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81.
Bilodeau Gauthier S Houle D Gagnon C Côté B Messier C 《Journal of environmental quality》2008,37(3):871-879
Dendrochemistry has been used for the historical dating of pollution. Its reliability is questionable due primarily to the radial mobility of elements in sapwood. In the present study, the extractability of seven elements was characterized to assess their suitability for the monitoring of environmental conditions. Nine mature sugar maple trees (Acer saccharum Marsh.), a wide-ranging species in eastern North America that has suffered decline in past decades, were sampled in three Quebec watersheds along a soil acidity gradient. Five-year groups of annual tree rings were treated by sequential chemical extractions using extractants of varying strength (deionized H2O, 0.05 M HCl, and concentrated HNO(3)) to selectively solubilize the elements into three fractions (water-soluble, acid-soluble, and residual). Monovalent K; divalent Ba, Ca, Cd, Mg, Mn; and trivalent Al cations were found mostly in the water-soluble, acid-soluble, and residual fractions, respectively. Forms more likely to be mobile within the tree (water-soluble and acid-soluble) do not seem to be suitable for temporal monitoring because of potential lateral redistribution in sapwood rings. However, certain elements (Cd, Mn) were responsive to current soil acidity and could be used in spatial variation monitoring. Extractability of Al varied according to soil acidity; at less acidic sites, up to 90% of Al was contained in the residual form, whereas on very acidic soils, as much as 45% was found in the water-soluble and acid-soluble fractions. Sequential extractions can be useful for determining specific forms of metals as key indicators of soil acidification. 相似文献
82.
Leaf accumulation of trace elements and polycyclic aromatic hydrocarbons (PAHs) in Quercus ilex L 总被引:1,自引:0,他引:1
De Nicola F Maisto G Prati MV Alfani A 《Environmental pollution (Barking, Essex : 1987)》2008,153(2):376-383
Quercus ilex L. leaves were collected four times in one year at six urban sites and one remote area in order to determine trace element and PAH accumulation through concomitant analyses of unwashed and water-washed leaves. Both unwashed and washed leaves showed the highest amounts of trace elements and PAHs in the urban area. Unwashed leaves showed greater differences between urban and remote areas and among the urban sites than washed leaves for trace element and PAH concentrations. Water-washing resulted in a significant (P<0.001) decrease in leaf concentrations of Cr, Cu, Fe, Pb, V and Zn. By contrast, Cd and total PAH concentrations showed no differences between unwashed and washed leaves. 相似文献
83.
Solute transport in fractured rocks is of major interest in many applications, from the petroleum industry to ground water management. This work focuses on the dispersion process in a transparent replica of a real single fracture. The fracture exhibits strong changes in heterogeneity, with the first half very heterogeneous and the second half fairly homogeneous. Three models have been used to interpret the tracer experiments: the classical advection-dispersion equation (ADE), the continuous time random walk (CTRW), and the stratified model. The main goals were to test these models and to study possible correlations between fitting parameters and heterogeneities. As expected, the solution derived from the ADE equation appears to be unable to model long-time tailing behavior. On the other hand, the results confirm the CTRW robustness and the coefficient beta seems well correlated to heterogeneities. Finally, the stratified model is also able to describe non-Fickian dispersion. The parameters defined by this model are correlated to the heterogeneities of the fracture. 相似文献
84.
Rao PS Ansari MF Gavane AG Pandit VI Nema P Devotta S 《Environmental monitoring and assessment》2007,128(1-3):323-328
Petroleum refineries are largest chemical industries that are responsible for the emission of several pollutants into the
atmosphere. Benzene is among the most important air pollutants that are emitted by petroleum refineries, since they are involved
in almost every refinery process. Volatile organic compounds (VOCs) are a major group of air pollutants, which play a critical
role in atmospheric chemistry. These contribute to toxic oxidants, which are harmful to ecosystem, human health and atmosphere.
