Various Natural (various + natural)

Distribution by Scientific Domains


Selected Abstracts


Long-term corrosion-induced copper runoff from natural and artificial patina and its environmental impact,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2006
Sofia Bertling
Abstract The overall objective of this paper is to present an extensive set of data for corrosion-induced copper dispersion and its environmental interaction with solid surfaces in the near vicinity of buildings. Copper dispersion is discussed in terms of total copper flows, copper speciation and bioavailability at the immediate release situation, and its changes during transport from source to recipient. Presented results are based on extensive field exposures (eight years) at an urban site, laboratory investigations of the runoff process, published field data, generated predictive site-specific runoff rate models, and reactivity investigations toward various natural and manmade surfaces, such as those in soil, limestone, and concrete. Emphasis is placed on the interaction of copper-containing runoff water with different soil systems through long-term laboratory column investigations. The fate of copper is discussed in terms of copper retention, copper chemical speciation, breakthrough capacities, and future mobilization based on changes in copper concentrations in the percolate water, computer modeling using the Windermere Humic Aqueous Model, and sequential extractions. The results illustrate that, for scenarios where copper comes in extensive contact with solid surfaces, such as soil and limestone, a large fraction of released copper is retained already in the immediate vicinity of the building. In all, both the total copper concentration in runoff water and its bioavailable part undergo a significant and rapid reduction. [source]


AN EVALUATION OF SURFACE HARDNESS OF NATURAL AND MODIFIED ROCKS USING SCHMIDT HAMMER: STUDY FROM NORTHWESTERN HIMALAYA, INDIA

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2009
VIKRAM GUPTA
ABSTRACT. Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. [source]


Handheld ultrasound device for detection of non-opaque and semi-opaque foreign bodies in soft tissues,

JOURNAL OF CLINICAL ULTRASOUND, Issue 4 2003
Angela D. Levy MD
Abstract Purpose The aim of this study was to determine whether a portable handheld ultrasound device can be used to visualize non-opaque and semi-opaque foreign bodies in soft tissues and to characterize their sonographic appearance. Methods Twenty-two fragments composed of various natural and man-made materials and ranging from 4 to 20 mm in the maximum longitudinal dimension were embedded into 2 thawed turkey breasts. Two sonographers who were unaware of the number, dimensions, and locations of the fragments used a handheld ultrasound device to detect and characterize the fragments on the basis of their surface echogenicity and acoustic shadowing. The sonographic appearance of each fragment was compared with its actual characteristics. Results All 22 embedded fragments were successfully identified and localized on sonography. Surface echogenicity and acoustic shadowing varied among the fragments. For some fragments, the sonographically measured maximum longitudinal dimension differed substantially from the actual dimension. Conclusions Use of a portable handheld ultrasound device is effective for the detection of foreign bodies with a diameter greater than 4 mm in soft tissues. The sonographic appearances of non-opaque and semi-opaque foreign bodies vary in their patterns of surface echogenicity and acoustic shadowing. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 31:183,188, 2003 [source]


Comparative assessment of the water balance and hydrology of selected Ethiopian and Kenyan Rift Lakes

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3 2008
Tenalem Ayenew
Abstract The study area is part of the East African Rift system, characterized by a cluster of lakes occupying an extremely faulted rift floor with geothermal manifestations. Some of the lakes illustrated contrasting water levels and size evolution over the last few decennia, believed to have been caused by various natural and anthropogenic factors. The relative importance of these factors, however, is unknown. This study attempts to present the hydrology of the lakes in a broader context, by giving more emphasis to lake water level fluctuations and to the water balance. These factors have far-reaching implications in regard to future management of the lake basin water. It also provides information on the relation of the groundwater with the lakes, and with the local and regional groundwater flow system from the adjacent highlands to the floor of the Rift. The methods utilized in this study include conventional hydrogeological field surveys, and hydrometeorological and data analyses, coupled with digital image processing and spatial analysis under a Geographic Information System environment. Ancillary supporting information has been obtained from environmental isotopes and hydrochemical data. The study results indicate the terminal Ethiopian lakes changed in size and water level significantly over the last half century. In contrast, the Kenyan lakes only exhibited slight changes. The lakes in both countries exhibit a striking similarity in their subsurface hydraulic connection, and are strongly governed by complex rift geological structures. Groundwater plays a vital role in the water balance of the study lakes. The study results indicate that future sustainable use of the study lakes demands that serious attention be given to the role of the groundwater component of the lake water balances. [source]


Identifying environmental signals from population abundance data using multivariate time-series analysis

OIKOS, Issue 11 2009
Masami Fujiwara
Individual organisms are affected by various natural and anthropogenic environmental factors throughout their life history. This is reflected in the way population abundance fluctuates. Consequently, observed population dynamics are often produced by the superimposition of multiple environmental signals. This complicates the analysis of population time-series. Here, a multivariate time-series method called maximum autocorrelation factor analysis (MAFA) was used to extract underlying signals from multiple population time series data. The extracted signals were compared with environmental variables that were suspected to affect the populations. Finally, a simple multiple regression analysis was applied to the same data set, and the results from the regression analysis were compared with those from MAFA. The extracted signals with MAFA were strongly associated with the environmental variables, suggesting that they represent environmental factors. On the other hand, with the multiple regression analysis, one of the important signals was not identifiable, revealing the shortcoming of the conventional approach. MAFA summarizes data based on their lag-one autocorrelation. This allows the identification of underlying signals with a small effect size on population abundance during the observation. It also uses multiple time series collected in parallel; this enables us to effectively analyze short time series. In this study, annual spawning adult counts of Chinook salmon at various locations within the Klamath Basin, California, were analyzed. [source]