A new technique for collection,concentration and determination of gaseous tropospheric formaldehyde

This article describes an improved technique for making in situ measurements of gaseous tropospheric formaldehyde (CH₂O). The new technique is based on nebulization/reflux principles that have proved very effective in quantitatively scrubbing water soluble trace gases (e.g. CH₂O) into aqueous mediums, which are subsequently analyzed. Atmospheric formaldehyde extractions and analyses have been performed with the nebulization/reflux concentrator using an acidified dinitrophenylhydrazine solution that indicate that quantitative analysis of CH₂O at global background levels (∼ 0.1 ppbv) is feasible with 20-min extractions. Analysis of CH₂O, once concentrated, is accomplished using high performance liquid chromatography (HPLC) with ultraviolet photometric detection. The CH₂O-hydrazone derivative, produced by the reaction of 2,4-dinitrophenylhydrazine in H₂SO₄ acidified aqueous solution, is detected as CH₂O.     

Analysis of gaseous diisocyanates in air using chemosorption sampling

A sampling procedure for 2,4- and 2,6-toluenediisocyanate (TDI) and 4,4′-diphenylmethane diisocyanate (MDI) in the range 0.007-0.7 mg/m³ in a 15 L air sample is described. The sampling is performed with 9-(N-methylaminomethyl)-anthracene (MAMA) adsorbed on a solid sorbent, Amberlite XAD-2. The recoveries are 80–100% in this chemosorption reaction. The urea derivatives are desorbed with N,N-dimethylformamide and analysed by high performance liquid chromatography (HPLC). Samples and prepared chemosorption tubes are stable for at least two weeks if stored in the dark. To complete the investigation, field measurements of TDI were performed in an industrial atmosphere.     

The equilibrium of ammonium chloride aerosol with gaseous hydrochloric acid and ammonia under tropospheric conditions

Using thermodynamic data, the equilibrium constant for dissociation of solid ammonium chloride aerosol into gaseous hydrogen chloride and ammonia has been calculated. The existence of solid ammonium chloride aerosols is thermodynamically possible at temperatures and concentrations observed in the troposphere, but significant gas phase concentrations of hydrogen chloride and ammonia will also be present.     

Radical-driven carbonyl-to-acid conversion and acid degradation in tropospheric aqueous systems studied by CAPRAM

Model studies on the aqueous phase radical-driven processing of carbonyl compounds and acids in clouds and deliquescent particles were performed. The model exposed that aqueous radical conversions of carbonyl compounds and its oxidation products can contribute potentially to the formation of functionalised organic acids. The main identified C₂–C₄ organic gas phase precursors are ethylene glycol, glycolaldehyde, glyoxal, methylglyoxal and 1,4-butenedial. The aqueous phase is shown to contribute significantly with about 93%/63%, 47%/8%, 31%/4%, 7%/4%, 36%/8% to the multiphase oxidative fate of these compounds under remote/urban conditions. Interestingly, the studies revealed that aqueous chemical processing is not only limited to in-cloud conditions but also proceeds in deliquescent particle phase with significant fluxes. Oxalic acid is shown to be formed preferably in deliquescent particles subsequent to the in-cloud oxidations. Mean aqueous phase oxalate formation fluxes of about 12, 42 and 0.4 ng m^?3 h^?1 in the remote, urban and maritime scenario, respectively. Additionally, the turnovers of the oxidation of organics such as methylglyoxal by NO₃ radical reactions are identified to be competitive to their OH pendants. At the current state of CAPRAM, mean C₂–C₄ in-cloud oxidation fluxes of about 0.12 and 0.5 μg m^?3 h^?1 are modelled under the idealised remote and urban cloud conditions.Finally, turnovers from radical oxidations were compared with those of thermal reactions. It is demonstrated that, based on the sparse kinetic data available organic accretion reaction might be of interest in just a few cases for cloud droplets and aqueous particles but generally do not reach the oxidative conversion rates of the main radical oxidants OH and NO₃. Interestingly, oxidation reactions of H₂O₂ are shown to be competitive to the OH radical conversions in cases when H₂O₂ is not readily used up by the S(IV) oxidation.     

