拉萨市环境空气中NO2变化特征分析

选取用长光程差分光谱法监测的拉萨市2000年7月-2004年6月环境空气质量监测数据,分析了NO₂变化特征.结果表明:目前拉萨市ρ(NO₂)在<环境空气质量标准>(GB3095-1996)一级标准之内,但呈逐渐上升趋势.拉萨市ρ(NO₂)月均值呈明显的"U"字型分布规律,即1月和年末10-12月高,其他时间低;每年10月至次年1月,ρ(NO₂)月均值超过年均值,月均最高值均出现在12月;每日在8:00-12:00,20:00-24:00有2个高峰值区.汽车尾气、当地居民生活中的燃烧过程是目前拉萨市NO₂的主要产生源,特殊边界层气象条件影响拉萨市环境空气中ρ(NO₂)的变化规律.      

Superior activity of iron–manganese supported on kaolin for NO abatement at low temperature

A series of Fe–Mn catalysts was prepared using different supports(kaolin, diatomite, and alumina) and used for NO abatement via low-temperature NH_3-selective catalytic reduction(SCR).The results showed that 12 Fe–10 Mn/Kaolin(with the concentration of Fe and Mn 12 and 10 wt.%, respectively) exhibited the highest activity, and more than 95.8% NO conversion could be obtained within the wide temperature range of 120–300℃.The properties of the catalysts were characterized by inductively coupled plasma-atomic emission spectrometry(ICP-AES), thermogravimetry(TG), Brunner–Emmet–Teller(BET)measurements, X-ray diffraction(XRD), H_2-temperature programmed reduction(H_2-TPR),NH_3-temperature programmed desorption(NH_3-TPD), X-ray photoelectron spectroscopy(XPS), scanning electron microprobe(SEM) and energy dispersive spectroscopy(EDS)techniques.The support effects resulted in significant differences in the components and structures of catalysts.The 12 Fe–10 Mn/Kaolin catalyst exhibited better dispersion of active species, optimum low-temperature reduction behavior, the largest amount of normalized Br?nsted acid sites, and the highest Mn~(4+)/Mn and Fe~(3+)/(Fe~(3+)+ Fe~(2+)), all of which may be major reasons for its superior catalytic activity.     

Oral administration of potassium bromate, a major water disinfection by-product, induces oxidative stress and impairs the antioxidant power of rat blood

Potassium bromate (KBrO₃) is a widely used food additive, a water disinfection by-product and a known nephrotoxic agent. The effect of KBrO₃ on rat blood, especially on the anti-oxidant defense system, was studied in this work. Animals were given a single oral dose of KBrO₃ (100 mg/kg body weight) and sacrificed 12, 24, 48, 96 and 168 h after this treatment. Blood was collected from the animals and separated into plasma and erythrocytes. KBrO₃ administration resulted in increased lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased the reduced glutathione content indicating the induction of oxidative stress in blood. Methemoglobin levels and methemoglobin reductase activity were significantly increased while the total anti-oxidant power was greatly reduced upon KBrO₃ treatment. Nitric oxide levels were enhanced while vitamin C concentration decreased in KBrO₃ treated animals. The activities of major anti-oxidant enzymes were also altered upon KBrO₃ treatment. The maximum changes in all these parameters were 48 h after the administration of KBrO₃ and then recovery took place. These results show for the first time that KBrO₃ induces oxidative stress in blood and impairs the anti-oxidant defense system. Thus impairment in the anti-oxidant power and alterations in the activities of major anti-oxidant enzymes may play an important role in mediating the toxic effects of KBrO₃ in the rat blood. The study of such biochemical events in blood will help elucidate the molecular mechanism of action of KBrO₃ and also for devising methods to overcome its toxic effects.     

