扩散管差分法测定大气中氨和颗粒物铵盐

本文用扩散管差分法和多种叠层滤膜法大气中颗的铵盐和气态氨,扩散管关分法可以有铲分离测量颗粒物铵盐和气态氨,避免了采样时惰性上颗粒物硝酸铵分解的人为影响。     

大气中颗粒物,硝酸和氨同时采集方法

本文探讨了三层采样头同时采集大气中颗粒物气态硝酸和气态氨的方法。用国产1号有机膜采集颗粒物,5％NaCl浸渍玻璃纤维膜采集气态硝酸,5％H_3PO_4—1％草酸溶液浸渍玻璃纤维膜采集气态氨,并对滤膜的选择及采样过程中可能产生的误差进行了探讨。结果表明,用这种方法同时采集大气中颗粒物、硝酸和氨是简便可行的。     

大气中硝酸和颗粒物同时采集方法的研究

用5％氯化钠溶液浸渍的国产玻璃纤维滤膜采集大气中气态硝酸的效率为95±2.1％,该膜采样后至少可以保存50天不影响测定结果。按90lmin~(-1)的流量采样一小时,可以测定大气中浓度在2—110μgm~(-3)范围的硝酸。该膜测定的硝酸浓度和Whatman 41浸渍膜测定结果相对误差为10％。氯化钠溶液浸渍膜在采集过程中对SO_2的吸收率为2.9％。表明:选用有机膜,5％NaCI溶液浸渍膜和25％K_2CO_3-10％Gly溶液浸渍,同时采集大气中颗粒物、气态硝酸和二氧化硫是可行的。     

环形扩散管和滤膜联用采集和测定大气中气固相物质

建立了环形扩散管(annular diffusion denuder)和滤膜连用的采样装器。采用涂渍1％碳酸钠甲醇水溶液和5％亚磷酸甲醇溶液的两段环形扩散管串联分别收集气态HNO_3,HCl,SO_2和NH_3、空气经扩散管后,继而抽入滤膜采样头,用Teflon滤膜采集颗粒物,Nylon滤膜收集由Teflon滤膜上颗粒物挥发产生的气态HNO_3和HCl。样品提取后,用离子色谱法测定SO_4~(2-),NO_3~-和Cl~-;采用流动注射荧光法测定NH_4~+。当采样流速为10L/min,采样24h,环形扩散管对气态硝酸、氯化氢和二氧化硫的检出限(3σ)为0.04—0.09μg/m~3,对氨的检出限为0.12μg/m~3。实验结果表明本法适用于大气和室内空气的采样和测定。     

大气颗粒物中可溶性离子在线分析方法的建立与应用

大气颗粒物中可溶性离子通常采用膜累积采样,然后再进行浸提、分析．虽然应用较为广泛,但是却具有采样分析周期较长、操作繁琐、易产生杂质等缺点,一般只能得到12h或24h的平均值,很难得到逐时变化．此外,由于NO3^-,NO2^-和Cl^-等容易挥发,膜累积采样法往往无法准确测量这些组分．为了准确测量半挥发性成分,减少采样损失,常采用扩散管加底膜的方法,     

硫／石灰石滤柱的自养反硝化动力学模型

本文对用硫作为电子供体，硝酸盐作为电子受体，由脱氮硫杆菌进行的自养反硝化过程的动力学模型进行了研究。结果表明，硝酸盐在滤料表面生物膜中的扩散过程对硫／石灰石滤柱的反硝化动力学影响很大。若扩散速率慢，硝酸盐只能穿过生物膜的一部分，则滤柱的反硝化速率遵循１／２级反应动力学；若扩散速率快，硝酸盐能穿过整个生物膜，则滤柱的反硝化速率遵循零级反应动力学。     

重庆市区大气颗粒物的物相组成分析

大气颗粒物组成非常复杂 ,包括晶态和非晶态的无机物与有机物 .同一个元素往往又以多种形态出现 ,而某些元素含量又较低 ,这些都给物相鉴定带来了很大的困难 .本文用Ｘ 射线衍射物相分析(ＸＲＤ)对重庆市区大气颗粒污染物的物相组成进行了研究 .在对大气颗粒物的Ｘ 射线衍射分析中 ,采用丙酮 二碘甲烷重液体系对颗粒物样品进行了密度梯度分级处理 ,鉴定出重庆市区大气颗粒物中存在的 1 0种物相 ,并初步讨论了重庆市区的污染来源和分布规律 .1　样品的采集与制备样品采集利用了ＵＶ1 3Ｈ 1型安德逊采样器及玻璃纤维膜 (采集的颗粒物为ＰＭ1 0…     

