Subsurface structure derived from detailed gravity and magnetic investigations along the Pala-Maneri traverse of the Main Central Thrust,NW Himalaya

A detailed, integrated gravity and magnetic study across the Main Central Thrust (MCT) along the Pala-Maneri traverse in Uttaranchal, NW Himalaya was carried out. The gravity data was acquired using a CG-3 gravity meter with an accuracy of 0.005 mGal, while magnetic data was acquired using a proton precession magnetometer with a station interval of 20 m. Data was collected along a 11.7 km, NE-SW traverse from Pala to Maneri along the proposed route of a hydroelectric headrace tunnel. The measured variation in the gravity field was approximately 70 mGal, with two prominent highs recorded at distances of 0.5 km, 7.5 km and lows at 3.0 km, 10.5 km from Maneri. The gravity highs can be attributed to presence of high-density rocks along the thrust planes. The sharp gravity low recorded at 10.5 km distance possibly indicates a sympathetic fault of the MCT that is highly saturated with fluids (water). The broad gravity low between 2.5 km and 4.0 km distance is likely to represent the gravity signature of the MCT itself. The measured variation in the magnetic field was approximately 285 nT. The associated gravity and magnetic signatures located several faults along the traverse including presence of the MCT at Kumaltigad.     

午后多重极光弧观测研究

本文利用2001-2003年南极中山站175天全天空摄像机观测,对午后多重极光弧的出现率及其与Kp指数的关系进行了统计分析,结果表明午后多重极光弧出现率呈一单峰分布,最大发生率出现在1445UT(1645MLT),其位置在1500MLT极光热点(1300-1700MLT)近夜侧的部分。与地磁活动指数Kp的相关统计分析表明,Kp值为2-3之间时多重极光弧有较大的出现率,这说明中等地磁活动情形下午后多重极光弧有较高的出现率。事件分析表明多重极光弧的强度变化与地磁Pc5脉动具有较高的相关性,并且有类似的频谱特征,这说明午后多重极光弧可能与同时出现的Pc5地磁脉动有关。     

Estuarine ecological risk based on hepatic histopathological indices from laboratory and in situ tested fish

Juvenile Senegalese soles were exposed through 28-day laboratory and field (in situ) bioassays to sediments from three sites of the Sado estuary (W Portugal): a reference and two contaminated by metallic and organic contaminants. Fish were surveyed for ten hepatic histopathological alterations divided by four distinct reaction patterns and integrated through the estimation of individual histopathological condition indices. Fish exposed to contaminated sediments sustained more damage, with especial respect to regressive changes like necrosis. However, differences were observed between laboratory- and field-exposed animals, with the latest, for instance, exhibiting more pronounced fatty degeneration and hepatocellular eosinophilic alteration. Also, some lesions in fish exposed to the reference sediment indicate that in both assays unaccounted variables produced experimental background noise, such as hyaline degeneration in laboratory-exposed fish. Still, the field assays yielded results that were found to better reflect the overall levels of contaminants and physico-chemical characteristics of the tested sediments.     

Change in the magnetic properties of bituminous coal intruded by an igneous dike, Dutch Creek Mine, Pitkin County, Colorado

Magnetization measurements have been made on natural coke–coal samples collected at various distances from a felsic porphyry dike in a coal seam in Dutch Creek Mine, Colorado to help characterize the nature and distribution of the iron-bearing phases. The magnetization passes through a maximum at the coke-to-coal transition about 31 cm from the dike contact. The magnetic measurements support the geochemical data indicating that magmatic fluids along with a high-temperature gas pulse moved into the coal bed. Interaction of the magmatic fluids with the coal diminished the reducing power of the thermal gas pulse from the dike to a point about 24 cm into the coal. The hot reducing gas penetrated further and produced a high temperature (400–525°C) zone (at about 31 cm) just ahead of the magmatic fluids. Metallic iron found in this zone is the principal cause of the observed high magnetization. Beyond this zone, the temperature was too low to alter the coal significantly.     

