大气光化学烟雾反应机理比较(Ⅰ)O3和NOx的比较

在相同初始和排放条件下,对四种应用较广的光化学烟雾反应机理(CB4-99,RADM2,RACM,SAPRC99)进行了比较。研究发现：对于O3,在低VOCs/NOx时,四种机理模拟结果相关较小,平均相对标准偏差为7%,在高VOCs/NOx时,平均相对标准偏差为26%,差距较大;对于NOx,多数情况下RACM和RADM2的模拟结果较高,CB4-99和SAPRC99的模拟值偏低,其原因主要来源于不同机理中O3的生成对NOx及VOCs的敏感性不同而造成的。在用模式模拟O3和NOx时,应特别注意机理不同而带来的模拟结果差异。     

易挥发有机化合物在Pt/Al_2O_3-Si纤维催化剂上的低温氧化

本文合成了一种新型的Pt负载在Al_2O_3涂膜强力富硅纤维载体的催化剂,研究低温下催化易挥发有机化合物的行为.用四种有机化合物检验实验参数对催化剂分解有机化合物分解率的影响.讨论了流速、浓度、有机物的本性、预热温度、反应热等参数的影响,并给出了催化剂对苯、甲苯在特定实验条件下的活化能、反应级数和指前因子的数值.     

Pd-K/MgAlO催化剂上的NOx存储、脱附和还原过程

利用程序升温脱附(TPD)、程序升温表面反应(TPSR)和原位红外光谱(in situ IR)等技术研究了Pd-K/MgAlO催化剂上的NOx存储、脱附和还原过程.结果表明,NOx在Pd-K/MgAlO上主要以硝酸根和亚硝酸根的形式存储.在Pd的催化作用下,部分亚硝酸根被氧化为强酸性的硝酸根,变得更容易存储.由NOx-TPD计算得到Pd-K/MgAlO的NOx存储容量高达890.4 μmol·g-1.此外,在NOx脱附及H2还原的实验中均发现了Pd催化的亚硝酸盐歧化分解反应,该反应通过亚硝酸盐溢流至Pd位实现.亚硝酸盐的溢流产生了两个作用:促进NOx低温脱附及促进H2对存储NOx的还原.此发现为NOx存储物种的溢流机理提供了一个有力的证据.     

武汉城区NOx污染特征及其变化趋势

武汉城区大气中NOx的污染,一日中以早晨最重,下午最轻;一年中,冬季的浓度比夏季高出37.7%.交通稠密区和商业集中区大气中的NOx年日均浓度分别比郊区高5倍和4.3倍.统计研究的结果表明,九年间特别是近六年来,武汉城区大气中NOx年日均值呈上升趋势.从1984年～1989年,大气中的NOx日均浓度平均每年以7%的速度递增,其超标率平均每年以0.8%的速度递增.     

Stochastic pollution, costly sanctions, and optimality of emission permit banking

This paper identifies a new economic motive for pollution regulations that allow polluting firms to bank and borrow emission permits over time. When aggregate pollution is stochastic, an intertemporal permit trading regime can provide firms with efficient incentives for pollution abatement without the need for costly government enforcement actions that would otherwise be required.     

Is atmospheric oxidation capacity better in indicating tropospheric O3 formation?

● This study summarizes and evaluates different approaches that indicate O₃ formation. ● Isopleth and sensitivity methods are useful but have many prerequisites. ● AOC is a better indicator of photochemical reactions leading to O₃ formation. Tropospheric ozone (O₃) concentration is increasing in China along with dramatic changes in precursor emissions and meteorological conditions, adversely affecting human health and ecosystems. O₃ is formed from the complex nonlinear photochemical reactions from nitrogen oxides (NO_x = NO + NO₂) and volatile organic compounds (VOCs). Although the mechanism of O₃ formation is rather clear, describing and analyzing its changes and formation potential at fine spatial and temporal resolution is still a challenge today. In this study, we briefly summarized and evaluated different approaches that indicate O₃ formation regimes. We identify that atmospheric oxidation capacity (AOC) is a better indicator of photochemical reactions leading to the formation of O₃ and other secondary pollutants. Results show that AOC has a prominent positive relationship to O₃ in the major city clusters in China, with a goodness of fit (R²) up to 0.6. This outcome provides a novel perspective in characterizing O₃ formation and has significant implications for formulating control strategies of secondary pollutants.     

液相催化加氢法去除Cr(Ⅵ)

采用浸渍法合成出Pd/Al2O3催化剂,通过ICP、XRD、TEM和Zeta电位等表征手段对催化剂的组成和形貌进行了表征.在液相催化加氢还原Cr(Ⅵ)的反应中,分别研究了催化剂加入量、Cr(Ⅵ)初始浓度、pH值、Pd负载量等因素的影响.结果表明,该催化剂表面酸性影响催化还原效果,此反应属于吸附抑制型.     

