The control of polluted surface runoff and the assessment of possible impacts on groundwater is a concern at the local and
regional scale. On this background, a study investigates possible impacts of organic and inorganic pollutants (including bacteria)
originating from a permeable asphalt parking lot on the water quality immediately beneath it. The functioning of the permeable
pavement, including clogging and restricted vertical percolation, was also evaluated. Four nested sample ports (shallow and
deep) were installed below low- and high-traffic areas, including one port outside the parking lot. At least initially there
was a good hydraulic connection between the parking surface and the shallow sample ports. The presence of a geotextile layer
at the base of the parking lot structure, however, was identified in lab tests as one factor restricting vertical percolation
to the deeper ports. Clogging of the permeable surface was most pronounced in heavy traffic areas and below snow pile storage
areas. Corroborated by high electric conductivity and chloride measurements, sand brought in by cars during winter was the
principal cause for clogging. No bacteria or BOD were found in percolating water. Polycyclic aromatic hydrocarbons (PAH) were
present at concentrations near minimum detection limit. Nutrients (nitrate and phosphate) were being leached into the ground
via the permeable parking lot surface at annual flux rates of 0.45–0.84 g/m2/year. A multi-species tracer test demonstrated a retention capacity of the permeable parking lot structure of >90% for metals
and 27% for nutrients, respectively. 相似文献
The research shows that in the Celje area (Slovenia), the historical anthropogenical emissions are 1,712 tons of Zn and 9.1 tons
of Cd. For Zn, this value represents approximately 0.3% of the total Zn production in that area. Close to the former zinc
smelting plant, the “Zn precipitation” has been estimated to be up to 0.036 mm. The 100-year Zn production left behind a heavily
contaminated area with maximum concentrations of Zn of up to 5.6% in attic dust and 0.85% in the soil, and 456 mg/kg of Cd
in attic dust and 59.1 mg/kg in the soil. The calculation of historical emissions is based on the data of heavy metals concentration
in the attic dust at 98 sampling points and on the data from 19 measurement sites of the weight of total monthly air deposit.
The main idea behind determining past emissions is that when the weight of the deposited dust on a small area is multiplied
by the concentration of the element in that area, the mass of the polluter which has been transported to the place of interest
by air can be calculated. If we sum up all the weight over the whole geochemical anomaly, we get the quantity of historical
emissions. 相似文献
Numerical modelling was done at the Cold Lake Air Weapons Range, Canada, to test whether the dissolved RDX and nitrate detected
in groundwater come from the same sources, and to predict whether contamination poses a threat to the surface water receptors
near the site. Military live fire training activities may indeed pose a risk of contamination to groundwater resources, however
field investigations on military bases are quite recent, and little information is available on the long-term behaviour of
munition residues related contaminants. Very limited information was available about the contaminant source zones, which were
assigned based on our knowledge of current training activities. The RDX plume was well represented with the model, but the
heterogeneous distribution of nitrate concentrations was more difficult to reproduce. It was nonetheless determined that both
contaminants originate from the same areas. According to the model, both contaminants should reach the nearby river, but concentrations
in the river should remain very low if the source zone concentration does not change. Finally, the model allowed the recommendation
of a new location for the main bombing target, which would offer added protection to the river and the lake into which it
flows. 相似文献
The paper is dedicated to the review of methods of seismic hazard analysis currently in use, analyzing the strengths and weaknesses of different approaches. The review is performed from the perspective of a user of the results of seismic hazard analysis for different applications such as the design of critical and general (non-critical) civil infrastructures, technical and financial risk analysis. A set of criteria is developed for and applied to an objective assessment of the capabilities of different analysis methods. It is demonstrated that traditional probabilistic seismic hazard analysis (PSHA) methods have significant deficiencies, thus limiting their practical applications. These deficiencies have their roots in the use of inadequate probabilistic models and insufficient understanding of modern concepts of risk analysis, as have been revealed in some recent large scale studies. These deficiencies result in the lack of ability of a correct treatment of dependencies between physical parameters and finally, in an incorrect treatment of uncertainties. As a consequence, results of PSHA studies have been found to be unrealistic in comparison with empirical information from the real world. The attempt to compensate these problems by a systematic use of expert elicitation has, so far, not resulted in any improvement of the situation. It is also shown that scenario-earthquakes developed by disaggregation from the results of a traditional PSHA may not be conservative with respect to energy conservation and should not be used for the design of critical infrastructures without validation. Because the assessment of technical as well as of financial risks associated with potential damages of earthquakes need a risk analysis, current method is based on a probabilistic approach with its unsolved deficiencies.
