K, which is contributed about 90% by o-OTA + NO₂, and the main products are o-cresol and anti-HONO. The half-lives of the OTA-NO₂ reaction in some polluted areas of China are 35 times longer than those of the OTA-O₂ reaction. In the atmosphere, the NO₂- and O₂- initiated reactions of OTAs have the same ability to form cresols as [NO₂] is up to 142.1 ppmV, which is impossible to achieve. It implies that under the experimental condition, the [NO₂]/[O₂] should be controlled to be less than 7.8 × 10⁻⁵ to simulate real atmospheric oxidation of toluene. Our results reveal that for the photooxidation of toluene, the yield of cresol is not affected by the concentration of NO₂ under the atmospheric environment.     

Remediation of preservative ethylparaben in water using natural sphalerite: Kinetics and mechanisms

As a typical class of emerging organic contaminants(EOCs), the environmental transformation and abatement of preservative parabens have raised certain environmental concerns. However, the remediation of parabens-contaminated water using natural matrixes(such as, naturally abundant minerals) is not reported extensively in literature. In this study, the transformation kinetics and the mechanism of ethylparaben using natural sphalerite(NS) were investigated. The results show that around 63% of ethy...     

Formation of sulfur oxide groups by SO2 and their roles in mercury adsorption on carbon-based materials

The presence of SO₂ display significant effect on the mercury (Hg) adsorption ability of carbon-based sorbent. Yet the adsorption and oxidation of SO₂ on carbon with oxygen group, as well as the roles of different sulfur oxide groups in Hg adsorption have heretofore been unclear. The formation of sulfur oxide groups by SO₂ and their effects on Hg adsorption on carbon was detailed examined by the density functional theory. The results show that SO₂ can be oxidized into SO₃ by oxygen group on carbon surface. Both C-SO₂ and C-SO₃ can improve Hg adsorption on carbon site, while the promotive effect of C-SO₂ is stronger than C-SO₃. Electron density difference analyses reveal that sulfur oxide groups enhance the charge transfer ability of surface unsaturated carbon atom, thereby improving Hg adsorption. The experimental results confirm that surface active groups formed by SO₂ adsorption is more active for Hg adsorption than the groups generated by SO₃.     

典型工程纳米材料对微藻的毒性效应研究进展

近年来,随着纳米技术的快速发展,工程纳米材料由于其良好的物理化学特性而广泛应用于各行各业。然而,在生产、使用和丢弃含有工程纳米材料产品的过程中不可避免地导致纳米材料释放到水环境中。工程纳米材料已在世界多地的水环境中被检测到,给水生态系统和人体健康带来潜在风险。由于水环境的复杂性,工程纳米材料在水体中的环境行为、毒性效应等生态风险还未得到充分的研究。本文以微藻为模型生物,总结了典型工程纳米材料,包括纳米金属、纳米氧化物、碳纳米材料以及量子点的毒性效应。探讨了工程纳米材料在水中的环境行为以及与其它污染物的复合毒性效应,讨论了工程纳米材料自身理化性质和环境因素对其毒性的影响。从生理指标和组学指标出发分析了工程纳米材料对微藻的毒性机制,并展望了工程纳米材料毒性研究的发展方向,以期为工程纳米材料的毒性评价提供一定的理论依据,促进纳米材料的绿色发展。     

窄孔径含磷棉秆生物质炭的制备及对四环素的吸附机制

以棉秆为生物质原料,磷酸为改性剂,一步碳化制备了兼具高比表面积(1 916 m²·g^-1)和孔体积(1.398 2 mL·g^-1)的窄孔径含磷棉秆生物质炭(CSP),并研究了其对四环素(TC)的吸附行为.结果表明,磷酸改性制备的窄孔径含磷棉秆生物质炭对TC吸附量高达669mg·g^-1,是未改性棉秆炭的43.6倍;红外光谱(FTIR)、 X射线(XPS)和等温吸附研究表明,CSP对TC的高吸附量是表面络合、氢键、孔隙填充和π-π色散等多种吸附力共同作用的结果,其中磷酸改性赋予的高活性磷酸酯类基团(P—O—C)与TC分子间的化学络合作用强且贡献度高,是吸附量显著提升的最关键因素.静态等温吸附与热力学研究结果进一步证实TC在含磷棉秆炭吸附过程中化学吸附起主要作用,吸附过程属于自发的吸热过程.研究结果可为利用棉秆资源定向制备高效吸附TC的高活性磷掺杂生物质炭提供了一种潜在的简便高效途径.     

NaOH改性鱼骨粉材料对Cd(II)的吸附

以鱼骨粉（FBM）为原料,利用NaOH处理制备高性能改性鱼骨粉材料（FBM_T）,通过比表面积仪（BET）、X射线衍射仪（XRD）、傅里叶红外光谱（FTIR）、扫描电镜-光电子能谱（SEM-EDS）、透射电镜（TEM）等手段对吸附前后材料形貌、孔结构、功能基团进行表征分析.结果表明,与FBM相比,FBM_T出现一定数目中孔和大孔,具备了高孔容和平均孔径,分别增加68.57%和24.69%.FBM_T材料表面-OH、C=O和PO₄^3-等官能团含量增加,显示出一定的缓冲性能.FBM和FBM_T对Cd（Ⅱ）的吸附经历快速的分配和慢速的吸附两个阶段,符合准二级动力学模型,相关系数R²分别达到0.8635及0.9480.Langmuir模型较好地拟合FBM和FBM_T对Cd（Ⅱ）的等温吸附过程,对Cd（Ⅱ）饱和吸附量由改性前的9.28mg/g增至改性后的22.47mg/g,对应的吸附强度K_F值也随之增加.分离因子0 < R_L < 1表明Cd（Ⅱ）的去除过程为有利吸附.功能材料与Cd（Ⅱ）的作用机理主要包括阳离子专性吸附、静电吸附、离子交换、表面络合及沉淀作用.以上研究为鱼骨粉修复Cd污染提供一种经济有效的方法.     

