排序方式: 共有15条查询结果,搜索用时 31 毫秒
1.
Sellin Arne Alber Meeli Keinänen Markku Kupper Priit Lihavainen Jenna Lõhmus Krista Oksanen Elina Sõber Anu Sõber Jaak Tullus Arvo 《Regional Environmental Change》2017,17(7):2135-2148
Regional Environmental Change - Increasing atmospheric humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water... 相似文献
2.
Addition of pesticide-primed soil containing adapted pesticide degrading bacteria to the biofilter matrix of on farm biopurification systems (BPS) which treat pesticide contaminated wastewater, has been recommended, in order to ensure rapid establishment of a pesticide degrading microbial community in BPS. However, uncertainties exist about the minimal soil inoculum density needed for successful bioaugmentation of BPS. Therefore, in this study, BPS microcosm experiments were initiated with different linuron primed soil inoculum densities ranging from 0.5 to 50 vol.% and the evolution of the linuron mineralization capacity in the microcosms was monitored during feeding with linuron. Successful establishment of a linuron mineralization community in the BPS microcosms was achieved with all inoculum densities including the 0.5 vol.% density with only minor differences in the time needed to acquire maximum degradation capacity. Moreover, once established, the robustness of the linuron degrading microbial community towards expected stress situations proved to be independent of the initial inoculum density. This study shows that pesticide-primed soil inoculum densities as low as 0.5 vol.% can be used for bioaugmentation of a BPS matrix and further supports the use of BPS for treatment of pesticide-contaminated wastewater at farmyards. 相似文献
3.
Maie Bachmann Maksim Säkki Jaan Kalda Jaanus Lass Viiu Tuulik Hiie Hinrikus 《The Environmentalist》2005,25(2-4):165-171
Summary This study focuses on discrimination of changes, produced by low-level microwave exposure in intensity and time variability
of the human EEG at rest. The power spectral density (PSD) method and nonlinear scaling analysis of the length distribution
of low variability periods (LDLVP) were selected for analysis of the EEG signal. During the study, 19 healthy volunteers were
exposed to a microwave (450 MHz) of 217 Hz frequency on-off modulation. The field power density at the scalp was 0.16 mW/cm2. The experimental protocol consisted of ten cycles of repetitive microwave exposure. Signals from frontal, temporal, parietal
and occipital EEG channels on EEG theta, alpha and beta rhythms were analysed. Exposure to microwave causes average increase
of EEG activity. LDLVP analysis discriminated significant effect in time variability for 2 subjects (11%). PSD method detected
significant changes in intensity for 4 subjects (21%). The effect of low-level microwave exposure is stronger on EEG beta
rhythm in temporal and parietal regions of the human brain. 相似文献
4.
Maie Bachmann Ruth Tomson Jaan Kalda Maksim Säkki Jaanus Lass Viiu Tuulik Hiie Hinrikus 《The Environmentalist》2007,27(4):511-517
This study was aimed to investigate the changes in the human electroencephalographic (EEG) signal caused by modulated low-level
microwaves. The 450 MHz microwave exposure modulated at 40 Hz and 70 Hz frequencies was applied to a group of 15 volunteers.
The field power density at the scalp was 0.16 mW/cm2. Ten cycles of the exposure (1 min on and 1 min off) at both modulation frequencies were applied. Analysis of the EEG signal
was performed using three different methods: nonlinear method of scaling analysis for length distribution of low variability
periods (LDLVP), relative changes in EEG energy (S-parameter) and beta ratio (H-parameter). The analysis revealed significant changes caused by microwave for the whole group (H-parameter method). The exposure caused increase of the EEG beta power (S-parameter method). Statistically significant changes in EEG were detected for four subjects (26.7%) at 40 Hz modulation frequency
(LDLVP method). 相似文献
5.
Truu Jaak Heinaru Eeva Talpsep Ene Heinaru Ain 《Environmental science and pollution research international》2002,9(1):8-14
The oil-shale industry has created serious pollution problems in northeastern Estonia. Untreated, phenol-rich leachate from semi-coke mounds formed as a by-product of oil-shale processing is discharged into the Baltic Sea via channels and rivers. An exploratory analysis of water chemical and microbiological data sets from the low-flow period was carried out using different multivariate analysis techniques. Principal component analysis allowed us to distinguish different locations in the river system. The riverine microbial community response to water chemical parameters was assessed by co-inertia analysis. Water pH, COD and total nitrogen were negatively related to the number of biodegradative bacteria, while oxygen concentration promoted the abundance of these bacteria. The results demonstrate the utility of multivariate statistical techniques as tools for estimating the magnitude and extent of pollution based on river water chemical and microbiological parameters. An evaluation of river chemical and microbiological data suggests that the ambient natural attenuation mechanisms only partly eliminate pollutants from river water, and that a sufficient reduction of more recalcitrant compounds could be achieved through the reduction of wastewater discharge from the oil-shale chemical industry into the rivers. 相似文献
6.
A modification of the classical Ekman model of oceanic wind-driven currents including the Stokes drift and stratification
effects is discussed. The modification is formulated as an application of turbulence mechanics accounting for the curvature
effect of velocity fluctuation streamlines. It is shown that similar to the Stokes drift effect, the presence of a density
jump layer (pycnocline) decreases the veering of the flow velocity vector at the surface from the direction of the wind stress.
