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221.
222.
Anthropogenic influences on hydrocarbon contents of sediments deposited in eastern Lake Ontario since 1800 总被引:3,自引:0,他引:3
The amounts and types of extractable hydrocarbon components in sediment cores from the Rochester Basin of eastern Lake Ontario
provide a record of environmental changes that have accompanied the settlement and population growth of the surrounding land
areas. Sediments deposited prior to the mid-1800s contain low concentrations of hydrocarbons that are dominated by land-plant
wax components. Concentrations begin to rise in the late 1800s as erosion of soil and nutrients from watershed areas accelerated.
This pattern continues into modern times. Episodes of enhanced aquatic productivity are sometimes recorded in twentieth-century
sediments by the dominance of algal hydrocarbons, but land-plant components typically predominate. Petroleum residues begin
to appear in sediments deposited in the late 1800's but remain minor constituents of the hydrocarbon contents of modern sediments
in the Rochester Basin.
Received: 21 March 1995 · Accepted: 11 August 1995 相似文献
223.
224.
Di Baofeng Katsenis Loukas Stamatopoulos Constantine A. Panoskaltsis Vassilis P. 《Landslides》2021,18(6):2297-2307
Landslides - Earthquake-induced landslides involve excessive movement of slopes, usually along slip surfaces. This seismic movement of slopes may depend crucially on (a) the soil response along the... 相似文献
225.
Relationships among bottom-water dissolved oxygen (DO), vertical stratification, and the factors responsible for stratification-destratification in this shallow, low tidal-energy estuary were studied using a 15-yr set of biweekly measurements, along with some recent continuous-monitoring data. Hypoxia develops only when there is both vertical water-column stratification and warm water temperature (>15°C). In July, 75% of the DO readings were <5 mg 1?1, and one-third were <1 mg 1?1. Severe hypoxia occurs more frequently in the upper half of the estuary than near the mouth. Both the time series data and correlation analysis results indicate that stratification events and DO levels are tightly coupled with variations in freshwater discharge and wind stress. Stratification can form or disappear in a matter of hours, and episodes lasting from one to several days seem to be common. Estimated summertime respiration rates in the water and sediments are sufficient to produce hypoxia if the water is mixed only every 6–12 d. There has been no trend toward lower bottom water DO in the Pamlico River Estuary over the past 15 yr. *** DIRECT SUPPORT *** A01BY059 00002 相似文献
226.
The zonal structure of the distribution of filaments is considered. The mean latitudes of two filament bands are calculated in each solar hemisphere at the minima of the sunspot cycle in the period 1924–1986: middle latitude
2, m
and low latitude
1, m
. It is shown that the mean latitude of the filament band
2, m
at the minimum -m of the cycle correlates, with = 0.94, with the maximum - M sunspot area S(M) and maximum Wolf number W(M) in the succeeding solar cycle M. It is shown that the mean latitude of the low-latitude filament band
1, m
is linearly dependent on the mean latitude filament band
2, m + 1 at the succeeding minimum. We found a correlation of the latitude of the low-latitude filament band
1, m
with the maximum sunspot area in the M + 1 cycle. This enables us to predict the power of two succeeding 11-year solar cycles on the basis of the latitude of filament bands at the minimum of activity, 1985–1986: W(22) - 205 ± 10, W(23) - 210 ± 10. The importance of the relationships found for theory and applied aspects is emphasized. An attempt is made to interpret the relationships physically. 相似文献
227.
Under the Maxwell-Boltzmann approach, the study of nuclear reactions in dense astrophysical plasmas under various cases (such as resonant, non-resonant, modified non-resonant, non-resonant under electron screening, and so on) leads to a class of complicated reaction rate integrals. It is shown that this general class of integrals can be identified with an integral involving the product of twoH-functions. This latter integral is evaluated in this article, and following Buschman (1979), several similar results in the published literature are shown to be incorrect. 相似文献
228.
The quantitative distribution and grain-size composition of the suspended particulate matter (SPM) in the marginal filter
of the Severnaya Dvina River during the summer low-water periods of 2001–2005 were first analyzed in seawater on board of
the vessel immediately after its sampling (without preliminary treatment) using a Coulter counter. This analysis revealed
the main regularities in the transformation of the grain-size spectra at successive salinity steps of the marginal filter
as well as the boundaries between these steps based on the data obtained by direct complex studies of the SPM dispersion.
It is established that the water salinity is the main factor that controls the changes in the grain-size distribution and
the composition of the particulate matter in the marginal filter. The concentrations of the pelitic fraction and the salinity
demonstrate negative correlations between each other. It is shown that the areas characterized by the mass development of
phytoplankton are located along the outer boundary of the marginal filter (at the biological step), where the salinity amounts
to 23–24 psu. The content of the suspended forms of some chemical (lithogenic) elements and the Corg indicating the SPM’s genetic composition and their relations with the grain-size composition of the latter and the environments
are studied. 相似文献
229.
The reproduction of dynamic processes in the stratosphere at extratropical latitudes is considered in calculations of the atmospheric module of the global climate model of the Institute of Numerical Mathematics, Russian Academy of Sciences, with an upper boundary of 0.2 hPa (~60 km) for the period from 1979 to 2008 in comparison with the data observational. Changes in temperature, zonal wind, activity of planetary waves, heat fluxes in the lower stratosphere, and sudden stratospheric warmings with the displacement and splitting of the polar vortex, as well as the distribution of associated circulation anomalies in the troposphere, are analyzed. 相似文献
230.