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From 1998 to 2002 investigations were carried out to estimate both the quantity and quality (heavy metal contents) of suspended matter loads discharged into a floodplain area measuring approx. 5 km2 of the Central German river Weiße Elster, a tributary of the river Saale in the Elbe river basin. Flood sediments, suspended particulate matter, and floodplain soils were investigated especially for the main pollutants Cd, Zn, Cu, Pb, Cr, and Hg. Supplementary gamma spectroscopy examinations were performed to help to identify the age of deposits in order to estimate sedimentation rates for last decades. The recent flood sediments are contaminated by up to 33 times the geogenic background (Cd). Up to 55% of the total annual SPM load of the river Weiße Elster is relocated into the investigated retention area in the flood‐stricken year 2002. The sedimentation rates for the last 50 years vary between 0.5 mm/a and 1 mm/a in far away and rarely flooded parts and between 1 mm/a and 2 mm/a in the frequently flooded parts of the inflow of the retention area. 相似文献
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Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations. 相似文献
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Carbon isotope geochemistry of the Precambrian Lomagundi carbonate province,Rhodesia 总被引:1,自引:0,他引:1
Manfred Schidlowski Rudolf Eichmann Christian E. Junge 《Geochimica et cosmochimica acta》1976,40(4):449-455
Carbon isotope measurements carried out on 67 dolomite samples from the Middle Precambrian Lomagundi Group (Rhodesia) have yielded a δ13C mean of +8.2 ± 2.6%. vs PDB. With the outcrop of these dolomites extending over a distance of almost 300 km, the Lomagundi dolomite faces is likely to represent the largest isotopically anomalous sedimentary carbonate province ever recorded. It is concluded that the anomalous carbonates formed in a closed basin whose δ13C level had been substantially increased as a result of a preferential removal (within sedimentary organics) of the light carbon isotope. 相似文献
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Numerical modeling of the terrestrial oxygen budget based on the revised δ13Ccarb record by Veizeret al. (1980) has shown that total photosynthetic oxygen has varied between ±7% and ±10% of its average reservoir size (~3.2 × 1022 g) during the last 800 myr as a result of oscillations of the sedimentary reservoir of organic carbon. Calculated curves of oxygen evolution display a distinct minimum in the Early Paleozoic framed by two maxima in the Latest Proterozoic and the Mesozoic. The sympathetic relationship observed between the curves of total oxygen evolution and respective functions for the partial reservoir of sulfate-bound oxygen suggests that the O2 required for an additional conversion of sulfide to sulfate was most probably provided by excess burial of organic carbon, the results of the modeling thus adding credence to current interpretations proposed for the negative correlation between the secular and trends. 相似文献
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Christian E. Junge 《Pure and Applied Geophysics》1961,50(1):94-95
An automatic condensation nuclei counter was developed for the concentration range of about 1 to 400 particles per cubic centimeter. After expansion, the water droplets are photographed when they are still suspended in the air so that the counter can be considered an absolute one. The volume in which the droplets are counted is determined by the size of the picture of the droplets as a function of their distance from the focal plane. To eliminate any effect of decreasing pressure with altitude, the cloud chamber is filled with clean air prior to expansion to about half an atmosphere above ambient pressure. This counter was used to obtain vertical profiles of condensation nuclei up to altitudes of 27 km with high altitude balloons. A total of seven profiles was obtained over a period of about one year at 47° N over the United States. Because of the restrictions in the range of the meter no data could be obtained below 5 km. The profiles show the following main features:
- 1.Although there are pronounced fluctuations in the individual flights the average nuclei concentration of 200 to 300/cm3 remains fairly constant from 5 km to the tropopause. 相似文献