Groundwater chemical pollution risk: assessment through a soil attenuation index

Aquifer vulnerability is frequently estimated through methodologies that don’t consider most physical and chemical soil parameters. A soil attenuation index is proposed to estimate groundwater chemical pollution risk, that takes into account organic carbon content, pH, cation exchange capacity, clay content, phreatic depth and landscape position. The attenuation index is constructed by a methodology similar to that developed for water quality index. P, Mn and Zn concentrations in groundwater from selected places were used to validate the proposed index.     

Atmospheric boundary layer over steep surface waves

Turbulent air-sea interactions coupled with the surface wave dynamics remain a challenging problem. The needs to include this kind of interaction into the coupled environmental, weather and climate models motivate the development of a simplified approximation of the complex and strongly nonlinear interaction processes. This study proposes a quasi-linear model of wind-wave coupling. It formulates the approach and derives the model equations. The model is verified through a set of laboratory (direct measurements of an airflow by the particle image velocimetry (PIV) technique) and numerical (a direct numerical simulation (DNS) technique) experiments. The experiments support the central model assumption that the flow velocity field averaged over an ensemble of turbulent fluctuations is smooth and does not demonstrate flow separation from the crests of the waves. The proposed quasi-linear model correctly recovers the measured characteristics of the turbulent boundary layer over the waved water surface.     

Studies of aerosol optical depth with the use of Microtops II sun photometers and MODIS detectors in coastal areas of the Baltic Sea

In this paper we describe the results of a research campaign dedicated to the studies of aerosol optical properties in different regions of both the open Baltic Sea and its coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with the use of the hand-held Microtops II sun photometers. The studies were complemented with aerosol data provided by the MODIS. In order to obtain the full picture of aerosol situation over the study area, we added to our analyses the air mass back-trajectories at various altitudes as well as wind fields. Such complex information facilitated proper conclusions regarding aerosol optical depth and Ångström exponent for the four locations and discussion of the changes of aerosol properties with distance and with changes of meteorological factors. We also show that the Microtops II sun photometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results.     

Faunal communities at sites of gas- and oil-bearing fluids in Lake Baikal

Macro- and meiofaunal communities were examined at four geomorphologically distinct sites with different gas- and oil-bearing fluid characteristics in the northern, central and southern basins of Lake Baikal. All sites had elevated concentrations of bicarbonate, nitrate, sulphate and chloride ions in pore fluids, with highest values at the Frolikha vent. Elevated levels of iron ions were found in pore waters of the St. Petersburg methane seep and the Gorevoy Utes oil seep. The chemical composition of pore waters at the Malenky mud volcano was similar to that reported in earlier work. Consistent with published data, the Frolikha vent (northern basin) and the St. Petersburg methane seep (central basin) were characterised by methane of mixed genesis (thermogenic + biogenic), whereas the methane source was mainly thermogenic at the Gorevoy Utes oil seep (central basin) and biogenic at the Malenky mud volcano (southern basin). In contrast to marine seep ecosystems, the macrofauna was dominated only by amphipods, giant planarians and oligochaetes, whereas bivalves were absent; the meiofauna was similar to its marine counterpart, being dominated by nematodes, cyclops, harpacticoids and ostracods. A statistically significant positive relationship was revealed between faunal abundance and the availability of bacterial mats on seep sediments. Moreover, ANOVA tests showed significant increases in both meiozoobenthic and macrozoobenthic densities at “hot spot” vent/seep sites relative to discharge-free reference sites. The isotopic composition of carbon and nitrogen at various trophic levels of these benthic vent/seep communities was found to differ markedly from that reported by earlier studies for the pelagic and other benthic food webs in Lake Baikal. As in marine seeps, the macrofauna had variable isotopic signatures. Light δ¹³C and δ¹⁵N values suggest the utilization of chemosynthetically fixed and/or methane-derived organic matter. By contrast, the heavy δ¹³C signatures of some mobile amphipods likely reflect consumption of photosynthetically derived carbon. These findings would at least partly explain why Lake Baikal is a notable outlier in global temperature–biodiversity patterns, exhibiting the highest biodiversity of any lake worldwide but at an extremely cold average temperature.     

Catastrophic detachment and high-velocity long-runout flow of Kolka Glacier, Caucasus Mountains, Russia in 2002

In September 2002, a catastrophic geomorphic event occurred in the Caucasus Mountains, southern Russia, in which almost the entire mass of Kolka Glacier detached from its bed, accelerated to a very high velocity (max. 65–80 m/s), and traveled a total distance of 19 km downstream as a glacier-debris flow. Based on the interpretation of satellite imagery obtained only 8.5 h before the event occurred, the analysis of seismograms from nearby seismic stations, and subsequent detailed field observations and measurements, we suggest that this remarkable event was not a response to impulse loading from a rock avalanche in the mountainside above the glacier, or to glacier surging, but due entirely to the static and delayed catastrophic response of the Kolka glacier to ice and debris loading over a period of months prior to the September 20 detachment. We reconstruct the glacier-debris flow using field observations in conjunction with the interpretation of seismographs from nearby seismic stations and successfully simulate the behaviour (runout, velocity, and deposition) of the post-detachment glacier-debris flow using a three-dimensional analytical model. Our demonstration of a standing-start hypothesis in the 2002 Kolka Glacier detachment has substantial implications for glacier hazard assessment and risk management strategies in valleys downstream from unstable debris-covered glaciers in the mountain regions of the world.     

