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1.
Alkane hydrocarbons (propane, isobutane, and n-butane) from liquefied petroleum gas (LPG) are present in major quantities throughout Mexico City air because of leakage of the unburned gas from numerous urban sources. These hydrocarbons, together with olefinic minor LPG components, furnish substantial amounts of hydroxyl radical reactivity, a major precursor to formation of the ozone component of urban smog. The combined processes of unburned leakage and incomplete combustion of LPG play a significant role in causing the excessive ozone characteristic of Mexico City. Reductions in ozone levels should be possible through changes in LPG composition and lowered rates of leakage. 相似文献
2.
Dilution of a photochemical system containing hydrocarbons and oxides of nitrogen can lead to higher ozone concentrations than are observed in a static system. This effect was observed in an outdoor smog chamber with a hydrocarbon mix simulating urban systems. 相似文献
3.
The field of atmospheric chemistry is data-limited, primarily because of the challenge of measuring the key chemical constituents in the global environment. Several recent advances, however, in rugged, portable, remotesensing, ground-based instrumentation and accurate, fast-response airborne instrumentation have provided powerful tools for the understanding of stratospheric ozone, particularly in polar regions. Current discoveries of the role of heterogeneous chemical processes point to the need for better techniques for characterization of stratospheric aerosols. In the troposphere, advances in in situ, sensitive methods for detecting reactive nitrogen compounds have demonstrated the role that these compounds have in controlling global oxidation processes, but better measurements of the reservoir species by which the long-ranged transport of pollutant-reactive nitrogen compounds is thought to occur are urgently needed. The role of hydrocarbons, particularly those of natural origin, in ozone formation in rural areas has focused attention on the requirement for better speciation of these ubiquitous compounds. Lastly, rigorous instrument intercomparison experiments have provided unbiased estimates of measurement capabilities. 相似文献
4.
Calculations indicate that chlorofluoromethanes produced by man can greatly affect the concentrations of stratospheric ozone in future decades. This effect follows the release of chlorine from these compounds in the stratosphere. Present usage levels of chlorofluoromethanes can lead to chlorine-catalyzed ozone destruction rates that will exceed natural sinks of ozone by 1985 or 1990. 相似文献
5.
为了揭示臭氧(O3)浓度升高对城市森林光合作用的影响机理,利用开顶式气室研究了高浓度O3对沈阳城内油松光合生理特性的影响。结果表明:与对照(自然O3浓度,约45 nmol/mol)相比,在O3浓度升高(80±8)nmol/mol条件下,油松针叶的叶绿素含量降低,而类胡萝卜素含量则呈现出先升高后降低的变化趋势;净光合速率和Hill反应活力明显下降,降幅分别为18.36%~45.95%和11.35%~20.84%;羧化效率降低,降幅为7.50%~26.59%;叶绿体ATP酶活性受到抑制,但Ca2+-ATP酶活性与Mg2+-ATP酶活性的变化趋势略有差异。同时O3浓度升高抑制了油松针叶可溶性糖和淀粉含量的积累,说明O3浓度升高对油松光合作用具有较强的抑制作用。 相似文献
6.
Dickerson RR Huffman GJ Luke WT Nunnermacker LJ Pickering KE Leslie AC Lindsey CG Slinn WG Kelly TJ Daum PH Delany AC Greenberg JP Zimmerman PR Boatman JF Ray JD Stedman DH 《Science (New York, N.Y.)》1987,235(4787):460-465
Acid deposition and photochemical smog are urban air pollution problems, and they remain localized as long as the sulfur, nitrogen, and hydrocarbon pollutants are confined to the lower troposphere (below about 1-kilometer altitude) where they are short-lived. If, however, the contaminants are rapidly transported to the upper troposphere, then their atmospheric residence times grow and their range of influence expands dramatically. Although this vertical transport ameliorates some of the effects of acid rain by diluting atmospheric acids, it exacerbates global tropospheric ozone production by redistributing the necessary nitrogen catalysts. Results of recent computer simulations suggest that thunderstorms are one means of rapid vertical transport. To test this hypothesis, several research aircraft near a midwestern thunderstrom measured carbon monoxide, hydrocarbons, ozone, and reactive nitrogen compounds. Their concentrations were much greater in the outflow region of the storm, up to 11 kilometers in altitude, than in surrounding air. Trace gas measurements can thus be used to track the motion of air in and around a cloud. Thunderstorms may transform local air pollution problems into regional or global atmospheric chemistry problems. 相似文献
7.
