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991.
Coastal Habitat Use and Residency of Juvenile Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae)
John K. Carlson Michelle R. Heupel Dana M. Bethea Lisa D. Hollensead 《Estuaries and Coasts》2008,31(5):931-940
Coastal habitat use and residency of a coastal bay by juvenile Atlantic sharpnose sharks, Rhizoprionodon terraenovae, were examined by acoustic monitoring, gillnet sampling, and conventional tag–recapture. Acoustic monitoring data were used to define the residency and movement patterns of sharks within Crooked Island Sound, Florida. Over 3 years, sharks were monitored for periods of 1–37 days, with individuals regularly moving in and out of the study site. Individual sharks were continuously present within the study site for periods of 1–35 days. Patterns of movement could not be correlated with time of day. Home range sizes were typically small (average?=?1.29 km2) and did not vary on a yearly basis. Gillnet sampling revealed that juvenile Atlantic sharpnose sharks were present in all habitat types found within Crooked Island Sound, and peaks in abundance varied depending on month within a year. Although telemetry data showed that most individuals remained within the study site for short periods of time before emigrating, conventional tag–recapture data indicates some individuals return to Crooked Island Sound after extended absences (maximum length?=?1,352 days). Although conventional shark nursery theory suggests small sharks remain in shallow coastal waters to avoid predation, juvenile Atlantic sharpnose sharks frequently exited from protected areas and appear to move through deeper waters to adjacent coastal bays and estuaries. Given the high productivity exhibited by this species, the benefit gained through a nursery that reduces predation may be limited for this species. 相似文献
992.
This paper deals with groundwater hydrology at a prominent fracture zone landslide slope (Nuta–Yone landslides) in Japan with
an objective to explore an efficient method for the application of landslide stability enhancement measures. The correlation
analyses between the hydrological parameters and ground surface movement data at this landslide resulted in low correlation
values indicating that the geological formation of the area is extremely complex. For the purpose of understanding the groundwater
flow behavior in the landslide area, a three-dimensional transient groundwater flow model was prepared for a part of the landslide
slope, where the levels of effectiveness of applied landslide stability enhancement measures (in the form of multilayered
deep horizontal drains) are different, and was calibrated against the measured water surface elevations at different piezometer
locations. The parameter distributions in the calibrated model and the general directions of the groundwater flow in terms
of flow vectors and the results of particle tracking at the model site were interpreted to understand the reasons for variations
in effectiveness of existing landslide stability enhancement measures and to find potentially better locations for the implementation
of future landslide stability enhancement measures. From the modeling results, it was also understood that groundwater flow
model can be effectively used in better planning and locating the landslide stability enhancement measures. 相似文献
993.
印度板块和亚洲大陆在何时何地碰撞 总被引:1,自引:0,他引:1
印度板块和亚洲大陆的初始碰撞时间是所有相关的喜马拉雅-西藏造山体系演化模式的主控条件,并严重影响到对众多与青藏高原隆升和东亚大陆挤出相关的地质过程速率的解释,以及对新生代全球气候变化的理解。尽管印度板块和亚洲大陆汇聚的速率在55Ma突然减缓被广泛地认为是初始碰撞的标志,但这次碰撞所造成的主要构造效应直到20多个百万年以后才显现出来。对印度板块和亚洲大陆相对位置的重新估算,表明它们在55Ma时并没有达到可以彼此发生碰撞的距离。基于来自西藏新的野外证据和对已有数据的重新评估,认为初始碰撞发生在始新世—渐新世之交(约34Ma),并对55Ma时发生的地质事件提出了另一种解释 相似文献
994.
位于乌鲁木齐市南湖路以西的煤炭采空区面积达67 100.5m^2,区内构造从南到北主要由八道湾向斜和七道湾背斜组成,地层产状变化不大。该矿区开采较深,且采空区塌陷区有明显的地下水活动迹象。在对深孔大体积采空区注浆时,比较各种常见注浆治理方法,均存在不同的制约因素,故决定采用灌浆爆破压密法对采空区进行压实加固。经现场爆破试验,该区重复爆破次数在3~5次左右。灌浆爆破压密处理后,对不同土层进行取样对比分析,得到其相应密度(增加)及空隙比(减少)的变化分别为:杂填土14.1%,-7.9%;素填土5.9%,-3.3%;塌落煤层7.8%,-7.7%。根据压缩数据及现场测量,处理后的土体沉降2~4m,部分空体地段的沉降量达10~20m,治理效果明显。 相似文献
995.
