Photocatalytic removal of nitrogen oxides via titanium dioxide

We studied the removal of nitrogen oxides pollutants via TiO₂ Degussa P25 powder by photocatalysis. Parameters such as mass of catalyst, geometric irradiated surface, catalyst morphology, and thermal treatment were tested to explain the photocatalytic concentration decrease of nitrogen oxides. According to our working conditions, the conversion rates increased until an optimal value of the TiO₂ weight, 35% of NO concentration and around 20% of NOx, was decomposed by the photocatalysis. The NOx removal increased proportionally with the irradiated geometric surface. The structural transformation of anatase to rutile performed by thermal treatment involved the decrease of the photocatalytic activity.     

The ecotoxicology of titanium dioxide nanoparticles,an important engineering nanomaterial

Abstract

Titanium dioxide nanoparticles (nano-TiO₂) are useful because of their unique physicochemical properties. The wide application of nano-TiO₂ has raised concerns regarding its potential threat to organisms and the environment. Therefore, the production and application of nano-TiO₂ in the global market is summarized in this paper. This review presents the adverse effects of nano-TiO₂ in vivo, including potential exposure routes such as transdermal, oral and inhalative exposure, risk evaluation of nanotoxicity in vitro using bacteria, microorganisms, cells and biological molecules), physicochemical characterization of nano-TiO₂ regarding crystal structure, size, shape, surface characteristics and coatings, and the mechanisms of toxicity of nano-TiO₂ based on environmentally relevant test species and cells. This review aims to fill deficiencies in toxicological research and to facilitate the assessment of the environmental risks by nano-TiO₂ which is conducive to designing safer nanoproducts in our daily life.

• Highlights

• Presented the possible human health hazards related to nano-TiO2 exposure.

• Identified the current research deficiencies in this area.

• Summarized the underlying toxicity mechanisms.

• Summarized the compound toxicity of NPs.

     

太湖流域近地表大气二氧化碳本底体积分数观测研究

基于2003年1月至2005年6月用气相色谱法对太湖流域近地表大气中二氧化碳本底体积分数的监测资料,对太湖流域近地表大气二氧化碳体积分数的变化特征进行了分析研究。结果表明:在观测时段内,太湖流域近地表大气二氧化碳体积分数平均值为(413.7±19.2)×10-6,且呈上升的趋势,主要受人类活动、工农业生产和交通运输业发展的影响;二氧化碳体积分数季节变化明显,冬春季高,夏秋季低,冬季出现峰值,平均体积分数为(417.8±3.7)×10-6,夏季出现谷值,平均体积分数为(400.8±14.7)×10-6,一年中最高值(424.0±1.1)×10-6出现在12月份,最低值(387.7±1.4)×10-6出现在8月份,主要受源汇强度变化影响;二氧化碳体积分数日变化基本呈双峰态,这是源汇强度变化和边界层稳定程度相互作用的结果。     

广州市园林绿化植物苗木对二氧化硫和二氧化氮吸收能力分析

采用人工模拟熏气法,研究了36种广州市园林绿化植物对SO2和NO2气体吸收净化能力,以系统聚类分析方法为依据,将参试植物的吸收净化能力划分为强性、较强、中等、较弱及弱5个等级。结果显示,在不同SO2质量浓度（0.259和0.448 mg.m-3）环境下,黄槐、鸡冠刺桐、红花银桦、木棉、红千层、大花紫薇、复羽叶栾树吸收SO2能力具有强或较强的能力,而罗汉松、竹柏、深山含笑、乐昌含笑、观光木、樟树、阴香、双翼豆、印度紫檀、大花五桠果、长芒杜英、五月茶、海南蒲桃、芒果、海南红豆、糖胶树和幌伞枫吸收SO2能力表现为较弱或弱;在NO2质量浓度（0.149和0.428 mg.m-3）环境下,黄槐、黄葛榕、红花银桦、红千层、麻楝、复羽叶栾树、大花紫薇和小叶榄仁吸收净化NO2能力为较强或强,而深山含笑、五月茶、芒果、海南红豆、糖胶树和桂花叶片对NO2吸收能力表现为较弱或弱。在不同SO2和NO2浓度环境下,黄槐、红花银桦、红千层、复羽叶栾树和大花紫薇叶片对SO2和NO2吸收净化能力表现为强或较强,而深山含笑、五月茶、芒果、海南红豆、糖胶树叶片对SO2和NO2吸收净化能力为较弱或弱。研究结果为珠三角城市功能型园林植物选择和广东生态景观林带建设提供科学依据。     