It is shown also that in the pycnocline the decrease of the norm of the velocity vector as well as its rotation with depth
is smaller than in the regions adjacent to the pycnocline. If the Stokes drift and stratification effects are neglected, the
model reduces to the classical Ekman solution with the coefficient of the turbulent shear viscosity replaced by an effective
viscosity coefficient. The vertical distributions of velocity predicted by the modified model are compared with the velocity
data measured in the Drake Passage and within the Long-Term Upper Ocean Study (LOTUS) in the North Atlantic. 相似文献
7.
A quasi-stationary model of vertical distribution of concentration of suspended particular matter in the bottom layer of 1D
open channel with a sloped bottom and varying free surface slope is discussed. The model proceeds from the balance between
the turbulent diffusion and settling with the buoyancy flux effects on the medium turbulence neglected. The model outcome
is formulated in the form of an analytic formula for the vertical distribution of concentration. It is shown that the derived
formula embraces two basic types of vertical distribution of concentration, one with a monotonic decrease of concentration
gradient and the other with a gradient maximum (lutocline) located at some distance from the bottom. The first distribution
type realizes for a relatively large settling velocity or low intensity of turbulence and the second type for a small settling
velocity or high intensity of turbulence. The skill of the model to mimic realistic situations is demonstrated on data measured
in the Jiaojiang Estuary (China). 相似文献
8.
SPECIAL CASES OF WATER SUPPLY INTERFERENCE CAUSED BY URBAN DEVELOPMENT NEAR TORONTO,ONTARIO, CANADA1
Donald N. Jeffs Jaak Viirland 《Journal of the American Water Resources Association》1970,6(5):746-753
Since 1961, control over water-supply interference problems in the Province of Ontario has been provided under The Ontario Water Resources Commission Act. A section of The Act requires persons taking more than 10,000 imperial gallons per day of water for purposes other than domestic, stock or fire-fighting to have a permit and to take the water in accordance with specified terms and conditions. Construction of some new wells, sewers, and roads to meet the needs of urban development has caused interference with both ground- and surface-water supplies. In cases of serious interference, the Commission has required that steps be taken to restore water supplies or prevent continued interference. Two cases are described where municipalities in the Toronto area restored supplies to overcome serious interference with several private wells and streamflow during testing and operation of a 500-imperial gpm municipal well adjacent to a normally effluent stream, and varying degrees of interference with private wells caused by dewatering at rates up to 2000-imperial gpm for the installation of a trunk sewer. 相似文献
9.
Assessment of growth and stemwood quality of Scots pine on territory influenced by alkaline industrial dust 总被引:1,自引:0,他引:1
Long-term influence of alkaline dust (pH 12.3–12.7) pollution emitted over 40 years from a cement plant in Estonia was the
reason of alkalisation (pH 6.7–7.9) and high concentrations of K, Ca and Mg in the soil of affected territories. Although
dust emission has diminished during the last 10 years, the disbalances in nutrition substrate and their influence on the growth
of trees are notable up to now. The study of morphological and physical properties of 70–80-year-old Scots pine (Pinus sylvestris L.) crown, stems and stemwood from three different air pollution zones showed serious deviations in comparison with a relatively
healthy forest in an unpolluted area. The specimens from polluted trees, if compared to reference site, showed significantly
smaller height growth, radial increment and width of annual rings of sapwood. In heartwood wider annual rings were found in
polluted areas. In the period of heartwood formation the dust pollution level emitted from the plant was relatively modest
and cement dust, which contains elements necessary for mineral nutrition of trees, may have acted as fertiliser. The moisture
content in sapwood and heartwood, especially in the upper layers of stems, was lower in the polluted area than in reference
site trees. Regression analysis revealed a strong dependence between latewood percentage and sapwood or heartwood in stems
of Scots pine in all sample plots. 相似文献
10.
Sorption kinetics and its effects on retention and leaching. 总被引:1,自引:0,他引:1
Tineke de Wilde Jan Mertens Pieter Spanoghe Jaak Ryckeboer Peter Jaeken Dirk Springael 《Chemosphere》2008,72(3):509-516
Sorption of pesticides to substrates used in biopurification systems is important as it controls the system's efficiency. Ideally, pesticide sorption should occur fast so that leaching of the pesticide in the biopurification system is minimized. Although modeling of pesticide transport commonly assumes equilibrium, this may not always be true in practice. Sorption kinetics have to be taken into account. This study investigated the batch sorption kinetics of linuron, isoproturon, metalaxyl, isoxaben and lenacil on substrates commonly used in a biopurification system, i.e. cow manure, straw, willow chopping, sandy loam soil, coconut chips, garden waste compost and peat mix. The first-order sorption kinetics model was fitted to the observed pesticide concentrations versus time resulting in an estimated kinetic rate constant alpha. Sorption appeared to be fast for the pesticides linuron and isoxaben, pesticides which were classified as immobile, while less mobile pesticides displayed an overall slower sorption. However, the substrate does not seem to be the main parameter influencing the sorption kinetics. Coconut chips, which is a substrate with a high organic matter content showed slow sorption for most of the pesticides. The effect of different estimated alpha values on the breakthrough of pesticides through a biopurification system was evaluated using the HYDRUS 1D model. Significant differences in leaching behavior were observed as a result of the obtained differences in sorption kinetics. 相似文献