Impact of copper smelting on lakes in the southern Ural Mountains,Russia, inferred from chironomids     

Stephen?J.?BrooksEmail author  Valery?Udachin  Ben?J.?Williamson 《Journal of Paleolimnology》2005,33(2):229-241

Karabash (52°2 N, 60°10 E) is a copper smelting town in the southern Ural Mountains of Russia. The town is affected by sulphur dioxide emissions and deposition of metal-rich particulates from the smelter, acid drainage from old mine workings, and leachates from disused waste dumps and tailings dams. The close proximity of houses to these sources of pollution is of concern to human health and has devastated terrestrial vegetation in the environs. The environmental impact of the smelter on lakes in the area has been assessed using chironomids. Short sediment cores were taken from 16 lakes within a 50 km radius of the smelter and the composition of the chironomid fauna from the bottom of each core, representing conditions prior to the commissioning of the smelter in 1910, was compared with the present chironomid fauna in the surface sediments. Redundancy analysis (RDA) showed that changes in the chironomid fauna of most lakes were driven by trophic change, independent of the industrial activity. Lakes and ponds adjacent to the smelter and waste dumps, which directly receive contaminated waters were devoid of macro- and mesofauna and flora, but there is no evidence that other lakes have been severely impacted by smelter emissions. Local geology ensures that the lakes are well-buffered to the effects of acid deposition which will limit the bioavailability of metals in the water column and sediment.  相似文献   

Long term changes in ice and discharge regime of rivers in the Baltic region in relation to climatic variability     

Maris Klavins  Agrita Briede  Valery Rodinov 《Climatic change》2009,95(3-4):485-498

The river ice regime is considered a sensitive indicator of climate change and within this study long term changes (in case of River Daugava starting from 1530, but for other studied rivers starting from first half of twentieth century) river ice regimes in the Baltic region have been studied. The ice cover duration on the rivers (17 rivers) in the Baltic countries and Belarus has decreased during the recent decades. In addition to this, long term observational records of ice break on the rivers of the studied region exhibit a pattern of periodic changes in the intensity of ice regime. Both the ice regime and the seasonal river discharge are shown to be strongly influenced by large-scale atmospheric circulation processes over North Atlantic that manifests through close correlation with North Atlantic Oscillation index.  相似文献   

Modeling the 2.7?km in Diameter, Shallow Marine Ritland Impact Structure     

Valery Shuvalov  Henning Dypvik  Elin Kalleson  Ronny Sets?  Fridtjof Riis 《Earth, Moon, and Planets》2012,108(3-4):175-188

The newly discovered Ritland impact structure (2.7?km in diameter) has been modeled by numerical simulation, based on detailed field information input. The numerical model applies the SOVA multi-material hydrocode, which uses the ANEOS equation of state for granite, describing thermodynamical properties of target and projectile material. The model displays crater formation and possible ejecta distribution that strongly supports a 100?m or less water depth at the time of impact. According to the simulations resurge processes and basinal syn- and postimpact sedimentation are highly dependent on water depth; in more than 100?m of water depth, much more powerful resurge processes are generated than at water depths shallower than 100?m (the Ritland case). In Ritland the 100?m high (modeled) crater rim formed a barrier and severely reduced the resurge processes. In the case of deeper water, powerful resurge processes, tsunami wave generations and related currents could have triggered even more violent crater fill sedimentation. The presented model demonstrates the importance of understanding the interactions between water layer and both syn-impact crater fill and ejecta distribution. According to the presented simulations ejecta blocks up to 10?m in diameter could be transported up to about 5?km outside the crater rim.  相似文献   

A mechanism for the production of crater rays     

Valery SHUVALOV 《Meteoritics & planetary science》2012,47(2):262-267

Abstract– A mechanism for the production of crater rays is proposed that is based on the interaction of impact‐induced shock waves with existing (old) craters. Numerical simulations are used to test this idea, and to study the influence of inherited craters’ size and location on the rays’ parameters. The results of the simulations show that crater rays (at least, some of them) could be produced through this mechanism.  相似文献   

The eastern extent of the Barents–Kara ice sheet during the Last Glacial Maximum based on seismic-reflection data from the eastern Kara Sea     

Leonid Polyak  Frank Niessen  Valery Gataullin  & Valery Gainanov 《Polar research》2008,27(2):162-174

We present sub-bottom profiling (sparker and Parasound) results from the eastern Kara Sea, on the Eurasian Arctic margin, which enable the identification of the Last Glacial Maximum (LGM) ice extent. The analysed profiles show that glacigenic diamicton is ubiquitous at the seafloor, east of about 95°E and 78°N. The eastern margin of this diamicton is expressed in a conspicuous morainic ridge at the entrance to the Vilkitsky Strait, and to the south the diamicton projection aligns with the LGM limit mapped at the north-western Taymyr. The bottom of the Voronin Trough further north is also covered with diamicton and has numerous erosional bedforms, indicating a streamlined flow of grounded ice along the trough. Accurate dating of the diamicton is not attainable, but the correlation of pre-diamict sediments to well-dated sections in the Laptev Sea, and available ¹⁴C ages from sediments on top of the diamicton, indicate its LGM age. These results support the palaeogeographic reconstruction that assumes the extension of the LGM Barents–Kara ice sheet as far east as Taymyr. This configuration implies that LGM ice blocked the drainage of the Ob and Yenisey rivers on the Kara shelf. This inference is consistent with the presence of large (>100 km wide) lenses of basin infill adjacent to the southern margin of the diamicton. However, the limited distribution of the eastern Kara ice lobe, not extending on Severnaya Zemlya, suggests that the ice was fairly thin and short-lived: insufficient for the accumulation of the gigantic proglacial lakes that occurred during earlier glaciations.  相似文献   