Treatment,residual chlorine and season as factors affecting variability of trihalomethanes in small drinking water systems

Seasonal variability in source water can lead to challenges for drinking water providers related to operational optimization and process control in treatment facilities. The objective of this study is to investigate seasonal variability of water quality in municipal small water systems (<3000 residents) supplied by surface waters. Residual chlorine and trihalomethanes (THM) were measured over seven years (2003–2009). Comparisons are made within each system over time, as well as between systems according to the type of their treatment technologies. THM concentrations are generally higher in the summer and autumn. The seasonal variability was generally more pronounced in systems using chlorination plus additional treatment. Chloroform, total THM (TTHM) and residual chlorine concentrations were generally lower in systems using chlorination plus additional treatment. Conversely, brominated THM concentrations were higher in systems using additional treatment. Residual chlorine was highest in the winter and lowest in the spring and summer. Seasonal variations were most pronounced for residual chlorine in systems with additional treatment. There was generally poor correlation between THM concentrations and concentrations of residual chlorine. Further study with these data will be beneficial in finding determinants and indicators for both quantity and variability of disinfection byproducts and other water quality parameters.     

Cerium dioxide and composites for the removal of toxic metal ions

The presence of contaminants in potable water is a cause of worldwide concern. In particular, the presence of metals such as arsenic, lead, cadmium, mercury, chromium can affect human health. There is thus a need for advanced techniques of water decontamination. Adsorbents based on cerium dioxide (CeO₂), also named ‘ceria,’ have been used to remove contaminants such as arsenic, fluoride, lead and cadmium. Ceria and composites display high surface area, controlled porosity and morphology, and abundance of functional groups. They have already found usage in many applications including optical, semiconductor and catalysis. Exploiting their attractive features for water treatment would unravel their potential. We review the potential of ceria and its composites for the removal of toxic metal ions from aqueous medium. The article discusses toxic contaminants in water and their impact on human health; the synthesis and adsorptive behavior of ceria-based materials including the role of morphology and surface area on the adsorption capacity, best fit adsorption isotherms, kinetic models, possible mechanisms, regeneration of adsorbents; and future perspectives of using metal oxides such as ceria. The focus of the report is the generation of cost-effective oxides of rare-earth metal, cerium, in their standalone and composite forms for contaminant removal.     

Characterization of chlorine and heavy metals for the potential recycling of bottom ash from municipal solid waste incinerators as cement additives

Bottom ash is an inevitable by-product from municipal solid waste (MSW) incineration plants. Recycling it as additives for cement production is a promising disposal method. However, the heavy metals and chlorine are the main limiting factors because of the potential environmental risks and corrosion of cement kilns. Therefore, investigating heavy metal and chlorine characteristics of bottom ash is the significant prerequisite of its reuse in cement industries. In this study, a correlative analysis was conducted to evaluate the effect of the MSW components and collection mode on the heavy metal and chlorine characteristics in bottom ash. The chemical speciation of insoluble chlorine was also investigated by synchrotron X-ray diffraction analysis. The results showed that industrial waste was the main source of heavy metals, especially Cr and Pb, in bottom ash. The higher contents of plastics and kitchen waste lead to the higher chlorine level (0.6 wt.%–0.7 wt.%) of the bottom ash. The insoluble chlorine in the MSW incineration bottom ash existed primarily as AlOCl, which was produced under the high temperature (1250°C) in incinerators.

