Heavy metal contamination of roadside topsoil in Osogbo,Nigeria: its relationship to traffic density and proximity to highways   总被引：12，自引：0，他引：12  

S.?O.?FakayodeEmail author  B.?I.?Olu-Owolabi 《Environmental Geology》2003,44(2):150-157

The levels of lead, cadmium, copper, nickel and zinc were determined in the roadside topsoil in Osogbo, Nigeria, with the view to determining the effect of traffic density and vehicular contribution to the soil heavy metal burden. The levels of the metals at the high density roads were significantly higher than the corresponding levels at the medium and low traffic density roads. The average levels of Pb, Cd, Cu, Ni, and Zn in all road locations at a distance of 5 m from the roads were 68.74ᆶ.82, 0.60ǂ.31, 21.19ᆟ.34, 8.38DŽ.40, and 42.45ᆥ.68 mg/kg, respectively. Pb, Cd, and Cu were of average levels of 92.07ᆩ.25, 0.76ǂ.35 and 27.69 mg/kg, respectively at a distance of 5 m from the road at high traffic density roads, while the levels of Ni and Zn averaged 9.65DŽ.61 and 56.27ᆟ.58 mg/kg, respectively. There was a rapid decrease in the level of the metals with distance, with the metal levels at a distance of 50 m from the road almost reaching the natural background levels of the metals at the control sites. The levels of the metals were also determined at the four major motor parks and at the seven mechanic workshop settlements. The levels of the metals at the motor parks and mechanic workshops were far above the levels at the control sites. The levels of Pb, Cd, Cu, Ni, and Zn at the motor parks were 519ᇝ.0, 3.6ǂ.8, 37.9ᆠ.5, 17.3dž.6 and 71.9ᆟ.3 mg/kg, respectively, with the levels of Pb, Cd, Cu, Ni, and Zn at the mechanic workshops averaging 729.57뀶.93, 4.59ǃ.01, 116.6ᆮ.8, 30.21Nj.40, and 88.74ᆰ.11 mg/kg, respectively.  相似文献   

Models of the dust envelope of the unique object FG Sagittae     

M. B. Bogdanov  O. G. Taranova 《Astronomy Reports》2003,47(7):535-539

We use JHKLM photometric data obtained in 1998–2001 to model the dust envelope of the unique object FG Sge, which formed around the star after several consecutive cycles of dust condensation beginning in Autumn 1992. Models with a spherically symmetric, extended envelope consisting of a mixture of spherical particles of amorphous carbon and silicon carbide with an MRN size distribution were fitted to match the mean observed spectral energy distributions of FG Sge during brightness maximum and minimum after 1998 for two values of the luminosity and effective temperature of the central star. The stellar-wind parameters and mass-loss rate have been estimated in each case. The observational data for the brightness maximum and minimum cannot be described by models with a fixed luminosity or fixed distance to the star. This is a consequence of the object’s unusual behavior, with synchronous flux decreases in all the observed bands. The inability of the model to adequately describe the minimum-brightness state is probably associated with the abrupt disruption of the spherical symmetry of the envelope due to the formation of a small, dense dust cloud in the line of sight.  相似文献   

Spatially explicit measures of production of young alewives in Lake Michigan: Linkage between essential fish habitat and recruitment     

Tomas?O.?H??kEmail author  Edward?S.?Rutherford  Shannon?J.?Brines  Doran?M.?Mason  David?J.?Schwab  Michael?J.?McCormick  Timothy?J.?DeSorcie 《Estuaries and Coasts》2003,26(1):21-29