为了揭示臭氧（O3）浓度升高对城市森林光合作用的影响机理,利用开顶式气室研究了高浓度O3对沈阳城内油松光合生理特性的影响。结果表明:与对照（自然O3浓度,约45 nmol/mol）相比,在O3浓度升高（80±8 ）nmol/mol条件下,油松针叶的叶绿素含量降低,而类胡萝卜素含量则呈现出先升高后降低的变化趋势;净光合速率和Hill反应活力明显下降,降幅分别为18.36%～45.95%和11.35%～20.84%;羧化效率降低,降幅为7.50%～26.59%;叶绿体ATP酶活性受到抑制,但Ca2+ ATP酶活性与Mg2+ ATP酶活性的变化趋势略有差异。同时O3浓度升高抑制了油松针叶可溶性糖和淀粉含量的积累,说明O3浓度升高对油松光合作用具有较强的抑制作用。 相似文献
8.
Russell A Milford J Bergin MS McBride S McNair L Yang Y Stockwell WR Croes B 《Science (New York, N.Y.)》1995,269(5223):491-495
Control strategies for urban ozone traditionally have been based on mass reductions in volatile organic compounds (VOCs). Studies show, however, that some organic gas species (such as alkanes and alcohols) form an order of magnitude less ozone than equal mass emissions of others (such as alkenes and aldehydes). Chemically detailed photochemical models are used to assess uncertainty and variability in reactivity quantification. VOC control strategies based on relative reactivity appear to be robust with respect to nationwide variations in environmental conditions and uncertainties in the atmospheric chemistry. Control of selective organic gas species on the basis of reactivity can offer cost savings over traditional strategies. 相似文献
9.
随着环境的不断恶化,大规模灾害的频繁发生,如何防灾、减灾已经成为城市建设中一项不容忽视的艰巨任务。在城市的各类防灾系统中,绿地防灾是一种既能为城市提供自然空间又有助于防灾救援的有效手段。具有防灾与减灾功能的城市绿地在整个城市的防灾与减灾中起着重要的作用,本文以上海大连路公共绿地(应急避难示范园)的建设为例阐诉了绿地防灾与减灾功能的具体应用。 相似文献
10.
Polycyclic aromatic hydrocarbons in soils and recent sediments 总被引：1，自引：0，他引：1
Soils and recent marine sediments contain a complex polycyclic aromatic hydrocarbon assemblage. There is a high degree of similarity in the molecular weight distribution of the many series of alkyl homologs of these aromatic hydrocarbons, and this distribution varies little over a wide range of depositional environments. The evidence suggests that these hydrocarbons are formed in natural fires, are dispersed and mixed by air transport, and are eventually deposited into surface sediments. The analytical, geochemical, and environmental implications of these findings are discussed. 相似文献
11.
The sulfidation of materials upon exposure to the atmosphere has traditionally been attributed entirely to reactions with sulfur-containing gases and water vapor. New laboratory results demonstrate that the sulfidation of polycrystalline copper can be markedly enhanced both by solar radiation and by the ubiquitous atmospheric ozone, thus indicating that the high rates of corrosion in urban areas are a result of a complex sequence of multicomponent photochemical processes. 相似文献
12.
城市公园声景分析及GIS声景观图在其中的应用 总被引：1，自引：0，他引：1
通过对泰安市东湖公园和南湖公园的实地勘测与问卷调查,对两公园春季的声景现状和使用者对其声景的主观评价进行了调查,利用GIS系统初步建立了两公园声景的数据库和声景观图,并对公园的声景进行分析。结果表明,以春季为例,城市公园的声景主要由自然声、人工声和机械声构成,其中自然声最受游客喜爱。公园声景的组成和特征受公园周边环境和游客使用情况影响较大,这主要是由城市公园的性质决定的。声景观图不仅能够全面有效地描述城市公园的声景,还可以作为分析公园声景的有效方法,为城市公园声景的记录和设计提供了新的途径。 相似文献
13.
14.