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腐殖质对二氧化锰引起的五氯酚转化反应的影响

研究了在二氧化锰催化引起的五氯酚的转化反应中,腐殖质前身化合物的加入对五氯酚去除率的影响,并以p-coumaricacid为代表研究了体系pH值、反应时间、二氧化锰的质量浓度以及腐殖质前生物的浓度和分子结构对去除率的影响。结果表明,反应的最佳pH值范围是4～4.70,去除率在80%左右。五氯酚在24h内去除速率较快,去除率达到75%左右;反应到168h,去除速率趋于0,去除率达到80%左右。相同条件下,无p-coumaricacid的对照体系中,对应的反应时间内去除率仅分别为20%和25%左右。五氯酚的去除率还随二氧化锰质量浓度和p-coumaricacid浓度的增加而增大。当二氧化锰的质量浓度由0增加到100g·L-1时,去除率由0增大为95%;而当p-coumaricacid的浓度由0增加到1mmol·L-1时,去除率由25%增大到100%左右。此外,不同腐殖质前身物的分子结构和浓度对去除率分别起到了提高、不明显改变和降低的作用。     

太湖春季水-气界面碳通量日变化观测研究

利用静态箱观测法对春季太湖不同生态类型(藻型、草型)的湖区春季水-气界面碳通量进行了昼夜连续观测,结果表明,水-气界面碳通量存在显著日变化规律,其极值均出现在凌晨5:00和下午2:00左右,但不同湖区碳通量的日变化存在明显差异。在富营养化较严重的梅梁湾湖区,昼间主要为大气CO2的汇,其平均碳通量为-7.74 mg/(m2h),夜间主要为大气CO2的源,其碳通量为5.32 mg/(m2h);湖心区域,夜间为大气CO2的源,日间在源和汇间波动。而在水质较好的东太湖区域,昼夜均为大气CO2的源,其平均碳通量为11.63 mg/(m2h)。     

Effect of the ultraviolet/chlorine process on microbial community structure,typical pathogens,and antibiotic resistance genes in reclaimed water

• UV/chlorine can effectively remove VBNC pathogens, ARGs and MGEs in reclaimed water. • Microbial community was changed with reduced diversity during UV/chlorine process. • CRBs-carried MGEswere the predominant groups during UV/chlorine process. • No direct co-selection strategy was shared between UV/chlorine and resistome. Urban wastewater contains a wide range of pathogens and antibiotic resistance genes (ARGs), which are a serious concern if reusing treated wastewater. However, few studies have explored the microbial communities in reclaimed water using ultraviolet (UV)/chlorine treatment and assessed the changes of the resistome. This study investigated the occurrence of typical pathogens, ARGs, and bacterial communities in UV/chlorine-treated reclaimed water samples. The numbers of culturable and viable but non-culturable pathogens were effectively reduced to 0 CFU/mL within 1–10 and 10–30 min after UV/chlorine treatment, respectively. Meanwhile, the physicochemical indices of water quality were not affected. UV/chlorine treatment could significantly change the bacterial community structure of reclaimed water, showing a decrease in bacterial abundance and diversity. Chlorine-resistant Acinetobacter and Mycobacterium were the dominant bacterial genera (>50%) after UV/chlorine treatment. Moreover, the number of ARGs and mobile genetic elements (MGEs) decreased with an increase in UV/chlorine exposure. However, eight ARGs and three MGEs were consistently detected in more than three seasons, making these major concerns because of their potential role in the persistence and dissemination of antibiotic resistance. Overall, the results of this study suggest that UV/chlorine treatment can potentially improve the microbiological safety of reclaimed water. And more attention should be paid to the pathogens that are both chlorine-resistant and carry MGEs because of their potential for resistance transmission.     

Effect of titanium dioxide nanoparticles on the expression of apoptotic markers in mouse blastocysts

Oocyte maturation, embryo development and expression of apoptotic-specific genes were evaluated in blastocysts of mice treated with titanium dioxide nanoparticles. Female mice received 0, 50 or 100?mg/kg/day titanium dioxide intraperitoneally for five consecutive days. After the last injection, pregnant mare serum gonadotropin and, 48?h later, human chorionic gonadotropin were administered intraperitoneally for induction of ovulation. After 14?h, mice were sacrificed and oocytes were collected. The number of mature oocytes was evaluated and then fertilization was carried out in vitro and the numbers of fertilized and cleaved oocytes and of blastocysts and the expression of Bax, caspase 3, and Bcl-xL genes in blastocysts were evaluated. The number of mature, fertilized and cleaved oocytes and of blastocyst embryos in the experimental groups were not different from control. The expression of Bax and caspase 3 genes was significantly elevated in the experimental groups compared to control, while expression of the Bcl-xL gene was significantly lower in the high dose group. Uptake of titanium dioxide nanoparticles at daily doses of 50?mg/kg and more may affect embryo development by alteration of pro-apoptotic and anti-apoptotic gene expression.     

