The study zone is located in the city of Padova (the Veneto region, NE Italy). The industrial activities present in this area
since 1950 have produced very high concentrations of Pb, Zn, Cu, Pcb and oils until a depth of 7 m. The unsaturated and the
saturated zones are both polluted. Because of the abundance of Pb values it was decided to analyze the lead distribution in
the studied zone. In many studies of the polluted sites, the geometry of the investigated volume is highly anisotropic. Generally
we have an extension of some hectares in the horizontal plane and of a few meters in depth. It is likely that different horizontal
spatial continuity structures in pollution distribution are found at different depths both for the layered nature of the medium
and for the transition between unsaturated and saturated conditions. In such conditions the decision to divide a 3D problem
into 1D and 2D problems can be useful. Initially the studied volume was divided into seven layers up to 5 m in depth; the
study was then approached in two phases. First, the Pb values in the vertical direction were analyzed, considering a derive
along z, and estimating the values using the Kriging with Trend (KT) method. Thus it was possible to increase the data in the z direction, especially in the deeper layers. Second, 500 realizations of the Pb distribution for each of the seven layers
were simulated using the simulated annealing procedure. Finally, results were presented and discussed for each layer in terms
of median and probability maps. 相似文献
Application of recent advances in numerical weather prediction (NWP) has the potential of allowing delivery of flood warning to extend well beyond the typical lead times of operational flood warning at the river basin scale. A prototype system, a European Flood Forecasting System (EFFS) developed to deliver such pre-warnings, aiming at providing a pre-warning at lead times of between 5 and 10 days is described. Considerable uncertainty in the weather forecast at these lead times, however, means that resulting forecasts must be treated probabilistically, and although probabilistic forecasts may be easy to disseminate, these are difficult to understand. This paper explores the structure of operational flood warning, and shows that integration in the flood warning process is required if the pre-warning is to fulfil its potential. A simple method of summarising the information in the pre-warning is presented, and the system in hindcast mode is shown to give clear indication of an upcoming major event in the Rhine basin up to 10 days before the actual event. Finally recommendations on the use of data assimilation to embed the EFFS system within an operational environment are given. 相似文献
Meteoric smoke particles (MSPs) form through the vaporization of meteoroids and the subsequent re-condensation of metallic species in the mesosphere. Recently, iridium and platinum enrichments have been identified in Greenland ice layers and attributed to the fallout of MSPs supplying polar latitudes with cosmic matter during the Holocene. However, the MSP fallout to Antarctica during the Earth's climatic history remains essentially unknown.
We have determined iridium and platinum in deep Antarctic ice from Dome C and Vostok dated back to 240 kyrs BP. We find high super-chondritic fluxes during warm periods and low meteoric accretion during glacial times, a pattern that is opposite to any known climatic variation in dust fallout to polar regions. The proposed explanation of this accretion regime is a weaker polar vortex during warm periods, allowing peripheral air masses enriched in volcanic iridium and platinum to penetrate inland to Antarctica. The MSP signal emerges only during cold phases and is four times lower than in the Greenland ice cap where more snow accumulates. This suggests that wet deposition is an important route of cosmic material to the Earth's surface. 相似文献
In past years, seismic response of asymmetric structures has been frequently analysed by means of single-storey models, because
of their simplicity and low computational cost. However, it is widely believed that use of more realistic multi-storey models
is needed in order to investigate effects of some system characteristics (such as overstrength, higher modes of vibration,
etc.) that make behaviour of multi-storey schemes different from that of single-storey systems. This paper examines effects
of the overstrength in element cross-sections on the seismic behaviour of multi-storey asymmetric buildings. It is shown that
in actual buildings this characteristic, which is sometimes very variable both in plan and along the height of the building,
may lead to distributions of ductility demands different from those expected according to the results from single-storey models.
Consequently, torsional provisions, which aim at reducing ductility demands of single-storey asymmetric systems to those of
the corresponding torsionally balanced systems, should be re-checked in light of the behaviour of realistic multi-storey buildings. 相似文献
An archaeometric study of the stone materials employed in the Late Baroque historical monuments of the ancient city centre of Catania was carried out. Lithological maps of a selection of monuments, transferred to a digital format, revealed that the stone materials are both magmatic and sedimentary rocks, the colours of which are matched in a peculiar type of bichromy. Particular attention focused on sedimentary rocks, which consist of various types of limestone quarried near the city of Syracuse (Hyblean Plateau, south-eastern Sicily). Carbonate rocks were characterised in terms of mineralogy, petrography and geochemistry, by studying rock samples from both monuments and historical extraction sites. Results showed that, although only one name was historically attributed to the above lithotypes (i.e. “Pietra di Siracusa‘’), they were quarried from many locations and, as they belong to various geological formations, they therefore exhibit great variety. In order to examine the durability of Hyblean limestones employed in works of cultural heritage interest, salt crystallisation tests were carried out according to standard procedure norms (UNI EN 12370 (1999) Determination of resistance to crystallisation of salts, 6p). Results are consistent with the forms of deterioration observed in the monuments, and highlight the close relationship between textural characteristics and damage. Our purpose is to provide a basic tool, which may be useful both for conserving monuments of cultural heritage and for their restoration. 相似文献
Iron is the most abundant transition metal in the atmosphere and can play a significant role in cloudwater chemistry where its reactivity is closely related to the partitioning between Fe(II) and Fe(III). The objective of this work is to determine the total iron content and the iron speciation in a free tropospheric site, and to understand which factors influence these parameters. We collected 147 samples of cloudwater during 34 cloud events over a period of four years at the puy de Dôme summit. Besides iron we measured other chemical compounds, solar radiation, physico-chemical and meteorological parameters potentially connected with iron reactivity. The total iron concentrations ranged from 0.1 to 9.1 μM with the major frequency occurring at low levels. The pH and presence of organic complexants seem to be the most significant factors connected with total dissolved iron; while the iron oxidation state seems to be an independent factor. Light intensity, presence of complexants or oxidants (H2O2) do not influence the Fe(II)/Fe(Total) ratio, that was quite constant at about 0.75. This could be due to the potential redox that forces the Fe(II)-Fe(III) couple to the reduced form or, more probably to the complexation by Natural Organic Matter, that can stabilize iron in its reduced form and prevent further oxidation. Our field measurements did not show the diurnal cycle observed in surface water and predicted by models of atmospheric chemistry. This result prompts a more careful review of the role of iron and, by analogy, all the transition metals in atmospheric liquid phase, often over-estimated in the literature. 相似文献
An integrated approach to real-time prediction of point rainfall is presented. This is based on the assumption that hourly rainfall at a station can be predicted by a Multivariate AutoRegressive Integrated Moving Average (MARIMA) process. The real-time calibration of the multivariate model is performed by combining radar maps and data from rain gages. Accordingly, radar maps provide the basic information for a storm tracking procedure which enables to detect the direction and the speed of storm movement. Storm tracking is used to select those stations which are characterized by the highest Lagrangian cross-correlation of observed precipitation, and which are therefore best suitable for application of the multivariate model. The parameters of the multivariate model are finally estimated using only observed rainfall at the selected stations throughout the current event. Preliminary results of an application to some events which occurred in northern Italy show that the combined use of radar and rain gages allows for an increased efficiency of the MARIMA model performances, as compared with empirical selection of stations to be considered by the multivariate model. The multivariate approach performs better also when it is compared with simple nowcasting procedures based on rain gage data or on radar data used separately. Finally, some considerations are issued in view of a systematic use of this technique to nowcast rainfall intensity in small urban or natural catchments, with a response time of less than 1 or 2 h. 相似文献