The variability of pollutants is an important factor in determining human exposure to these chemicals. The ambient air concentrations
of benzene were measured in several sites around the Digboi petroleum refinery, near the city of Gowahati in northeast India,
during winter and summer 2004. The seasonal and spatial variations of the ambient air concentrations of this benzene were
investigated and analyzed. An estimation of the contribution of the refinery to the measured atmospheric levels of benzene
was also performed. The ambient air mixing ratios of benzene in a large area outside the refinery was generally low, in ppbv
range, much lower than the ambient air quality standards. This article presents the temporal and spatial variation of air
pollution in and around petroleum refinery and showed that no health risk due to benzene is present in the areas adjacent
to the refinery. 相似文献
85.
Coastal Flood Risk Analysis Using Landsat-7 ETM+ Imagery and SRTM DEM: A Case Study of Izmir, Turkey
Demirkesen AC Evrendilek F Berberoglu S Kilic S 《Environmental monitoring and assessment》2007,131(1-3):293-300
The Intergovernmental Panel on Climate Change (IPCC) reports an acceleration of the global mean sea-level rise (MSLR) in the twentieth century in response to global climate change. If this acceleration remains constant, then some coastal areas are most likely to be inundated by the year 2100. The ability to identify the differential vulnerability of coastlines to future inundation hazards as result of global climate change is necessary for timely actions to be taken. Yildiz et al. (Journal of Mapping, 17, 1-75, 2003) reported that the local MSLR in the city of Izmir rose at a rate of 6.8 +/- 0.9 mm year(-1) between 1984 and 2002. In this study, the spatial distribution of the coastal inundation hazards of Izmir region was determined using not only land-use and land-cover (LULC) types derived from the maximum likelihood classification of Landsat-7 Enhanced Thematic Mapper Plus (ETM+) multi-spectral image set but also the classification of the digital elevation model (DEM) acquired by the shuttle radar topography mission (SRTM). Coastal areas with elevations of 2 and 5 m above mean sea-level vulnerable to inundation were found to cover 2.1 and 3.7% of the study region (6,107 km(2)), respectively. Our findings revealed that Menemen plain along Gediz river, and the settlements of Karsiyaka, Alacati, Aliaga, Candarli and Selcuk are at high risk in order of decreasing vulnerability to permanent and episodic inundation by 2100 under the high MSLR scenarios of 20 to 50 mm year(-1). 相似文献
86.
Abstract: Estimating the risk of extinction for populations of endangered species is an important component of conservation biology. These estimates must be made from data that contain both environmental noise in the year-to-year transitions in population size (so-called "process error"), random errors in sampling, and possible biases in sampling ( both forms of observation errors). To determine how much faith to place in estimated extinction rates, it is important to know how sensitive they are to observation error. We used three simple, commonly employed models of population dynamics to generate simulated population time series. We then combined random observation error or systematic biases with those data, fit models to the time series data, and observed how close the extinction dynamics of the fitted models compared with the dynamics of the underlying models. We found that systematic biases in sampling rarely affected estimates of extinction risk. We also found that even moderate levels of random observation error do not significantly affect extinction estimates except over a small range of process errors, corresponding to the region where extinction risk is most uncertain. With more substantial sampling error, estimates of extinction risk degraded rapidly. Field census techniques for a variety of taxa often involve observation errors within ±32% of actual population sizes. For typical time series used in conservation, therefore, we often may not need to be overly concerned about observation errors as an extra source of imperfection in our estimated extinction rates. 相似文献
87.
88.
L. Zane L. Ostellari L. Maccatrozzo L. Bargelloni J. Cuzin-Roudy F. Buchholz T. Patarnello 《Marine Biology》2000,136(2):191-199
Meganyctiphanes norvegica (M. Sars)is a pelagic crustacean that plays a key role in marine food webs of North Atlantic Ocean and marginal seas. We
studied eight population samples collected in the European Atlantic and Mediterranean Sea. By means of single strand conformation
polymorphism analysis (SSCP) and direct sequencing, we investigated a segment of 158 base pairs of the mitochondrial gene
coding for the subunit 1 of NADH dehydrogenase. We found 12 sequence variants among the 385 individuals studied. Analysis
of molecular variance (AMOVA) showed that 14.75% of the total genetic variability was explained by differences between populations,
thus indicating absence of panmixia for these populations. Pairwise comparisons revealed three distinct genetic pools: the
first one represented by Cadiz Bay, the second one by the Ligurian Sea, and the third one included all the NE Atlantic samples.