中国八大湖泊冬季水-气界面CO2通量

采用静态箱-气相色谱法对中国不同地区八个湖泊(洞庭湖、鄱阳湖、巢湖、南四湖、洪泽湖、抚仙湖、洱海、滇池)冬季水体的水-气界面CO2通量进行了24h连续观测。结果表明:冬季洞庭湖、巢湖、洱海和滇池24h均为大气CO2的汇,其通量分别为-23.78、-16.08、-24.38、-17.94mg·m-2·h-1;鄱阳湖、南四湖水体则为大气CO2的源,其通量分别为35.76、27.64mg·m-2·h-1;洪泽湖和抚仙湖在晴天时为大气CO2的汇,夜间或阴天为大气CO2的源,但从24h的平均通量来看,洪泽湖为大气CO2的汇,通量为-26.56mg·m-2·h-1;抚仙湖为大气CO2的源,通量16.01mg·m-2·h-1。     

碘代X射线造影剂的环境浓度、分析方法与毒性评估研究进展

碘代X射线造影剂(ICMs)是使用最广泛的血管内药物,近年来在水生环境中频繁检出.由于其高稳定性、高极性和持久性,ICMs会在水生环境中持续存在并且难以被降解.在水生环境中会与消毒剂、天然有机物结合生成具有毒性的消毒副产物(DBPs),由于其本身毒性以及转化产物DBPs的毒性增强了环境健康风险,进而引发了人们的密切关注.本文介绍了ICMs的环境浓度、分析方法以及毒性风险.重点描述了ICMs的前处理技术、检测方法及ICMs毒性评价现状,并展望了以后ICMs毒性的研究方向.     

Effects of humic acid and surfactants on the aggregation kinetics of manganese dioxide colloids

The aggregation of common manganese dioxide (MnO₂) colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered (e.g. water treatment) and natural aquatic environments. Nevertheless, little is known about the aggregation kinetics of MnO₂ colloids and the effect of humic acid (HA) and surfactants on these. In this study, the early stage aggregation kinetics of MnO₂ nanoparticles in NaNO₃ and Ca(NO₃)₂ solutions in the presence of HA and surfactants (i.e., sodium dodecyl sulfate (SDS), and polyvinylpyrrolidone (PVP)) were modeled through time-resolved dynamic light scattering. In the presence of HA, MnO₂ colloids were significantly stabilized with a critical coagulation concentration (CCC) of ~300 mmol·L^-1 NaNO₃ and 4 mmol·L^-1 Ca(NO₃)₂. Electrophoretic mobility (EPM) measurements confirmed that steric hindrance may be primarily responsible for increasing colloidal stability in the presence of HA. Moreover, the molecular and/or chemical properties of HA might impact its stabilizing efficiency. In the case of PVP, only a slight increase of aggregation kinetics was observed, due to steric reactions originating from adsorbed layers of PVP on the MnO₂ surface. Consequently, higher CCC values were obtained in the presence of PVP. However, there was a negligible reduction in MnO₂ colloidal stability in the presence of 20 mg·L^-1SDS.     

