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61.
F. S. Birch 《Ground water》1984,22(4):427-432
Bedrock depths can be calculated readily from ground magnetic profiles using either Werner deconvolution or Fourier spectral analysis. For crystalline basement rocks of New England and eastern Canada, a vertical dike is a useful magnetic source model. Formulae for these methods are presented along with some practical guidelines for implementing them. Six field examples from metamorphic and igneous areas in New Hampshire show that bedrock depths from spectral analysis agree well with estimates from seismic refraction, from wells and from outcrops. The Werner estimates are much more variable but commonly bracket the others. At several of these sites, measurements by other geophysical methods would be impractical, more expensive, or restricted to certain times of the year. 相似文献
62.
This study investigated physico-chemical characteristics of the water column and chemistry of suspended particulate material
(SPM) under quiescent, high-wind and high-wind/heavy-rainfall conditions in Homebush Bay, a highly contaminated embayment
of Port Jackson (Australia) to distinguish source and possible adverse effects to benthic and pelagic animals. Mean concentrations
in surficial sediment were <1, 14, 181, 141, 37, 290 and 685 μg g−1 for Cd, Co, Cr, Cu, Ni, Pb and Zn, respectively. Sediment chemistry indicated these metals had multiple sources, i.e. the
estuary, stormwater and industry. Mean total suspended solids (TSS) were 7, 17 and 20 mg L−1 during quiescent, high-rainfall and heavy rainfall/high wind conditions, respectively, whereas SPM Cd, Co, Cr, Cu, Ni, Pb
and Zn concentrations varied between 13–25, 166–259, 127–198, 38–82, 236–305 and 605–865 μg g−1, respectively under these conditions. TSS and total water metal concentrations were lowest during quiescent conditions. High
TSS and metal loads in surface water characterised high-rainfall events. Wind-induced resuspension contributed the greatest
mass of SPM and metals to the water column. Benthic animals may be adversely affected by Pb and Zn in sediment. Total water
Cu and Zn concentrations may pose a risk to filter-feeding animals in the water column due to resuspension of contaminated
sediment. 相似文献
63.
Lead distribution on a public shotgun range 总被引:1,自引:0,他引:1
James R. Craig David Edwards Donald J. Rimstidt Patrick F. Scanlon Thomas K. Collins Oliver Schabenberger Jeffrey B. Birch 《Environmental Geology》2002,41(8):873-882
64.
We present a comprehensive set of observations of the interaction of p-mode oscillations with sunspots using surface-focused seismic holography. Maps of travel-time shifts, relative to quiet-Sun travel times, are shown for incoming and outgoing p modes as well as their mean and difference. We compare results using phase-speed filters with results obtained with filters that isolate single p-mode ridges, and we further divide the data into multiple temporal frequency bandpasses. The f mode is removed from the data. The variations of the resulting travel-time shifts with magnetic-field strength and with the filter parameters are explored. We find that spatial averages of these shifts within sunspot umbrae, penumbrae, and surrounding plage often show strong frequency variations at fixed phase speed. In addition, we find that positive values of the mean and difference travel-time shifts appear exclusively in waves observed with phase-speed filters that are dominated by power in the low-frequency wing of the p 1 ridge. We assess the ratio of incoming to outgoing p-mode power using the ridge filters and compare surface-focused holography measurements with the results of earlier published p-mode scattering measurements using Fourier?–?Hankel decomposition. 相似文献
65.
We fix three typographical errors in “Linear Sensitivity of Helioseismic Travel Times to Local Flows” (Astronomische Nachrichten, Vol. 328, Issue 3, p. 228) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献