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排序方式: 共有367条查询结果,搜索用时 31 毫秒
61.
WILLIAM E. HOGSETT JAMES E. WEBER DAVID TINGEY ANDREW HERSTROM E. HENRY LEE JOHN A. LAURENCE 《Environmental management》1997,21(1):105-120
/ The risk tropospheric ozone poses to forests in the United States is dependent on the variation in ozone exposure across the distribution of the forests in question and the various environmental and climate factors predominant in the region. All these factors have a spatial nature, and consequently an approach to characterization of ozone risk is presented that places ozone exposure-response functions for species as seedlings and model-simulated tree and stand responses in a spatial context using a geographical information systems (GIS). The GIS is used to aggregate factors considered important in a risk characterization, including: (1) estimated ozone exposures over forested regions, (2) measures of ozone effects on species' and stand growth, and (3) spatially distributed environmental, genetic, and exposure influences on species' response to ozone. The GIS-based risk characterization provides an estimation of the extent and magnitude of the potential ozone impact on forests. A preliminary risk characterization demonstrating this approach considered only the eastern United States and only the limited empirical data quantifying the effect of ozone exposures on forest tree species as seedlings. The area-weighted response of the annual seedling biomass loss formed the basis for a sensitivity ranking: sensitive-aspen and black cherry (14%-33% biomass loss over 50% of their distribution); moderately sensitive-tulip popular, loblolly pine, eastern white pine, and sugar maple (5%-13% biomass loss); insensitive-Virginia pine and red maple (0%-1% loss). In the future, the GIS-based risk characterization will include process-based model simulations of the three- to 5-year growth response of individual species as large trees with relevant environmental interactions and model simulated response of mixed stands. The interactive nature of GIS provides a tool to explore consequences of the range of climate conditions across a species' distribution, forest management practices, changing ozone precursors, regulatory control strategies, and other factors influencing the spatial distribution of ozone over time as more information becomes available.KEY WORDS: Ecological risk assessment; GIS; Ozone; Risk characterization; Forests; Trees 相似文献
62.
O3 decomposition catalysts with excellent performance still need to be developed. In this study, Ag-modified manganese oxides (AgMnOx) were synthesized by a simple co-precipitation method. The effect of calcination temperature on the activity of MnOx and AgMnOx catalysts was investigated. The effect of the amount of Ag addition on the activity and structure of the catalysts was further studied by activity testing and characterization by a variety of techniques. The activity of 8%AgMnOx for ozone decomposition was significantly enhanced due to the formation of the Ag1.8Mn8O16 structure, indicating that this phase has excellent performance for ozone decomposition. The weight content of Ag1.8Mn8O16 in the 8%AgMnOx catalyst was only about 33.76%, which further indicates the excellent performance of the Ag1.8Mn8O16 phase for ozone decomposition. The H2 temperature programmed reduction (H2-TPR) results indicated that the reducibility of the catalysts increased due to the formation of the Ag1.8Mn8O16 structure. This study provides guidance for a follow-up study on Ag-modified manganese oxide catalysts for ozone decomposition. 相似文献
63.
Chengdu is a megacity in the southwest of China with high ozone (O3) mixing ratio. Observation of volatile organic compounds (VOCs), NO2 and O3 with high temporal resolution was conducted in Chengdu to investigate the chemical processes and causes of high O3 levels. The hourly mixing ratios of VOCs, NO2, and O3 were monitored by an online system from 28 August to 7 October, 2016. According to meteorological conditions, Chengdu, with relative warm weather and low wind speed, is favorable to O3 formation. Part of the O3 in Chengdu may be transported from the downtown area. In O3 episodes, the average mixing ratios of NO2 and O3 were 20.20?ppbv and 47.95?ppbv, respectively. In non-O3 episodes, the average mixing ratios of NO2 and O3 were 16.38?ppbv and 35.15?ppbv, respectively. The average mixing ratio of total VOCs (TVOCs) was 40.29?ppbv in non-O3 episodes, which was lower than that in O3 episodes (53.19?ppbv). Alkenes comprised 51.7% of the total O3 formation potential (OFP) in Chengdu, followed by aromatics which accounted for 24.2%. Ethylene, trans-pentene, propene, and BTEX (benzene, ethylbenzene, toluene, m/p-xylene, o-xylene) were also major contributors to the OFP in Chengdu. In O3 episodes, intensive secondary formations were observed during the campaign. Oxygenated VOCs (OVOCs), such as acetone, Methylethylketone (MEK), and Methylvinylketone (MVK) were abundant. Isoprene rapidly converted to MVK and Methacrolein (MACR) during O3 episodes. Acetone was mainly the oxidant of C3-C5 hydrocarbons. 相似文献
64.
Analysis of the relationship between ambient levels of O3, NO2 and NO as a function of NOx in the UK
Monitoring data from the UK Automatic Urban and Rural Network are used to investigate the relationships between ambient levels of ozone (O3), nitric oxide (NO) and nitrogen dioxide (NO2) as a function of NOx, for levels ranging from those typical of UK rural sites to those observed at polluted urban kerbside sites. Particular emphasis is placed on establishing how the level of ‘oxidant’, OX (taken to be the sum of O3 and NO2) varies with the level of NOx, and therefore to gain some insight into the atmospheric sources of OX, particularly at polluted urban locations. The analyses indicate that the level of OX at a given location is made up of NOx-independent and NOx-dependent contributions. The former is effectively a regional contribution which equates to the regional background O3 level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. The local oxidant source has probable contributions from (i) direct NO2 emissions, (ii) the thermal reaction of NO with O2 at high NOx, and (iii) common-source emission of species which promote NO to NO2 conversion. The final category may include nitrous acid (HONO), which appears to be emitted directly in vehicle exhaust, and is potentially photolysed to generate HOx radicals on a short timescale throughout the year at southern UK latitudes. The analyses also show that the local oxidant source has significant site-to-site variations, and possible reasons for these variations are discussed. Relationships between OX and NOx, based on annual mean data, and fitted functions describing the relative contributions to OX made by NO2 and O3, are used to define expressions which describe the likely variation of annual mean NO2 as a function of NOx at 14 urban and suburban sites, and which can take account of possible changes in the regional background of O3. 相似文献
65.