大气中二氧化硫和颗粒物同时采集方法的研究

本文探讨了双层采样头同时采集大气中的SO_2和颗粒物的方法。用国产玻璃纤维滤膜,25％K_2CO_3-10％Gly溶液制作浸渍膜。该浸渍膜理场采集大气中SO_2的效率为96％,采样后至少可以保存50d以供分析。试验结果表明,浸渍膜法和盐酸付玫瑰苯胺法测定大气中SO_2的结果相近,相对偏差为4.4％,两种方法测定SO_2浓度结果有着良好的线性关系(Υ=0.996)。用此法可使大气中的气相与固相物质有选择地在一股气流中同时进行采集。     

大气化学非均相反应摄取系数的测定

摄取系数是表征大气非均相反应的重要物理化学参数,也是大气颗粒物表面摄取气体能力的重要量化指标.本文综述了摄取系数的主要概念、主要测定方法和影响因素,以NaCl与NO2非均相反应为例,讨论了用漫反射傅立叶转换红外原位反应器扩散实验方式测定反应摄取系数的方法和误差,分析了气体扩散深度与红外穿透厚度对测定结果的影响,并测定了初始反应摄取系数.     

天津市大气颗粒物铅的同位素丰度比测定

对天津市 2 1个玻璃纤维滤膜大气颗粒物样品采用稀酸浸出法溶解后 ,测量了铅浓度、铅含量和同位素丰度比 (2 0 6Ｐｂ/2 0 7Ｐｂ) .并采用聚类分析方法对样品进行分组讨论 .1　样品的采集和测定本文旨在观察汽油无铅化进程中 ,大气颗粒物中铅来源的变化情况 .1 998年和 1 999年是汽油无铅化的关键时期 .大气颗粒物样品由天津市环境保护监测中心提供 ,采集于玻璃纤维滤膜上 .采样地点是天津市侯台站和天津市站两个国控站点 .采用ＫＢ 2 0型中流量采样器采集 2 4ｈ的ＴＳＰ样品 .从1 998年 1 1月到 1 999年 2月期间共采集样品 2 1个 .消解大气…     

New insights into the formation of ammonium nitrate from a physical and chemical level perspective

● Factor analysis of ammonium nitrate formation based on thermodynamic theory. ● Aerosol liquid water content has important role on the ammonium nitrate formation. ● Contribution of coal combustion and vehicle exhaust is significant in haze periods. High levels of fine particulate matter (PM_2.5) is linked to poor air quality and premature deaths, so haze pollution deserves the attention of the world. As abundant inorganic components in PM_2.5, ammonium nitrate (NH₄NO₃) formation includes two processes, the diffusion process (molecule of ammonia and nitric acid move from gas phase to liquid phase) and the ionization process (subsequent dissociation to form ions). In this study, we discuss the impact of meteorological factors, emission sources, and gaseous precursors on NH₄NO₃ formation based on thermodynamic theory, and identify the dominant factors during clean periods and haze periods. Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution. The dust source is dominant emission source in clean periods; while a combination of coal combustion and vehicle exhaust sources is more important in haze periods. And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate. The findings of this work inform the design of effective strategies to control particulate matter pollution.     

Significance of cellular nitrate content in natural populations of marine phytoplankton growing in shipboard cultures

Phytoplankton intracellular nitrate concentrations have been monitored in a 56-h experiment on a shipboard culture of surface sea water from an upwelling region. These measurements were related to parameters of biomass (particulate nitrogen) and nitrate assimilation using the ¹⁵N isotope technique and the nitrate reducase (NR) assay. The procedure for measuring cellular nitrate concentrations is described. This parameter exhibited diurnal variations, ranging from 3.1 to 20.6 ng-at nitrate per g-at particulate nitrogen, and could be correlated positively with NR activity. Nitrogen budgets show that NR activity represents only 12% of nitrate incorporation in organic phytoplankton material when nitrate is available in the sea water. However, upon depletion of the environmental nitrate (zero uptake), NR activity can fully account for the decrease of internal nitrate. From the results, it seems that internal nitrate content is a better index of nitrate consumption by marine phytoplankton than the external concentration of nitrate-nitrogen.     