Arsenic Speciation in Lichens and in Coarse and Fine Airborne Particulate Matter by HPLC–UV–HG–AFS

A three-step sequential extraction procedure with Milli-Q, CaCl₂ and H₃PO₄ was applied for extraction of arsenic species in lichen transplants and airborne particulate matter (fine and coarse fractions). The samples used in this work were collected in 1994–1995 near coal-fired power plants. Both transplant lichens and airborne particulate matter were submitted to the same environment simultaneously. Arsenic species identification and quantification was performed by HPLC–UV–HG–AFS. Inorganic forms of arsenic (arsenite and arsenate) were present in significant amounts in most of the samples. Only in lichens also organic forms of arsenic (monomethyl arsonic acid and dimethyl arsinic acid) were identified which may indicate biotransformation of inorganic arsenic.     

Factors and Trends in the Formation of Natural–Technogenic Associations of Polycyclic Aromatic Hydrocarbons in the Snow–Soil System

Doklady Earth Sciences - The content of polycyclic aromatic hydrocarbons (PAHs) in soil and snow cover near the carbon black plants in Moscow, Omsk, and Samara regions was studied. The differences...     

Circulation and currents in the southwestern East/Japan Sea: Overview and review

A review is made of circulation and currents in the southwestern East/Japan Sea (the Ulleung Basin), and the Korea/Tsushima Strait which is a unique conduit for surface inflow into the Ulleung Basin. The review particularly concentrates on describing some preliminary results from recent extensive measurements made after 1996. Mean flow patterns are different in the upstream and downstream regions of the Korea/Tsushima Strait. A high velocity core occurs in the mid-section in the upstream region, and splits into two cores hugging the coasts of Korea and Japan, the downstream region, after passing around Tsushima Island located in the middle of the strait. Four-year mean transport into the East/Japan Sea through the Korea/Tsushima Strait based on submarine cable data calibrated by direct observations is 2.4 Sv (1 Sv = 10⁶ m³ s⁻¹). A wide range of variability occurs for the subtidal transport variation from subinertial (2–10 days) to interannual scales. While the subinertial variability is shown to arise from the atmospheric pressure disturbances, the longer period variation has been poorly understood.Mean upper circulation of the Ulleung Basin is characterized by the northward flowing East Korean Warm Current along the east coast of Korea and its meander eastward after the separation from the coast, the Offshore Branch along the coast of Japan, and the anticyclonic Ulleung Warm Eddy that forms from a meander of the East Korean Warm Current. Continuous acoustic travel-time measurements between June 1999 and June 2001 suggest five quasi-stable upper circulation patterns that persist for about 3–5 months with transitions between successive patterns occurring in a few months or days. Disappearance of the East Korean Warm Current is triggered by merging the Dok Cold Eddy, originating from the pinching-off of the meander trough, with the coastal cold water carried Southward by the North Korean Cold Current. The Ulleung Warm Eddy persisted for about 20 months in the middle of the Ulleung Basin with changes in its position and spatial scale associated with strengthening and weakening of the transport through the Korea/Tsushima Strait. The variability of upper circulation is partly related to the transport variation through the Korea/Tsushima Strait. Movements of the coastal cold water and the instability of the polar front also appear to be important factors affecting the variability.Deep circulation in the Ulleung Basin is primarily cyclonic and commonly consists of one or more cyclonic cells, and an anticyclonic cell centered near Ulleung Island. The cyclonic circulation is conjectured to be driven by a net inflow through the Ulleung Interplain Gap, which serves as a conduit for the exchange of deep waters between the Japan Basin in the northern East Sea and the Ulleung Basin. Deep currents are characterized by a short correlation scale and the predominance of mesoscale variability with periods of 20–40 days. Seasonality of deep currents is indistinct, and the coupling of upper and deep circulation has not been clarified yet.