Traditional deterministic or scenario-based seismic hazard analysis methods provide a reliable and in general robust design basis for applications such as the design of critical infrastructures, especially with systematic sensitivity analyses based on validated phenomenological models. Deterministic seismic hazard analysis incorporates uncertainties in the safety factors. These factors are derived from experience as well as from expert judgment. Deterministic methods associated with high safety factors may lead to too conservative results, especially if applied for generally short-lived civil structures. Scenarios used in deterministic seismic hazard analysis have a clear physical basis. They are related to seismic sources discovered by geological, geomorphologic, geodetic and seismological investigations or derived from historical references. Scenario-based methods can be expanded for risk analysis applications with an extended data analysis providing the frequency of seismic events. Such an extension provides a better informed risk model that is suitable for risk-informed decision making. 相似文献
The petrological parameters Na8 and Fe8, which are Na2O andFeO contents in mid-ocean ridge basalt (MORB) melts correctedfor fractionation effects to MgO = 8 wt%, have been widely usedas indicators of the extent and pressure of mantle melting beneathocean ridges. We find that these parameters are unreliable.Fe8 is used to compute the mantle solidus depth (Po) and temperature(To), and it is the values and range of Fe8 that have led tothe notion that mantle potential temperature variation of TP= 250 K is required to explain the global ocean ridge systematics.This interpreted TP = 250 K range applies to ocean ridges awayfrom hotspots. We find no convincing evidencethat calculated values for Po, To, and TP using Fe8 have anysignificance. We correct for fractionation effect to Mg# = 0·72,which reveals mostly signals of mantle processes because meltswith Mg# = 0·72 are in equilibrium with mantle olivineof Fo89·6 (vs evolved olivine of Fo88·1–79·6in equilibrium with melts of Fe8). To reveal first-order MORBchemical systematics as a function of ridge axial depth, weaverage out possible effects of spreading rate variation, local-scalemantle source heterogeneity, melting region geometry variation,and dynamic topography on regional and segment scales by usingactual sample depths, regardless of geographical location, withineach of 22 ridge depth intervals of 250 m on a global scale.These depth-interval averages give Fe72 = 7·5–8·5,which would give TP = 41 K (vs 250 K based on Fe8) beneathglobal ocean ridges. The lack of Fe72–Si72 and Si72–ridgedepth correlations provides no evidence that MORB melts preservepressure signatures as a function of ridge axial depth. We thusfind no convincing evidence for TP > 50 K beneath globalocean ridges. The averages have also revealed significantcorrelations of MORB chemistry (e.g. Ti72, Al72, Fe72,Mg72, Ca72, Na72 and Ca72/Al72) with ridge axial depth. Thechemistry–depth correlation points to an intrinsic linkbetween the two. That is, the 5 km global ridge axial reliefand MORB chemistry both result from a common cause: subsolidusmantle compositional variation (vs TP), which determines themineralogy, lithology and density variations that (1) isostaticallycompensate the 5 km ocean ridge relief and (2) determine thefirst-order MORB compositional variation on a global scale.A progressively more enriched (or less depleted) fertileperidotite source (i.e. high Al2O3 and Na2O, and low CaO/Al2O3)beneath deep ridges ensures a greater amount of modal garnet(high Al2O3) and higher jadeite/diopside ratios in clinopyroxene(high Na2O and Al2O3, and lower CaO), making a denser mantle,and thus deeper ridges. The dense fertile mantle beneath deepridges retards the rate and restricts the amplitude of the upwelling,reduces the rate and extent of decompression melting, givesway to conductive cooling to a deep level, forces melting tostop at such a deep level, leads to a short melting column,and thus produces less melt and probably a thin magmatic crustrelative to the less dense (more refractory) fertile mantlebeneath shallow ridges. Compositions of primitive MORB meltsresult from the combination of two different, but geneticallyrelated processes: (1) mantle source inheritance and (2) meltingprocess enhancement. The subsolidus mantle compositional variationneeded to explain MORB chemistry and ridge axial depth variationrequires a deep isostatic compensation depth, probably in thetransition zone. Therefore, although ocean ridges are of shalloworigin, their working is largely controlled by deep processesas well as the effect of plate spreading rate variation at shallowlevels. KEY WORDS: mid-ocean ridges; mantle melting; magma differentiation; petrogenesis; MORB chemistry variation; ridge depth variation; global correlations; mantle compositional variation; mantle source density variation; mantle potential temperature variation; isostatic compensation相似文献
This paper reports our research on China’s world cities. Formal network analysis of air passenger linkages for recent years
among China’s most populous cities and among many of the world’s largest cities allows us to identify the country’s leading
world city from among the leading Mainland candidates, Beijing, Shanghai and Guangzhou. We theorize our findings about China’s
world cities in relation to both global forces (and China’s increasing entanglement with them) and the policies and actions
of the national state. We examine the national and global urban network through a longitudinal, two-level analysis of airline
passenger travel for four time points between about 1990 and 2005. We show that Beijing was China’s leading world city at
the beginning of the time period, a status it lost nationally in as early as 1995, and then globally 10 years later. On the
other hand Shanghai became China’s leading world city, and it acquired this status first nationally in 2000, and then globally
in 2005. The changing status of the Chinese capital corresponds to the country’s increasing involvement with the capitalist
world economy. Shanghai’s ascendance as the leading world city in China may indicate that global forces have come to play
an increasingly important role relative to that of the developmental state.
Until recently the traditional spatial configuration of the European geography was based upon the core-periphery model. The
‘pentagon’, broadly defined as lying between London, Paris, Milan, Munich and Hamburg, was seen as the core area characterised
by having the highest concentration of economic development in the European Union (EU), with the remainder of the European
territory viewed as peripheral, albeit to varying degrees. In a number of cases such peripheral areas equated with clear regional
disparities. The elaboration of the European Spatial Development Perspective (ESDP) (CEC, European spatial development perspective, towards balanced and sustainable development in the territory of the
European Union, 1999) challenged this core-periphery model. European spatial planning policies, aimed at encouraging social
and economic, and with ever increasing importance, territorial cohesion, seek amongst other aspects to encourage the development
of a balanced and polycentric urban system. This paper adopts a network analysis approach to the analysis of air passenger
flows between some 28 principal European metropolitan urban regions. The evaluation of these flows contributes to an enhanced
comprehension of the spatial dynamics of the European metropolitan territory which goes beyond that deriving from the more
standard analyses of the individual components of the urban system. Several indicators are used, deriving from gravitational
modelling techniques, to analyse the complexity of the air passenger flows. A multidimensional scaling (MDS) technique is
introduced in order to interpret and visualise the resulting spatial configuration and positioning of the different metropolitan
centres within the conceptual European ‘space of air passenger flows’, thereby contrasting with the more traditional map-based
geographical image of Europe, based upon Cartesian coordinates.