The identification and protection of essential habitats for early life stages of fishes are necessary to sustain fish stocks. Essential fish habitat for early life stages may be defined as areas where fish densities, growth, survival, or production rates are relatively high. To identify critical habitats for young-of-year (YOY) alewives (Alosa pseud oharengus) in Lake Michigan, we integrated bioenergetics models with GIS (Geographic Information Systems) to generate spatially explicit estimates of potential population production (an index of habitat quality). These estimates were based upon YOY alewife bioenergetic growth rate potential and their salmonine predators’ consumptive demand. We compared estimates of potential population production to YOY alewife yield (an index of habitat importance). Our analysis suggested that during 1994–1995, YOY alewife habitat quality and yield varied widely throughout Lake Michigan. Spatial patterns of alewife yield were not significantly correlated to habitat quality. Various mechanisms (e.g., predator migrations, lake circulation patterns, alternative strategies) may preclude YOY alewives from concentrating in areas of high habitat quality in Lake Michigan.  相似文献   

Lithospheric Tidal Effects from Observations in Deep Wells     

A. E. Rosaev  O. A. Esipko 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):203-207

A number of deep and superdeep wells have been drilled in Russia. The wells where all drilling activities have been finished, but the research activities still continue, are of a great scientific and practical interest for studying the present-day geological processes taking place in the Earth's interior. Vorotilovo deep well (VDW), drilled in a central part of Russian platform, is one of those wells-geolaboratories. The depth of the well is 5374 m, the temperature at the bottom is 95°C, open borehole in the range 689–5374 m.As a result of geophysical fields monitoring, the complex nature of spatio-temporal variations that depend on the influence of various natural factors was determined in the VDW.Lunar tides are one of the important factors that define the geophysical fields' variations in the VDW. The relation between temperature variations in the VDW and the tide (monthly) phase is detected. The dependence of such influence on the depth of measurement agrees with the model of 'layered' Earth where every layer has a particular response on tidal force.The continuation of the measurements, improvement of data analyses methods and extension of collaboration of specialists from different branches of science, are required in order to obtain more exact results and improve their interpretation.  相似文献   

Eight new magnetic stars with large continuum depressions     

V. G. El’kin  D. O. Kudryavtsev  I. I. Romanyuk 《Astronomy Letters》2003,29(6):400-404

Observations with the 6-m telescope revealed eight new magnetic, chemically peculiar stars: HD 29925, HD 40711, HD 115606, HD 168796, HD 178892, HD 196691, HD 209051, and BD+32°2827. Zeeman observations of all these objects have been carried out for the first time. We selected candidates by analyzing the depression profile at a wavelength of λ5200 Å. This technique for selecting candidate magnetic stars was shown to be efficient: we found magnetic fields in 14 of the 15 objects that we selected for our observations with a Zeeman analyzer. A maximum longitudinal field strength B _e exceeding 8 kG was found in HD 178892; in HD 209051 and HD196691, B _e reaches 3.3 and 2.2 kG, respectively. For the remaining stars, we obtained lower limits of the longitudinal field (more than several hundred G).  相似文献   

Landslide-induced wave in a small volcanic lake: Kasu Tephra Cone,Papua New Guinea     

T.?P.?WagnerEmail author  C.?O.?McKee  J.?Kuduon  R.?Kombua 《International Journal of Earth Sciences》2003,92(3):405-406

The south crater wall of a Quaternary tephra cone in the Highlands of Papua New Guinea collapsed on 20 April 1999 and sent a 150,000-m ³ landslide into its lake. Displacing 5–10% of the lake's volume, the landslide induced a 15-m-high wave which flattened vegetation throughout the crater interior, and broke over a low saddle in the crater's east rim where it destroyed two houses and injured 11 people, killing one.  相似文献   

Physical Properties of Dust in the Martian Atmosphere: Analysis of Contradictions and Possible Ways of Their Resolution     

Dlugach  Zh. M.  Korablev  O. I.  Morozhenko  A. V.  Moroz  V. I.  Petrova  E. V.  Rodin  A. V. 《Solar System Research》2003,37(1):1-19