Assessment of cement’s dust impact on the soil using principal component analysis and GIS 总被引:2,自引:1,他引:1
Z. Zerrouqi M. Sbaa Ph.D. M. Oujidi Ph.D. M. Elkharmouz S. Bengamra A. Zerrouqi 《International Journal of Environmental Science and Technology》2008,5(1):125-134
To evaluate the impact of the cement’s dust emitted by the eastern Moroccan cement factory (Oujda Holcim) and deposited on the soil of the Ain Lahjar commune, 58 samples of soil were collected around the factory on a radius of 3 km approximately. The physicochemical analyses of the upper 3 cm of the soil surface samples correspond to the pH, electrical conductivity, the chlorides and the oxides of Ca, Al, Fe, K, Mn, S and Si which were analyzed by the fluorescence of X-rays. The preliminary results demonstrate that this dust are especially basic and contain a high free lime (43% CaO). The principal component analysis (applied on the 58 samples of soil) allows deducting that the free lime and the sulfur oxide are the tracer elements of this form of pollution. Furthermore, the spatial projection of the factor scores of the principal component analysis using the geographical information system permits to determine the spatial distribution of more polluted areas of soils as well as to estimate their surface (63.3% of the survey zone). 相似文献
996.
Bioaccumulation of heavy metals in organs of fresh water fish Cyprinus carpio (Common carp) 总被引:3,自引:2,他引:1
R. Vinodhini M.Sc. M.Phil. M. Narayanan M.Sc. Ph.D. 《International Journal of Environmental Science and Technology》2008,5(2):179-182
The objective of the present study is to determine the bioaccumulation of heavy metals in various organs of the fresh water fish exposed to heavy metal contaminated water system. The experimental fish was exposed to Cr, Ni, Cd and Pb at sublethal concentrations for periods of 32 days. The elements Cd, Pb, Ni and Cr were assayed using Shimadzu AA 6200 atomic absorption spectrophotometery and the results were given as μ/g dry wt. The accumulation of heavy metal gradually increases in liver during the heavy metal exposure period. All the results were statistically significant at p < 0.001. The order of heavy metal accumulation in the gills and liver was Cd > Pb > Ni > Cr and Pb > Cd > Ni > Cr. Similarly, in case of kidney and flesh tissues, the order was Pb > Cd > Cr > Ni and Pb > Cr > Cd > Ni. In all heavy metals, the bioaccumulation of lead and cadmium proportion was significantly increased in the tissues of Cyprinus carpio (Common carp). 相似文献
997.
Influence of biotic-abiotic factors on the degradation of novaluron in tropical soil 总被引:2,自引:2,他引:0
P. Das Ph.D. R. Pal Ph.D. A. Chowdhury 《International Journal of Environmental Science and Technology》2008,5(3):425-429
In this study, the degradation of novaluron (benzoylphenyl urea insect growth regulator) was investigated under controlled laboratory conditions in clay loam alluvial and coastal saline soils of West Bengal, India. The application rates were field rate (FR); 2FR and 10FR. The incubation study was carried out at 30 °C and 60% of maximum water holding capacity of both the soils. Degradation of novaluron in both the soils followed first order reaction kinetics at all application rates under non-sterile and sterile conditions. The half-lives of novaluron in non-sterilized soils ranged from 17.0–17.8 days (alluvial soil) and 11.4–12.7 days (coastal saline soil), while the values in case of the sterilized soils were 53.7–59.0 days (alluvial soil) and 28.9–29.8 days (coastal saline soil) respectively. The novaluron degradation patterns were found to be highly influenced by soil types, application rates, and biotic abiotic factors. Abiotic factors strongly influenced novaluron degradation in both the soils. Biotic degradation was higher in alluvial soil compared to the coastal saline soil. 相似文献
998.
