Geoecological Characteristics of Lake Seliger

Data of hydrological and hydrochemical observations conducted in August 2000 at Lake Seliger and its major tributaries are presented. The analyzed characteristics included: O₂, H₂S, CH₄, microelements; mineral and organic compounds of P and N, ionic composition components (HCO₃ ^–, Cl^–, Na⁺, K⁺, dry residue, pH; color index, electrical conductivity. Bottom sediment samples were analyzed for microelement concentrations, CH₄, oil hydrocarbons. The influence of the basin on the ecological state of the lake was assessed, and tendencies in the evolution of its ecosystem are analyzed. It is shown that the ecological conditions of the lake has not changed significantly since 1960–1991, however, nutrient concentrations in the lake water was found to increase.     

Behavior of Strontium,Fluorine, and Boron in the Kuban and Don Mouth Areas

The distributions of concentrations of dissolved Sr, Ca, F, and B in the Kuban and Don mouth areas are studied. It is found that the behavior of F and B is conservative, whereas that of Sr and Ca is slightly nonconservative and is associated with the spatial heterogeneity of the structure of the zone where the river and sea waters are mixing (this heteromogeneity can arise because of dissimilar transformation of continental river runoff in different areas of the near-mouth coastal waters). It is shown that the parameters of linear relationships between the concentrations of Sr and Ca and the chlorides content of water differ in accordance with the seasonal variations in the chemical composition of the river and the Sea of Azov waters; for F and B, such regularity is not found.     

Once Again about the Structural Approach to the Analysis of Empirical Data

Structural approach to the analysis of sulfur forms concentrations in bottom sediment in three reaches of the Northern Dvina River located near Arkhangelsk and Solombala pulp-and-paper mills (APPM and SPPM, respectively) was used to show that combining all the available data, when searching for relationships between the characteristics, is non-constructive. The correlation between the characteristics of the right and left banks and the delta are shown to be different. The effect of APPM wastewater is shown to disturb the chain of transformations of sulfate and sulfide sulfur forms in bottom sediment at the left bank of the river and enhance the oxidation of reduced sulfur compounds.     

Analysis of Time Series of the Ufa River Water Pollution by Benz[a]pyrene

Mathematical analysis of time series is shown to be applicable to assessing the factors governing benz[a]pyrene concentration in the Ufa River water. The contributions of the deterministic and random components to the total benz[a]pyrene concentration. Seasonal increase (October–January, March–April) and decrease (February, May–September) in benz[a]pyrene concentrations in the Ufa River are established.     

Tracking recent recovery from eutrophication in a high arctic lake (Meretta Lake, Cornwallis Island, Nunavut, Canada) using fossil diatom assemblages

Meretta Lake (Resolute Bay, Cornwallis Island, Nunavut, Canada) is a high arctic lake that received raw sewage for almost 50 years from the Canadian Department of Transport Base. The lake was sampled from 1968–72 during the International Biological Programme, as part of the Char Lake Project. As the number of users at the Transport Base declined throughout the 1990s, so too did the lake's nutrient levels, and Meretta Lake is now classified as oligotrophic. A previous diatom-based paleolimnological study revealed marked species assemblage shifts coincident with sewage inputs beginning in the late 1940s; however, because the core was taken at a time when nutrient levels were still relatively high (i.e., 1993), the diatom record did not yet track any signs of recovery. In this present study, we examined fossil diatom assemblages from a sediment core taken in 2001. Our results indicate a shift to the pre-impact diatom assemblages in the most recent sediments, indicating that the paleolimnological record is tracking the decreased nutrient inputs to this high arctic lake, and confirms that no significant lags exist in these largely ice-covered lakes.     

Size Scaling of Cross Correlation Between Multiple Variables

Reservoir models have large uncertainty because of spatial variability and limited sample data. The ultimate aim is to use simultaneously all available data sources to reduce uncertainty and provide reliable reservoir models for resource assessment and flow simulation. Seismic impedance or some other attribute provides a key source of data for reservoir modeling. These seismic data are at a coarser scale than the hard well data and it not an exact measurement of facies proportions or porosity. A requirement for data integration is the cross-covariance between the well and seismic data.The size-scaling behavior of the cross correlation for different measurement scales was nvestigated. The size-scaling relationship is derived theoretically and validated by numerical studies (including an example with real data). The limit properties of the cross-correlation coefficient when the averaging volume becomes large is shown. After some averaging volume, the volume-dependent cross-correlation coefficient reaches a limit value. This plateau value is controlled mainly by the large-scale behavior of the cross and direct variograms.The cross correlation can increase or decrease with volume support depending on the relative importance of long- and short-scale covariance structures. If the direct and cross variograms are proportional, there is no change in the cross correlation as the averaging volume changes. Our study shows that the volume-dependent cross-correlation coefficient is sensitive to the shape of the cross variogram and differences between the direct variograms of the well data and seismic data.     

Siberian river run-off and Late Quaternary glaciation in the southern Kara Sea, Arctic Ocean: preliminary results

The extent of the Barents-Kara Ice Sheet during the eastern Last Glacial Maximum (LGM) is not yet fully known. A detailed echo-sounding survey performed during the Boris Petrov Expedition 2001 permitted the detailed mapping of part of it. Based on the profiling results, a southern connection between the LGM Barents-Kara Ice Sheet and a local ice sheet on Taymyr Peninsula appears to be unlikely. Based on sediment core data and profiling results, most of the terrigenous river-derived material accumulated in the estuaries during late Holocene times, whereas during early Holocene times of lowered sea level major amounts were transported further offshore and accumulated on the shelf. During the post-glacial sea level rise, the main depocentre migrated southward, reaching its present position no earlier than about 6 cal. Ky BP (or 5.2 Kya). Future studies of accelerator mass spectrometry (AMS) ¹⁴C-dated sediment cores will allow a detailed reconstruction of the variability of fluvial sediment discharge and the history of glaciation in the Kara Sea during late Quaternary times.     

Modelling detrital cooling-age populations: insights from two Himalayan catchments

The distribution of detrital mineral cooling ages in river sediment provides a proxy record for the erosional history of mountain ranges. We have developed a numerical model that predicts detrital mineral age distributions for individual catchments in which particle paths move vertically toward the surface. Despite a restrictive set of assumptions, the model permits theoretical exploration of the effects of thermal structure, erosion rate, and topography on cooling ages. Hypsometry of the source‐area catchment is shown to exert a fundamental control on the frequency distribution of bedrock and detrital ages. We illustrate this approach by generating synthetic ⁴⁰Ar/³⁹Ar muscovite age distributions for two catchments with contrasting erosion rates in central Nepal and then by comparing actual measured cooling‐age distributions with the synthetic ones. Monte Carlo sampling is used to assess the mismatch between observed and synthetic age distributions and to explore the dependence of that mismatch on the complexity of the synthetic age signal and on the number of grains analysed. Observed detrital cooling ages are well matched by predicted ages for a more slowly eroding Himalayan catchment. A poorer match for a rapidly eroding catchment may result from some combination of large analytical uncertainties in the detrital ages and inhomogeneous erosion rates within the basin. Such mismatches emphasize the need for more accurate thermal and kinematic models and for sampling strategies that are adapted to catchment‐specific geologic and geomorphic conditions.