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71.
Chemical signals of epiphytic lichens in southwestern North America; natural versus man-made sources for airborne particulates 总被引:1,自引:0,他引:1
Stephen R. Getty David S. Gutzler Yemane Asmerom Charles K. Shearer Scott J. Free 《Atmospheric environment (Oxford, England : 1994)》1999,33(30):2261
Ambient airborne particulate matter (PM) in southwestern North America consists of naturally derived desert dust, plus anthropogenic inputs from several sources. Epiphytic lichens (Usnea sp.) in this region are a useful biomonitor for the airborne PM because they derive nutrients and moisture largely from incorporated atmospheric aerosols, and not by absorption from the host tree limb from which they are suspended. Using a broad-based sampling strategy from southern Chihuahua, Mexico, to northern New Mexico, USA, we show that select elemental abundance ratios and lead isotopes from epiphytic lichens are useful for distinguishing between sources of airborne PM, and for gauging anthropogenic inputs into desert ecosystems. Abundance patterns of the trace elements La, Nd, and Sm in the lichens suggest origination from continental crust, but rare earth elements display a pronounced enrichment relative to the major element Fe by a factor of about 5. This enrichment appears related to geologic weathering, aeolian transport, and grain-size biases toward trace-element-rich mineral grains in the arid setting. Using the metal Pb as an indicator of human inputs, epiphytic lichens typically show Pb enrichments by a factor of about 25–60 over typical upper crustal values. Regional-scale differences in Pb isotope ratios of these lichens relate to different pollutant sources in southwestern North America. 相似文献
72.
Yuting Wei Xiao Tian Junbo Huang Zaihua Wang Bo Huang Jinxing Liu Jie Gao Danni Liang Haofei Yu Yinchang Feng Guoliang Shi 《Frontiers of Environmental Science & Engineering》2023,17(11):137
73.
涡旋结构是湍流流场重要的研究内容之一,也是影响特殊火行为的重要因素之一,如涡旋在飞火传播中起着非常重要的作用。火羽流涡旋结构的详细分析对火灾蔓延特性的研究有重要指导意义。该文对轴对称热羽流和平面热羽流进行了直接数值模拟,分别基于涡旋动力学及涡旋稳定性角度对计算结果进行详细分析。研究表明平面热羽流的涡量值明显高于轴对称热羽流,平面热羽流具有较低的脉动频率。从涡量输运方程出发,分析得出拉伸项的存在降低了轴对称热羽流的混合强度。 相似文献
74.
Hanyun Cheng Xu Dong Yang Yang Yiqing Feng Tao Wang Muhammad Ali Tahir Liwu Zhang Hongbo Fu 《环境科学学报(英文版)》2021,33(2):11-17
Monolayer-ordered gold nanoring arrays were prepared by ion-sputtering method and used as surface enhanced Raman spectroscopy (SERS) substrates to test the individual atmospheric aerosols particle. Compared to other methods used for testing atmospheric aerosols particles, the collection and subsequent detection in our work is performed directly on the gold nanoring SERS substrate without any treatment of the analyte. The SERS performance can be tuned by changing the depth of the gold nanoring cavity as originating from coupling of dipolar modes at the inner and outer surfaces of the nanorings. The electric field exhibits uniform enhancement and polarization in the ordered Au nanoring substrate, which can improve the accuracy for detecting atmospheric aerosol particles. Combined with Raman mapping, the information about chemical composition of individual atmospheric aerosols particle and distribution of specific components can be presented visually. The results show the potential of SERS in enabling improved analysis of aerosol particle chemical composition, mixing state, and other related physicochemical properties. 相似文献
75.
针对坡地建筑外立面开口火溢流行为,为了预测不同坡地角度时圆形开口建筑火溢流的外立面热羽流温度分布规律,采用1∶8缩尺寸建筑火灾模型,开展圆形开口建筑火溢流实验研究。结果表明:在建筑火灾燃烧状态稳定下,对于确定开口尺寸、火源功率以及坡地坡度(倾斜挡墙)下,带有圆形开口的燃烧室内温度基本均匀且保持一致;针对圆形开口建筑,倾斜挡墙坡度越大,外立面的温度越高;基于热羽流温度实验数据,建立考虑不同开口尺寸、火源功率和倾斜挡墙角度影响下圆形开口建筑火灾溢出热羽流的竖向温度预测模型。 相似文献
76.
