Growth of northern deciduous trees under increasing atmospheric humidity: possible mechanisms behind the growth retardation

Regional Environmental Change - Increasing atmospheric humidity—a climate trend predicted for northern Europe—will reduce water flux through vegetation. Diminished transpirational water...     

Minimal pesticide-primed soil inoculum density to secure maximum pesticide degradation efficiency in on-farm biopurification systems

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.     

Analysis of river pollution data from low-flow period by means of multivariate techniques

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.     

A modification of the classical Ekman model accounting for the Stokes drift and stratification effects

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.     

A model of vertical distribution of suspended matter in an open channel flow

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).     

Assessment of growth and stemwood quality of Scots pine on territory influenced by alkaline industrial dust

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.     

SPECIAL CASES OF WATER SUPPLY INTERFERENCE CAUSED BY URBAN DEVELOPMENT NEAR TORONTO,ONTARIO, CANADA1

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.     

Sorption kinetics and its effects on retention and leaching.

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.     

Landscape pattern and census area as determinants of the diversity of farmland avifauna in Estonia

Landscape structure affects farmland bird species richness and diversity at different scales. We develop a predictive, metric-based model for farmland bird species richness in different bird guilds and study how the research area size influences the relationship between bird diversity and landscape metrics. Thirty research locations (randomly selected, each containing four counting points) were located in three counties of Estonia. In early summer 2002 and 2004, two bird counts per point were carried out in each research location. Three landscape metrics (patch density, edge density and Shannon’s diversity index) were calculated at three spatial scales: 100- and 200-m buffer zones around the count points and in a 1 km² at 1 m × 1 m grain size. Using generalized additive mixed models with repeated measures, we found in most cases that the proportion of variance explained between the bird variables and landscape metrics increased with an increased study area thus demonstrating the effect of scale. Thus, a larger research area is recommended for landscape metrics. At large scales, however, all used landscape metrics were equally good predictors for bird species richness.     

Low-Level Microwave Radiation Effect on Nerve Pulse Conduction Velocity

Summary This study is aimed to investigate dependence of nerve pulse conduction velocity on low-level microwave exposure. The changes in fiber membrane permeability or myelin sheath, caused by microwave, should affect nerve pulse conduction velocity. Experimental investigation was carried out for nerve pulse conduction velocity with and without applied microwave field and different orientations of its polarization to the nerve fiber. Microwave radiation of 450 MHz was applied polarized perpendicular or parallel to the nerve fiber. The measured field power density at the skin was 0.87 mW/cm². Special program was developed for calculation of the nerve pulse conduction velocity in LabView environment. The right nervus medianus motor nerve fibers of 35 young subjects were under the study. The experimental protocol included ten measurements in every cycle of five different exposure conditions. No changes in average values of the conduction velocities discovered in different exposure conditions. Theoretical calculations based on Hodgkin-Huxley model confirm only a weak possible effect. The results showed that low-level microwave radiation did not cause statistically significant change in nerve pulse conduction velocity in human motor nerve fiber.