Modelling concentrations of airborne primary and secondary PM10 and PM2.5 with the BelEUROS-model in Belgium

The Eulerian Chemistry-Transport Model BelEUROS was used to calculate the concentrations of airborne PM₁₀ and PM_2.5 over Europe. Both primary as well as secondary particulate matter in the respirable size-range was taken into account. Especially PM_2.5 aerosols are often formed in the atmosphere from gaseous precursor compounds. Comprehensive computer codes for the calculation of gas phase chemical reactions and thermodynamic equilibria between compounds in the gas-phase and the particulate phase had been implemented into the BelEUROS-model. Calculated concentrations of PM₁₀ and PM_2.5 are compared to observations, including both the spatial and daily, temporal distribution of particulate matter in Belgium for certain monitoring locations and periods. The concentrations of the secondary compounds ammonium, nitrate and sulfate have also been compared to observed values. BelEUROS was found to reproduce the observed concentrations rather well. The model was applied to assess the contribution of emissions derived from the sector agriculture in Flanders, the northern part of Belgium, to PM₁₀- and PM_2.5-concentrations. The results demonstrate the importance of ammonia emissions in the formation of secondary particulate matter. Hence, future European emission abatement policy should consider more the role of ammonia in the formation of secondary particles.     

The rapid response of the marine diatom Skeletonema costatum to changes in external and internal nutrient concentration

A nitrogen-deficient batch culture of the marine diatom Skeletonema costatum, when resupplied with a mixture of nitrate and ammonium, showed an initial enhanced nitrate uptake rate leading to a large internal concentration (pool) of nitrate. Following this initial nitrate uptake event, nitrate uptake ceased, and nitrate assimilation was inhibited until the ammonium present was used. At this point, nitrate uptake resumed and nitrate assimilation began. No internal ammonium pool was observed during nitrate utilization, but a large nitrate pool remained throughout the utilization of external nitrate. The internal nitrate pool decreased rapidly after exhaustion of nitrate from the culture medium, but growth of cellular particulate nitrogen continued for about 24 h. A mathematical simulation model was developed from these data. The model cell consisted of a nitrate pool, ammonium pool, dissolved organic nitrogen pool, and particulate nitrogen. It was found that simple Michaelis-Menten functions for uptake and assimilation gave inadequate fit to the data. Michaelis-Menten functions were modified by inclusion of inhibitory and stimulatory feedback from the internal pools to more accurately represent the observed nutrient utilization.     

Natürliche Oberflächenfilme im Seegebiet vor Sylt

The physical and chemical properties of the sea surface can be altered considerably by the formation of slicks and the accumulation of particles (including plankton). Investigations of natural slicks near the island of Sylt consisted of analyses of the dissolved and particulate surface-active substances, as well as the identification of plankton and bacteria collected by a surface-film sampler. The analyzed surface material consisted primarily of phytoplankton (Prorocentrum micans in particular), bacteria, detritus and dissolved compounds of fatty acids. These fatty acid compounds alone would not account for the slick. The slick appeared to be caused by the calm weather, the active accumulation of P. micans at the surface, and the increase in bacteria associated with this accumulation. Here a decrease was observed in the dissolved surface-active substances compared with the concentration usually found in normal surface waters, of which the total fatty acid content in a sample was taken as indicator. In some cases a correlation was found between fatty acids and particulate matter in naturally occurring slicks. Particularly large variations were found in the fatty acid patterns in the filtrate and filter residue at a time when no slick was present and no particulate matter had accumulated at the surface.

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Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft im Rahmen des SFB 94, Hamburg, unterstützt.     

