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111.
Background, Aims and Scope Secondary inorganic aerosol (SIA), i.e. particulate sulphate (S(VI)), ammonium and nitrate (N(V)) is formed from gaseous
precursors i.e., sulfur dioxide (S(IV)), ammonia and nitrogen oxides, in polluted air on the time-scale of hours to days.
Besides particulate ammonium and nitrate, the respective gaseous species ammonia and nitric acid can be formed, too. SIA contributes
significantly to elevated levels of respirable particulate matter in urban areas and in strongly anthropogenically influenced
air in general.
Methods The near-ground aerosol chemical composition was studied at two stationary sites in the vicinity of Berlin during a field
campaign in summer 1998. By means of analysis of the wind field, two episodes were identified which allow to study changes
within individual air masses during transport i.e., a Lagrangian type of experiment, with one station being upwind and the
other downwind of the city. By reference to a passive tracer (Na+) and estimates on dry depositional losses, the influences
of dispersion and mixing on concentration changes can be eliminated from the data analysis.
Results and Discussion Chemical changes in N(-III), N(V) and S(VI) species were observed. SIA i.e., N(V) and S(VI), was formed from emissions in
the city within a few hours. The significance of emissions in the city was furthermore confirmed by missing SIA formation
in the case of transport around the city. For the two episodes, SIA formation rates could be derived, albeit not more precise
than by an order of magnitude. N(V) formation rates were between 1.4 and 20 and between 1.9 and 59 % h-1 on the two days,
respectively, and S(VI) formation rates were > 17 and > 10 % h-1. The area south of the city was identified as a source of
ammonia.
Conclusion The probability of occurrence of situations during which the downwind site (50 km downwind of Berlin) would be hit by an
urban plume is > 7.4%. Furthermore, for the general case of rural areas in Germany it is estimated that for more than half
of these there is a significant probability to be hit by an urban plume (> 8%). The S(VI) formation rates are higher than
explainable by homogeneous gas-phase chemistry and suggest the involvement of heterogeneous reactions of aerosol particles.
Recommendation and Outlook The possible contribution of heterogeneous processes to S(VI) formation should be addressed in laboratory studies. Measurements
at more than two sites could improve the potential of Lagrangian field experiments for the quantification of atmospheric chemical
transformations, if a second downwind site is chosen in such a way that, at least under particular stability conditions, measurements
there are representative for the source area. 相似文献
112.
113.
Longauer R Gömöry D Paule L Blada I Popescu F Mankovska B Müller-Starck G Schubert R Percy K Szaro RC Karnosky DF 《Environmental pollution (Barking, Essex : 1987)》2004,130(1):85-92
The effects of air pollution on the genetic structure of Norway spruce, European silver fir and European beech were studied at four polluted sites in Slovakia, Romania and Czech Republic. In order to reduce potential effects of site heterogeneity on the health condition, pair-wise sampling of pollution-tolerant and sensitive trees was applied. Genotypes of sampled trees were determined at 21 isozyme gene loci of spruce, 18 loci of fir and 15 loci of beech. In comparison with Norway spruce, fewer genetic differences were revealed in beech and almost no differentiation between pollution-tolerant and sensitive trees was observed in fir. In adult stands of Norway spruce, sensitive trees exhibited higher genetic multiplicity and diversity. The decline of pollution-sensitive trees may result thus in a gradual genetic depletion of pollution-exposed populations of Norway spruce through the loss of less frequent alleles with potential adaptive significance to altered stressing regimes in the future. Comparison of the subsets of sensitive and tolerant Norway spruce individuals as determined by presence or absence of discolorations ("spruce yellowing") revealed different heterozygosity at 3 out of 11 polymorphic loci. 相似文献
114.
115.
116.