Atmospheric aerosols play an important role in forming the Martian climate. However, the basic physical properties of the Martian aerosols are still poorly known; there are many contradictions in their estimates. We present an analytical overview of the published results and potentialities of various methods. We consider mineral dust. Zonally averaged data obtained from mapping IR instruments (TES and IRTM) give the optical thickness of mineral aerosols ₉ = 0.05–0.1 in the 9-m band for quite atmospheric conditions. There is a problem of comparing these estimates with those obtained in the visible spectral range. We suggest that the commonly used ratio _vis/₉ >2 depends on the interpretation and it may actually be smaller. The ratio _vis/₉ 1 is in better agreement with the IRIS data (materials like montmorillonite). If we assume that _vis/₉ = 1 and take into account the nonspherical particle shape, then the interpretation of ground-based integrated polarimetric observations ( < 0.04) can be reconciled with IR measurements from the orbit. However, for thin layers, the sensitivity of both methods to the optical thickness is poorly understood: on the one hand, polarimetry depends on the cloud cover and, on the other hand, the interpretation of IR measurements requires that the atmospheric temperature profile and the surface temperature and emissivity be precisely known. For quite atmospheric conditions, the local optical-thickness estimates obtained by the Bouguer–Lambert–Beer method and from the sky brightness measured from Viking 1 and 2 and Mars Pathfinder landers are much larger: = 0.3–0.6. Estimates of the contrasts in images from theVikingorbiters yield the same values. Thus, there is still a factor of 3 to 10 difference between different groups of optical-thickness estimates for the quiet atmosphere. This difference is probably explained by the contribution of condensation clouds and/or by local/time variations.  相似文献   

Eliminating Virtual Impactors with the Very Large Telescope: An ESO Program with the FORS2 Camera     

A.?BoattiniEmail author  G.?D’Abramo  H.?Scholl  O.?R.?Hainaut  R.?West  G.?Hahn  R.?Michelsen  G.?Forti  P.?Pravec  G.?B.?Valsecchi 《Earth, Moon, and Planets》2003,93(4):239-248

We have used the ESO Very Large Telescope (VLT) to perform as trometric observations of Near Earth Asteroids (NEAs) having remote collision possibilities with the Earth. The observations were made for those objects which became too faint to be observed elsewhere. Using the 4 hours allocated in the semester April–September 2003, 5 faint NEAs were observed. As a result, no NEA that could impact the Earth was lost.  相似文献   

Subcellular distribution of heavy metals in livers and kidneys of Stenella coeruleoalba and Tursiops truncatus from the Mediterranean Sea     

Storelli MM  Marcotrigiano GO 《Marine pollution bulletin》2002,44(1):74-79

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Transition from Gaseous Compounds to Aerosols in Titan's Atmosphere     

Sébastien LebonnoisE.L.O. Bakes  Christopher P. McKay 《Icarus》2002,159(2):505-517

We investigate the chemical transition of simple molecules like C₂H₂ and HCN into aerosol particles in the context of Titan's atmosphere. Experiments that synthesize analogs (tholins) for these aerosols can help illuminate and constrain these polymerization mechanisms. Using information available from these experiments, we suggest chemical pathways that can link simple molecules to macromolecules, which will be the precursors to aerosol particles: polymers of acetylene and cyanoacetylene, polycyclic aromatics, polymers of HCN and other nitriles, and polyynes. Although our goal here is not to build a detailed kinetic model for this transition, we propose parameterizations to estimate the production rates of these macromolecules, their C/N and C/H ratios, and the loss of parent molecules (C₂H₂, HCN, HC₃N and other nitriles, and C₆H₆) from the gas phase to the haze. We use a one-dimensional photochemical model of Titan's atmosphere to estimate the formation rate of precursor macromolecules. We find a production zone slightly lower than 200 km altitude with a total production rate of 4×10⁻¹⁴ g cm⁻² s⁻¹ and a C/N?4. These results are compared with experimental data, and to microphysical model requirements. The Cassini/Huygens mission will bring a detailed picture of the haze distribution and properties, which will be a great challenge for our understanding of these chemical processes.  相似文献