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301.
J. Cambrollé S. Redondo-Gómez E. Mateos-Naranjo T. Luque M. E. Figueroa 《Russian Journal of Ecology》2014,45(3):215-222
Glaucium flavum Crantz. is a short-lived perennial herb distributed in coastal zones from the Black Sea to southern, western and north-western Europe. Despite its diminishing area of distribution and potential pharmacological value, little is known about the ecophysiological features of this coastal species. We investigated the photosynthetic performance of G. flavum by measuring gas exchange, chlorophyll fluorescence, photosynthetic pigment concentration and leaf water content over the space of a year in a coastal habitat of SW Spain. We also measured the variation in total concentrations of nitrogen, phosphorus, sulphur, potassium, calcium and magnesium, in the leaves and soil, throughout the study period. G. flavum showed a high resistance to summer drought conditions which appeared to be due to the high degree of stomatal control. The potential photochemical efficiency of photosystem II showed minimum values during the winter, indicating that low temperatures can produce negative effects within the photosynthetic apparatus. However, the marked decline in net photosynthesis during the winter seems to be mainly related to a loss of metabolic activity. Although leaf nutrient concentrations were, in general, within the normal ranges, phosphorus availability seems to be limited by the high calcium concentrations detected in the soil of the study site. Our study points out the efficiency of the different physiological adaptations of this rare and endangered coastal species in coping with the strong seasonal variability of the Mediterranean climate. 相似文献
302.
The influence of socioeconomic, environmental, and demographic factors on municipality-scale land-cover change in Mexico 总被引:3,自引:0,他引:3
Martha Bonilla-Moheno T. Mitchell Aide Matthew L. Clark 《Regional Environmental Change》2012,12(3):543-557
Land-cover change is the result of complex multi-scale interactions between socioeconomic, demographic, and environmental factors. Demographic change, in particular, is thought to be a major driver of forest change. Most studies have evaluated these interactions at the regional or the national level, but few studies have evaluated these dynamics across multiple spatial scales within a country. In this study, we evaluated the effect of demographic, environmental, and socioeconomic variables on land-cover change between 2001 and 2010 for all Mexican municipalities (n?=?2,443) as well as by biome (n?=?4). We used a land-cover classification based on 250-m MODIS data to examine the change in cover classes (i.e., woody, mixed woody, and agriculture/herbaceous vegetation). We evaluated the trends of land-cover change and identified the major factors correlated with woody vegetation change in Mexico. At the national scale, the variation in woody vegetation was best explained by environmental variables, particularly precipitation; municipalities where woody cover increased tended to be in areas with low average annual precipitation (i.e., desert and dry forest biomes). Demographic variables did not contribute much to the model at the national scale. Elevation, temperature, and population density explained the change in woody cover when municipalities were grouped by biome (i.e., moist forest, dry forest, coniferous forest, and deserts). Land-cover change at the biome level showed two main trends: (1) the tropical moist biome lost woody vegetation to agriculture and herbaceous vegetation, and (2) the desert biome increased in woody vegetation within more open-canopy shrublands. 相似文献
303.
This paper describes a study directed towards the laboratory simulation of parameters of the office environment related to air borne gaseous and particulate pollutants and initial operating experience of a particulate test chamber, instrumentation, and control techniques. Also discussed is the design of a simple gaseous test chamber being constructed. Gas dilution procedures, control and general operating approach are described. 相似文献
304.
305.
Konrad T. Semrau 《Journal of the Air & Waste Management Association (1995)》2013,63(12):587-594
Geographic variation in the prevalence of respiratory disease between communities has been used to incriminate air pollution at low concentrations in the production of disease. Though demographic factors and the design and conduct of survey research affect the validity of these observations, there are other complex factors which are often neglected. From several community studies planned or conducted by the authors, illustrations will be given of the effect of the following six frequently neglected factors: the reliability of the air pollution monitoring network; the validity of the air pollution monitoring network; the competing effect of differential migration of population; the competing effect of occupational pollution of members of the population; the competing effect of socioeconomic factors; and the competing effect of personal air pollution—tobacco smoking. 相似文献
306.
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308.
S. F. Liang C. V. Sternling T. R. Galloway 《Journal of the Air & Waste Management Association (1995)》2013,63(7):605-607
This paper presents a simplified analysis to determine the variables that affect the empirical correlation factor used in the lead peroxide method. The rate of sulfation has been determined from two different models. In the first model, the mass transfer rate is calculated from the gas phase resistance alone whereas in the second model, the diffusion resistance in the gel phase is assumed to be the rate limiting step. Although the gas phase and the gel phase resistances may be both important in the actual case, it has been found that the correlation factor based on the first model is adequate to describe general experimental observations. Reasonable agreement has been obtained between the measured and the calculated va|ue of the correlation factor. 相似文献
309.
J.N. Driscoll A.W. Berger J.H. Becker J.T. Funkhouser J.R. Valentine 《Journal of the Air & Waste Management Association (1995)》2013,63(2):119-122
The nitrate ion selective electrode was investigated as an alternative approach to the present colorimetric determination of nitrate resulting from oxidative absorption of nitrogen oxides from combustion effluents. The electrode offers advantages of speed and relatively simple experimental procedure. Replicate measurements of 10?4–10?2M nitric acid solutions using bracketing standards show that the electrode approach is capable of good precision (coefficient of variation = ±4%). Comparison of a method utilizing the nitrate electrode with the more laborious phenol disulfonic acid method for the measurement of nitrogen oxides in both oil and gas fired combustion effluents showed agreement within 4% of the mean even in the presence of high levels of SO2. The correlation coefficient found for PDS vs nitrate electrode is 0.987. 相似文献
310.
Bruce Lighthart Victor E. Hiatt August T. Rossano Jr 《Journal of the Air & Waste Management Association (1995)》2013,63(10):639-642
Aerosols of Serratia marcescens ATCC 274 were suspended in a 709L rotating drum at 20 ± 1 °C and high to mid-range relative humidities. At specified times after bacterial aerosolization, sulfur dioxide was added to concentrations of 2.5, or 5 mg/m3. Viable cell decay rate constants, in control aerosols without added sulfur dioxide, increased rapidly from near 100% to 60% RH in the first hour (termed: young aerosol) of suspension, and from a minimum rate constant at 80% in the succeeding four hours (termed: old aerosol).Upon addition of sulfur dioxide to a cloud of S. marcescens, generally, viable cell decay rate constants increased further. One exception was at 80% relative humidity where maximum resistance to SO2 accelerated death was observed for old aerosols. Cells in young aerosols were particularly sensitive to SO2 addition at mid-range humidities, while in older aerosols the cells were insensitive to up to 5 mg SO2/m3 introduced at high RH; but were up to 10 times more sensitive than cells in young aerosols to a given increase (from 2.5 to 5 mg/m3) in SO2 concentration at mid-range humidities. 相似文献