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31.
High ground-level ozone continues to be an important human, animal, and plant health impediment in the United States and especially in California's San Joaquin Valley (SJV). According to California state and regional air quality agencies, dairies are one of the major sources of volatile organic compounds (VOCs) in the SJV. A number of recently conducted studies reported emissions data from different dairy sources. However, limited data are currently available for silage and otherfeed storages on dairies, which could potentially contribute to ozone formation. Because the impact of different VOCs on ozone formation varies significantly from one molecular species to another, detailed characterization of VOC emissions is essential to include all the important contributors to atmospheric chemistry and especially atmospheric reactivity. The present research study identifies and quantifies the VOCs emitted from various silages and other feedstuffs. Experiments were conducted in an environmental chamber under controlled conditions. Almost 80 VOCs were identified and quantified from corn (Zea mays L.), alfalfa (Medicago sativa L.),and cereal (wheat [Triticum aestivum L.] and oat [Avena sativava L.] grains) silages, total mixed ration (TMR), almond (Amygdalus communis L.) shells and hulls using gas chromatography-mass spectrometry and high performance liquid chromatography. The results revealed high concentrations of emitted alcohols and other oxygenated species. Lower concentrations of highly reactive alkenes and aldehydes were also detected. Additional quantitation and monitoring of these emissions are essential for assessment of and response to the specific needs of the regional air quality in the SJV. 相似文献
32.
Uptake of different forms of antimony by wheat and rye seedlings 总被引:1,自引:0,他引:1
Shtangeeva I Steinnes E Lierhagen S 《Environmental science and pollution research international》2012,19(2):502-509
Purpose
The objectives of the research were to study how antimony (Sb) chemical form present in the growth medium can affect Sb uptake by plants and estimate effects of Sb on wheat and rye seedlings, in particular, assess variations in concentrations of nutrients resulting from bioaccumulation of Sb. 相似文献33.
Gregory E. Insarov Serguei M. Semenov Irina D. Insarova 《Environmental monitoring and assessment》1999,55(2):279-298
The issue of biological monitoring of the local consequences of anticipated global climate change is considered for the Central Negev Highlands, Israel. Epilithic lichens are suggested as biological monitors. The proposed methodology of such monitoring consists of a sampling scheme, including lichen measurement along transects on flat calcareous rocks, and construction of a trend detection index (TDI). TDI is a sum of lichen species cover with coefficients chosen so as to ensure maximum ability to detect global climate trends. Coefficients have been estimated in a study of lichens along an altitudinal gradient from 500 to 1000 m a.s.l. The gradient study demonstrated that the TDI index is performed better than other integrated indices. Recommendations on this system to monitor climate change with epilthic lichens are given. Measuring, for instance, a hundred transects in fifty plots (two transet per plot scheme) allows one to detect a climate-driven change in the epilithic lichen community corresponding to a 0.8 °C shift in annual mean temperature. Such resolution appears sufficient in view of global warming of 2.5 °C considered by the Intergovernmental Panel on Climate Change as a realistic prediction for the end of the next century. 相似文献
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The modelling of the transformation processes in the river sediments is an important and still not investigated problem that is a key for water quality. The relation between nutrients transformation rate and moisture in sediments was investigated by means of analogous modelling. The mathematical dependences of the connection were derived, and only two of them were linear—at the early stage of COD (organic) change and at the late stage of transformation of phosphates that metabolically connected the biodegradation of organics with oxidative phosphorylation. The rest mathematical dependences were the polynomials of third order. This study confirmed that the leading factors which influence the transformation rate of nutrients are the sediment surface, particular organic matter and porosity of the medium, as well as the concentration on the sediment surface of micro-organisms, enzymes, co-metabolites, etc. The presented data from ecological modelling of the transformation processes in the parafluvial sediments showed how can the hydrological models be enlarged and enriched in their application to the key and critical (risk) fluctuations in the river functioning. The mathematical dependences and coefficients were extracted in our complex study to be included in HSPF model as an enlarged module. As far as the investigated transformation processes in the parafluvial have more universal significance, the results can be applied in the other models, bounded river water and sediment quality. 相似文献
39.
Natalia Demchenko Irina Chubarenko GertJan van Heijst 《Environmental Fluid Mechanics》2012,12(2):161-183
The thermal bar—a hydrodynamic phenomenon, arising in natural basins due to successive changes of the water temperature across
the temperature of maximum density (Tm, which is close to 4°C)—has been studied in laboratory experiments and by numerical simulations. The experiments were performed
in a rectangular tank with an inclined bottom, filled with water with initial temperature T0 < Tm and then heated at the surface. During the heating a basin-wide circulation develops, consisting of down-slope cascades in
regions where T < Tm, a subsurface off-shore jet in the region where T > Tm, and a compensating flow at intermediate depths towards the shallow part of the tank, supplying both off-shore flows with
waters from deeper regions. Analysis of the water temperature and density fields as well as the currents has revealed that
the location of the convergence zone of the surface current (when formed) does not coincide with that of the Tm-isotherm.
The thermal bar front is typically understood as a convergence zone near the 4°C-isotherm, formed due to the effect of cabbeling.
Our experiments demonstrate, however, that the front is associated with the leading edge of the subsurface current. The increasing
distance between the 4°C-isotherm and the subsurface jet has been recorded in the laboratory experiments. Numerical simulation
results corroborate the laboratory experiments. A scaling analysis predicts the speed of propagation of this frontal zone
to be U ~ [g × Δρ/ρ × H]1/2, where H is the depth (increasing with time) of the upper thermo-active layer, ρ0 a reference density, and Δρ is the characteristic horizontal density difference across the front. A combined analysis of
laboratory, field and numerical data has corroborated this law. 相似文献
40.
A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation 总被引:1,自引:0,他引:1
William P.L. Carter David R. Cocker III Dennis R. Fitz Irina L. Malkina Kurt Bumiller Claudia G. Sauer John T. Pisano Charles Bufalino Chen Song 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7768-7788
A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NOx and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NOx and simplified ambient surrogate–NOx experiments to demonstrate the utility of the facility for mechanism evaluation under low NOx conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NOx levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations. 相似文献