The Measurement of Active Chlorine in the Atmosphere by Chemical Amplification     

D. Perner  T. Arnold  J. Crowley  T. Klüpfel  M. Martinez  R. Seuwen 《Journal of Atmospheric Chemistry》1999,34(1):9-20

Chemical amplification, CA, a method commonly used for the detection of peroxy radicals, HO₂ and RO₂, was found to be sensitive towards ClOx (Cl+ClO+OClO) as well. ClOx is reduced by NO to Cl atoms which react with carbon monoxide in the presence of O₂. The reaction sequence thus initiated oxidizes CO to CO₂ and NO to NO₂, with a chain length of 300 ± 60. This allows the atmospheric ClOx content to be measured under ambient conditions with a detection limit of better than 1 ppt. In parallel peroxy radicals are indicated with a chain length of 160 ± 15. Chemical amplification is not specific and does not indicate which radical chain it is seeing. Identification relies solely on plausibility. During the ARCtic Tropospheric Ozone Chemistry (ARCTOC) campaign in spring 1995 and 1996 the CA technique was used at Ny-Ålesund. ClOx at mixing ratios of up to 2 ppt were found in the boundary layer under certain conditions. The low concentrations of ClOx indicate that the arctic boundary ozone depletion is mainly driven by bromine.  相似文献   

The role of bromine and chlorine chemistry for arctic ozone depletion events in Ny-Ålesund and comparison with model calculations     

M. Martinez  T. Arnold  D. Perner 《Annales Geophysicae》1999,17(7):941-956

During the Arctic Tropospheric Ozone Chemistry (ARCTOC) campaigns at Ny-Ålesund, Spitsbergen, the role of halogens in the depletion of boundary layer ozone was investigated. In spring 1995 and 1996 up to 30 ppt bromine monoxide were found whenever ozone decreased from normal levels of about 40 ppb. Those main trace gases and others were specifically followed in the UV-VIS spectral region by differential optical absorption spectroscopy (DOAS) along light paths running between 20 and 475 m a.s.l. The daily variation of peroxy radicals closely followed the ozone photolysis rate J(O₃(O¹D)) in the absence of ozone depletion most of the time. However, during low ozone events this close correlation was no longer found because the measurement of radicals by chemical amplification (CA) turned out to be sensitive to peroxy radicals and ClO_x. Large CA signals at night can sometimes definitely be assigned to ClO_x and reached up to 2 ppt. Total bromine and iodine were both stripped quantitatively from air by active charcoal traps and measured after neutron activation of the samples. Total bromine increased from background levels of about 15 ppt to a maximum of 90 ppt during an event of complete ozone depletion. For the spring season a strong source of bromine is identified in the pack ice region according to back trajectories. Though biogenic emission sources cannot be completely ruled out, a primary activation of halogenides by various oxidants seems to initiate an efficient autocatalytic process, mainly driven by ozone and light, on ice and perhaps on aerosols. Halogenides residing on pack ice surfaces are continuously oxidised by hypohalogenous acids releasing bromine and chlorine into the air. During transport and especially above open water this air mixes with upper layer pristine air. As large quantities of bromine, often in the form of BrO, have been observed at polar sunrise also around Antarctica, its release seems to be a natural phenomenon. The source strength of bromine from halogen activation on the pack ice, as based on the measured inorganic bromine levels, averages about 10¹² Br-atoms m⁻² s⁻¹ during sunlit periods in Arctic spring. The total source strength of inorganic bromine from sunlit polar regions may therefore amount to 30 kt y⁻¹.  相似文献   

Rates and patterns of erosion on inter-tidal shore platforms,Kaikoura Peninsula,South Island,New Zealand     