Dry deposition and particle size distributions of nitrate and sulfate in ambient air

This study reports the dry deposition pollutants of anion species (NO₃ ^‐ and SO₄ ^‐2) in the Ping Tung City of Southern Taiwan. Several deposition properties are discussed in this paper. It included dry deposition flux, anion species size distribution and deposition velocities. Noll Rotary Impactor (NRI) and Microorifice Uniform Deposit Impactor (MOUDI) were used to collect ambient air coarse and fine particulate. Dry deposition plate was applied to collect particle deposition flux. Dionex 2000i/SP Ion Chromatography equipped with 4 mm AG4A‐SC and AS4A‐SC column was employed to analyze the anion species. The eluent solution is 1.8 mM sodium carbonate/1.7 mM sodium bicarbonate. The measured dry deposition flux of nitrate ranged from 0.63 to 3.96 mg/m²‐day and averaged 2.12 mg/m²‐day, while the measured dry deposition of sulfate ranged from 1.17 to 9.53 mg/m²‐day and averaged 3.92 mg/m²‐day. The particle size distribution of nitrate has bimodal particle size distributions. However, the sulfate displayed uniform particle size distribution for all four sampling sites. Mean cumulative fraction (F%) of nitrate in the particle size range below 1, 2.5, 10 and 25 μm, in sequence, were 34.6%, 60.9%, 91.0% and 97.6%, respectively. However, the mean F% of sulfate in the particle size range below 1, 2.5, 10 and 25 um, in sequence, were 57.3%, 82.6%, 90.3% and 98.0%, respectively. The sulfate has more F% in the submicron particles. The mean MMD _o of nitrate and sulfate are 2.35 and 0.87 μm, respectively. The mean dry deposition velocities of nitrate and sulfate are 0.45 and 0.38 cm/sec, respectively.     

Emission factors and chemical characterisation of fine particulate emissions from modern and old residential biomass heating systems determined for typical load cycles

It is already well known that there are significant differences regarding the emissions, especially particulate matter (PM) emissions, of old and modern as well as automatically and not automatically controlled biomass based residential heating systems. This concerns their magnitude as well as their chemical composition. In order to investigate emission factors for particulate emissions and the chemical compositions of the PM emissions over typical whole day operation cycles, a project on the determination and characterisation of PM emissions from the most relevant small-scale biomass combustion systems was performed at the BIOENERGY 2020+ GmbH, Graz, Austria, in cooperation with the Institute for Process and Particle Engineering, Graz University of Technology. The project was based on test stand measurements, during which relevant operation parameters (gaseous emissions, boiler load, flue gas temperature, combustion chamber temperature etc.) as well as PM emissions have been measured and PM samples have been taken and forwarded to chemical analyses. Firstly, typical whole day operation cycles for residential biomass combustion systems were specified for the test runs. Thereby automatically fed and automatically controlled boilers, manually fed and automatically controlled boilers as well as manually fed stoves were distinguished. The results show a clear correlation between the gaseous emissions (CO and OGC) and the PM₁ emissions. It is indicated that modern biomass combustion systems emit significantly less gaseous and PM emissions than older technologies (up to a factor of 100). Moreover, automatically fed systems emit much less gaseous and PM emissions than manually fed batch-combustion systems. PM emissions from modern and automatically controlled systems mainly consist of alkaline metal salts, while organic aerosols and soot dominate the composition of aerosols from old and not automatically controlled systems. As an important result comprehensive data concerning gaseous and PM emissions of different old and modern biomass combustion systems over whole day operation cycles are now available. Derived from these data, correlations between burnout quality, particulate emissions as well as particle composition of the PM emissions can be deduced.     

大气汞氧化还原过程与机制的计算化学研究进展

大气中汞的氧化还原反应对于其全球生物地球化学循环起着极其重要的作用,它促进了汞在全球范围内的扩散.汞主要以气态元素汞的形态释放到大气中,并经历复杂的均相和非均相化学反应,被氧化为活性气态汞和颗粒态汞;同时,活性气态汞也可经过光致还原反应光解生成气态元素汞.计算化学是一种基于理论方法利用计算软件来对化学现象和本质进行解释...     

Particulate pollution case studies which illustrate uses of individual particle analysis by scanning electron microscopy

Individual particle analysis by scanning electron microscopy is a high resolution analytical technique which can provide the detail necessary to solve many particulate pollution problems. In an electron microscope a beam of electrons is focused on a specimen resulting in a number of signals which are used to collect chemical and morphological information from individual features either manually or automatically. Case studies are presented which illustrate the applications of the technique to three paniculate pollution problems of differing complexity.