The past two decades have witnessed an increasing interest in the use of space-time models for a wide range of environmental
problems. The fundamental tool used to embody both the temporal and spatial components of the phenomenon in question is the
covariance model. The empirical estimation of space-time covariance models can prove highly complex if simplifying assumptions
are not employed. For this reason, many studies assume both spatiotemporal stationarity, and the separability of spatial and
temporal components. This second assumption is often unrealistic from the empirical point of view. This paper proposes the
use of a model in which non-separability arises from temporal non-stationarity. The model is used to analyze tropospheric
ozone data from the Emilia-Romagna Region of Italy. 相似文献
Nowadays, adaptation has become a key focus of the scientific and policy-making communities and is a major area of discussion in the multilateral climate change process. As climate change is projected to hit the poorest the hardest, it is especially important for developing countries to pay particular attention to the management of natural resources and agricultural activities. In most of these countries such as Cameroon, forest can play important role in achieving broader climate change adaptation goals. However, forest generally receives very little attention in national development programme and strategies such as policy dialogues on climate change and poverty reduction strategies. Using a qualitative approach to data collection through content analysis of relevant Cameroon policy documents, the integration of climate change adaptation was explored and the level of attention given to forests for adaptation analysed. Results indicate that, with the exception of the First National Communication to UNFCCC that focused mostly on mitigation and related issues, current policy documents in Cameroon are void of tangible reference to climate change, and hence failing in drawing the relevance of forest in sheltering populations from the many projected impacts of climate change. Policies related to forest rely on a generalized concept of sustainable forest management and do not identify the specific changes that need to be incorporated into management strategies and policies towards achieving adaptation. The strategies and recommendations made in those documents only serve to improve understanding of Cameroon natural resources and add resilience to the natural systems in coping with anthropogenic stresses. The paper draws attention to the need to address the constraints of lack of awareness and poor flow of information on the potentials of forests for climate change adaptation. It highlights the need for integrating forest for adaptation into national development programmes and strategies, and recommends a review of the existing environmental legislations and their implications on poverty reduction strategy and adaptation to climate change. 相似文献
Twenty-five strains of filamentous fungi, encompassing 14 different species and belonging mainly to Ascomycetes, were tested for their ability to degrade benzo[a]pyrene (BaP) in mineral liquid medium. The most performing isolates for BaP degradation (200 mg?l?1) in mineral medium were Cladosporium sphaerospermum with 29 % BaP degradation, i.e., 82.8 μg BaP degraded per day (day?1), Paecilomyces lilacinus with 20.5 % BaP degradation, i.e., 58.5 μg BaP day?1, and Verticillium insectorum with 22.3 % BaP degradation, i.e., 64.3 μg BaP day?1, after only 7 days of incubation. Four variables, e.g., biomass growth on hexadecane and glucose, BaP solubilization, activities of extracellular- and mycelium-associated peroxidase, and polyethylene glycol degradation, were also studied as selective criteria presumed to be involved in BaP degradation. Among these variables, the tests based on polyethylene glycol degradation and on fungal growth on hexadecane and glucose seemed to be the both pertinent criteria for setting apart isolates competent in BaP degradation, suggesting the occurrence of different mechanisms presumed to be involved in pollutant degradation among the studied micromycetes. 相似文献
Abstract Sustainable development is one of the most important ideas, and goals of our time. It is defined as “development which meets the needs and aspirations of the current generation and develops safe and sound society for future generation”. Achieving sustainable development thus involves a vigorous and urgent debate on different dimensions. The different dimensions of sustainability as a framework involve all issues such as science, technology, economic growth and development, health, education, finance investment and trade, politics, natural disasters, population growth and terrorism, etc. No single dimension is responsible to develop sustainable society. This article mainly described the integrated relationship among the three dimensions of sustainability. 相似文献
Petroleum products are generally volatile hydrocarbon mixtures. These mixtures may contaminate land surfaces, the unsaturated zone and ground waters at numerous sites and thus represent a long-term source of environmental subsurface pollution. Based on laboratory and field evidence obtained by our research groups and others we emphasize in the present review paper the effect of leaching on the abiotic processes controlling the fate of volatile petroleum hydrocarbon mixtures (VPHMs) in the soil environment. The modification of petroleum hydrocarbon mixtures due to changes in the soil water content is considered the result of a “leaching phenomenon”. The experimental evidence of VPHM behavior in the porous media is linked to four major processes: retention, redistribution and attenuation in the subsurface, and dissolution in the soil water.
