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101.
R.M. Moore J.D. Burton P.J.LeB. Williams M.L. Young 《Geochimica et cosmochimica acta》1979,43(6):919-926
Fractionation by ultra-filtration of the dissolved organic material (DOM) in the River Beaulieu, with typical concentrations of dissolved organic carbon (DOC) of 7–8 mg C/l, showed it to be mainly in the nominal molecular weight range of 103–105, with 16–23% of the total DOC in the fraction > 105. The molecular weight distribution of DOM in the more alkaline River Test (average DOC, 2 mg C/l) was similar. In the River Beaulieu water, containing 136–314 βg Fe/l in ‘dissolved’ forms, 90% or more of this Fe was in the nominal molecular weight fraction > 105. Experiments showed that DOM of nominal molecular weight <105 could stabilize Fe(III) in ‘dissolved’ forms. The concentrations of ‘dissolved’ Fe in the river water probably reflect the presence of colloidal Fe stabilized by organic material and this process may influence the apparent molecular weight of the DOM. Dissolved. Mn (100–136 βg/l) in the River Beaulieu was mainly in true solution, probably as Mn(II), with some 30% in forms of molecular weight greater than ca 104.During mi xing in the Beaulieu Estuary, DOC and dissolved Mn behave essentially conservatively. This contrasts with the removal of a large fraction of the dissolved Fe (Holliday and LISS, 1976, Est. Coastal Mar. Sci. 4, 349–353). Concentrations of lattice-held Fe and Mn in suspended particulate material were essentially uniform in the estuary, at 3.2 and 0.012%, respectively, whereas the non-lattice held fractions decreased markedly with increase in salinity. For Mn the decrease was linear and could be most simply accounted for by the physical mixing of riverborne and marine participates, although the possibility that some desorption occurs is not excluded. The non-linear decrease in the concentration of non-lattice held Fe in particulates reflected the more complex situation in which physical mixing is accompanied by removal of material from the ‘dissolved’ fraction. 相似文献
102.
David F. Reid Willard S. Moore William M. Sackett 《Earth and Planetary Science Letters》1979,43(2):227-236
The Mn-fiber technique for extracting radium from seawater has proved useful for studying the marine geochemistry of228Ra. In the Gulf of Mexico, this technique was used to measure the surface and near-surface distribution of226Ra and228Ra. The observed surface distribution of228Ra, and particularly the radium activity ratio (228/226) can be explained by known circulation patterns, or, when local surface currents are not well understood, may provide insight into their general characteristics.The radium activity ratio has increased from 0.5 in 1968 to 0.7 in 1973 in the surface Gulf of Mexico. This observed increase cannot be attributed to known anthropogenic or natural source perturbations within the Caribbean Sea-Gulf of Mexico system. Possible causes include a change in the residence time for near-surface water, or variations in the relative dominance of the two sources for water entering the eastern Caribbean; the North Equatorial Current and the Guiana Current.The temporal distribution of228Ra is unstable and naturally variable over a time period less than or equal to five years in the Gulf of Mexico and by extrapolation, the Caribbean Sea. Therefore, its usefulness in calculations of eddy diffusion coefficients for these regions is greatly diminished. 相似文献
103.
Willard S. Moore Herbert W. Feely Yuan-Hui Li 《Earth and Planetary Science Letters》1980,49(2):329-340
Measurements of the228Ra/226Ra activity ratio in the waters of the Greenland, Norwegian and Labrador Seas and Baffin Bay reveal strong horizontal gradients in the surface waters. The coastal waters are dominated by228Ra injection from nearshore sediments. There is an inverse correlation between the228Ra/226Ra activity ratio and salinity in the 30–36‰ salinity range. Vertical profiles indicate that the228Ra/226Ra activity ratio is also strongly coupled toσθ except for some regions where228Ra is being injected into higher density water as these isopycnals intersect coastal areas. We use these measurements in the area of formation of North Atlantic Deep Water to estimate that this water mass forms with a228Ra/226Ra activity ratio of 0.10. 相似文献
104.