Analysis of driving forces behind diversified carbon dioxide emission patterns in regions of the mainland of China

China has large regional disparities in carbon dioxide CO₂ emissions with economic development among its 31 provincial mainland regions. This paper investigates these disparities in CO₂ emission patterns and identifies the factors underlying the differences. Results show that the 30 study China's mainland provinces (Tibet not included) can be divided into seven groups with three typical CO₂ emission patterns. Index decomposition results indicate that changes in economic development, the industrial sector, and technology contribute far more to increased CO₂ emissions than do population, energy structure, and other sectors. Close inspection reveals that different industry structures and technology contribute greatly to the differences observed in CO₂ emissions between provinces with similar economic output. This study highlights the importance of region-specific industrial structure adjustment policies, especially for regions transitioning to heavy industry and for those still in the primary stages of industrialization. The potential application of a domestic carbon emissions trading system, to encourage regional investment in updated technology, is also discussed.     

Decomposition analysis of energy-related carbon dioxide emissions in the iron and steel industry in China

This work aims to identify the main factors influencing the energy-related carbon dioxide (CO₂) emissions from the iron and steel industry in China during the period of 1995–2007. The logarithmic mean divisia index (LMDI) technique was applied with period-wise analysis and time-series analysis. Changes in energyrelated CO₂ emissions were decomposed into four factors: emission factor effect, energy structure effect, energy consumption effect, and the steel production effect. The results show that steel production is the major factor responsible for the rise in CO₂ emissions during the sampling period; on the other hand the energy consumption is the largest contributor to the decrease in CO₂ emissions. To a lesser extent, the emission factor and energy structure effects have both negative and positive contributions to CO₂ emissions, respectively. Policy implications are provided regarding the reduction of CO₂ emissions from the iron and steel industry in China, such as controlling the overgrowth of steel production, improving energy-saving technologies, and introducing low-carbon energy sources into the iron and steel industry.     

蜂窝式MnO_x/PG-CC催化剂的制备及低温选择性催化还原法脱硝性能

采用悬浮浆液法将凹凸棒石(PG)涂覆于堇青石蜂窝陶瓷(CC)基体上,制取PG-CC涂层载体,利用过饱和浸渍法负载MnOx制备MnOx/PG-CC催化剂应用于柴油车尾气SCR脱硝.考察了制备条件对催化剂低温SCR活性的影响,采用BET、SEM-EDS、XRD手段对催化剂的理化性质进行了分析表征,探讨了催化剂结构特性与活性间的构效关系.研究发现,堇青石基体经PG涂层后,对活性组分的一次负载量显著增加,由3%增至13%,对应的催化剂低温脱硝活性显著提高,在100℃脱硝活性由10%提高到78%.结果分析表明,堇青石基体经PG涂层后比表面积大幅度增加,可以承载更高的活性组分,且活性组分具有更好的分散性,从而使得催化剂的活性点增加;另一方面,PG涂层催化剂具有更高的表面Mn4+/Mn3+价态比,更有利于催化剂的低温选择性催化还原法(SCR)活性.活性组分Mn Ox与PG涂层之间的协同作用是导致催化剂低温SCR脱硝活性得以提升的关键因素.研究结果表明,通过对堇青石蜂窝基体进行凹凸棒石涂层后采用浸渍法负载锰氧化物,可制备出具有较高低温SCR活性的蜂窝式模块催化剂.     

以膨润土为载体的碳酸盐吸收剂对二氧化碳的吸收

采用膨润土为载体,KHCO3为前驱物通过喷雾-干燥法制成固体碳酸钾吸收剂,制成的固体吸收剂粒径大小为0.5—2.0 mm,密度为1.73 g.mL-1.通过K2CO3负载量、吸收温度、吸收时间、床层纵横比等因素考察固体吸收剂对CO2气体的吸收效率及循环反应特性.分析碳酸钾吸收剂对CO2的吸收机理,并与以碳酸氢钠为前驱物制备的吸收剂进行对比,比较两种吸收剂对CO2吸收效果的差异性.通过XRD测试吸收剂吸收反应前后组成的变化,BET多点法测试吸收剂比表面积,扫描电镜观察吸收剂表面形态特征.结果表明,碳酸钾吸收剂和碳酸钠吸收剂对CO2气体均具有较高的吸收量,相比而言碳酸钾吸收剂的碳酸化反应速率较快,而且经过多次循环反应后吸收效果未发生衰减,在60℃—80℃范围内,碳酸钾吸收剂对CO2的吸收能力最佳.