Seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi

We present the diurnal and seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi, India. Ambient NH3, NO and NO2 were measured continuously during winter, summer and autumn seasons using NH3- and NOx-analyzer, which operates by chemiluminescence method with a higher estimation e ciency (> 90%) than the chemical trap method (reproducibility 4.7%). Prominent diurnal, day-to-day and seasonal variations of ambient mixing ratio of NH3, NO, NO2 and SO2 were observed during the study period. Seasonal variation with higher mixing ratio in winter was observed for all measured trace gases except NO. Day-night variation of all measured trace gases observed was higher in winter in comparison with summer. Late morning increase in NO2 mixing ratio might be attributed to conversion of NO to NO2 with the interaction of O3.     

扩散法测定沈阳市环境空气中的二氧化氮

被动式个体采样器（passive personal sampler）是基于气体分子扩散或渗透原理,采集空气中气态或蒸汽态污染物的一种采样方法,它不使用任何电源和抽气动力,是一种无泵采样器,可连续采样,并可作为环境空气质量评价的监测。国内外开展室内被动式扩散采样器的研究和应用的文章很多,并逐步应用于室内环境空气的监测方面,特别是对人体健康的影响评价。但是,在使用中要特别注意风速对气体污染物的采样速率的影响,为此文章介绍了利用中国预防医学科学院环境卫生监测所研制的室内分子扩散采样器[1],并自制挡风筒,使分子扩散采样器暴露在一个恒定的风速环境中,排除风速对采样速率的影响,应用于室外环境监测沈阳市环境空气中的二氧化氮的方法。经实验室性能评价能够满足实验室测试的要求,并经有动力的溶液吸收管法现场对比测试,两种测试结果一致。为室外环境监测二氧化氮提供了一个经济、准确,有实用价值的采样方法。     

Simultaneous removal of NO and SO2 from dry gas stream using non-thermal plasma

In order to investigate the feasibility of sequential removal NO and SO_2 using non-thermal plasma and adsorbent simultaneously,the removal of NO and SO_2 from dry gas stream(NO/SO_2/N_2/O_2)with very little O_2 using non-thermal plasma was investigated using a coaxial dielectric barrier discharge.Comparative experiments were carried out in the dry gas stream with and without Ar respectively at O_2 concentration of 0.1%.The results showed that NO could be removed remarkably and it would be enhanced in the presence of Ar in the dry gas stream.It seems that SO_2 could not be removed unless there is Ar in the dry gas stream.The mechanism of removal of NO and SO_2 in the dry gas stream was discussed.     

砍伐干扰对华北落叶松林下土壤有效氮含量空间异质性的影响

为揭示砍伐干扰对森林土壤有效氮(NO3--N和NH4+-N)含量空间异质性的影响,并为进一步认识森林生态系统N素循环及森林系统结构和功能提供基础依据.选取华北落叶松砍伐干扰林分(样地A)和未砍伐干扰林分(样地B),采用基于地统计学中区域化变量理论的格局分析方法.对样地林下土壤(0～30cm)有效氮含量的空间异质性特征进...     

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.     

Role of NO in Hg oxidation over a commercial selective catalytic reduction catalyst V2O5–WO3/TiO2

Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst, V₂O₅–WO₃/TiO₂, to investigate mercury oxidation in the presence of NO and O₂. Mercury oxidation was improved by NO, and the efficiency was increased by simultaneously adding NO and O₂. With NO and O₂ pretreatment at 350°C, the catalyst exhibited higher catalytic activity for Hg⁰ oxidation, whereas NO pretreatment did not exert a noticeable effect. Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O₂. Although NO promoted Hg⁰ oxidation at the very beginning, excessive NO counteracted this effect. The results show that NO plays different roles in Hg⁰ oxidation; NO in the gaseous phase may directly react with the adsorbed Hg⁰, but excessive NO hinders Hg⁰ adsorption. The adsorbed NO was converted into active nitrogen species (e.g., NO₂) with oxygen, which facilitated the adsorption and oxidation of Hg⁰. Hg⁰ was oxidized by NO mainly by the Eley–Rideal mechanism. The Hg⁰ temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O₂.     