Experimental Investigation of Turbulent Momentum Transfer in a Neutral Boundary Layer over a Rough Surface     

Severine Tomas  Olivier Eiff  Valery Masson 《Boundary-Layer Meteorology》2011,138(3):385-411

The turbulent characteristics of the neutral boundary layer developing over rough surfaces are not well predicted with operational weather-forecasting models. The problem is attributed to inadequate mixing-length models, to the anisotropy of the flow and to a lack of controlled experimental data against which to validate numerical studies. Therefore, in order to address directly the modelling difficulties for the development of a neutral boundary layer over rough surfaces, and to investigate the turbulent momentum transfer of such a layer, a set of hydraulic flume experiments were carried out. In the experiments, the mean and turbulent quantities were measured by a particle image velocimetry (PIV) technique. The measured velocity variances and fluxes \({(\overline{{u_{i}^{\prime}}{u_{j}^{\prime}}})}\) in longitudinal vertical planes allowed the vertical and longitudinal gradients (?/?z and ?/?x) of the mean and turbulent quantities (fluxes, variances and third-order moments) to be evaluated and the terms of the evolution equations for ?e/?t, \({\partial \overline{u^{\prime 2}}/\partial t}\), \({\partial \overline{w^{\prime 2}}/\partial t}\) and \({\partial \overline{{u^{\prime}}{w^{\prime}}}/\partial t}\) to be quantified, where e is the turbulent kinetic energy. The results show that the pressure-correlation terms allow the turbulent energy to be transferred equitably from \({\overline{{u^{\prime}}^{2}}}\) to \({\overline{{w^{\prime}}^{2}}}\). It appears that the repartition between the constitutive terms of the budget of e, \({\overline{{u^{\prime}}^{2}}}\), \({\overline{{w^{\prime}}^{2}}}\) and \({\overline{{u^{\prime}}{w^{\prime}}}}\) is not significantly affected by the development of the rough neutral boundary layer. For the whole evolution, the transfers of energy are governed by the same terms that are also very similar to the smooth-wall case. The PIV measurements also allowed the spatial integral scales to be computed directly and to be compared with the dissipative and mixing length scales, which were also computed from the data.  相似文献   

Standard prediction of solar cycles     

A. V. Kryachko  A. A. Nusinov 《Geomagnetism and Aeronomy》2008,48(2):145-148

To make a long-term prediction of the solar cycle in a standard way (GOST 25645.302-83), it is necessary to know the instant of the activity minimum onset, the determination of which is difficult during the decline stage of the previous cycle. The dependence of the long-term prediction error on the time of shift (t) relative to the solar activity minimum instant (i.e., the situation when a certain time before the minimum onset, rather than the time of this minimum, is the initial point of calculations) has been studied. It has been indicated that one should not know the exact time of the activity minimum onset in order to make prediction according to GOST, and such a prediction can be performed with an approximately identical error if the lead time is t ～ 1 year and more relative to the activity minimum onset. An analysis of the dependence of prognostic W _max values on t for cycles 18–23 indicated that prognostic W _max values are overestimated at small (to ～ 1 year) uncertainties in the time of activity minimum onset. It has been obtained that W _max = 96 ± 13 for cycle 24 on the assumption that this cycle began in April 2007.  相似文献   

The dipole-quadrupole cycle of the background solar magnetic field     

Valery P. Mikhailutsa 《Solar physics》1995,159(1):29-44

The evolution of the background magnetic field with the solar cycle has been studied using the dipole-quadrupole magnetic energy behaviour in a cycle. The combined energy of the axisymmetric dipole, non-axisymmetric quadrupole, and equatorial dipole is relatively lowly variable over the solar cycle. The dipole field changed sign when the quadrupole field was near a maximum, andvice versa. A conceptual picture involving four meridional magnetic polarity sectors proposed to explain these features may be in agreement with equatorial coronal hole observations. The rate of sector rotation is estimated to be 8 heliographic degrees per year faster than the Carrington rotation (P = 27.23^d synodic). Polarity boundaries of sectors located 180° apart show meridional migrations in one direction, while the boundaries of the other two sectors move in the opposite direction. A simple model of how the magnetic field energy varies, subject to specifying reasonable initial photospheric magnetic and velocity field patterns, follows the observed evolution of the dipole and quadrupole field energies quite nicely.  相似文献   

Nonlinear magneto-acoustic waves in the solar atmosphere     

Csar A. Mendoza-Briceo  Miguel H. Ibez  Valery M. Nakariakov 《Dynamics of Atmospheres and Oceans》2001,34(2-4)

The weakly nonlinear evolution of quasi-isentropic magnetoacoustic waves in the solar atmosphere is analyzed. The plasma is assumed to be initially homogeneous, in thermal equilibrium and with a straight and homogeneous magnetic field frozen in. Additionally, the plasma is assumed to be cooled by the standard cooling function in the range of 10⁴ K<T<10⁷ K and heated by a mechanism which is proportional to the density and temperature. The range of temperature where the plasma is isentropically unstable, the e-folding time for thermal instability and the corresponding time and length-scale for wave breaking are found.  相似文献   

On the recording of regions with increased plasma density on the Sun     

L. N. Kurochka  I. P. Kryachko  E. Markova 《Solar physics》1992,139(2):275-277

For the purpose of studying the statistics, dynamics, and morphology of parts of the solar surface with enhanced emission measure and considerable inhomogeneities of electron concentration, it is suggested that a new type of solar observation be introduced: taking filtergrams by means of interference filters, calculated for the Balmer continuum limit and the region of the blue continuum. To determine accurately the inhomogeneity of the electron concentration in an object, it is suggested to scan the surface of the object and record the spectrum of the blue continuum by means of a spectrochronograph.  相似文献