Sunday and workday variations in photochemical air pollutants in new jersey and new york 总被引：2，自引：0，他引：2
Concentration distributions of air contaminants and meteorological variables in New Jersey and New York for workdays (Mondays through Fridays, omitting holidays) and Sundays are compared by means of quantile-quantile plots. The ozone distributions are slightly higher on Sundays, and the primary pollutant distributions are lower. These results raise serious questions about the validity of current concepts underlying ozone reduction in urban atmospheres. 相似文献
15.
施林翊 《新疆农业大学学报》2006,29(1):90-94
调查了威胁吐鲁番市城镇建设生态安全的自然、环境因素，认为风害、沙害、夏季酷热、终年极端干旱是主要影响因素，在对发生危害的原因进行分析的基础上，依据生态保护及可持续发展原理，提出吐鲁番市及其周边城镇安全建设的指导思想是减风、治沙、降温、增湿，逐步改善吐鲁番市的牛态环境条件，据此设计出了保护山地天然林、封育荒漠林、建好绿洲防护林、实施计划用水及实施林园结合、发展城市林业等切实可行的生态安全建设技术措施。 相似文献
16.
近地层臭氧对农作物产量影响的风险评估模型研究进展 总被引：1，自引：0，他引：1
近地层臭氧污染及其对农作物产量和粮食安全的负面效应已成为国内外广泛关注的焦点之一,建立适宜且更为精确的模型开展臭氧影响下的农作物产量损失评估对于粮食安全保障及臭氧污染控制具有重要的意义。综述了浓度响应、剂量响应和通量响应等统计模型的发展及其在产量损失评估中的应用,评述了其优缺点和通量响应模型的不确定性,同时,通过臭氧干沉降模型的研究进展及其与通量响应模型的优势比较,提出了基于观测和臭氧干沉降模型开展臭氧影响下的自然农田作物产量损失评估技术新的研究方向。 相似文献
17.
Severe reduction of stratospheric ozone over Antarctica has focused increasing concern on the biological effects of ultraviolet-B (UVB) radiation (280 to 320 nanometers). Measurements of photosynthesis from an experimental system, in which phytoplankton are exposed to a broad range of irradiance treatments, are fit to an analytical model to provide the spectral biological weighting function that can be used to predict the short-term effects of ozone depletion on aquatic photosynthesis. Results show that UVA (320 to 400 nanometers) significantly inhibits the photosynthesis of a marine diatom and a dinoflagellate, and that the effects of UVB are even more severe. Application of the model suggests that the Antarctic ozone hole might reduce near-surface photosynthesis by 12 to 15 percent, but less so at depth. The experimental system makes possible routine estimation of spectral weightings for natural phytoplankton. 相似文献
18.
PO Wennberg TF Hanisco L Jaegle DJ Jacob EJ Hintsa EJ Lanzendorf JG Anderson R Gao ER Keim SG Donnelly LAD Negro DW Fahey SA McKeen RJ Salawitch CR Webster RD May RL Herman MH Proffitt JJ Margitan EL Atlas SM Schauffler F Flocke CT McElroy TP Bui 《Science (New York, N.Y.)》1998,279(5347):49-53
The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected. 相似文献
19.
Parrish DD Holloway JS Trainer M Murphy PC Fehsenfeld FC Forbes GL 《Science (New York, N.Y.)》1993,259(5100):1436-1439
Measurement of the levels of ozone and carbon monoxide (a tracer of anthropogenic pollution) at three surface sites on the Atlantic coast of Canada allow the estimation of the amount of ozone photochemically produced from anthropogenic precursors over North America and transported to the lower troposphere over the temperate North Atlantic Ocean. This amount is greater than that injected from the stratosphere, the primary natural source of ozone. This conclusion supports the contention that ozone derived from anthropogenic pollution has a hemisphere-wide effect at northern temperate latitudes. 相似文献
20.
Changes in stratospheric ozone 总被引：2，自引：0，他引：2
Cicerone RJ 《Science (New York, N.Y.)》1987,237(4810):35-42
The ozone layer in the upper atmosphere is a natural feature of the earth's environment. It performs several important functions, including shielding the earth from damaging solar ultraviolet radiation. Far from being static, ozone concentrations rise and fall under the forces of photochemical production, catalytic chemical destruction, and fluid dynamical transport. Human activities are projected to deplete substantially stratospheric ozone through anthropogenic increases in the global concentrations of key atmospheric chemicals. Human-induced perturbations may be occurring already. 相似文献