Ground motion parameters of Shillong plateau: One of the most seismically active zones of northeastern India

Strong ground motion parameters for Shillong plateau of northeastern India are examined. Empirical relations are obtained for main parameters of ground motions as a function of earthquake magnitude, fault type, source depth, velocity characterization of medium and distance. Correlation between ground motion parameters and characteristics of seismogenic zones are established. A new attenuation relation for peak ground acceleration is developed, which predicts higher expected PGA in the region. Parameters of ...     

A simple method to model the reduced environment of lake bottom sapropel formation

The Kambala and Barchin brackish lakes(Baraba steppe,southern West Siberia) contain an organic-rich sapropel layer that was formed in oxygen-depleted waters.We measured the bulk sediment elemental composition,the water chemistry and determined the mineralogical composition and predominant biota species(Diatoms and Cyanobacteria in phytoplankton community respectively) in the lakes.The result indicates that the first lake has a siliceous type of sapropel and the second a carbonaceous one.A computer thermodynamic model was developed for chemical interaction in water-bottom sediment systems of the Kambala and Barchin Lakes.The surface sodium bicarbonate waters are supersaturated with respect to calcite,magnesite(or low Mg-calcite),quartz and chlorite with minor strontianite,apatite and goethite(pH8.9-9.3,Eh 0.3 V).Nevertheless,it is shown that during sapropel deposition,deep silt waters should be anoxic(Eh0 V).The virtual component CH_2O has been used to create an anoxic environment suitable for pyrite formation due to the biotic community impact and abiotic reduction.Thermodynamic calculation has shown that silt water is not necessarily euxinic(anoxic and sulfidic).Depending on Eh,sulfate sulfur can dominate in solution,causing the formation of gypsum together with pyrite.An attempt was made to find a reason for solution supersaturation with respect to Ca and Mg ions due to their complexation with humic acids.     

Periglacial landscape evolution and environmental changes of Arctic lowland areas for the last 60 000 years (western Laptev Sea coast, Cape Mamontov Klyk)

Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat–sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.     

Evaluation of the possible presence of clathrate hydrates in Europa's icy shell or seafloor

Several substances besides water ice have been detected on the surface of Europa by spectroscopic sensors, including CO₂, SO₂, and H₂S. These substances might occur as pure crystalline ices, as vitreous mixtures, or as clathrate hydrate phases, depending on the system conditions and the history of the material. Clathrate hydrates are crystalline compounds in which an expanded water ice lattice forms cages that contain gas molecules. The molecular gases that may constitute Europan clathrate hydrates may have two possible ultimate origins: they might be primordial condensates from the interstellar medium, solar nebula, or jovian subnebula, or they might be secondary products generated as a consequence of the geological evolution and complex chemical processing of the satellite. Primordial ices and volatile-bearing compounds would be difficult to preserve in pristine form in Europa without further processing because of its active geological history. But dissociated volatiles derived from differentiation of a chondritic rock or cometary precursor may have produced secondary clathrates that may be present now. We have evaluated the current stability of several types of clathrate hydrates in the crust and the ocean of Europa. The depth at which the clathrates of SO₂, CO₂, H₂S, and CH₄ are stable have been obtained using both the temperatures observed in the surface [Spencer, J.R., Tamppari, L.K., Martin, T.Z., Travis, L.D., 1999. Temperatures on Europa from Galileo photopolarimeter-radiometer: Nighttime thermal anomalies. Science 284, 1514-1516] and thermal models for the crust. In addition, their densities have been calculated in order to determine their buoyancy in the ocean, obtaining different results depending upon the salinity of the ocean and type of clathrate. For instance, assuming a eutectic composition of the system MgSO₄H₂O for the ocean, CO₂, H₂S, and CH₄ clathrates would float but SO₂ clathrate would sink to the seafloor; an ocean of much lower salinity would allow all these clathrates to sink, except that CH₄ clathrate would still float. Many geological processes may be driven or affected by the formation, presence, and destruction of clathrates in Europa such as explosive cryomagmatic activity [Stevenson, D.J., 1982. Volcanism and igneous processes in small icy satellites. Nature 298, 142-144], partial differentiation of the crust driven by its clathration, or the local retention of heat within or beneath clathrate-rich layers because of the low thermal conductivity of clathrate hydrates [Ross, R.G., Kargel, J.S., 1998. Thermal conductivity of Solar System ices, with special reference to martian polar caps. In: Schmitt, B., De Berg, C., Festou, M. (Eds.), Solar System Ices. Kluwer Academic, Dordrecht, pp. 33-62]. On the surface, destabilization of these minerals and compounds, triggered by fracture decompression or heating could result in formation of chaotic terrain morphologies, a mechanism that also has been proposed for some martian chaotic terrains [Tanaka, K.L., Kargel, J.S., MacKinnon, D.J., Hare, T.M., Hoffman, N., 2002. Catastrophic erosion of Hellas basin rim on Mars induced by magmatic intrusion into volatile-rich rocks. Geophys. Res. Lett. 29 (8); Kargel, J.S., Prieto-Ballesteros, O., Tanaka K.L., 2003. Is clathrate hydrate dissociation responsible for chaotic terrains on Earth, Mars, Europa, and Triton? Geophys. Res. 5. Abstract 14252]. Models of the evolution of the ice shell of Europa might take into account the presence of clathrate hydrates because if gases are vented from the silicate interior to the water ocean, they first would dissolve in the ocean and then, if the gas concentrations are sufficient, may crystallize. If any methane releases occur in Europa by hydrothermal or biological activity, they also might form clathrates. Then, from both geological and astrobiological perspectives, future missions to Europa should carry instrumentation capable of clathrate hydrate detection.