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961.
962.
963.
A. F. Grachev I. L. Kamensky O. A. Korchagin H. A. Kollmann 《Izvestiya Physics of the Solid Earth》2007,43(9):766-772
The paper presents preliminary results derived from the study of He isotopy in a transitional clay bed at the critical 65-Ma boundary in the Gams area (Eastern Alps). The ratio 3He/4He is shown to decrease from bottom to top of the transitional layer, and the difference between its values in the lower-and uppermost sublayers of the layer exceeds by more than ten times the measurement uncertainty (5%). The ratio 3He/4He is smallest in the upper part of the section, where all features of an impact event (spherules of pure nickel, diamonds, and awaruite) are established. The general inference of our study is that 3He enrichment in the lower part of the Gams section is related not to cosmic matter but to a change in the conditions in the source area, most likely, to volcanic activity. The effect of the latter has been established, independent of He isotopic studies, from anomalous concentrations of As, Pb, Cu, and Zn and from the presence of particles of gold, copper, and titanomagnetite similar in composition to its basaltic varieties. 相似文献
964.
965.
Seismic tomography shows that upwelling beneath Iceland is confined to the upper mantle 总被引:3,自引:0,他引:3
966.
967.
H.J.B. Birks 《Journal of Paleolimnology》2001,25(1):111-115
A recently discovered error in the part of the computer program WACALIB that implements maximum likelihood (ML) calibration has been discovered and corrected. The new version of WACALIB has been re-run with all the data-sets from which results based on the earlier version of WACALIB had been published. The new results suggest that ML regression and calibration perform as well or even better than weighted averaging (WA), at least when judged by the apparent root mean squared error. Further work involving cross-validation is required to evaluate more fully the relative performance of WA and ML approaches. 相似文献
968.
Controls on the nature and distribution of an alga in coal mine-waste environments and its potential impact on water quality 总被引:2,自引:0,他引:2
A dominant non-bacterial microorganism that may strongly impact environmental conditions in acid mine drainage at several
Indiana coal mine sites is a single-celled protozoan, Euglena mutabilis. Field data suggest E. mutabilis has high tolerance for elevated total dissolved solids (TDS), to 18 g/l, and acid conditions to pH 1.7. Distribution is restricted
to unmixed effluent pH<4.6, with prolific growth between pH 3.0 and 3.5. Additional factors influencing E. mutabilis include preference for areas with lower mineral/colloidal precipitation rates and a stable substrate of iron-rich precipitates.
Initial studies indicate that in areas of prolific growth it contributes to oversaturation of dissolved oxygen by up to 200%.
The presence of small orange intracellular crystalline-like structures, similar in color to iron oxyhydroxides, suggests that E. mutabilis may be sequestering iron, and possibly other metals. Further work is needed to determine if E. mutabilis contributes to natural mitigation of poor water quality at these and other coal mine sites.
Received: 13 January 2000 · Accepted: 2 May 2000 相似文献
969.
Groundwater contamination: risk management and assessment for landfills in Mar del Plata, Argentina 总被引:3,自引:0,他引:3
This study presents a program for risk management in the contamination of groundwater resulting from leachate in landfills
at Mar del Plata (Argentina). The program includes prediction, prevention, monitory observation and mitigation as actions
that must be taken prior to, during, and after contamination occurs. This routine aids in the identification of weak points
and failures of the program for those who are in charge of making decisions, and will allow better use of limited financial
and technical resources based on planning, thus minimizing disconnected determinations.
Results of the prediction stage were confirmed through monitoring. The presence of a plume of contamination more than 100 m
from the landfill was shown, thus proving that implementation of a monitoring plan to follow the development of the contaminated
plume must be implemented, particularly in populated areas which depend on residential wells for their water supply.
Received: 8 May 2000 · Accepted: 14 August 2000 相似文献
970.