长江三角洲2018年土壤NO排放特征

土壤是大气一氧化氮（NO）重要的来源之一,在大气化学中起着重要的作用.基于最新的BDSNP算法构建长三角地区2018年土壤NO排放清单,并进一步分析其时空特征和不确定性.结果表明,长三角地区2018年土壤NO排放量为213.6 kt,占人为源NO_x排放总量的7.3%,排放高值区主要集中在安徽省北部和江苏省大部分地区.从月变化来看,土壤NO排放在6月达到峰值,占全年排放的19.9%,占6月人为源NO_x排放量的19.7%;从小时变化来看,土壤NO排放在16:00点达到峰值,占全天的5.5%.土壤NO排放包括土壤本底、氮肥施用和氮沉降这3个部分;氮肥施用是土壤NO排放的主要来源,占比高达77.8%.随着机动车和工业等NO_x排放的深入减排,土壤NO排放的重要性将日益凸显.     

中国旱作农田一氧化氮排放及减排:Meta分析

农田是大气污染物一氧化氮（NO）的主要排放源之一.与水稻田相比,旱作农田NO排放量和排放系数高,但其异质性及影响因素尚不明确.目前,我国农田NO排放和减排的研究以原位观测为主,缺乏系统的整合（Meta）分析.通过收集文献数据,定量分析玉米-冬小麦、水稻-冬小麦旱地阶段、蔬菜、茶园和果园等旱作体系NO排放量和排放系数的异质性及主要影响因素;定量评价减量施氮、有机肥替代化肥、配施新型增效氮肥和施用生物质炭等管理措施对NO排放量和排放系数的影响.收集相关文献共计49篇（发表于2006~2021年）.结果表明,玉麦轮作、茶园和果园体系年排放量平均值分别为1.44、7.45和0.92 kg ·hm^-2,在这3个体系间有显著性差异（P<0.05）,稻麦轮作旱地阶段和蔬菜季节排放量平均值分别为2.13 kg ·hm^-2和2.09 kg ·hm^-2.在玉麦轮作、稻麦轮作旱地阶段和茶园体系中,NO排放量均与施氮量呈正相关关系（P<0.01）,但在蔬菜和果园体系中二者无显著相关性.玉麦轮作、稻麦轮作旱地阶段、蔬菜、茶园和果园体系排放系数平均值分别为0.31%、0.71%、0.96%、1.74%和0.13%,除玉麦轮作分别与稻麦轮作旱地阶段和蔬菜体系间的差异不显著外（P>0.05）,在其余体系间均有显著性差异（P<0.01）.由于各体系间排放系数差异大,在编制区域或全国农田NO排放清单时,有必要对各作物体系采用不同的排放系数.减量施氮仅在减氮比例高于25%时可显著降低NO排放量（36%）,但对排放系数的影响不显著.由于减氮比例过高可能会造成作物减产,尚需进一步确定既不影响作物产量又降低NO排放的减氮比例.有机肥替代化肥在土壤有机碳含量低［ω（SOC）<15 g ·kg^-1］或酸性（pH<7）条件下以及配施新型增效氮肥在玉麦轮作农田中可显著降低NO排放量（-46%~-38%）和排放系数（-62%~-45%）,施用生物质炭的影响不显著.可为不同田间条件下分别采取有效的NO减排措施提供依据.     

近地面NO_2浓度卫星遥感估算问题

对卫星遥感监测大气NO_2的差分算法涉及的科学问题进行了综述,包括去除大气散射和地表反射噪声影响、大气拉曼散射引起的Ring效应校正、不同大气成分分离和观测垂直归一化等问题。国际上通过剔除平流层NO_2获得对流层柱浓度产品,文章绕开平流层NO_2获取问题,提出了结合大气化学模式模拟的垂直廓线直接估算近地面NO_2浓度技术方法,以更好地满足环境空气质量的观测需求,阐述了几个影响NO_2反演精度的相关问题。     

Detailed in-furnace measurements with reburning of superfine pulverized coal in high CO2 concentration

This paper presents detailed measurements of gaseous species during the reburning process with high CO₂ concentration in a bench-scale furnace. Superfine pulverized coal, with the average particle size below or around 20 μm, is used as the reburning fuel. The data of flue gas concentration (NO_x, HCN, NH₃, CH₄, O₂, CO, CO₂ etc.) is obtained in order to reveal the intrinsic connection between NO_x emissions and other influential gaseous species at different positions of the furnace. The finding concludes that the advantage of superfine pulverized coal with regard to NO reduction is more efficient in homogeneous stage rather than heterogeneous stage. Meanwhile, the evolution of HCN and CH₄ agrees well with each stage of NO reduction, which indicates that these gaseous species are favorable for NO abatement. Eventually, oxygen consumption rate for superfine pulverized coal is relatively faster, conducive to strengthen both homogeneous and heterogeneous NO reduction under CO₂ reburning condition.