Atmospheric contamination by pesticides: Determination in the liquid, gaseous and particulate phases

Between 1991 and 1993, 18 fogwater samples, 31 rainwater samples and 17 atmosphere (gas and particles) samples were analysed for 13 pesticides (pp’DDT,pp’DDD,pp’DDE, aldrin, dieldrin, lindane, hexachlorobenzene, fenpropathrin, mecoprop, methyl-parathion, atrazine, isoproturon and aldicarb). The samples were collected in a rural area where some of the compounds are in use (experimental INRA farm, “Institut National de la Recherche Agronomique” in Colmar, Eastern France, 80,000 inhabitants). This paper briefly presents the analytical methodology used and, in detail, the contamination level of the different atmospheric phases. The contamination levels are roughly constant throughout the year in all the atmospheric phases and the most abundant pesticides are those commonly used on the experimental INRA farm and other surrounding farms. Nevertheless, some pesticides not used since the 1970s such as 1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane (pp’DDT) and 2,2-Bis(4-chlorophenyl)-1,1-dichloroethane (pp ’DDD) are also detected in the atmosphere of Colmar. A small increase in the pesticide concentrations in the atmosphere (gas and particles) was observed during treatments.     

Evaluation of passive sampling of gaseous mercury using different sorbing materials

Environmental Science and Pollution Research - Atmospheric mercury monitoring is essential because of its potential human health and ecological impacts. Current automated monitoring systems include...     

Springtime depletion of tropospheric ozone,gaseous elemental mercury and non-methane hydrocarbons in the European Arctic,and its relation to atmospheric transport

Using a trajectory climatology for the period 1992–2001 we have examined how seasonal changes in transport cause changes in the concentrations of tropospheric ozone (O₃), gaseous elemental mercury (GEM) and non-methane hydrocarbons (NMHCs) observed at the Mt. Zeppelin station, Ny-Ålesund (78.9°N, 11.9°E). During April–June O₃ depletion events were frequently observed in connection with air transport across the Arctic Basin. The O₃ loss was most pronounced in air masses advected close to the surface. This result supports the idea that the O₃ depletion reactions take place in the lowermost part of the atmosphere in the central Arctic Basin. A strong positive correlation between springtime O₃ depletion events and the oxidation of GEM to divalent mercury was found. During air mass advection from Siberia, the Barents Sea and the Norwegian Sea the strongest correlation was observed during April–May, whereas air masses originating from the Canadian Arctic and the central Arctic areas showed the highest O₃–GEM correlation in May–June. We suggest that this 1-month lag could either be due to the position of the marginal ice zone or temperature differences between the northwestern and northeastern air masses. In connection with springtime O₃ depletion events low concentrations of some NMHCs, especially ethane and ethyne, were observed, indicating that both bromine (ethyne oxidant) and chlorine radicals (ethane oxidant) are present in the Arctic atmosphere during spring. In winter, negative correlations between O₃ and NMHCs were found in connection with air transport from Europe and Siberia, which we interpret as O₃ destruction taking place in industrially contaminated plumes.     

Atmospheric particulate nitrate sampling errors due to reactions with particulate and gaseous strong acids

The significance of particulate nitrate loss from inert filters due to reactions with particulate and gaseous strong acids was assessed. Laboratory as well as atmospheric results from California's South Coast Air Basin support such loss by reaction of ammonium nitrate with paniculate H₂SO₄. Nitrate loss by reaction with gaseous HCl, not previously reported, was found to be significant in laboratory trials.     

广州某地大气中二噁英气/粒相间特征分析——以2012年7月测试为例

选取广州某地大气环境作为研究对象,采用高分辨气质联用色谱对气相、颗粒相中17种二噁英(PCDD/Fs)单体进行分析。结果表明,研究区域大气PCDD/Fs主要集中于颗粒相,且气相和颗粒相中PCDD/Fs均表现出"源"特征。颗粒相中PCDD/Fs单体以OCDD、1,2,3,4,6,7,8-HpCDF、OCDF、1,2,3,4,6,7,8-HpCDD为主;气相中PCDD/Fs单体以1,2,3,7,8-PeCDF、2,3,4,7,8-PeCDF、1,2,3,4,7,8-HxCDF、1,2,3,4,6,7,8-HpCDF为主。颗粒相中PCDD/Fs浓度随着氯原子数的增加而增加,气相中PCDD/Fs随着氯原子数的增加而减少。气相中主要毒性贡献单体为2,3,4,7,8-PeCDF,其与气相总毒性当量浓度的相关系数为0.908;颗粒相中主要毒性贡献单体为2,3,4,7,8-PeCDF、2,3,4,6,7,8-HxCDF,与颗粒相总毒性当量浓度的相关系数分别为0.851、0.883。主成分分析结果表明,颗粒相和气相的毒性当量浓度具有相似的分布特征。     

Intercomparison of methods for sampling and analysis of atmospheric mercury species

An intercomparison for sampling and analysis of atmospheric mercury species was held in Tuscany, June 1998. Methods for sampling and analysis of total gaseous mercury (TGM), reactive gaseous mercury (RGM) and total particulate mercury (TPM) were used in parallel sampling over a period of 4 days. The results show that the different methods employed for TGM compared well whereas RGM and TPM showed a somewhat higher variability. Measurement results of RGM and TPM improved over the time period indicating that activities at the sampling site during set-up and initial sampling affected the results. Especially the TPM measurement results were affected. Additional parallel sampling was performed for two of the TPM methods under more controlled conditions which yielded more comparable results.     

