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61.
W. Winiwarter H. Bauer A. Caseiro H. Puxbaum 《Atmospheric environment (Oxford, England : 1994)》2009,43(7):1403-1409
Atmospheric concentration measurements of tracers for primary biological aerosol particles (PBAPs) have been used to obtain estimates of their release into the atmosphere. Emission flux data of surrogate compounds, for which concurrent concentration measurements were available, were used to quantify the release of PBAPs as PM10 mass. Results indicate fungal spores to be the most important contributors. One other main source is plant debris. Area-based emission rates of 24 kg km?2 and year (range 6–90) have been assessed. Results scaled for Europe indicate a contribution of PBAPs to PM10 concentrations in the low percentage range, with a maximum in summer when concentration levels are small. This is consistent with the range of measurements. Despite of the large uncertainties, results contribute to clarify the potential contribution of biological particles to global load of particle mass. 相似文献
62.
Numerical simulation of reactive processes in an experiment with partially saturated bentonite 总被引:2,自引:0,他引:2
Bentonites are preferred materials for use as engineered barriers for high-level nuclear waste repositories. Simulation of geochemical processes in bentonite is therefore important for long-term safety assessment of those repositories. In this work, the porewater chemistry of a bentonite sample subject to simultaneous heating and hydration, as studied by Cuevas et al. [Cuevas, J., Villar, M., Fernández, A., Gómez, P., Martín, P., 1997. Porewaters extracted from compacted bentonite subjected to simultaneous heating and hydration. Applied Geochemistry 12, 473-481.], was assessed with a non-isothermal reactive transport model by coupling the geochemical software PHREEQC2 with the object-oriented FEM simulator GeoSys/RockFlow. Reactive transport modelling includes heat transport, two-phase flow, multicomponent transport and geochemical reactions in the liquid phase, i.e. ion exchange, mineral dissolution/precipitation and equilibrium reactions. Simulations show that the easily soluble minerals in bentonite determine the porewater chemistry. Temperature affects both two-phase flow and geochemical reactions. Porosity change due to dissolution/precipitation is low during the experiment. However, changes of the effective porosity caused by bentonite swelling can be very large. The simulated results agree well with the experimental data. 相似文献
63.
We have examined the sensitivity of sequential two photon laser induced fluorescence (LIF) detection of elemental mercury, Hg(0) in the gas phase. The most sensitive approach involves an initial laser excitation of the 6(3)P1-6(1)S0 transition at 253.7 nm, followed by excitation with a second laser to the 7(1)S0 level. Blue shifted fluorescence is observed on the 6(1)P1-6(1)S0 transition at 184.9 nm. The excitation scheme, involving sequential excitation of two atomic transitions, followed by detection of the emission from a third is extremely specific and precludes detection of anything other than atomic mercury. Using our 10 Hz laser system we have achieved a detection sensitivity of 0.1 ng m(-3) at a sampling rate of 0.1 Hz, i.e. averaging 100 laser shots at a pressure of one atmosphere in air. At low concentrations we sampled simultaneously with an automated mercury analyzer (Tekran 2537A), to ensure accuracy. We have examined the linearity of the technique, generating flows containing mercury concentrations between 1 and 10,000 ng m(-3) using a permeation tube and dynamic dilution, but relying on the concentrations given by the Tekran at low levels and the concentration calculated from dilution at high levels. We find that the detection is linear over the five orders of magnitude that we were able to vary the concentration. Our measured detection limits in He and Ar are much lower as these gases are inefficient fluorescence quenchers. 相似文献
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65.
Reddy KJ Kumar JR Narayana SL Ramachandraiah C Thriveni T Reddy AV 《Environmental monitoring and assessment》2007,124(1-3):309-320
N-ethyl-3-carbazolecarboxaldehyde-3-thio- semicarbazone (ECCT) as an new analytical reagent used for the development of a
highly sensitive extractive spectrophotometric method for the determination of copper(II). The ECCT forms a greenish-yellow
colored 1:1 (M:L) complex with copper(II) at pH 3.0, which is well extracted into n-butanol and shows maximum absorbance at
380nm. The color of the complex is stable for more than forty eight hours. The system obey Beer's law in the range 0.4–3.6
with 2.243 × 104lmol−1cm−1, 2.83 × 10-3μgcm−2 molar absorptivity and Sandell's sensitivity respectively. The regression coefficient is 0.412 with 0.99 correlation coefficient.
The precision and accuracy of the method was checked by finding the relative standard deviation (0.422%). This developed method
has been successfully employed for the determination of copper(II) in environmental and pharmaceutical samples. The method
is evaluated by analyzing samples from the bureau of analyzed samples (BCS 233, 266, 216/1, 207 and 179) and by inter comparison
of experimental values using AAS. 相似文献
66.
de Bauer Mde L Hernández-Tejeda T 《Environmental pollution (Barking, Essex : 1987)》2007,147(3):446-453
The first report on oxidant-induced plant damage in the Valley of Mexico was presented over 30 years ago. Ozone is known to occur in the Mexico City Metropolitan Area and elsewhere as the cause of chlorotic mottling on pine needles that are 2 years old or older as observed in 1976 on Pinus hartwegii and Pinus leiophylla. Visible evidences for the negative effects of ozone on the vegetation of central Mexico include foliar injury expressed as chlorotic mottling and premature defoliation on pines, a general decline of sacred fir, visible symptoms on native forest broadleaved species (e.g. Mexican black cherry). Recent investigations have also indicated that indirect effects are occurring such as limited root colonization by symbiotic fungi on ozone-damaged P. hartwegii trees and a negative influence of the pollutant on the natural regeneration of this species. The negative ozone-induced effects on the vegetation will most likely continue to increase. 相似文献
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70.
Territoriality should lead to strict dominance, as territory holders typically control access to resources and exclude others
from their use. In feeding territories, dominance should be reflected in foraging success and ultimately in reproduction differences;
however, these successive links have rarely been made explicit. Therefore, we investigated a population of brown skuas Catharacta antarctica lonnbergi, in which only part of the breeding population occupied feeding territories within penguin colonies. We identified the dominance
hierarchy and determined the foraging success of the participants in fights for access to penguin carcasses within the territories.
Furthermore, we monitored offspring growth from parents with and without feeding territories. Our results indicated a clear
dominance hierarchy with territorial birds in their own territory dominating over territorial breeders from other territories,
non-territorial breeders and non-breeding birds. However, territory owners could not completely exclude others from access
to food. Foraging success was positively related to dominance scores: The dominant territory owners received 63% of a carcass,
whereas non-territorial pairs could get less than 10%. The link between foraging success and offspring development was less
clear: Although male chicks of non-territorial parents suffered from lower growth rates and, thus, delayed fledging, there
were no such differences in female chicks. Territoriality in skuas did not imply a complete occupation of food, but guaranteed
optimal growth conditions for offspring. Non-territorial individuals were forced to search for alternative resources, and
the restricted access to the preferred food resulted in inferior conditions for offspring development, making this foraging
strategy less rewarding. 相似文献