贝加尔湖的污染与富营养化     

Evgeniya N. Tarasov  Alexander A. Mamontov  Elena A. Mamontova 《湖泊科学》1998,10(S1):167-179

The long term systematic investigations of ion composition components (bicarbonates, chlorides, sulphates, magnesium, calcium, sodium, potassium) and trophic status components (suspension, chlorophyll-a, mineral and organic forms phosphorus and nitrogen, carbon, silica) of water from the lake proper, its tributaries and atmospheric precipitation, which make up the main share of substance supply in to the lake, as well as the Angara river, being the source of substance discharge allowed the lake recent state to be evaluated in terms of both chemical pollution and possible eutrophication of its water. The similar (in terms of river runojf) periods of 50-ies and 80-ies have been compared. It was revealed that as a result of industrial activity 409 thousand tons of mineral substances (27.2 thousand tons of chlorides, 162 thousand tons of sulphates and over 200 thousand tons of organic substances) are supplied in the lake annually. The supply of substances of the anthropogenic origin is higher for the South Baikal than that for the North and Middle Baikal (the sum of mineral substances in 3.6 times; sulphates in 5 times, organic substances, including hydrocarbons in 7 times).The absence of abundant phytoplankton in the period studied when the ratio of silica to phosphorus is optimum (over 100), as well as a revers correlation between winter nitrogen content and spring of chlorophyll-a concentration in the Baikal water and revers dependence between the suspension and chlorophyll-a along the Selenga river valley lead to the conclusion that Baikal water contains toxicants. It is verified by the presence of polychlorbiphenyls (PCB), poly-chlordibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) for the whole food web with the maximum PCDD/PCDF (TEQ to 175 P g · g^-1) concentration in the seal blubber. The levels are comparable with those reported for ringed seal (phoca hispida), living in the Baltic sea and Bar-row Strait Inlet in the Canadian Arctic.  相似文献   

Contribution to knowledge regarding the sources of earthquakes on the island of Ischia (Southern Italy)     

Cubellis  Elena  Luongo  Giuseppe  Obrizzo  Francesco  Sepe  Vincenzo  Tammaro  Umberto 《Natural Hazards》2020,100(3):955-994

Natural Hazards - This paper analyses data regarding the seismicity and ground deformations of the island of Ischia. The goal is to describe these phenomena as a space–time process, exploring...  相似文献   

Sedimentary iron inputs stimulate seagrass (Posidonia oceanica) population growth in carbonate sediments     

Núria Marbà  Carlos M. Duarte  Marianne Holmer  Maria Ll. Calleja  Elvira Álvarez  Elena Díaz-Almela  Neus Garcias-Bonet 《Estuarine, Coastal and Shelf Science》2008

The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using direct census of tagged plants. The meadows examined ranged from meadows undergoing a severe decline to expanding meadows (specific net population growth, from −0.14 yr⁻¹ to 0.05 yr⁻¹). Similarly, Fe inputs to the meadows ranged almost an order of magnitude across meadows (8.6–69.1 mg Fe m⁻² d⁻¹). There was a significant, positive relationship between sedimentary iron inputs and seagrass net population growth, accounting for 36% of the variability in population growth across meadows. The relationship obtained suggested that seagrass meadows receiving Fe inputs below 43 mg Fe m⁻² d⁻¹ are vulnerable and in risk of decline, confirming the pivotal role of Fe in the control of growth and the stability of seagrass meadows in carbonate sediments.  相似文献   

Microbially mediated methane and sulfur cycling in pockmark sediments of the Gdansk Basin, Baltic Sea   总被引：2，自引：2，他引：0  

Nikolay V. Pimenov  Marina O. Ulyanova  Timur A. Kanapatsky  Elena F. Veslopolova  Pavel A. Sigalevich  Vadim V. Sivkov 《Geo-Marine Letters》2010,30(3-4):439-448

