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511.
Atmospheric phenanthrene pollution modulates carbon allocation in red clover (Trifolium pratense L.)
Desalme D Binet P Epron D Bernard N Gilbert D Toussaint ML Plain C Chiapusio G 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2759-2765
The influence of atmospheric phenanthrene (PHE) exposure (160 μg m−3) during one month on carbon allocation in clover was investigated by integrative (plant growth analysis) and instantaneous 13CO2 pulse-labelling approaches. PHE exposure diminished plant growth parameters (relative growth rate and net assimilation rate) and disturbed photosynthesis (carbon assimilation rate and chlorophyll content), leading to a 25% decrease in clover biomass. The root-shoot ratio was significantly enhanced (from 0.32 to 0.44). Photosynthates were identically allocated to leaves while less allocated to stems and roots. PHE exposure had a significant overall effect on the 13C partitioning among clover organs as more carbon was retained in leaves at the expense of roots and stems. The findings indicate that PHE decreases root exudation or transfer to symbionts and in leaves, retains carbon in a non-structural form diverting photosynthates away from growth and respiration (emergence of an additional C loss process). 相似文献
512.
Lakhani A Parmar RS Satsangi GS Prakash S 《Environmental monitoring and assessment》2007,133(1-3):435-445
Fog water samples were collected in the months of December and January during 1998–2000 at Agra, India. The samples were analyzed
for pH, major anions (F−, Cl−, SO4
2−, NO3
−, HCOO− and CH3COO−), major cations (Ca2+, Mg2+, Na+ and K+) and NH4
+ using ion chromatography, ICP-AES and spectrophotometer methods, respectively. pH of fog water samples ranged between 7.0
and 7.6 with a volume weighted mean of 7.2, indicating its alkaline characteristic. NH4
+ contributed 40%, SO4
2− and NO3
− accounted for 28%, while Ca2+, Mg2+, Na+ and K+ accounted for 16% of the total ionic concentration. The ratios of Mg2+/Ca2+ and Na+/Ca2+ in fog water indicates that 50–75% of fog water samples correspond to the respective ratios in local soil. Significant correlation
between Ca2+, Mg2+, Na+ and K+ suggests their soil origin. The order of neutralization, NH4
+ (1.4) > Ca2+ (0.28) > Mg2+ (0.12), indicates that NH4
+ is the major neutralizing species. Fog water and atmospheric alkalinity were also computed and were found to be 873 and 903 neqm−3, respectively. Both of these values are higher than values reported from temperate sites and thus indicate that at the present
level of pollutants, there is no risk of acid fog problem. The study also shows that the alkaline nature of fog water is due
to dissolution of ammonia gas and partly due to interaction of fog water with soil derived aerosols. 相似文献
513.
改进遗传神经网络方法在大气环境质量评价中的应用 总被引:8,自引:0,他引:8
运用双极性压缩函数适应度定标和基于排挤方法的选择算子改进标准遗传算法(SGA),使其成为简单通用、快速收敛的并行全局搜索算法。利用该算法优化误差反向传播网络(BPN),克服了BPN收敛慢和不具有全局收敛性的缺陷,在此基础上,建立大气环境质量评价模型,并将该模型用于实例。结果表明,该方法用于大气环境质量评价是可行的。 相似文献
514.
A statistical study was performed over 145 profiles of meteorological balloons, equipped with microthermal sensors, from the
ground to the midstratosphere. This study put into evidence the lognormal distribution of the fluctuations of the structure
constant of temperature, the fluctuations of the buoyancy force and the vertical shear of the horizontal wind speed. We show
that these quantities, computed over a large scale (100 m), are correlated up to the midstratosphere. A model is adjusted
to estimate the optical turbulence strength from the macroscopic meteorological parameters. The model performances, to estimate and forecast the strength and the altitude
of the optical turbulent layers, are quantified and compared with other already defined models. This model was shown to have
the best performances and put into evidence a new relation to describe the turbulence on a large scale. 相似文献
515.
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519.
为探究地下公共建筑能见度降低场景中,个体及小群体楼梯上行疏散特征,在某公共建筑楼梯间进行个体疏散和小群体疏散实验,分析不同能见度条件下个体在梯段及平台上的疏散速度、疏散行为、小群体特征等关键参数。研究结果表明:梯段速度受能见度影响程度大于平台速度,在正常能见度条件下,小群体行为会对疏散移动速度产生负面影响,在低能见度条件下,小群体行为有助于提升疏散效率,表现在小群体平均速度高于群体中最慢个体速度且小群体和个体之间的速度差异较小。 相似文献
520.
In the period between 1999 and 2000 epiphytic bryophytes were taken as bioindicators for air pollution by use of the IAP method
(Index of Atmospheric Purity) and the VDI method within the Association of Engineers standards list (adapted from guideline
3799, 1995) in the heavy industrialized town of Linz, Austria. 52 study sites (265 trees) were analysed regarding species
richness, coverage, and vitality. Q-values (sensitivity factors), calculated for each species showed significant differences
for the various host tree species. The results gained by the IAP and the VDI methods were diverse, regarding the various sites
where only 25% were classified identical. These differences can mainly be attributed to the differing host tree species and
the size of the recording area on the various trees. Clusters of similar pollution levels were calculated and drawn as maps
for both methods tested. Comparing the results of the IAP and the VDI methods with data derived from technical measurements
(SO2, NO, NO2, and dust) a correlation between IAP-indices and SO2 concentrations could be observed. No correlation was detected between the results derived from VDI recording and for NO,
NO2, and dust. 相似文献