Gotzon Gangoiti Milln M. Milln Rosa Salvador Enrique Mantilla 《Atmospheric environment (Oxford, England : 1994)》2001,35(36):2163
During the warm season (March–September), high ozone concentrations have been reported at the coastal and mountain monitoring stations of the eastern Iberia coast (Millán et al., J. Geophys. Res. 102 (D7) 8811, J. Appl. Meteorol. 4 (2000) 487). The vegetation protection threshold of current Directive 92/72/EEC and the World Health Organisation guideline for the protection of crops and semi-natural vegetation are systematically exceeded during the whole period. The main objective of the present study is to search for the origin of these chronic pollution levels: to search for the reason(s) for such high O3 concentrations during such a long period. A mesoscale model is used to reproduce the diurnal cycle of winds and stability/layering over the Western Mediterranean Basin (WMB), at a sufficient space/temporal resolution, under a typical recursive synoptic condition during the warm season: data from the flight tracks of the European Project—Regional Cycles of Air Pollution in the West-Central Mediterranean Area—are used to substantiate the model results. Times of residence and the final distribution of pollutants entering the WMB are estimated using single-particle Lagrangian trajectories and a multiple-particle dispersion model. Our results show that the marine boundary layer and the lower troposphere in the region between the Balearic Islands and eastern Iberia are subject to a flow regime that tends to accumulate pollutants within large circulations, covering the entire western basin. We have also shown a diurnal pulsation of the Tramontana/Mistral wind regime, which can transport new pollutants into the area (background concentrations of 50–65 ppb of O3 of continental European origin) that are added to local emissions and re-circulated within the coastal breezes at eastern Iberia for periods of more than five days. Local emissions and wind configuration contribute to increase the O3 concentrations up to 100 ppb and even more. 相似文献
66.
67.
E. Martínez J. Albaladejo A. Notario E. Jimnez 《Atmospheric environment (Oxford, England : 1994)》2000,34(29-30)
The atmospheric reaction of the methylthiyl radical (CH3S) with O3 was investigated as a function of temperature (259–381 K), in the pressure range of 25–300 Torr, using the technique of laser photolysis/laser-induced fluorescence. The resulting Arrhenius expression, with an uncertainty of ±2σ, was k1(T=259–381 K)=(1.02±0.30)×10−12 exp[(432±77) K/T] cm3 molecule−1 s−1. The obtained rate constant k1 was independent of pressure over the limited range employed. Our results are compared with the previous studies carried out, at single temperature and as a function of temperature, by different techniques. 相似文献
68.
从保护臭氧层,保护环境的角度出发,介绍了氯氟烃化合物对环境的影响。阐述了用制冷剂R22代替R502在低蒸发温度应用时需要解决的问题和如何解决。 相似文献
69.
采用黄磷乳浊液为吸收剂,考察了黄磷浓度、反应温度、搅拌速度、氧气浓度、烟气流量等影响因素对脱硝率的影响,并且通过添加碳酸钙进行改性,提高了体系的脱硝率。结果表明,脱硝率随黄磷浓度增大、反应温度升高、搅拌速度增大而升高;随烟气流量的增大而下降;加入碳酸钙改性可以明显提高体系脱硝效果;烟气流量400 m L/min,反应温度50℃,搅拌速度1 200 r/min,氧气浓度12%,黄磷浓度6 g/L,碳酸钙浓度2 g/L的条件下,处理NO浓度为0.06%的烟气,反应30 min体系脱硝率可达到84.76%。 相似文献
70.
MnxCe1- xO2(x: 0.3–0.9) prepared by Pechini method was used as a catalyst for the thermal catalytic oxidation of formaldehyde(HCHO). At x = 0.3 and 0.5, most of the manganese was incorporated in the fluorite structure of Ce O2 to form a solid solution. The catalytic activity was best at x = 0.5, at which the temperature of 100% removal rate is the lowest(270°C). The temperature for 100% removal of HCHO oxidation is reduced by approximately 40°C by loading 5 wt.% Cu Oxinto Mn0.5Ce0.5O2. With ozone catalytic oxidation, HCHO(61 ppm) in gas stream was completely oxidized by adding 506 ppm O3 over Mn0.5Ce0.5O2 catalyst with a GHSV(gas hourly space velocity) of 10,000 hr-1at 25°C. The effect of the molar ratio of O3 to HCHO was also investigated. As O3/HCHO ratio was increased from 3 to 8, the removal efficiency of HCHO was increased from 83.3% to 100%. With O3/HCHO ratio of 8, the mineralization efficiency of HCHO to CO2 was 86.1%. At 25°C, the p-type oxide semiconductor(Mn0.5Ce0.5O2) exhibited an excellent ozone decomposition efficiency of 99.2%,which significantly exceeded that of n-type oxide semiconductors such as Ti O2, which had a low ozone decomposition efficiency(9.81%). At a GHSV of 10,000 hr-1, [O3]/[HCHO] = 3 and temperature of 25°C, a high HCHO removal efficiency(≥ 81.2%) was maintained throughout the durability test of 80 hr, indicating the long-term stability of the catalyst for HCHO removal. 相似文献