77.
C. Leroy 《Journal of environmental radioactivity》2010,101(11):937-944
Atmospheric releases of krypton-85, from the nuclear fuel reprocessing plant at the AREVA NC facility at La Hague (France), were used to test Gaussian models of dispersion. In 2001-2002, the French Institute for Radiological Protection and Nuclear Safety (IRSN) studied the atmospheric dispersion of 15 releases, using krypton-85 as a tracer for plumes emitted from two 100-m-high stacks. Krypton-85 is a chemically inert radionuclide. Krypton-85 air concentration measurements were performed on the ground in the downwind direction, at distances between 0.36 and 3.3 km from the release, by neutral or slightly unstable atmospheric conditions. The standard deviation for the horizontal dispersion of the plume and the Atmospheric Transfer Coefficient (ATC) were determined from these measurements. The experimental results were compared with calculations using first generation (Doury, Briggs) and second generation (ADMS 4.0) Gaussian models. The ADMS 4.0 model was used in two configurations; one takes account of the effect of the built-up area, and the other the effect of the roughness of the surface on the plume dispersion. Only the Briggs model correctly reproduced the measured values for the width of the plume, whereas the ADMS 4.0 model overestimated it and the Doury model underestimated it. The agreement of the models with measured values of the ATC varied according to distance from the release point. For distances less than 2 km from the release point, the ADMS 4.0 model achieved the best agreement between model and measurement; beyond this distance, the best agreement was achieved by the Briggs and Doury models. 相似文献
78.
华北地区某电厂排烟冷却塔烟气抬升高度的光学照相法实测结果显示,选用S/P模式计算出排烟冷却塔烟气括升高度是合理的。在环境风速小、空气潮湿条件下,采用排烟冷却塔排放方式有利于污染物稀释扩散;在环境风速大、空气干燥、逆温等不利气象条件时,采用排烟冷却塔排放方式,烟气抬升高度较低。 相似文献
79.
Casanovas R Morant JJ López M Hernández-Girón I Batalla E Salvadó M 《Journal of environmental radioactivity》2011,102(8):742-748
The automatic real-time environmental radiation surveillance network of Catalonia (Spain) comprises two subnetworks; one with 9 aerosol monitors and the other with 8 Geiger monitors together with 2 water monitors located in the Ebre river. Since September 2006, several improvements were implemented in order to get better quality and quantity of data, allowing a more accurate data analysis. However, several causes (natural causes, equipment failure, artificial external causes and incidents in nuclear power plants) may produce radiological measured values mismatched with the own station background, whether spurious without significance or true radiological values. Thus, data analysis for a 50-month period was made and allowed to establish an easily implementable statistical criterion to find those values that require special attention. This criterion proved a very useful tool for creating a properly debugged database and to give a quick response to equipment failures or possible radiological incidents. This paper presents the results obtained from the criterion application, including the figures for the expected, raw and debugged data, percentages of missing data grouped by causes and radiological measurements from the networks. Finally, based on the discussed information, recommendations for the improvement of the network are identified to obtain better radiological information and analysis capabilities. 相似文献
80.
Zhang W Bean M Benotto M Cheung J Ungar K Ahier B 《Journal of environmental radioactivity》2011,102(12):1065-1069
A high volume aerosol sampler ("Grey Owl") has been designed and developed at the Radiation Protection Bureau, Health Canada. Its design guidance is based on the need for a low operational cost and reliable sampler to provide daily aerosol monitoring samples that can be used as reference samples for radiological studies. It has been developed to provide a constant air flow rate at low pressure drops (∼3 kPa for a day sampling) with variations of less than ±1% of the full scale flow rate. Its energy consumption is only about 1.5 kW for a filter sampling over 22,000 standard cubic meter of air. It has been demonstrated in this Fukushima nuclear accident related aerosol radioactivity monitoring study at Sidney station, B.C. that the sampler is robust and reliable. The results provided by the new monitoring system have been used to support decision-making in Canada during an emergency response. 相似文献