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911.
Ozone dynamics in our study area (Castellon, Spain) is both strongly bound to the mesoscale circulations that develop under
the effect of high insolation (especially in summer) and conditioned by the morphological characteristics of the Western Mediterranean
Basin. In this work we present a preliminary analysis of ozone time series on five locations in Castellon for the period 1997–2003.
We study their temporal and spatial variations at different scales: daily, weekly, seasonally and interannually. Because both
the O3 concentration and its temporal variation depend on the topographic location of the observing station, they can show large
differences within tens of kilometer. We also contrast the variation in the ozone concentration with the variations found
for meteorological variables such as radiation, temperature, relative humidity and recirculation of the air mass. The link
between elevated ozone concentrations and high values of the recirculation factor (r=0.7–0.9) shown the importance of recirculating flows on the local air pollution episodes. 相似文献
912.
鞍山大气中有机氯农药的污染特征研究 总被引:2,自引:0,他引:2
布设鞍钢工业区6个点位,周边2个点位,居民区2个点位和千山对照点等11个点位,分别在采暖期和非采暖期测定大气中有机氯农药的含量,掌握了鞍山市大气中有机氯农药空间和时间变化趋势。全年有机氯农药各组分和ΣOPC浓度最高的功能区均为工业区周边,最低的功能区是千山对照点,六六六、滴滴涕和ΣOPC浓度变化趋势为工业区周边工业区居住区千山对照点,全市各功能区采暖期有机氯农药各组分和ΣOPC总浓度均高于非采暖期。 相似文献
913.
914.
序批式人工湿地冬季低温脱氮的效能研究 总被引:6,自引:2,他引:4
针对目前连续流人工湿地脱氮效率低、易堵塞及冬季效能下降的问题,提出了采用新型间歇流序批式人工湿地处理小城镇污水的方案,研究探讨了两级序批式人工湿地在冬季低温条件下,停留时间及排空闲置时间对脱氮效能的影响.试验结果表明,在冬季低温5~10 ℃、每级序批式湿地运行工况为瞬时进水-反应24h-瞬时排水-排空闲置12h、氮负荷为1.92g·m-2·d-1、进水COD、NH 4-N和TN浓度分别为143mg·L-1、27.0mg·L-1和32.0mg·L-1时,出水COD、NH4 -N和TN浓度分别为27mg·L-1、3.9mg·L-1和16.5mg·L-1,COD、NH4 -N和TN的去除率分别为81.12%、85.56%和48.44%. 相似文献
915.
916.
粪大肠菌群快速测定——纸片法的应用 总被引:1,自引:0,他引:1
赵凌宇 《环境监测管理与技术》2007,19(4):18-20
采集苏州具有代表性的地表水水体22个点位的样品,进行粪大肠菌群的测定方法比较,结果表明,《粪大肠菌群快速测定--纸片法》适于测定受粪便污染程度较轻的湖泊水体.但是,该方法的培养时间对阳性管率有明显影响,认为16 h~18 h是比较理想的培养时间. 相似文献
917.
918.
Two species of butterflies, Euphydryas aurinia and Melitaea phoebe, coexist as two metapopulations in a 38-patch network in Hebei Province, China. A Markovian model, whose transition matrix is the product of two matrices which represent the local extinction and recolonization process respectively, is used to describe the metapopulation dynamics. The application of this model to the metapopulation, consisting of 12 local populations in the northern subregion, shows that the expected life times of E. aurinia and M. phoebe are 160 and 121 years respectively and usually nearly half of the patches are occupied by E. aurinia, while only 1–3 patches are occupied by M. phoebe. We claim that E. aurinia can persist for a long time while M. phoebe faces relatively big extinction risk. By comparing the population dynamics with and without migration, we find M. phoebe benefits much more from migration than E. aurinia. Most patches are occupied mainly by local populations for E. aurinia, while by immigrants from the 8th patch for M. phoebe, meaning that E. aurinia has a classical metapopulation structure while M. phoebe has a source–sink metapopulation structure. 相似文献
919.
Many environmental problems are linked to multiphase flows encompassing ecological issues, chemical processes and mixing or
diffusion, with applications in different engineering fields. The transition from a supercritical flow to a subcritical motion
constitutes a hydraulic jump. This flow regime is characterised by strong interactions between turbulence, free surface and
air–water mixing. Although a hydraulic jump contributes to some dissipation of the flow kinetic energy, it is also associated
with increases of turbulent shear stresses and the development of turbulent eddies with implications in terms of scour, erosion
and sediment transport. Despite a number of experimental, theoretical and numerical studies, there is a lack of knowledge
concerning the physical mechanisms involved in the diffusion and air–water mixing processes within hydraulic jumps, as well
as on the interaction between the free-surface and turbulence. New experimental investigations were undertaken in hydraulic
jumps with Froude numbers up to Fr = 8.3. Two-phase flow measurements were performed with phase-detection conductivity probes.
Basic results related to the distributions of void fraction, bubble frequency and mean bubble chord length are presented.
New developments are discussed for the interfacial bubble velocities and their fluctuations, characterizing the turbulence
level and integral time scales of turbulence representing a “lifetime” of the longitudinal bubbly flow structures. The analyses
show good agreement with previous studies in terms of the vertical profiles of void fraction, bubble frequency and mean bubble
chord length. The dimensionless distributions of interfacial velocities compared favourably with wall-jet equations. Measurements
showed high turbulence levels. Turbulence time scales were found to be dependent on the distance downstream of the toe as
well as on the distance to the bottom showing the importance of the lower (channel bed) and upper (free surface) boundary
conditions on the turbulence structure. 相似文献
920.
S. Rocky Durrans Steven J. Burian Stephan J. Nix Ahmed Hajji Robert E. Pitt Chi-Yuan Fan Richard Field 《Journal of the American Water Resources Association》1999,35(5):1213-1221
Hydrologic modeling of urban watersheds for designs and analyses of stormwater conveyance facilities can be performed in either an event-based or continuous fashion. Continuou simulation requires, among other things, the use of a time series of rainfall amounts. However, for urban drainage basins, which are typically small, the temporal resolution of the rainfall time series must be quite fine, and often on the order of 5 to 15 minutes. This poses a significant challenge because rainfall-gauging records are usually kept only for hourly or longer time steps. The time step sizes in stochastic rainfall generators are usually also too large for application to urban runoff modeling situations. Thus, there is a need for methods by which hourly rainfall amounts can be disaggregated to shorter time intervals. This paper presents and compares a number of approaches to this problem, which are based on the use of polynomial approximating functions. Results of these evaluations indicate that a desegregation method presented by Ormsbee (1989) is a relatively good performer when storm durations are short (2 hours), and that a quadratic spline-based approach is a good choice for longer-duration storms. Based on these results, the Ormsbee technique is recommended because it provides good performance, and can be applied easily to long time series of precipitation records. The quadratic spline-based approach is recommended as a close second choice because it performed the best most consistently, but remains more difficult to apply than the Ormsbee technique. Results of this study also indicate that, on average, all of the disaggregation methods evaluated introduce a severe negative bias into maximum rainfall intensities. This is cause for some well-justified concern, as the characteristics of runoff hydrographs are quite sensitive to maximum storm intensities. Thus, there is a need to continue the search for simple yet effective hourly rainfall disaggregation methods. 相似文献