负载型Mn-Ce／TiO2催化剂的制备及其低温脱硝活性

以成型TiO2作为载体,通过浸渍法制备了Mn-Ce／TiO2低温SCR催化剂,并系统研究了制备方法、煅烧条件、活性组分担载量、Mn含量等参数对催化剂催化还原NO性能的影响。结果表明,煅烧温度的升高会促使活性组分结晶度的提高,从而引起催化活性的降低,在500℃和600℃下所得Mn-Ce／TiO2催化剂活性组分为无定型态,表现出较高的脱硝活性。活性组分担载量的增加有利于催化活性的提高。Mn含量对Mn-Ce／TiO2催化剂的活性有较大影响,当Mn／（Mn＋Ce）摩尔比为40％和85％时,催化剂活性最高。     

焦化废水特征有机污染物反硝化降解速率特征分析

以焦化废水特征有机污染物苯酚、喹啉、吡啶和吲哚为碳源,研究了不同C/N(COD/NO3--N)比值进水条件下,反硝化过程中NO2--N积累特征及反硝化动力学特征.结果表明,进水C/N比在2.5~17的条件下,均会出现NO2--N积累的现象.当C/N比值为2.5时,NO2--N出现稳定积累.基于完全反硝化且COD去除率最高的进水条件为,进水C/N比为6.随着C/N比值从2.5增至17,达到NO2--N的最大积累量时间从140 min降至60 min,NO2--N的最大积累率从51.7%降至23.1%.相同进水C/N比条件下,在NO2--N积累阶段, NO3--N比还原速率大于NO2--N比还原速率,导致NO2--N积累;在NO2--N还原阶段, NO3--N比还原速率小于NO2--N比还原速率.不同进水C/N比条件下,在NO2--N积累阶段, NO2--N比积累速率基本不变,为0.072 g N/(g VSS·d)左右.不同进水C/N比值条件下,NO2--N积累阶段的表观碳氮比均大于NO2--N还原阶段的表观碳氮比.     

新型MnOx/CNTs催化剂低温选择性催化还原NO

采用等体积浸渍法制备了MnOx/CNTs催化剂,用于低温NH3选择性催化还原（SCR）NO的实验。使用BET,FT-IR,TEM和XRD对催化剂进行表征,结果表明：碳纳米管经混酸超声分散,增加了羧基活性基团,锰氧化物颗粒分布较均匀。在模拟烟气条件下,考察了催化剂的MnOx负载量、煅烧温度及质量和烟气流速比（W/F）对NO脱除率的影响。煅烧温度为773 K,MnOx负载量为10%时,NO脱除率达到98.56%;W/F为2-3 mg/（mL·min^-1）时NO的脱除率更高。     

中国华北地区冬季大气污染物航空测量(I)—空中气态污染物污染特征研究

为掌握致酸大气污染物SO₂和NO_x的空间浓度分布,并探讨上述污染物扩散、迁移和传输规律,进而研究其在酸性降水形成过程中的作用,在“八五”期间酸性降水的研究中,针对中国华北地区城市和工业集中以及S0₂和NO_x等酸性大气污染物排放量大的特点,以石家庄及其以东地区为飞行区域,进行了华北地区冬季空中S0₂和NO_x污染特征的航空测量。通过测定发现在华北地区1.5km左右的空中存在着S0₂和NO_x高浓度污染空域,同时S0₂存在着高浓度汇集区。      

FCC DeSOx and DeNOx additive technology

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中国上空民航飞机NO_x排放量及其分布初探

在中国范围内民航运输飞机及所配装的发动机的型号和有关设计工作参数等的基础上,借鉴目前国际上通行的方法,对飞机与发动机的运行过程进行简化和建模,并根据国际民航组织(ICAO)和美国航空航天管理局(NASA)等公布的航空发动机在海平面静态的排放数据,采用国际通用的油流量算法,对1997年中国上空民航飞机的氮氧化物(NOx)排放量进行了估算,并结合国内外有关数据进行了分析和比较.结果表明,中国各城市上空的大气污染程度有很大不同,大部分城市上空的大气目前已处于轻度污染,个别城市上空的大气污染程度已相当于欧美等发达国家1992年初的排放水平,其严重性亟待引起政府部门和有关专家的注意.