白鲢罗非鱼对微囊藻毒素急性、亚急性毒性响应

为了探究不同控藻鱼类对产毒微囊藻的适应机制,为生物操纵的鱼种选择提供依据,研究了白鲢和罗非鱼对微囊藻毒素（MC）的生物富集、降解,及两种鱼对毒素的抗性、解毒机制的差异性.结果发现：在喂食微囊藻实验中,白鲢、罗非鱼对MC日摄入量达到10mg/kg,2种鱼均对MC有较强抗性.微囊藻经鱼摄入后,MC总含量在白鲢、罗非鱼粪便中分别下降到71.5%、6.0%,罗非鱼对MC降解能力远高于白鲢.白鲢和罗非鱼的肝系数分别从（1.19±0.21）%、（2.24±0.19）%下降到（0.79±0.06）%、（1.72±0.07）%,均表现出显著差异性下降（P<0.05）.微囊藻毒素在白鲢、罗非鱼肌肉中积累量分别为（1.57±0.31）μg/kg、（10.81±6.52）μg/kg （鲜重）、肝脏中积累量分别为（4.28±1.64）mg/kg、（2.48±0.15）mg/kg （鲜重）.MC在白鲢、罗非鱼肌肉、肝脏中的积累量均存在显著差异性（P<0.05）.罗非鱼肌肉中毒素含量是白鲢的6.9倍.在微囊藻毒素LR （MC-LR）对白鲢和罗非鱼的急性毒性效应实验中,MC-LR对白鲢、罗非鱼的LD₅₀为270和790μg/kg,罗非鱼对毒素有更强耐受性.喂食毒藻和i.p.注射MC均导致白鲢和罗非鱼肝细胞内脂滴大量出现.2种鱼在MC-LR注射后,谷胱甘肽（GSH）含量均表现出6h内明显下降.6h后两种鱼GSH含量均逐步回升,二者差异显著（p<0.05）.实验结果表明,罗非鱼对MC降解能力远高于白鲢.白鲢主要摄食群体微囊藻的群体胶鞘和附着细菌,胞内微囊藻毒素释放量小,白鲢这种摄食机制导致它能以产毒微囊藻为食而受到较轻危害.罗非鱼体内消化酶对微囊藻和MC具较强的消化降解能力;GSH含量及相关酶活性水平高,对体内毒素清除效率高.从食用安全性角度出发,与罗非鱼相比,白鲢是更适合用于控制蓝藻水华的鱼种,可广泛应用于蓝藻水华控制中.     

大气中有机硫酸酯研究进展

介绍了国内外大气环境中有机硫酸酯（OSs）的研究现状,分别简述了OSs的理化特征及影响因素、不同分析方法及对应特征、OSs的分类、来源及形成机制、OSs在大气中的转化及归趋等内容,并对目前常见的OSs分子式和结构式以及三种典型的形成机制进行了归纳总结.聚焦目前OSs研究的前沿领域,探讨了目前OSs研究中有待解决的热点问题,并对未来的研究工作提出建议与展望.     

Monitoring biofouling based on aerobic respiration in reverse osmosis system

A monitoring method of biofouling in reverse osmosis (RO) system was proposed based on the fluorescent signal of resorufin, which is reduced by nicotinamide adenine dinucleotide released from viable cells during aerobic respiration. The fluorescent signal of resorufin reduced by planktonic cells and microorganisms of biofilm showed linearity, indicating its feasibility to monitor biofouling in a RO system. For the application of the method to the lab-scale RO system, the injection concentration of resazurin and the injection flow rate were optimized. Biofilm on RO membranes continuously operated in a lab-scale RO system was estimated by resorufin fluorescence under optimized detection condition. As a result, resorufin fluorescence on RO membrane showed a significant increase in which the permeability of RO system decreased by 30.48%. Moreover, it represented the development of biofilm as much as conventional biofilm parameters such as adenosine triphosphate, extracellular polymeric substances, and biofilm thickness. The proposed method could be used as a sensitive and low-cost technology to monitor biofouling without autopsy of membranes.     

紫外活化过硫酸盐降解二苯甲酮-4的动力学影响及降解机理与风险评价

活化PS（过硫酸盐）氧化工艺对于降解水中新兴微污染物具有潜在应用价值.为研究活化PS体系对BPs（二苯甲酮类）有机防晒剂的降解性能,以BP4（二苯甲酮-4）为研究对象,采用UV/PS（紫外活化过硫酸盐）工艺降解BP4,比较单一UV、单一PS和UV/PS 3种工艺对BP4的去除效果,考察各因素对UV/PS工艺去除BP4动力学的影响,同时探究BP4降解机理并进行风险评价.结果表明:BP4降解过程符合准一级反应动力学模型;最佳PS投加量为1.0 mmol/L,反应30 min后BP4去除率可达94%,增加PS投加量或降低初始c（BP4）均可促进BP4降解,无机阴离子（HCO₃-和Cl-）对BP4降解均有抑制作用,酸性条件有利于BP4降解;基于HPLC-MS/MS鉴定出8种中间产物,并提出降解路径,费氏弧菌毒性试验和ECOSAR v1.10软件预测表明,UV/PS工艺降解BP4过程中生成的中间产物比母物质毒性更高.研究显示,UV/PS工艺可有效去除BP4,但其中间产物可能会造成潜在的生态风险,后续需进一步深入研究.