Yorianta?Sasaerila Regine?Gries Gerhard?Gries Grigori?Khaskin Skip?King Stephen?Takács Hardi?) 《Chemoecology》2003,13(2):89-93
Summary. During peak calling activity by male oil palm bunch
moths, Tirathaba mundella Walker (Lepidoptera: Pyralidae), their
hairpencils, wings or entire body were extracted in hexane. Gas
chromatographic-electroantennographic detection (GC-EAD) analyses of
hair pencil extracts revealed four compounds that consistently elicited
responses from female antennae. The NMR spectrum of isolated compound 1,
and mass spectra and retention indices of compounds 1–4 suggested that
they were (3S,6S)-2,2,6-trimethyl-6-vinyl-tetrahydro-pyran-3-ol (1),
4-hydroxy-3-methoxy-benzaldehyde (2, vanillin),
6,10,14-trimethyl-2-pentadecanone (3), and
6,10,14-trimethyl-2-pentadecanol (4). Comparative GC and GC-MS analyses
of hair pencils extract and synthetic standards confirmed these
structural assignments. Moreover, comparative chromatography of
synthetic and hairpencil-isolated 1 on a Cyclodex-B column (which
separated the four stereoisomers with baseline resolution) revealed that
male T. mundella produce the SS-stereoisomer (SS-1). In field cage
bioassay experiments in Palembang, Indonesia, synthetic SS-1 and
vanillin in combination, but not singly, attracted female T. mundella.
SS-1 plus vanillin were as effective as male T. mundella in attracting
females. Compounds 3 and 4 did not enhance the blend's attractiveness.
Received October 11 2002; accepted March 14, 2003.
R1D="
Correspondence to: Gerhard Gries, email: gries@sfu.ca 相似文献
117.
118.
Summary Wild short-toed tree creepers in southern Germany were exposed to tape recordings of seven song types from other dialects or song institutions and sixteen song types from thirteen handreared Middle European birds. One song type from southern Germany was used as a control. The males reacted strongly to two slightly different Spaish dialects and not at all or only feebly to one song institution from Cyprus and four from Morocco. The song types of the hand-reared birds had less effect than controls. The songs of two birds from southern Germany hand-raised together were quite similar to those from Cyprus. We conclude that Cyprus and North Africa on the outskirts of the species distribution were colonized by short-toed tree creepers who had had no opportunity to learn their songs from adult conspecifics. 相似文献
119.
Gerhard H. Jirka 《Environmental Fluid Mechanics》2006,6(1):43-100
An integral model for the plane buoyant jet dynamics resulting from the interaction of multiple buoyant jet effluxes spaced
along a diffuser line is considered as an extension of the round jet formulation that was proposed in Part I. The receiving
fluid is given by an unbounded ambient environment with uniform density or stable density stratification and under stagnant
or steady sheared current conditions. Applications for this situation are primarily for submerged multiport diffusers for
discharges of liquid effluents into ambient water bodies, but also for multiple cooling tower plumes and building air-conditioning.
The CorJet model formulation describes the conservation of mass, momentum, buoyancy and scalar quantities in the turbulent
jet flow in the plane jet geometry. It employs an entrainment closure approach that distinguishes between the separate contributions
of transverse shear and of internal instability mechanisms, and contains a quadratic law turbulent pressure force mechanism.
But the model formulation also includes several significant three-dimensional effects that distinguish actual diffuser installations
in the water environment. These relate to local merging processes from the individual multiple jets, to overall finite length
effects affecting the plume geometry, and to bottom proximity effects given by a “leakage factor” that measures the combined
affect of port height and spacing in allowing the ambient flow to pass through the diffuser line in order to provide sufficient
entrainment flow for the mixing downstream from the diffuser. The model is validated in several stages: First, comparison
with experimental data for the asymptotic, self-similar stages of plane buoyant jet flows, i.e. the plane pure jet, the pure
plume, the pure wake, the advected line puff, and the advected line thermal, support the choice of the turbulent closure coefficients
contained in the entrainment formulation. Second, comparison with data for many types of non-equilibrium flows with a plane
geometry support the proposed functional form of the entrainment relationship, and also the role of the pressure force in
the jet deflection dynamics. Third, the observed behavior of the merging process from different types of multiport diffuser
discharges in both stagnant and flowing ambient conditions and with stratification appears well predicted with the CorJet
formulation. Fourth, a number of spatial limits of applicability, relating to terminal layer formation in stratification or
transition to passive diffusion in a turbulent ambient shear flow, have been proposed. In sum, the CorJet integral model appears
to provide a mechanistically sound, accurate and reliable representation of complex buoyant jet mixing processes, provided
the condition of an unbounded receiving fluid is satisfied. 相似文献
120.