In this study, the environmental radioactivity measurements for Tokat and Sivas provinces in the northeast of Turkey were performed. Using gamma ray spectrometry, the activity concentrations of natural radionuclides in soil and travertine samples (232Th, 226Ra, and 40K) were determined. The annual effective dose equivalent, the absorbed doses rate in air, the radium equivalent, and the external hazard index were obtained from these activities. The activity concentrations vary from 9.09 to 17.04 Bq kg?1 for 232Th, from 36.53 to 76.95 Bq kg?1 for 226Ra, and from 216.56 to 576.59 Bq kg?1 for 40K in soil samples. The activity concentrations in travertines vary from 15.99 to 21.01 Bq kg?1 for 232Th, from 19.89 to 67.71 Bq kg?1 for 226Ra, and from 179.89 to 314.43 Bq kg?1 for 40K. The average dose rate in air for soil and travertine samples was 43.41 and 41.05 nGy h?1 respectively. The obtained results are presented and compared with other studies, and the results of this study are lower than the international recommended value (55 nGy h?1) given by UNSCEAR ( 2000). The results show that the region has a background radiation level within the natural limits. 相似文献
Natural Hazards - Many countries aim to efficiently allocate limited national research and development resources to produce optimal research. A proportion of limited national research and... 相似文献
Gully erosion is one of the greatest natural hazards in the loess areas of E. (Eastern) Poland. At the same time, permanent gullies are a major tourist attraction and can provide a basis for the development of geotourism. The study objective was to assess the possibilities of using the loess gullies for educational purposes. Detailed studies were conducted within the municipality of Kazimierz Dolny, an area with an extremely high concentration of permanent gullies. The questionnaire survey of students and tourists (nearly 300 surveys were completed) showed that the respondents’ knowledge of geomorphology was limited, despite their familiarity with gullies. In most cases, they were unable to accurately identify the determinants of gully erosion, its negative effects and methods for preventing it. An assessment of the tourism and geotourism potential of the municipality made it possible to identify the sites (gullies) that can perform an educational function, with regard to gully erosion. The establishment of the Ma?opolska Vistula Gap Geopark, whose highlights will include numerous loess gullies, can pave the way for the development of geotourism. 相似文献
The comparison between two series of optimal remediation designs using deterministic and stochastic approaches showed a number
of converging features. Limited sampling measurements in a supposed contaminated aquifer formed the hydraulic conductivity
field and the initial concentration distribution used in the optimization process. The deterministic and stochastic approaches
employed a single simulation–optimization method and a multiple realization approach, respectively. For both approaches, the
optimization model made use of a genetic algorithm. In the deterministic approach, the total cost, extraction rate, and the
number of wells used increase when the design must satisfy the intensified concentration constraint. Growing the stack size
in the stochastic approach also brings about same effects. In particular, the change in the selection frequency of the used
extraction wells, with increasing stack size, for the stochastic approach can indicate the locations of required additional
wells in the deterministic approach due to the intensified constraints. These converging features between the two approaches
reveal that a deterministic optimization approach with controlled constraints is achievable enough to design reliable remediation
strategies, and the results of a stochastic optimization approach are readily available to real contaminated sites. 相似文献
A high level of confidence in resource data is a key prerequisite for conducting a reliable economic feasibility study in deep water seafloor mining. However, the acquisition of accurate resource data is difficult when employing traditional point-sampling methods to assess the resource potential of polymetallic nodules, given the vast size of the survey area and high spatial variability in nodule distribution. In this study, we analyzed high-resolution acoustic backscatter intensity images to estimate nodule abundance and increase confidence levels in nodule abundance data. We operated a 120 kHz deep-towed sidescan sonar (DSL-120) system (1×1 m resolution) across a 75 km2 representative area in the Korean Exploration Area for polymetallic nodules in the Northeastern Equatorial Pacific. A deep-towed camera system was also run along two tracks in the same area to estimate the abundance of polymetallic nodules on the seafloor. Backscatter data were classified into four facies based on intensity. The facies with the weakest and strongest backscatter intensities occurred in areas of high slope gradient and basement outcrops, respectively. The backscatter intensities of the two other facies correlated well with the nodule abundances estimated from still-camera images. A linear fit between backscatter intensity and mean nodule abundance for 10 zones in the study area yielded an excellent correlation (r2 = 0.97). This allowed us to compile a map of polymetallic nodule abundance that shows greater resolution than a map derived from the extrapolation of point-sampling data. Our preliminary analyses indicate that it is possible to greatly increase the confidence level of nodule resource data if the relationship between backscatter intensity and nodule abundance is reliably established. This approach has another key advantage over point sampling and image analyses in that detailed maps of mining obstacles along the seafloor are produced when acquiring data on the abundance of polymetallic nodules. The key limitation of this work is a poor correlation between nodule coverage, as observed from photographs, and nodule abundance. Significant additional ground truth sampling using well located box cores should be completed to determine whether or not there is a real correlation between the backscatter and abundance. 相似文献
