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21.
区域化学输送模式中NOx和O3源示踪法的引入 总被引：4，自引：0，他引：4
发展了化学输送模式中氮氧化合物(NOx)和臭氧(O3)的一种源示踪方法,对这种示踪法及其应用模式作了详细介绍,并结合臭氧光化学反应机理的分析描述了NOx和O3示踪物浓度方程的推导过程。将这种示踪法引用到区域化学输送模式中,并以太原和石家庄地表NOx人为排放产生的活性氮化物和臭氧为例,演示了污染物向北京的输送过程,模拟的O3,NOx和NOz示踪物浓度时空分布与O3,NOx和NOz在大气中的衰减尺度分析一致,表明该示踪法是一种有效的研究区域氮氧化物以及臭氧来源和输送转化过程的方法。个例模拟分析结果显示:太原和石家庄的地表人为排放产生的NOx本身并不能输送到北京,但通过它们产生的O3和HNO3可以输送到北京,对北京地表附近大气污染造成影响。 相似文献
22.
本文给出了一个半拉格朗日形式的大气扩散模式。模式除考虑污染物在大气中的输送、弥散过程外,还加入了光化学反应过程。我们用此模式计算了1983年8月中旬兰州市西固地区的光化学烟雾浓度。计算结果和监测资料的对比表明,模式对这一地区O_3最大浓度值有较好的模拟能力,对O_3浓度的日变化及地理分布也有一定的模拟能力。 相似文献
23.
P. Herzsprung K. Friese G. Packroff M. Schimmele K. Wendt-Potthoff M. Winkler 《洁净——土壤、空气、水》1998,26(5):253-262
The investigated coal mining lakes (ML 111, ML 117, and ML 107) in the Lusatian lignite mining district are extremely acidic. The concentrations of iron in these geogenic acidified lakes are orders of magnitude higher than in acidic bog lakes and softwater lakes acidified by atmospheric deposition. For the most part ferric iron was the predominant species by a Fe(III) to Fe(II) ratio of more than 10. Density stratification of the water column leads to vertical concentration gradients of ferrous iron. Extremely high concentrations of ferrous iron were found in the anoxic layers above the sediment of ML 111 and ML 107. High concentrations of Fe(II) were correlated with high concentrations of carbon dioxide. A microbial potential to reduce ferric iron was found in the sediments. In ML 111 and ML 117 the concentrations of Fe(II) in the epilimnion were markedly higher than in the oxic hypolimnetic layers. It can be suggested that the occurence of ferrous iron in the epilimnion is of photochemical origin, as described for softwater lakes. Minimum concentrations of dissolved organic carbon in the epilimnion could be correlated to the increase of ferrous iron concentrations. Especially in springtime and summer the concentrations of Fe(II) in the epilimnion were higher than in the oxic hypolimnetic layer below. 相似文献
24.
Air samples were collected covering a full diurnal cycle during each month of the year 2002 at a mountaintop of Mt. Abu (24.6^∘ N, 72.7^∘ E, 1680 amsl). These samples were analyzed for C2−C4 NMHCs using a gas chromatograph (GC) equipped with flame ionization detector (FID). The seasonally averaged diurnal distributions of these NMHCs do not show significant variations in the summer season. While sharp peaks in the diurnal variation of some species during evening hours are additional features apart from higher levels in all NMHCs in the winter season. The seasonal variations in relatively long lived species (e.g. ethane, propane and acetylene) are observed to be more pronounced compared to those in reactive species (e.g. ethene, propene and butanes). The seasonal changes in transport patterns seem to be more dominant factor at this site for the observed variations in NMHCs than changes in OH radical concentration. The annual mean mixing ratios of ethane, ethene, propane, propene, i-butane, acetylene, and n-butane are 1.22 ± 0.58, 0.34 ± 0.24, 0.46
± 0.20, 0.17 ± 0.14, 0.21 ± 0.18, 0.41 ± 0.43, and 0.31 ± 0.35 ppbv, respectively. Only few pairs of NMHCs are observed to show good correlations, mainly due to transport of air masses with different degree of photochemical processing. A comparison of this measurement with data reported for other remote sites of the globe indicates lower levels of light NMHCs in the tropical sites. The annual mean mixing ratios of various C2−C4 NMHCs at Mt. Abu are lower by factors ranging between 3 to 9 compared to a nearest urban site of Ahmedabad. The annual mean propylene (propene) equivalent concentrations of about 1.12 and 8.62 ppbC were calculated for Mt. Abu and Ahmedabad, respectively. 相似文献