芜湖市臭氧污染特征与影响因素分析

为了解芜湖市O₃污染变化特征及与主要影响因子相关性,本文对芜湖市环境监测站点和基本气象站点的监测数据进行统计分析。结果表明,芜湖市O₃污染程度呈现西南向东北逐步加重的趋势,科创中心、济民医院和四水厂站点月度变化呈现双峰分布的特征,峰值出现在4月和6月,而监测站则是显著单峰型,峰值出现在6月。各站点O₃日变化均呈现显著的“单峰单谷”型,在15:00前后达到峰值。在NO₂/NO比值区间为10—20时,夜间更易出现高浓度O₃,而昼间O₃浓度高值更易出现在比值低于10时。PM_2.5和O₃间的相关性更趋向于非线性关系。温度和相对湿度对O₃的影响分别呈现正相关和负相关,O₃峰值易出现在温度为25—35 ℃、相对湿度为60%—80%的气象条件下。在东-东南风向下,O₃的超标天最多。     

废水生物脱氮中N2O和NOx的产生和作用

废水生物脱氮中N2O和NOx来源于硝化、反硝化、厌氧氨氧化和化学反硝化等过程．电子受体和供体浓度、pH、缓冲剂类型、有机负荷、微生物种类及其相互作用等都会影响这些气态中间产物的产生．NO2能够氧化氨和强化好氧和厌氧氨氧化，NO能够阻止C2H2对好氧氨氧化活性的抑制，两者对好氧氨氧化活性的恢复至关重要．所有这些表明，废水生物脱氮的气态中问产物N2O和NOx在氮的生物转化中具有重要的正面作用，甚至必不可少．基于NO2曝气技术和Brocadia anammoxidans与Nitrosomonas协同作用的废水生物脱氮新技术开发是今后一段时间的重要研究方向．图4参35     

英国污染减排的经验与启示

论述了英国实现污染物减排环境治理方面的成功经验和做法,其主要有健全完善的法规政策体系,强化运用环境经济手段,建立节能减排的长效机制,建立科学、成熟的战略环评体系(SEA),用最佳可行技术(BAT)防止和减少污染排放,注重公众参与促进全民减排。依据英国实现污染物减排环境治理方面的成功经验和做法,结合目前我国污染物减排工作的实际,对我国污染物减排工作提出了相应的对策与建议。     

Denitrification potential in a Louisiana wetland receiving diverted Mississippi River water

Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO₃^- was determined in sediment-water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO₃^- removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m^-2 d^-1 over 16 d for a 1750-mg NO₃-N m^-2 addition, and 170 mg N m^-2 d^-1 over 16 d for a 3500-mg NO₃-N m^-2 addition. The total N₂O-N emissions from the 1750- and 3500-mg NO₃-N m^-2 additions were 19 and 54 mg N m^-2 accounting for 1.1% and 1.5% of the applied NO₃-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m^-2 d^-1 (21 and 32 g N m^-2 yr^-1) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO₃^--N m^-2 of added nitrate in floodwater, respectively. The total N evolved over 11 d as N₂O + N₂ was equivalent to 436 and 921 mg N m^-2 (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO₃^- applied to the overlying water increased the rate of NO₃^- loss and N₂O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO₃^- application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO₃^- in the river water, reducing the amount of NO₃^- reaching to offshore areas.     

Analysis of the trade-off between economic growth and the reduction of nitrogen and phosphorus emissions in the Poyang Lake Watershed, China

Lake eutrophication leading to water pollution is a major global concern. In recent years, rapid economic growth and the increase in the intensity of resource exploitation in China have caused the influx of nitrogen and phosphorus into lakes. This in turn has led to more severe lake eutrophication, more frequent outbreaks of algal blooms, and the degradation of lake ecosystems. An effective plan balancing economic growth with the reduction of nitrogen and phosphorus emissions is greatly needed. The design and implementation of such a plan requires the collection and analysis of pertinent data. In this paper, we use the environmental computable general equilibrium (ECGE) model to identify the most effective way to balance economic growth with the reduction of nitrogen and phosphorus emissions. For the multiregional analysis, we use social accounting matrices (SAMs) and a provincial trade matrix based on the assumptions of the gravity model. We consider the Poyang Lake Watershed as a case study to illustrate the utility of the model. Based on present conditions in the Poyang Lake Watershed, restricting nitrogen and phosphorus emissions from sectors with the highest emissions is more effective for balancing economic growth and the reduction of nitrogen and phosphorus emissions than restricting nitrogen and phosphorus emissions from all sectors.     

Modelling assessment of PM10 exposure control policies in Northern Italy

To assess the impact of three different emission reduction scenarios on PM10 concentrations in Northern Italy, the TCAM multiphase model has been applied in the framework of the CityDelta III-CAFE EU project. The considered domain, that is characterized by high urban and industrial emissions and a dense road traffic, due to frequently stagnating meteorological conditions is often affected by severe PM10 levels, far from the European standard regulations. The impact evaluation has been performed in terms of both yearly mean values and 50 g/m³ exceedance days for the 2004 Base Case simulation. The results show that the three selected emission reduction scenarios up to 2020 improve air quality all over the domain, in particular, in the area with higher emission density.