Wayne J. Stephenson  Robert M. Kirk 《地球表面变化过程与地形》1998,23(12):1071-1085

This paper presents measured rates of erosion on shore platforms at Kaikoura Peninsula, South Island, New Zealand. Surface lowering rates were measured with a micro-erosion meter and traversing micro-erosion meter. The mean lowering rate for all shore platforms was 1·130 mm a⁻¹. Differences in lowering rates were found between different platform types and lithologies. The rate of surface lowering on Type A (sloping) mudstone platforms was 1·983 mm a⁻¹, and 0·733 mm a⁻¹ on Type B mudstone platforms (subhorizontal). On limestone platforms the lowering rate was 0·875 mm a⁻¹. A previously reported cross-shore pattern of surface lowering rates from Kaikoura was not found. Rates were generally higher on the landward margins and decreased in a seaward direction. Season is shown statistically to influence erosion rates, with higher rates during summer than winter. The interpretation given to this is that the erosive process is subaerial weathering in the form of wetting and drying and salt weathering. This is contrary to views of shore platform development that have favoured marine processes over subaerial weathering. Copyright © 1998 John Wiley & Sons, Ltd.  相似文献   

Oxygen-Containing Compounds Identified in Groundwater from Fuel Release Sites Using GCxGC-TOF-MS     

Kirk T. O'Reilly  Rachel E. Mohler  Dawn A. Zemo  Sungwoo Ahn  Renae I. Magaw  Catalina Espino Devine 《Ground Water Monitoring & Remediation》2019,39(4):32-40

This research continues a 7-year study of oxygen-containing organic compounds present in groundwater at gasoline and diesel fuel release sites that are quantified as diesel-range “total petroleum hydrocarbons” when measured by methods utilizing solvent extraction and gas chromatography. Two-dimensional gas chromatography with time-of-flight mass spectrometry was used to tentatively identify 1162 compounds (TICs) in 113 groundwater samples from 22 sites. Samples were collected from wells either upgradient of the release, within the source zone, or downgradient of the source but still within the plume of dissolved organics associated with release. The names and formulas of all TICs found in samples from each well type are presented and the results from upgradient and downgradient locations are compared in detail. About 60% of the most frequently detected TICs in downgradient wells were also detected in upgradient wells. A majority of these were saturated straight chain alkyl acids, commonly called fatty acids, or fatty acid esters. Of TICs frequently detected in downgradient wells but not upgradient wells, over half were branched alkyl alcohols. Hierarchical cluster analysis results suggest about 80% of the chemical composition of downgradient samples is more similar to upgradient samples than to source area samples. This similarity is due to the presence of the same types of fatty acids and esters. Principal component analysis indicates a continuum of biodegradation between the source area and downgradient samples with the latter becoming more consistent with upgradient samples. Results suggest some TICs may not be petroleum degradation intermediates but compounds synthesized by microorganisms through secondary production and carbon cycling.  相似文献   

Sensitivity analysis of pounding between adjacent structures          下载免费PDF全文

Vincent Crozet  Ioannis Politopoulos  Mingguan Yang  Jean‐Marc Martinez  Silvano Erlicher 《地震工程与结构动力学》2018,47(1):219-235

This article deals with sensitivity of the response of pounding buildings with respect to structural and earthquake excitation parameters. A comprehensive sensitivity analysis is carried out by means of Monte Carlo simulations of adjacent single degree of freedom impacting oscillators. This sensitivity analysis, based on Sobol's method, computes sensitivity indexes which provide a consistent measure of the relative importance of parameters such as the dimensionless main excitation frequency, the mass and frequency ratios of the structures, and the coefficient of restitution. Moreover, the influence of nonlinear behavior of the impacting structures is also considered. The consequences of pounding on the structures themselves are analyzed in terms of maximum force and nonlinear demand amplification compared with the case without pounding. As for the influence of pounding on the floor response spectra, the quantity of interest is the maximum impact impulse. The overall conclusions of this analysis are that the frequency ratio is the most important parameter as far as the maximum force and nonlinear demand are concerned. Regarding the maximum impact impulse, the mass and frequency ratios are, in general, the most influential parameters, the mass ratio being predominant for low frequencies of the oscillator of interest.  相似文献