In the Russian sector of the Gdansk Basin (Baltic Sea), high organic matter influx fuels microbial processes resulting in the formation of reduced sediments with elevated methane concentrations. Investigated areas of geoacoustic anomalies (～245 km²) were found to contain three distinct geomorphologic structures (pockmarks), with a total area of ～1 km². Methane anomalies recorded in the water above one of these pockmarks were traced as high as 10 m above the bottom. In pockmark sediments, sulfate reduction and anaerobic oxidation of methane (AOM) occurred at high rates of 33 and 50 µmol dm^?3 day^?1, respectively. Integrated over 0–180 cm sediment depths, AOM exceeded methanogenesis almost tenfold. High AOM rates resulted from methane influx from deeper sediment layers. The δ¹³C signature of methane carbon (?78.1 to ?71.1‰) indicates the biogenic origin of pockmark methane. In pockmark sediments, up to 70% of reduced sulfur compounds was possibly produced via AOM.  相似文献   

Multiple cycles of magnetic activity in the Sun and Sun-like stars and their evolution     

Elena Aleksandrovna Bruevich  Vasily Vladimirovich Bruevich  Boris Pavlovich Artamonov 《天文和天体物理学研究(英文版)》2018,(7)

The wavelet transform method for high-quality time-frequency analysis is applied to sets of observations of relative sunspot numbers and stellar chromosphere fluxes of 10 Sun-like stars.Wavelet analysis of solar data shows that in a certain interval of time there are several cycles of activity with periods of duration which vary considerably from each other:from quasi-biennial cycles to 100-yr cycles.Cyclic activity was detected in almost all Sun-like stars that we examined,even those that previously were not considered as stars with cyclic activity according to analysis using a Scargle periodogram.The durations of solar and stellar cycles significantly change during the observation period.  相似文献   

Coverage of Mars by Probes Slightly Off the Areostationary Orbit     

Elena Colella  Emiliano Ortore  Christian Circi  Ennio Condoleo 《Earth, Moon, and Planets》2017,120(1):31-39

This paper aims at investigating the feasibility of gaining complete and continuous coverage of an extended equatorial belt of Mars, under the effects of orbital perturbations. The problem could be solved by considering a minimum number of three probes, which move slightly off the Martian Areostationary Orbit. The proposed configurations allow the achievement of the goal without entailing corrective manoeuvres and presenting only a longitudinal motion with respect to the surface of Mars.  相似文献   

New sedimentological and palynological data from the Yarkand-Fergana Basin(Kyrgyz Tian Shan): Insights on its Mesozoic paleogeographic and tectonic evolution     

Julien Morin  Marc Jolivet  Dave Shaw  Sylvie Bourquin  Elena Bataleva 《地学前缘(英文版)》2021,12(1):183-202

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Geology of the Murcia Valley and Flood Plain Modifications in the Construction of the Circus Maximus,Rome, Italy     

Elena Carpentieri  Donatella de Rita  Giuseppe Della Monica 《Geoarchaeology》2015,30(6):483-494

This paper presents a morphological and hydrogeological reconstruction of the Murcia Valley at the location of the great Roman stadium Circus Maximus in Rome. We reconstruct a valley segment using ERT (electrical resistivity tomography) and geoarchaeological drilling data that identified three main layers. The basal layer, with high resistivity values and convex shapes, is correlated to alluvial gravel and lithified silt‐clay sediments. The middle layer shows low‐to‐medium resistivity values extending to concavities between the basal convex shapes. The very low resistivity values of this middle layer characterize elliptical to circular morphologies and have been ascribed to the presence of water‐saturated clay‐silt and peaty sediments. The surface layer is characterized by widespread lateral inhomogeneity interpreted as anthropogenic fill. The data indicate a pre‐Roman anastomosed alluvial plain subsequently modified by human intervention. In an effort to reclaim the valley for construction of the Circus, the Romans utilized the natural topography and created a central embankment, later becoming the Spina, by filling depressions with sand taken from adjacent bars. Our study contributes to (1) knowledge of the pre‐Roman landscape, (2) understanding anthropogenic modification of the Murcia Valley flood plain, and (3) archaeological interpretation of the monument.  相似文献