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《Environmental Forensics》2013,14(4):305-312
The distribution of metal contaminants between different size fractions of marine sediments is well known. However, the use of size normalization techniques may alter the ability or usefulness in identifying potential sources in complex environments. In a reassessment of metal data from the shelf area of Sydney, Australia, the mud and sand fractions were investigated separately by PCA and PLS methodologies. The analyses were able to produce clear distinctions between industrial/urban sources when based on a suite of metals rather than individual (single-element) concentrations. Signature analysis by PLS with copper, lead, zinc, manganese, chromium, cobalt, nickel, and cadmium demonstrated the dispersion of the fine-grained contaminated material to the south in the East Australian Current. However, due to the commonality between many of the metals, a subset of four metals was used to define the signature. This significantly improved separation, showing clear plumes extending ~30 km from the source rivers. 相似文献
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Alfonso Marzal Maribel Reviriego Florentino de Lope Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(10):1573-1580
Immune responses constitute a major way for hosts to defend themselves against parasites. Because hosts do not habitually
produce strong responses all the time, immune responses might be costly to produce or maintain. We tested experimentally if
the production of a response to a challenge with a novel antigen resulted in a cost in terms of fitness using the highly colonial
house martin Delichon urbica as a model system. We injected adult breeding birds during laying of the first clutch with either Newcastle disease virus
(NDV) or a control injection, and the clutch was subsequently removed to induce relaying. NDV stimulates the non-specific
immune system, causing production of antibodies during a period of more than 2 weeks. Accordingly, we found an increase in
leukocyte counts in experimental birds compared to controls. Experimental treatment reduced the frequency of re-laying, caused
a delay in timing of relaying and a reduction in brood size. Quality of nestlings in terms of body size, body mass and T-cell-mediated
immune response did not differ significantly between treatments. Overall, seasonal reproductive success differed significantly
between treatments, showing that the production of an immune response by adult birds is costly in terms of future fecundity. 相似文献
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