R. A. Oktyabrsky A. A. Vrzhosek A. M. Lennikov T. A. Yasnygina S. V. Rasskazov E. Yu. Moskalenko T. A. Velivetskaya 《Russian Journal of Pacific Geology》2008,2(4):325-335
New geochemical data are presented on the magmatic rocks of the Late Jurassic Koksharovka alkaline-ultrabasic massif, which is associated with deposits of vermiculite, apatite, V-bearing titanomagnetite, and placer isoferroplatinum. The REE geochemistry and strontium, oxygen, and carbon isotopic composition of carbonatites and related ijolites and pyroxenites, together with geological observations, point to the magmatic origin of the Koksharovka carbonatites. The origin of associated magmatic rocks is discussed. Trace element modeling of partial melting of mantle sources was conducted to decipher the genesis of the melts of the Koksharovka carbonatites and host titanite-kaersutite pyroxenites. 相似文献
999.
R. M. Lark 《Mathematical Geosciences》2008,40(7):729-751
The effect of outliers on estimates of the variogram depends on how they are distributed in space. The ‘spatial breakdown
point’ is the largest proportion of observations which can be drawn from some arbitrary contaminating process without destroying
a robust variogram estimator, when they are arranged in the most damaging spatial pattern. A numerical method is presented
to find the spatial breakdown point for any sample array in two dimensions or more. It is shown by means of some examples
that such a numerical approach is needed to determine the spatial breakdown point for two or more dimensions, even on a regular
square sample grid, since previous conjectures about the spatial breakdown point in two dimensions do not hold. The ‘average
spatial breakdown point’ has been used as a basis for practical guidelines on the intensity of contaminating processes that
can be tolerated by robust variogram estimators. It is the largest proportion of contaminating observations in a data set
such that the breakdown point of the variance estimator used to obtain point estimates of the variogram is not exceeded by
the expected proportion of contaminated pairs of observations over any lag. In this paper the behaviour of the average spatial
breakdown point is investigated for cases where the contaminating process is spatially dependent. It is shown that in two
dimensions the average spatial breakdown point is 0.25. Finally, the ‘empirical spatial breakdown point’, a tool for the exploratory
analysis of spatial data thought to contain outliers, is introduced and demonstrated using data on metal content in the soils
of Sheffield, England. The empirical spatial breakdown point of a particular data set can be used to indicate whether the
distribution of possible contaminants is likely to undermine a robust variogram estimator. 相似文献
1000.
Inversely-Mapped Analytical Solutions for Flow Patterns around and within Inclined Elliptic Inclusions in Fluid-Saturated Rocks 总被引:1,自引:0,他引:1
Chongbin Zhao Bruce E. Hobbs Alison Ord Shenglin Peng Liangming Liu 《Mathematical Geosciences》2008,40(2):179-197
In this paper, an inverse mapping is used to transform the previously-derived analytical solutions from a local elliptical
coordinate system into a conventional Cartesian coordinate system. This enables a complete set of exact analytical solutions
to be derived rigorously for the pore-fluid velocity, stream function, and excess pore-fluid pressure around and within buried
inclined elliptic inclusions in pore-fluid-saturated porous rocks. To maximize the application range of the derived analytical
solutions, the focal distance of an ellipse is used to represent the size of the ellipse, while the length ratio of the long
axis to the short one is used to represent the geometrical shape of the ellipse. Since the present analytical solutions are
expressed in a conventional Cartesian coordinate system, it is convenient to investigate, both qualitatively and quantitatively,
the distribution patterns of the pore-fluid flow and excess pressure around and within many different families of buried inclined
elliptic inclusions. The major advantage in using the present analytical solution is that they can be conveniently computed
in a global Cartesian coordinate system, which is widely used in many scientific and engineering computations. As an application
example, the present analytical solutions have been used to investigate how the dip angle of an inclined elliptic inclusion
affects the distribution patterns of the pore-fluid flow and excess pore-fluid pressure when the permeability ratio of the
elliptic inclusion is of finite but nonzero values. 相似文献