Forest responses to tropospheric ozone and global climate change: an analysis

In this paper an analysis is provided on: what we know, what we need to know, and what we need to do, to further our understanding of the relationships between tropospheric ozone (O(3)), global climate change and forest responses. The relationships between global geographic distributions of forest ecosystems and potential geographic regions of high photochemical smog by the year 2025 AD are described. While the emphasis is on the effects of tropospheric O(3) on forest ecosystems, discussion is presented to understand such effects in the context of global climate change. One particular strong point of this paper is the audit of published surface O(3) data by photochemical smog region that reveals important forest/woodland geographic regions where little or no O(3) data exist even though the potential threat to forests in those regions appears to be large. The concepts and considerations relevant to the examination of ecosystem responses as a whole, rather than simply tree stands alone are reviewed. A brief argument is provided to stimulate the modification of the concept of simple cause and effect relationships in viewing total ecosystems. Our knowledge of O(3) exposure and its effects on the energy, nutrient and hydrological flow within the ecosystem are described. Modeling strategies for such systems are reviewed. A discussion of responses of forests to potential multiple climatic changes is provided. An important concept in this paper is that changes in water exchange processes throughout the hydrological cycle can be used as early warning indicators of forest responses to O(3). Another strength of this paper is the integration of information on structural and functional processes of ecosystems and their responses to O(3). An admitted weakness of this analysis is that the information on integrated ecosystem responses is based overwhelmingly on the San Bernardino Forest ecosystem research program of the 1970s because of a lack of similar studies. In the final analysis, it is recommended that systems ecology be applied in examining the joint effects of O(3), carbon dioxide and ultraviolet-B radiation on forest ecosystems.     

Passive sampling of ambient, gaseous air pollutants: an assessment from an ecological perspective

During some past two decades there has been a growing interest among air pollution-vegetation effects-scientists to use passive sampling systems for quantifying ambient, gaseous air pollutant concentrations, particularly in remote and wilderness areas. On the positive side, excluding the laboratory analysis costs, passive samplers are inexpensive, easy to use and do not require electricity to operate. Therefore, they are very attractive for use in regional-scale air quality assessments. Passive samplers allow the quantification of cumulative air pollutant exposures, as total or average pollutant concentrations over a sampling duration. Such systems function either by chemical absorption or by physical adsorption of the gaseous pollutant of interest onto the sampling medium. Selection of a passive sampler must be based on its known or tested characteristics of specificity and linearity of response to the chemical constituent being collected. In addition, the effects of wind velocity, radiation, temperature and relative humidity must be addressed in the context of absorbent/adsorbent performance and sampling rate. Because of all these considerations, passive samplers may provide under- or overestimations of the cumulative exposures, compared to the corresponding data from co-located continuous monitors or active samplers, although such statistical variance can be minimized by taking necessary precautions. On the negative side, cumulative exposures cannot identify short-term (相似文献   

Evaluation of an intensive sampling and analysis method for carbon monoxide

This paper describes a portable, low-cost whole air sampler capable of collecting 12 1-L samples in tedlar bags and using a single "D" cell for power. The results are presented from two tests of an intensive sampling and analysis method for measuring ambient carbon monoxide (CO) concentrations in urban areas using this sampler. The method is evaluated in comparison with an approved continuous CO analyzer, in intercomparisons of the results of re-analysis of the samples, and by examination of the results from co-located samplers. The precision of the analytical method was found to be +/-0.30 ppmv. The precision of the sampling method was found to be +/-0.73 ppmv and therefore is the limiting factor in the method's overall precision. These values are sufficient to verify attainment of National Ambient Air Quality Standards (NAAQS) levels in urban areas. Improvements in the sampler and analytical procedure are discussed.     

Problems in the sampling and analysis of carbon particulate

Several thermal and wet chemical methods of separating organic from elemental carbon in particulate samples were examined. It is concluded that none of them represents an ideal separation procedure and that only a method-dependent operational definition of organic and elemental carbon is possible at this time. The best separation method appears to be a thermal procedure using 350°C air oxidation followed by pyrolysis in He at 950°C. There are also difficulties in sampling since dual filter techniques show that adsorption of organic compounds on various filter media accounted for at least 15 per cent of the total organic carbon collected during ambient sampling in Warren, MI. This adsorption further confuses the results and needs to be studied at other sampling sites.