Once VPHMs reach the soil surface, their residual concentration and composition is influenced by the amount and quality of the leaching water. The transport and natural attenuation of the VPHMs in the unsaturated zone is affected by the amount and rate of leaching. Since VPHM are a mixture of volatile and non-volatile hydrocarbons whose components differ by several orders of magnitude in their vapor pressure and water solubility, their fates in the soil environment under leaching will be diverse too. This will influence the temporal concentrations of the VPHM components and their distributions with depth, as vapors, solutes, or water-immiscible solutions. Wetting the soil before or after the VPHMs reach it, differentially affects the abiotic processes governing petroleum products behavior into the porous media. 相似文献
Here we review some of the main processes and key parameters affecting the mobility of radiocesium in soils of semi-natural areas. We further illustrate them in a collection of soil surface horizons which largely differ in their organic matter contents. In soils, specific retention of radiocesium occurs in a very small number of sorbing sites, which are the frayed edge sites (FES) born out of weathered micaceous minerals. The FES abundance directly governs the mobility of trace Cs in the rhizosphere and thus its transfer from soil to plant. Here, we show that the accumulation of organic matter in topsoils can exert a dilution of FES-bearing minerals in the thick humus of some forest soils. Consequently, such accumulation significantly contributes to increasing 137Cs soil-to-plant transfer. Potassium depletion and extensive exploration of the organic horizons by plant roots can further enhance the contamination hazard. As humus thickness depends on both ecological conditions and forest management. our observations support the following ideas: (1) forest ecosystems can be classified according to their sensitivity to radiocesium bio-recycling, (2) specific forest management could be searched to decrease such bio-recycling. 相似文献
Summary. Surrogate leaves treated with methanolic leaf
surface extracts of Brassica napus L. (cv Express) plants
that received three different sulphur fertilisation treatments
showed even more marked differences by the oviposition
choice of Delia radicum L. than the potted plants. This
confirms that the oviposition preference of D. radicum is
mediated by chemical compounds on the leaf surface and
that the quality of host-plants in terms of their nutrition
status can be perceived by the female insect.The oviposition data were positively correlated with the
content of fractionated surface extracts containing either
CIF (cabbage identification factor; 1,2-dehydro-3-thia-
4,10,10b-triaza-cyclopenta[.a.]fluorine-1-carboxylic acid)
or glucosinolates. Electrophysiological recordings from the
tarsal chemoreceptor sensilla C5 and D3,4 showed that receptor
neurons react to glucosinolate- and CIF-fractions. We
found that the chemosensory activity of specific glucosinolate-
and CIF-receptor neurons corresponded with the
respective behavioural activity in the oviposition choice
assays. The responses of D. radicum to glucosinolates in
the electrophysiological recordings studies corresponded
to the observed oviposition preference on plants or artificial
leaves characterised with an higher amount of glucosinolates
on leave surfaces. The presented data suggested
that CIF and glucosinolates are involved in host-plant
preference of D. radicum and are perceived by tarsal
chemoreceptors. 相似文献
In order to screen for the best species for mitigating nitrogen dioxide (NO2) by plants at urban levels, we investigated assimilation of nitrogen dioxide by 70 taxa of woody plants that are mostly utilized as roadside trees. They were fumigated with 15N-labeled NO2 at 0.1 microl l(-1) for 8h, and the amount of reduced nitrogen derived from NO2 (in mg Ng(-1) dry weight) in the leaves (designated NO2 assimilation capability hereafter) were determined. Data were analyzed in the comparison with the previously reported ones obtained at 4 microl l(-1) NO2. Among the 70 taxa, the value of NO2 assimilation capability differed by a factor of 122 between the highest (Prunus yedoensis; 0.061) and the lowest (Cryptomeria japonica; 0.0005). Based on the analysis of NO2 assimilation capability values at 0.1 and 4 micro l(-1) NO2, the 70 taxa of woody plants appeared to be classified into four types; those of high NO2 assimilation and high NO2 resistance, those of high NO2 assimilation but low NO2 resistance, those of low NO2 assimilation and low NO2 resistance, and those of low NO2 assimilation but high NO2 resistance. The first, second, third and fourth types include 13, 11, 35 and 11 taxa, respectively. The broad-leaf deciduous trees may have advantages of high biomass and fast growth as compared with woody plants of other habits. Thus, four broad-leaf deciduous species, Robinia pseudo-acacia, Sophora japonica, Populus nigra and Prunus lannesiana, were concluded here to be the best phytoremediators for the urban air. 相似文献
In this study, the decomposing deflagration properties of acetylene under temperatures down to −60 °C and pressures up to 0.2 MPa in a 1-L cylindrical closed vessel were experimentally investigated. The gases were ignited by an electric spark at the center of the vessel. The lower-limit pressures of decomposing deflagration by electric spark ignition were determined. The lower-limit pressure at 10 °C was 0.15 MPa, and it gradually increased with decreasing temperature. The lower-limit pressure at −60oC was 0.18 MPa. The flame propagation properties, such as the pressure, were measured with pressure transducers mounted along the vessel. The maximum decomposing deflagration pressures and pressure rising rates also increased with decreasing temperature. 相似文献