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251.
Bernd R. Sch?ne David L. Rodland Achim Wehrmann Bj?rn Heidel Wolfgang Oschmann Zengjie Zhang Jens Fiebig Lothar Beck 《Marine Biology》2007,150(6):1237-1252
The grey top-shell, Gibbula cineraria is a common member of temperate to cold water kelp forest communities, but its longevity and the age structure of its populations
remains unresolved. Combined measurements of shell growth rates (sclerochronology) and oxygen isotope composition allow analysis
of rate and timing of shell growth. Eight specimens were analyzed from the southern North Sea (near Helgoland, German Bight).
Three age groups were identified but external measurements (width, height, ornamentation patterns and number of whorls) and
shell weight are not adequate for ontogenetic age discrimination. Stable oxygen isotope data is consistent with shell growth
during the interval from April to December in isotopic equilibrium with seawater, and growth increments exhibit strong tidal
controls with fortnightly bundles well preserved. Reliable environmental proxy data (water temperature) can be extracted from
the shell aragonite using conventional stable oxygen isotope analyses, with a temporal resolution of days attainable during
intervals of maximum growth, but annual extremes are not always recorded in the shell. While demonstrating the utility of
G. cineraria as a environmental and potential paleoenvironmental proxy for kelp forest habitats, its longevity has been significantly
overestimated. 相似文献
252.
The concentration of solubilized aluminium in soils and waters increases due to environmental influences. To obtain information on the types of Al species occuring under these conditions, aluminium chloride solutions were prepared in a wide range of concentrations (10?1–10?5 mol·l?1 Al) and basicity (OH/Al=0,5–2,5), respectively, and then structurally characterized using the ferron method. For the freshly prepared solutions, a decrease in the portion of monomeric Al species is observed, with an increasing OH/Al-ratio; the formation of polymeric cations decreases to lower OH/Al-ratios with diminishing concentration. The portion of tridecameric cations (Al13) decreases with diminishing concentration, but so called transition polymers occur in these solutions. The transition polymers are instable under ageing; by inreasing the ageing time, a disproportion of these cations into monomeric and polymeric species can be observed. At extremly low Al concentrations (10?5 mol·l?1 Al), a condensation of the transition polymers into polymeric species occurs, after only a short ageing. The influence of admixtures of Mg2+-and Ca2+-ions, respectively, on the specification of the Al cations are only observed after longer ageing times; in this case, the formation of polymeric Al species is forced. The polymeric Al species therefore, seem to be especially preferred alongside the monomeric ones under biologically relevant concentrations. 相似文献
253.
An elemental analyzer in combination with stable isotope ratio mass spectrometry (EA-IRMS) was used to demonstrate that two samples of the chloropesticide Melipax discovered in two countries varied only by 0.1 per thousand in their delta 13C values. Gas chromatography interfaced to a stable isotope mass spectrometer (GC-IRMS) was used to study the delta 13C values of individual congeners in two technical polybrominated diphenyl ether products, i. e. DE-71 and DE-79, at three different concentration levels. Injections of 4 microg and 5.2 microg of DE-71 and DE-79 were most suited for the determinations. In both products, the delta 13C values were usually the more negative the higher the degree of bromination was. The delta 13C values of three hexabromo isomers BDE 138, BDE 153, and BDE 154 could be determined in both products. In all cases the delta 13C values of the three hexaBDEs were more depleted in delta 13C in the higher brominated technical octabromo diphenyl ether DE-79. 相似文献
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255.
Recent measurements at different locations suggest that the emission of mercury from soils may play a more pronounced role in the global mercury cycle as suggested by global emission inventories and global mercury cycling models. For up scaling and modelling of mercury emissions from soils a comprehensive assessment of the processes controlling the emission of mercury from soils is imperative. We have developed a laboratory flux measurement system (LFMS) to study the effect of major environmental variables on the emission of mercury under controlled conditions. We have investigated the effects of turbulent mixing, soil temperature and solar radiation on the emission of mercury from soils. The emission of mercury from soils is constant over time under constant experimental conditions. The response of the mercury emission flux to variations of the atmospheric transfer parameters such as turbulence requires a rapid adjustment of the equilibrium that controls the Hg(o) concentration in the soil air. It has been shown that the light-induced flux is independent of the soil temperature and shows a strong spectral response to UV-B. 相似文献
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259.
Newly hatched olive ridley sea turtles (Lepidochelys olivacea) were tested for their directional preferences in a sand-filled circular arena in total darkness. Hatchlings that had crawled about 5 m on the beach, toward the sea preferred the southwesterly direction that would have brought them to the water line, whereas hatchlings that had been denied this experience headed eastward, a direction of unclear origin. These data suggest that a short crawl across the natural beach can set the direction in which the young turtles subsequently move. The crawling experience was sufficient to acquire the compass course that they later follow, probably with the help of a magnetic compass, not only in the water, but already while still on land. 相似文献
260.