We also investigated one population from the Alboran Sea (within the Mediterranean basin, east of the Strait of Gibraltar).
This population was found to be genetically intermediate between the NE Atlantic samples and the Ligurian sample, suggesting
that the restriction to the gene flow is not associated with the Strait of Gibraltar, but possibly with the Oran–Almeria oceanographic
front. The present work indicates that M. norvegica, although endowed with a high dispersal capacity because of its pelagic habit, can develop separate breeding units inside
the same oceanic basin (the Atlantic). Furthermore, the Ligurian sample should be considered as a distinct evolutionary entity,
separated from the Atlantic population.
Received: 2 May 1999 / Accepted: 26 November 1999 相似文献
89.
Maternal investment in rhesus macaques (Macaca mulatta): reproductive costs and consequences of raising sons 总被引:1,自引:0,他引:1
Maternal investment in offspring is expected to vary according to offspring sex when the reproductive success of the progeny
is a function of differential levels of parental expenditure. We conducted a longitudinal investigation of rhesus macaques
to determine whether variation in male progeny production, measured with both DNA fingerprinting and short tandem repeat marker
typing, could be traced back to patterns of maternal investment. Males weigh significantly more than females at birth, despite
an absence of sex differences in gestation length. Size dimorphism increases during infancy, with maternal rank associated
with son’s, but not daughter’s, weight at the end of the period of maternal investment. Son’s, but not daughter’s, weight
at 1 year of age is significantly correlated with adult weight, and male, but not female, weight accounts for a portion of
the variance in reproductive success. Variance in annual offspring output was three- to fourfold higher in males than in females.
We suggest that energetic costs of rearing sons could be buffered by fetal delivery of testosterone to the mother, which is
aromatized to estrogen and fosters fat accumulation during gestation. We conclude that maternal investment is only slightly
greater in sons than in daughters, with mothers endowing sons with extra resources because son, but not daughter, mass has
ramifications for offspring sirehood. However, male reproductive tactics supersede maternal investment patterns as fundamental
regulators of male fitness.
Received: 23 July 1999 / Received in revised form: 23 February 2000 / Accepted: 13 March 2000 相似文献
90.
Previously published mtDNA cytochrome b sequences for Xyrichtys novacula (Linnaeus) and two morphologically distinct types of Xyrichtys larvae (Pisces: Labridae) included human cytochrome b sequence, presumably due to sample contamination and/or poor preservation of sample DNA. Those sequences had been used to
identify the two types of Xyrichtys larvae as X. novacula, but owing to the contamination, the identifications are invalid. Fresh specimens were collected: X.␣martinicensis (Cuvier and Valenciennes), X. novacula, X. splendens (Castelnau), and Xyrichtys sp. larvae of each of the two morphotypes (dorsal-forward eye and ventral-forward eye). The cytochrome b fragment was amplified from each specimen using the polymerase chain reaction. Comparison of the sequences with human cytochrome b sequence confirmed that the new sequences were not contaminated. The interspecific differences in Xyrichtys sequences were less than previously reported, but still greater than observed in many fish genera. Distance and parsimony
analyses indicated that X. novacula and X. martinicensis were more closely related to each other than to X. splendens. This conclusion differs from our previous conclusion that X. martinicensis and X. splendens were more closely related to each other than to X. novacula. Distance and parsimony analyses also demonstrated that both larval morphotypes were X. novacula and, thus, our previous conclusions regarding larval ecology and oceanographic transport remain unchanged.
Received: 12 March 1997 / Accepted: 24 October 1997 相似文献