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921.
Total concentrations and extractable fractionations of As and Sb were determined in soil samples from former mining sites in Scotland and Italy. Pseudo-total levels of As and Sb in the sample were between 50–17,428 mg/kg and 10–1,187 mg/kg (Scotland), and 16–691 mg/kg and 1.63–11.44 mg/kg (Italy). Between 0.001–0.63% and <0.001−8.82% of the total soil As and Sb, were extractable using, a single extraction bioavailability estimate. Data from an As-specific extraction procedure revealed that up to 60% of As was associated to amorphous Fe-Al oxyhydroxide phase in all soils. A non-specific-sequential extraction test also showed As to be strongly associated with Fe (and Al) oxyhydroxides at both locations. In the case of Sb, in addition to the crystalline Fe-oxide bound Sb the Al-silicate phase also appeared to be significant. At both sites Sb appears to be chemically more accessible than As with consistent availability despite the varied origin and host soil properties. 相似文献
922.
Green-Ruiz C Ruelas-Inzunza J Páez-Osuna F 《Environmental geochemistry and health》2005,27(4):321-329
In order to know the concentration of mercury in surface sediments, macroalgae and clams from Guaymas Bay, Mexico, 20 surface
sediment samples and several individuals of Codium amplivesciculatum (3), Enteromorpha clathrata (4), Gracilaria subsecundata (2), Ulva lactuca (2), Chione subrugosa (80) and Crassostrea gigas (40) were collected and their Hg concentration was measured by a cold vapor Hg analyzer, after acid digestion. In addition,
granulometric analysis and quantification of total organic carbon, aluminum, iron and manganese contents in sediments were
performed. A Pearsons correlation matrix was determined and, the enrichment factor, the geoaccumulation index and the biota-sediment
accumulation factor were calculated. Mercury concentrations in sediments ranged from 0.3 to 2.3 μg g−1, with the central and northern portions showing the highest values. Macroalgae had a content of Hg that oscillated from 0.058
to 0.134 μg g−1, while the average concentrations of this metal for clams and oysters were 0.063 and 0.230 μg g−1, respectively. A clear effect of Guaymas City and the anthropogenic activities carried out around the Guaymas Bay has been
observed and the enrichment factor and the geochemical index suggest that sediments from this coastal ecosystem are moderately
to strongly contaminated with Hg. However, according to the figure of the maximum human consumption of Hg per week recommended
by the World Health Organization, people can ingest clams without risk to their health. 相似文献
923.
The Gil-Márquez Complex is an exceptional outcrop of plutonic rocks ranging in composition from diorites to granites emplaced into Devonian terrigenous metasediments of the southernmost part of the Hercynian basement of Iberia. A combined study of this complex, including field geology, petrology, structural geology and geochemistry, reveals that it represents an ancient conduit of magma transport through the continental crust. This conduit allowed the intrusion of magmas of contrasted compositions. Two end-members and several hybrids are identified. The first end-member is a biotite granite and the second is a basaltic magma generated by partial melting of a depleted-mantle source. Both magmas rose through a common channel in which favorable conditions for unstable flow and magma mixing occurred. The observed relations in the Gil-Márquez Complex show that mixing in conduits may be an important mechanism for producing homogeneous hybrid magmas. 相似文献
924.
Mária Szabó Ákos Münnich Farkas Teichmann Mariann Huszka Lajos Veress Professor Zoltán Papp 《黑龙江环境通报》1990,10(12):761-769
We have analysed the sensitivity, specificity, and reliability of biochemical diagnosis based on microvillar membrane enzyme assay and using discriminant analysis in amniotic fluid samples obtained from 54 pregnancies at high risk for cystic fibrosis and 125 normal pregnancies. Our results show that amniotic fluid trehalase, alkaline phosphatase, alkaline phosphatase isoenzymes and gamma-glutamyltransferase enzyme activities measured during 16–20 gestational weeks, in spite of their non-specificity for cystic fibrosis, have a very good predictive value for fetal cystic fibrosis or exclude the possibility of the disease. Overall enzyme activity analysis provided over 90 per cent reliability of the method. 相似文献
925.
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927.
Apesteguía S 《Die Naturwissenschaften》2004,91(10):493-497
Ornithischian and theropod dinosaurs were morphologically diverse during the Cretaceous. In contrast, sauropods were relatively more conservative. The anatomy of Bonitasaura salgadoi, a new 9-m titanosaurian sauropod from Upper Cretaceous beds of Patagonia, suggests that sauropod anatomical diversity would have included unexpected items. Its unusual, rectangular lower jaw possesses narrow, anteriorly restricted teeth and shows evidence of a sharp keratinous sheath over the non-dentigerous region that probably worked to guillotine plant material. This discovery definitely demonstrates that titanosaurs acquired a mandibular configuration similar to that of some basal diplodocoids, as had already been suggested by the lower jaw of the controversial genus Antarctosaurus. This oral configuration, plus the beak-like structure and the skull shape, resemble some traits more commonly seen in Laurasian ornithischians, mostly unexpressed in southern continents. A high sauropod morphological diversity seems to be in agreement with the poorly represented ornithischian clades of the southern hemisphere.Communicated by G. Mayr 相似文献
928.
Unai?IriarteEmail author Jon?I?aki?álvarez-Uriarte Rubén?López-Fonseca Juan?Ramón?González-Velasco 《Environmental Chemistry Letters》2003,1(1):57-61
The relatively recent discovery of disinfection by-products has driven the main regulatory organisms to set maximum contaminant
levels for certain substances in drinking water. Trihalomethanes can be deemed as the most important group of by-products
in chlorinated surface waters. The present work has focused on trihalomethane formation in a full-scale water treatment plant.
We studied the effect of several factors, including ozonation, on trihalomethane levels in chlorinated treated water. The
treatment scheme also includes an ozonation step.
Electronic Publication 相似文献
929.
930.