排序方式： 共有16条查询结果，搜索用时 15 毫秒
1.
Rates for nitrification, phytoplankton uptake of ammonium, and regeneration of ammonium were measured in the Delaware River as functions of irradiance and nutrient concentrations, using 15N labeling methods. Phytoplankton uptake increased and nitrification rates declined with increased light intensity. The irradiance level required for maximum uptake by phytoplankton was similar to that for maximal inhibition of nitrification (about 300μEm−2 s−1). Daily, water-column averaged rates, calculated by integration of the observed rate-intensity relationships, indicate that light plays a key role in regulating the balance between oxidation of NH4+ by bacteria and assimilation by phytoplankton in the Delaware. The results show that uptake of ammonium by phytoplankton in the dark may exceed uptake in the light in optically thick systems. 相似文献
2.
Since the original suggestion by Gillett et al. (1969) it has generally been assumed that the region of partial transparency near 5 μm in Jupiter's atmosphere (the 5-μm window) is bounded by the v4 NH3 at 6.1 μm and the v3 CH4 band at 3.3 μm. New measurements of Jupiter and of laboratory phosphine (PH3) samples show that PH3 is a significant contributor to the continuum opacity in the window and in fact defines its short-wavelength limit. This has important implications for the use of 5-mu;m observations as a means to probe the deep atmospheric structure of Jupiter. The abundance of PH3 which results from a comparison of Jovian and laboratory spectra is about 3 to 5 cm-am. This is five to eight times less than that found by Larson et al. [Astrophys. J. (1977) 211, 972–979] in the same spectral region, but is in good agreement with the result of Tokunaga et al. [Astrophys. J. (1979) 232, 603–615] from 10-μm observations. 相似文献
3.
4.
A “snap shot” survey of the Mississippi estuary was made during a period of low river discharge, when the estuarine mixing zone was within the deltaic channels. Concentrations of H+, Ca2+, inorganic phosphorus and inorganic carbon suggest that the waters of the river and the low salinity (<5‰) portion of the estuary are near saturation with respect to calcite and sedimentary calcium phosphate. An input of oxidized nitrogen species and N2O was observed in the estuary between 0 and 4‰ salinity. The concentrations of dissolved NH4 + and O2, over most of the estuary, appeared to be influenced by decomposition of terrestrial organic matter in bottom sediments. The estuarine bottom also appears to be a source of CH4 which has been suggested to originate from petroleum shipping and refining operations. Estuarine mixing with offshore Gulf waters was the dominant influence on distributions of dissolved species over most of the estuary (i.e., from salinities >5‰). The phytoplankton abundance (measured as chlorophylla) increased as the depth of the mixed layer decreased in a manner consistent with that expected for a light-limited ecosystem. Fluxes of NO3 ?+NO2 ? and soluble inorganic phosphorus to the Gulf of Mexico were estimated to be 3.4±0.2×103 g N s?1 and 1.9±0.2 g P s?1 respectively, at the time of this study. 相似文献
5.
Fredric L. Prikle Thomas R. Bement Jo Ann Howell Charles D. Koch Newton K. Stablein Richard J. Beckman Gary L. Tietjen 《Journal of Geochemical Exploration》1983,18(3):175-187
Throughout the aerial radiometric reconnaissance survey portion of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program, the identification of outliers (anomalies) was an important approach to locating regions with radio-element concentrations that are either higher or lower than expected. The method introduced herein to locate such regions involves three steps: selection of a high (or low) threshold for the variate of interest; use of the sample percentile to identify all points of interest; and movement of a window over the selected data to locate significant clusters of observations. These steps, applied to aerial radiometric 214Bi (equivalent uranium) data collected over the Copper Mountain area in Wyoming, resulted in the identification of areas enriched in that variate. 相似文献
6.
7.
Ground-Water Remediation Using "Smart Pump and Treat" 总被引：1，自引：0，他引：1
Fredric Hoffman 《Ground water》1993,31(1):98-106
8.
David Gubbins Peter Molnar J. G. Olliver Petr Vanīček Kenji Satake Allan M. Rubin Waclaw M. Zuberek Janusz Niewiadomski Leszek Czechowski David J. Steveson Jacek Leliwa-Kopystyński Yu. N. Korenkov Fred Lipschultz Marek Jerczyński Krzysztof E. Haman Jerzy Radziwill Maciej Sadowski Maciej Sadowski 《Pure and Applied Geophysics》1990,132(3):599-637
9.
Volatile organic compounds (VOCs) are present in multiple water-bearing zones beneath and downgradient of Lawrence Livermore National Laboratory. This area is composed of interfingering unconsolidated alluvial sediments with hydraulic conductivities ranging over four orders of magnitude. The more permeable sediments exhibit moderate hydraulic interconnection horizontally and less interconnection vertically, and appear to consist largely of interconnected stream channel deposits. To optimize selection of monitoring well screened intervals in this complex environment, a technique that enables collection of saturated formation samples from each water-bearing zone without contamination from other VOC-containing zones was developed, tested, and implemented. The technique utilizes a wireline punch-coring system that allows the drill bit to be replaced with a core barrel without removing the drill rod from the borehole. To help ensure that a sample from one water-bearing zone is not contaminated by VOCs from another zone, the drilling fluid is replaced with new fluid before each sampling run. Overnight chemical analysis by gas chromatography enables field personnel to know the vertical distribution of VOCs as drilling proceeds. Since its first use in 1985, the technique has successfully characterized the presence or absence of VOCs in ground water in 123 of 140 wells, many with concentrations in ground water in the low parts-per-billion range. Our sampling technique is a cost-effective and rapid method of evaluating the vertical distribution of VOCs in ground water in a complex hydrogeologic environment. 相似文献
10.
Fredric Lipschultz 《Estuaries and Coasts》1981,4(2):143-145
Gaseous methane loss from a brackish, intertidal salt marsh sediment was measured in April, June, August, and October 1977. Twenty-four sediment cores were taken on each date. Annual loss of methane carbon from the mud flats was 10.7 g CH4?C per m2 per year, a value closer to freshwater values than marine systems. Loss of methane fromSpartina peat was low. 相似文献