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51.
52.
The nitrogen and carbon stable isotope ratios (δ15N and δ13C) of the pygmy mussel,Xenostrobus securis, were determined for three estuaries with varying levels of catchment disturbance in northern New South Wales, Australia.
The lower Manning River catchment supported the highest human population densities with 3% residential development and some
livestock agriculture (41%); the Wallamba River catchment was mostly livestock agriculture (56%) while the Wallingat River
catchment was mostly vegetated (79%). Mussels, estuarine particulate organic matter (POM), and livestock and human-derived
waste were collected in two stages during the austral summers of 2001–2002 and 2002–2003 for dual carbon-nitrogen stable isotope
analysis. The disturbed Manning and Wallamba River catchment mussels were enriched in15N by an average of 3.2‰ and 1.5‰, respectively, compared to the vegetated Wallingat River mussels. Mussel δ13C values ranged from −24.8‰ to −30.3‰ and showed an estuarine gradient becoming enriched with distance downstream within estuaries,
but were unable to distinguish patterns in catchment disturbance between estuaries. The δ15N and δ13C values of POM showed a similar pattern to mussels, indicating a direct link between them within each estuary. A multiple
regression model of mussel δ15N using the fractions of land used for livestock agriculture and residential development within 5 km zones from river networks
to a distance equivalent to a tidal ellipse from sites explained 67% of the variation in mussel δ15N with 95% of the differences lying within 1.6‰ of observed values. Increasing fractions of land used for livestock agriculture
depleted mussel δ15N values estimated by the regression equation, indicating the use of cow manure as a nutrient source with a value of 2.0‰.
Increasing fractions of land used for residential development enriched estimated mussel δ15N, indicating the use of human-derived waste with a value of 20.8‰. Pygmy mussels are a useful long-term bio-indicator for
the effects of anthropogenic catchment disturbance and nutrient enrichment in estuaries. 相似文献
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54.
KOMATIITE WITS-1, LOW CONCENTRATION NOBLE METAL STANDARD FOR THE ANALYSIS OF NON-MINERALIZED SAMPLES
WITS-1 is a sample of silicified komatiite collected from close to the Komati River type section, near Barberton in South Africa. Two thousand kg of this komatiite was crushed and prepared for standardization. Noble metal analysis of WITS-1 has been carried out by six laboratories using four different analytical methods. The data obtained from these sources were subjected to statistical analysis (F ratio and Student t test) and a suite of "preferred" values for the noble metal concentrations are reported. 相似文献
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57.
Victoria K. Pearson Mark A. Sephton Anton T. Kearsley Philip A. Bland Ian A. Franchi Iain Gilmour 《Meteoritics & planetary science》2002,37(12):1829-1833
Abstract— As the solar system formed, it inherited and perpetuated a rich organic chemistry, the molecular products of which are preserved in ancient extraterrestrial objects such as carbonaceous chondrites. These organic‐rich meteorites provide a valuable and tangible record of the chemical steps taken towards the origin of life in the early solar system. Chondritic organic matter is present in the inorganic meteorite matrix which, in the CM and CI chondrites, contains evidence of alteration by liquid water on the parent asteroid. An unanswered and fundamental question is to what extent did the organic matter and inorganic products of aqueous alteration interact or display interdependence? We have used an organic labelling technique to reveal that the meteoritic organic matter is strongly associated with clay minerals. This association suggests that clay minerals may have had an important trapping and possibly catalytic role in chemical evolution in the early solar system prior to the origin of life on the early Earth. 相似文献
58.
Prey importance and ontogenetic transitions in the diet of stocked and wild mulloway (Argyrosomus japonicus) were compared between a southeast Australian reverine estuary and a coastal lagoon. Stomach content analysis of fish captured
from these estuaries in 1997–1979, 1997–1998, and 2003–2005 revealed size-specific and estuary-specific diets. Mysid shrimp
were most common in diets of fish <250 mm total length (TL), and prawns were common in diets of fish measuring 301–450 mm.
Forage fish were most abundant in diets of mulloway >500 mm. Index of Relative Importance (IRI) of forage fish increased with
TL, while IRI of mysids decreased with TL. Prawn IRI was greatest for fish 150–600 mm TL. Comparisons between benthic resources
and dietary composition revealed that Georges River mulloway consumed prey categories in proportions similar to those in their
environment. No mysid shrimp were detected in the coastal lagoon or in the diet of mulloway captured there; growth was comparable
to the Georges River. Hatchery-reared fish fed<16 d after stocking, indicating normal behavioural adaptation after release.
Dietary information can be used to optimize stocking locations, times, and densities, as well as estimate potential effects
of mulloway on potential prey and wild conspecifics. 相似文献
59.
Wolf U. Reimold Christian Koeberl Cedric Wright Iain McDonald 《Meteoritics & planetary science》2001,36(5):747-749
Abstract— Gorter and Glikson (2000) proposed that the Fohn‐1 structure in the Timor Sea north of Australia probably is an impact structure. Examination of their evidence reveals that it is almost impossible to confirm any of their conclusions, as the authors do not provide sufficient detail of their experimental methods. Problems with the presentation of both seismic and geochemical data cast further doubt on their conclusions. Absence of evidence for shock metamorphism and non‐chondritic siderophile element patterns in the few samples analysed make it likely that Fohn‐1 is neither a probable, nor even a possible, impact structure. 相似文献
60.
Inclined K–Ar illite age spectra in brittle fault gouges: effects of fault reactivation and wall‐rock contamination 下载免费PDF全文
K–Ar clay fraction ages of brittle faults often vary with grain size, decreasing in the finer size fractions, producing an inclined age–grain‐size spectrum. K–Ar ages and mineralogical characterization of gouges from two normal faults in the Kongsberg silver mines, southern Norway, suggest that inclined spectra derived from brittle fault rocks reflect the mixing of inherited components with authigenic mineral phases. The ages of the coarsest and finest fractions constrain faulting at c. 260–270 Ma and reactivation around 200–210 Ma, respectively. This study demonstrates how wall‐rock contamination influences the K–Ar age of the coarsest size fractions and that authigenic illite and K‐feldspar can crystallize synkinematically under equivalent conditions and thus yield the same K–Ar ages. 相似文献