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111.
au a u naam u a nu¶rt; 1963–1973
. naam, m aum mun ma m mm nam aum n (II) na¶rt;am m u a uu ¶rt; u u,¶rt; ua ma u¶rt;, u u¶rt;a ma mn muna. mu u m ¶rt;u mam nm nmum n¶rt;auma amu m m mm II u a¶rt; ¶rt; n. 相似文献
112.
A new method for the sampling of sublimates from high-temperature volcanic gases has been used at Merapi volcano, Java, in 1978. The sublimates were collected on the inner walls of silica tubes introduced into fumarolic vents. Volcanic gases were allowed to move freely through the tubes and as they cooled, a fraction of the volatile components condensed on the inner walls of the tubes along the temperature gradient. The sublimates were then analyzed by a combination of light microscopy, scanning electron microscopy, electron microprobe and X-ray diffraction.Six successive zones of different compositions and mineralogical associations have been identified along the covered range of temperatures (900° to around 400°C). From the high to the low temperatures, these zones are composed of: (1) cristobalite, magnetite, hercynite; (2) molybdenite; (3) acmite; (4) halite, sylvite; (5) sphalerite, pyrite; and (6) galena. Equilibrium calculations show that these crystalline phases are stable for pS2, pC1, and pO2, values typical of magma-buffered gases that have not been contaminated by atmospheric oxygen.The deposits observed in the tubes may be useful in aiding the understanding of the mechanisms acting during the cooling of the gaseous phase on its way to the surface and before its emission into the atmosphere. 相似文献
113.
F. Le Guern 《Bulletin of Volcanology》1982,45(3):197-202
Volcanic contribution to the atmosphere can be re-evaluated as 5×107 ton/year of CO2, which is less than recent industrial contribution. Degassing is more abundant from volcanoes where magma convections are significant. Effective degassing occurs before the magma reaches the surface, that is, when the magma is fluid. Volcanic gas in the atmosphere can affect the population or the vegetation around volcanoes. 相似文献
114.
On February 20th, 1979, 142 inhabitants of Dieng Plateau (Indonesia) were asphyxiated by poisonous gases during a mild phreatic eruption. From later fields gas collection and analysis, the casualties are considered to be due to CO2 rich volcanic gases. 相似文献
115.
116.
117.
G. Bergametti A.L. Dutot J.P. Quisefit R. Vie Le Sage 《Journal of Volcanology and Geothermal Research》1983,15(4):355-367
A statistical analysis of volcanic aerosol based on 1,083 variables including concentration, grain-size and site variabilities establishes correlations between sites and among chemical elements.Variation curves of element concentration show parallel behaviour. High coefficients of correlation between anions and cations confirm associations between elements. 相似文献
118.
Improving the accuracy of tipping-bucket rain records using disaggregation techniques 总被引:1,自引:0,他引:1
We present a methodology able to infer the influence of rainfall measurement errors on the reliability of extreme rainfall statistics. We especially focus on systematic mechanical errors affecting the most popular rain intensity measurement instrument, namely the tipping-bucket rain-gauge (TBR). Such uncertainty strongly depends on the measured rainfall intensity (RI) with systematic underestimation of high RIs, leading to a biased estimation of extreme rain rates statistics. Furthermore, since intense rain-rates are usually recorded over short intervals in time, any possible correction strongly depends on the time resolution of the recorded data sets. We propose a simple procedure for the correction of low resolution data series after disaggregation at a suitable scale, so that the assessment of the influence of systematic errors on rainfall statistics become possible. The disaggregation procedure is applied to a 40-year long rain-depth dataset recorded at hourly resolution by using the IRP (Iterated Random Pulse) algorithm. A set of extreme statistics, commonly used in urban hydrology practice, have been extracted from simulated data and compared with the ones obtained after direct correction of a 12-year high resolution (1 min) RI series. In particular, the depth–duration–frequency curves derived from the original and corrected data sets have been compared in order to quantify the impact of non-corrected rain intensity measurements on design rainfall and the related statistical parameters. Preliminary results suggest that the IRP model, due to its skill in reproducing extreme rainfall intensities at fine resolution in time, is well suited in supporting rainfall intensity correction techniques. 相似文献
119.
Partitioning,bioavailability and origin of heavy metals from the Nador Lagoon sediments (Morocco) as a basis for their management 总被引:2,自引:0,他引:2
Nador Lagoon sediments show low trace element concentrations, and, in relation to the lagoon geochemical baseline, only some
anomalies for As, Cd, Cu and Pb in the NW of the lagoon deserve to be outstanding. The distribution of major, minor and trace
elements in the lagoon allows a breakdown in four zones. Between “Beni Ensar” and “Atelouane” (zone A), a quite confined zone
rich in organic matter and S, the most important trace-element anomalies (As, Cd, Co, Cu, Mn, Pb, Zn) were found, mainly around
industry and old mining activities. In the surrounding of the city of Nador (zone B), the anomalies correspond to Mn, Cu and
Zn. The coastal barrier and Kebdana channel (zone C) show moderately concentrations of Cd, Cr and Ni at specific sites. The
less polluted area is the SE of the lagoon (zone D), with no outstanding anomaly. In lagoon sediments, metal bioavailability
is very low. The metal partitioning patterns show that Cu, Pb and Zn present a low availability because they are bounded to
the residual, non-mobile phases of the sediments. Only in some sites, the fraction was associated with organic matter, which
could be liberated easily. Arsenic is concentrated in both the residual phases and the organic matter, the latter being more
available. Cadmium is mainly concentrated in some samples in the interchangeable fraction, which could be considered as a
potentially toxic element because it is easily released. Concerning the origin of these trace elements, those found in zone A
correspond mostly to a natural source by weathering of mount Gourougou volcanic rocks (As, Co, Cu, Pb and Zn), and to an anthropogenic
origin (Cd) owing to the presence of industry and old mines. In zone B, contributions of Cu and Zn enter the lagoon through
soil weathering and river-borne, and as anthropogenic pollution from urban wastes. In zone C the most important pollutant
is Cd deduced to be of anthropogenic origin from the close industry and intensive agriculture area. In spite of the intense
socio-economic activities developed in the Nador Lagoon (agriculture, industry, fishing, tourism) trace element concentrations
in the sediments are low and with scarce bioavailability. Only the NW sector is relativity polluted because of geogenic features. 相似文献
120.
A vane fitted to a standard shear vane tester is described, the purpose of which is to obtain better measurements of the rheological properties of soft, surficial, intertidal muds (and consequently, variations in their erodability). Specifications and geometry of this vane are presented. The computation procedure is detailed, so that the methodology can be applied to any vane tester. The main improvement is a greater vertical resolution, typically less than 1 cm. Sets of direct measurements with this equipment and correlation with dry densities for three intertidal mudflats (estuaries and bay) are presented. 相似文献