Recent cryochemical and photochemical findings for cyanoacetylene and cyanopolyacetylene-related molecules (including various
isomeric species), backed up with quantum-chemical predictions, are analysed. A new class of interstellar molecules, distinguished
by bare (hydrogen-less), unsaturated carbon-nitrogen chains of the general formula CnN2 is postulated. It is recommended to look for some relevant IR spectral features in space.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
In the Ulleung Basin, East Sea, the Dok Do seamount group comprises Dok Do (Dok Island), consisting of very small islets/rocks
and a large submerged volcanic edifice, and two voluminous tablemounts, Simheungtaek and Isabu. We attempted to reconstruct
the evolution of these seamounts, using virtual geomagnetic poles (VGPs) determined by the least-squares and the seminorm
magnetization methods, with 1,500 m upward continued magnetic anomalies. The VGPs of Dok Do with normal dipole anomaly, and
of Simheungtaek with normal dipole anomaly are located near the present magnetic pole. The VGP of Isabu with normal dipole
anomaly is located at low latitude, presumably due to overprints of reversals in the Tertiary, and the distortion of magnetization
and structures associated with volcanism after its formation. In contrast to the tablemounts, magnetic anomalies over Dok
Do are a combination of both normal polarity and reversed polarity dipoles in the northern hemisphere, indicating that Dok
Do has had at least two major eruptions, one during normal and another during reversed polarity intervals. From these results,
and information on the ages of the seamounts (either published radiometric ages of subaerial volcanic rocks, or ages reconstructed
in terms of reported elastic thickness incorporated into an existing cooling plate model), we tentatively propose that (1)
Isabu formed first, during a normal polarity interval after the opening of the East Sea had ceased; (2) this was followed
by an initial and subsequent large eruption of Dok Do during a normal polarity and a reversed polarity interval after about
5 Ma; and (3) the formation of Simheungtaek occurred in between that of Isabu and Dok Do in a normal polarity interval. The
pattern of normal/reversed magnetization is not inconsistent with the geomagnetic polarity timescale for at least the last
5 Ma. Nevertheless, precise ages of formation would need verification by additional geophysical/geochemical constraints. Evaluating
various possible models explaining the successive formation of the Dok Do seamounts, we currently favor fracturing and volcanism
related to compression-induced weakening of the extensional field from the late Miocene to Pliocene after the opening of the
East Sea. 相似文献
The Sanbagawa metamorphic rocks in the Besshi district, central Shikoku, are grouped into eclogite and noneclogite units. Chloritoid and barroisite-bearing pelitic schists occur as interlayers within basic schist in an eclogite unit of the Seba area in the Sanbagawa metamorphic belt, central Shikoku, Japan. Major matrix phases of the schists are garnet, chlorite, barroisite, paragonite, phengite, and quartz. Eclogite facies phases including chloritoid and talc are preserved only as inclusions in garnet. P–T conditions for the eclogite facies stage estimated using equilibria among chloritoid, barroisite, chlorite, interlayered chlorite–talc, paragonite, and garnet are 1.8 GPa/520–550 °C. Zonal structures of garnet and matrix amphibole show discontinuous growth of minerals between their core and mantle parts, implying the following metamorphic stages: prograde eclogite facies stage→hydration reaction stage→prograde epidote–amphibolite stage. This metamorphic history suggests that the Seba eclogite lithologies were (1) juxtaposed with subducting noneclogite lithologies during exhumation and then (2) progressively recrystallized under the epidote–amphibolite facies together with the surrounding noneclogite lithologies.
The pelitic schists in the Seba eclogite unit contain paragonite of two generations: prograde phase of the eclogite facies included in garnet and matrix phase produced by local reequilibration of sodic pyroxene-bearing eclogite facies assemblages during exhumation. Paragonite is absent in the common Sanbagawa basic and pelitic schists, and is, however, reported from restricted schists from several localities near the proposed eclogite unit in the Besshi district. These paragonite-bearing schists could be lower-pressure equivalents of the former eclogite facies rocks and are also members of the eclogite unit. This idea implies that the eclogite unit is more widely distributed in the Besshi district than previously thought. 相似文献