Concentrations of dissolved226Ra in Winyah Bay, South Carolina, and in the adjacent Atlantic Ocean are augmented by the desorption of radium from sediments in the low-salinity area of the estuary and diffusion from bottom sediments. Desorption of226Ra is reflected by lower concentrations in suspended sediments from higher-salinity regions of the estuary. Bottom sediments from the high-salinity region have lower226Ra/230Th activity ratios than those from the low-salinity end.The shape of the dissolved226Ra vs. salinity profile is influenced by the river discharge. During average-discharge conditions, desorption of226Ra from suspended and bottom sediments increases the dissolved226Ra concentrations by a factor of 3.5 as the water passes through Winyah Bay. High river discharge produces an initial increase of dissolved226Ra by a factor of 2 to 3 and apparently reflects only desorption from suspended sediments. By driving the salt wedge down the estuary and reducing the zone of contact of salt water with bottom sediments, the high-flow conditions sharply reduce the flux of226Ra from bottom sediments. 相似文献
105.
Terry Russell 《Sedimentary Geology》1980,25(4):277-290
Clasts of the Late Devonian Keepit Conglomerate of northeastern New South Wales, Australia, are predominantly andesites of isotropic nature that lack any apparent initial shape controls. Given adequate time in a particular environment, these clasts could be reasonably expected to develop shapes characteristic of abrasion within that environment.Clasts from both fluvial and marine resedimented conglomerates of the Keepit Conglomerate possess shape characteristics indicative of shaping within a fluvial environment. Maximum projection sphericity, and a plot of sphericity against either the oblate-prolate index or the flatness parameter C/A, were the most useful in indicating fluvial shaping processes. In addition, the Index and the dominant form classes of the Sneed and Folk Sphericity-Form diagram were in support of a fluvial history for the clasts.The occurrence of clasts exhibiting typical fluvial shapes in marine resedimented conglomerates indicates a lack of time and/or insufficient energy in a beach environment for reshaping of the clasts prior to resedimentation into deeper-water submarine-fan environments. This interpretation is consistent with and lends support to the interpretation, based on all other available data, for the Keepit Conglomerate of a history of rapid progradation of fluvial gravels into a relatively low-energy coastline environment, with periodic resedimentation of coarse sediment into deeper water. 相似文献
106.
Willard S. Moore Walter E. Dean S. Krishnaswami D.V. Borole 《Earth and Planetary Science Letters》1980,46(2):191-200
226Ra is used to document the growth histories of six manganese nodules from Oneida Lake, New York. Detailed sectioning and analysis reveal that there are discontinuous gradients in226Ra content in these samples. These gradients result from periods of rapid growth (>1 mm/100 years) separated by periods of no growth of erosion. Although the226Ra “age” of the nodules approximates the age of Oneida Lake, the nodules are not sediment-covered because they occur only in areas of the lake where fine-grained sediments are not accumulating. 相似文献
107.
Bioassay of a No. 2 fuel oil dispersion with shrimp in a continuous flow system using measured waterborne oil as the indicator of oil concentrations reveals a treatment more definable than those previously described in terms of volume ratios and produces lower lethal concentrations. Shrimp 96-h LC50 was 0.8 mg/l in this study as compared to values from 1.5 to 50 mg/l reported for other methods. Mean concentrations in tests do not give significant differences in concentration with respect to day of the test or spatial distribution in the exposure tanks. 相似文献
108.
109.
Three varieties of alpine-type ultramafic rocks are distinguish in the Norwegian Caledonides associated Basal Gneiss Complex. Type one rocks have primary (magmatic) olivine, clinopyroxene, orthopyroxene and chromite, and are partly or completely serpentinised. They are found exclusively in rocks of Cambro-Silurian age. Type two are polymetamorphic metaperidotites or sagvandites consisting of olivine, enstatite and carbonate minerals, with talc and amphibole commonly being present. They are found in medium- to high-grade metamorphic rocks. Type three also show a metamorphic mineral association of olivine, orthopyroxene and minor chromite, while clinopyroxene, amphibole and chrome-bearing chlorite may also be present in some samples. Garnet may or may not occur and, where present, is often surrounded by reaction rims of spinel and amphibole. The type three ultramafic bodies are serpentinised to varying degrees and occur in high-grade metamorphic gneisses which may also contain eclogites and anorthosites. Distinction of these three varieties of ultramafic body may be useful for correlation purposes and for more detailed studies on the nature of their metamorphism. 相似文献
110.
Sedimentary and igneous rocks of the Swaziland Sequence of South Africa (>3,200 my. old) contain total carbon (0.09–8.28%), organic carbon (0.04–1.95%) and sulfur (9–53,000 ppm). Amounts of organic carbon are generally high in the lower part of the Sequence (based on two samples from the Theespruit Formation). Sulfur content varies widely with no obvious correlations or trends. These rocks may contain clues to the early carbon and sulfur cycles on earth. 相似文献