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排序方式: 共有260条查询结果,搜索用时 265 毫秒
51.
Kangwei Li Chao Lin Chunmei Geng Stephen White Linghong Chen Zhier Bao Xin Zhang Yanyun Zhao Lixia Han Wen Yang Merched Azzi 《环境科学学报(英文版)》2020,32(9):14-22
A new state-of-the-art indoor smog chamber facility (CAPS-ZJU) has been constructed and characterized at Zhejiang University, which is designed for chemical mechanism evaluation under well-controlled conditions. A series of characterization experiments were performed to validate the well-established experimental protocols, including temperature variation pattern, light spectrum and equivalent intensity (JNO2), injection and mixing performance, as well as gases and particle wall loss. In addition, based on some characterization experiments, the auxiliary wall mechanism has been setup and examined. Fifty chamber experiments were performed across a broad range of experimental scenarios, and we demonstrated the ability to utilize these chamber data for evaluating SAPRC chemical mechanism. It was found that the SAPRC-11 can well predict the O3 formation and NO oxidation for almost all propene runs, with 6 hr Δ(O3 – NO) model error of –3% ± 7%, while the final O3 was underestimated by ~20% for isoprene experiments. As for toluene and p-xylene experiments, it was confirmed that SAPRC-11 has significant improvement on aromatic chemistry than earlier version of SAPRC-07, although the aromatic decay rate was still underestimated to some extent. The model sensitivity test has been carried out, and the most sensitive parameters identified are the initial concentrations of reactants and the light intensity as well as HONO offgasing rate and O3 wall loss rate. All of which demonstrated that CAPS-ZJU smog chamber could derive high quality experimental data, and could provide insights on chamber studies and chemical mechanism development. 相似文献
52.
Secondary organic aerosol (SOA) formation potential for six kinds of short aliphatic ethers has been studied. The size distribution, mass concentration, and yield of SOA formed by ethers photooxidation were determined under different conditions. The results showed that all six ethers can generate SOA via reaction with OH radicals even under no seed and NOx-free condition. The mass concentration for six seedless experiments was less than 10 µg/m3 and the SOA yields were all below 1%. The strong increase in the SOA formation was observed when the system contained ammonium sulfate seed particles, while SOA yield decreased under the high-NOx condition. SOA composition was analyzed using offline methods. Infrared spectra indicated that there are complex components in the particle-phase including carbonyls acid and aldehydes species. Moreover, the aqueous filter extracts were analyzed using ultraviolet-visible spectrometer and fluorescence spectrophotometer. For the fresh methyl n-butyl ether SOA, the largest absorption peak occurs at 280 nm and there exists slightly absorption in the 300–400 nm. Excitation-emission matrices display the distinct peak at excitation/emission = 470 nm/480 nm according to the fluorescence spectrum. These findings are important considerations of formation for ether SOA that can eventually be included in atmospheric models. 相似文献
53.
尾矿库在使用的过程中,由于设计或施工的不合理,有可能导致在坝底或坝外坡出现尾砂渗漏的情况,往往造成一定的环境污染.对尾矿库尾砂渗漏的反滤原理进行了总结,并运用这一原理对某尾矿库的尾砂渗漏问题进行了反滤分析及设计,取得了较好的应用效果. 相似文献
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56.
O3浓度升高对南方城市绿化树种氮素的影响 总被引:1,自引:0,他引:1
近地层臭氧(O3)浓度升高会降低树木的光合速率,抑制Rubisco酶的活性,势必会间接影响树木N素的吸收与分配.本研究利用开顶式气室研究过滤大气(CF,<20 nL·L-1)与O3浓度升高(E-O3,约150 nL·L-1)对10种南方城市常用绿化树种幼苗N素吸收和分配的影响.结果表明,与CF相比,E-O3使枫香叶生物量和马褂木茎生物量分别显著降低了20.9%和21.4%,使枫香和马褂木的根生物量显著降低了24.2%和32.5%.O3对被测树种茎中N素含量影响显著,而对叶和根中N素含量无显著影响.O3对被测树种整株树N素吸收总量(Ntu)、叶片N素吸收量及根的N素吸收量存在显著影响,而对茎N素吸收量无显著影响.与CF相比,E-O3使马褂木与木荷的Ntu分别显著降低了28.4%与22.7%,而使舟山新木姜子Ntu显著增加了15.5%.O3浓度升高对各树种N素吸收量在各器官中的分配无显著影响. 相似文献
57.
北京市典型绿化灌木阻滞吸附PM2.5能力研究 总被引:1,自引:0,他引:1
选取北京市典型绿化灌木物种大叶黄杨、小叶黄杨、紫叶小檗、矮紫杉,结合气室模拟与实地观测的方法,综合测定不同树种对PM2.5的吸附能力.同时,收集2012年12月~2013年5月间北京市区PM2.5浓度值,分析了北京市冬春季PM2.5污染特征.结果表明,由气室实验得到的4种植物对PM2.5阻滞吸附能力排序为:紫叶小檗>小叶黄杨>矮紫衫>大叶黄杨,其原因主要为叶片特征差异所致;室外测量结果表明,4种物种吸附能力排序为:小叶黄杨>紫叶小檗>矮紫衫>大叶黄杨.气室模拟与室外实测结果均表明,小叶黄杨和紫叶小檗具有较强的阻滞吸附PM2.5的能力;气室模拟与室外观测实验中植物阻滞吸附PM2.5能力的大小略有差异,其原因应与植物结构相关.同时,通过分析北京市PM2.5浓度的季节性变化,发现北京市冬季的PM2.5浓度值尤为高,且常绿灌木植物仍能表现出较好的阻滞吸附PM2.5的能力. 相似文献
58.
A. Alexiou P. Kostarakis V. N. Christofilakis T. Zervos A. A. Alexandridis K. Dangakis C. Soras V. V. Petrović B. M. Kolundžija A. R. Dordević 《The Environmentalist》2005,25(2-4):215-221
Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of
a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D
radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power
absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber
using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained
in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm
away from the head. 相似文献
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60.
Hyun-Deok Choi 《Environmental pollution (Barking, Essex : 1987)》2009,157(5):1673-1678
Mercury (Hg) emissions from the soils taken from two different sites (deciduous and coniferous forests) in the Adirondacks were measured in outdoor and laboratory experiments. Some of the soil samples were irradiated to eliminate biological activity. The result from the outdoor measurements with different soils suggests the Hg emission from the soils is partly limited by fallen leaves covering the soils which helps maintain relatively high soil moisture and limits the amount of heat and solar radiation reaching the soil surface. In laboratory experiments exposure to UV-A (365 nm) had no significant effect on the Hg emissions while the Hg emissions increased dramatically during exposure to UV-B (302 nm) light suggesting UV-B directly reduced soil-associated Hg. Overall these results indicate that for these soils biotic processes have a relatively constant and smaller influence on the Hg emission from the soil than the more variable abiotic processes. 相似文献