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661.
662.
Held AE Chang DP Niemeier DA 《Journal of the Air & Waste Management Association (1995)》2001,51(1):121-132
A series of twelve intensively monitored 1-hr CO dispersion studies were conducted near Davis, CA, in winter 1996. The experimental equipment included twelve CO sampling ports at elevations up to 50 m, three sonic anemometers, a tethersonde station, aircraft measurements of wind and temperature profile aloft, and a variety of conventional meteorological equipment. The study was designed to explore the role of vehicular exhaust buoyancy during worst-case meteorological conditions, such as low winds oriented in near-parallel alignment with the road during a surface-based nocturnal inversion. From the study, field estimates of the CO emission factor (EF) from a California vehicle fleet were computed using two different methods. The analysis suggests that the CT-EMFAC/EMFAC (EMission FACtor) models currently used to conduct federal conformity modeling significantly overpredict CO emissions for high-speed, free-flowing traffic on California highways. 相似文献
663.
David Alexander 《Environmental management》1980,4(1):27-34
The floods of 1966 in Northern Italy provoked varying reactions from officialdom and the press. Political and administrative problems received as much coverage as the environmental effects of the disaster, but learned opinion gained a new, if rather temporary, status in the newspapers of the time. In retrospect, economic recovery seems to have occurred more rapidly than predicted in the gloomy forecasts of the time, although a clear picture of the disruption caused by the floods 相似文献
664.
665.
666.
David Alexander 《Environmental management》1986,10(2):143-144
667.
Alexander C. Demetracopoulos George P. Korfiatis Efst. L. Bourodimos Edward G. Nawy 《Journal of the American Water Resources Association》1986,22(4):601-609
ABSTRACT: The movement of precipitation water infiltrating through the material (refuse) of solid waste landfills is examined via numerical solution of the equations of continuity, and motion (Darcy's Law). The solution of the equations is obtained by a fully implicit, finite-difference scheme. Both unsaturated and saturated surface conditions are considered, making the scheme suitable for real-time simulation of net precipitation and moisture redistribution events. A sensitivity analysis showed that for unsaturated surface conditions the solution is primarily affected by hydraulic conductivity and capillary diffusivity, and is relatively independent of the space and time steps. In addition, the precipitation averaging process is shown to be critical in the correct computation of moisture transport during the time period where the transition from unsaturated to saturated conditions occurs. The model presented herein is suitable for analysis of water movement through landfills, and the design of bottom collection systems. 相似文献
668.
Nitrogen management in bioreactor landfills 总被引:17,自引:0,他引:17
One scenario for long-term nitrogen management in landfills is ex situ nitrification followed by denitrification in the landfill. The objective of this research was to measure the denitrification potential of actively decomposing and well decomposed refuse. A series of 10-l reactors that were actively producing methane were fed 400 mg NO3-N /l every 48 h for periods of 19-59 days. Up to 29 nitrate additions were either completely or largely depleted within 48 h of addition and the denitrification reactions did not adversely affect the leachate pH. Nitrate did inhibit methane production, but the reactors recovered their methane-producing activity with the termination of nitrate addition. In well decomposed refuse, the nitrate consumption rate was reduced but was easily stimulated by the addition of either acetate or an overlayer of fresh refuse. Addition of acetate at five times the amount required to reduce nitrate did not lead to the production of NH4+ by dissimilatory nitrate reduction. The most probable number of denitrifying bacteria decreased by about five orders of magnitude during refuse decomposition in a reactor that did not receive nitrate. However, rapid denitrification commenced immediately with nitrate addition. This study shows that the use of a landfill as a bioreactor for the conversion of nitrate to a harmless byproduct, nitrogen gas, is technically viable. 相似文献
669.
Bumblebee detection of a flat circular disc (two-dimensional (2D) presentation) and a disc which was presented 10 cm in front
of a structured background (and thus provided three-dimensional (3D) cues) was compared. A dual choice test using a Y-maze
apparatus was conducted to estimate the minimum visual angle at which the bees were able to detect the disc. At large visual
angles of 15, 10 and 5° bees’ performance between the 2D and the 3D presentation did not differ. However, when the disc subtended
3° at the bee’s eye, the bees performed significantly better when 3D information was available. Overall, bees were able to
detect a target subtending a 40% smaller visual angle when it was presented in front of the structured background compared
to a 2D presentation. This suggests that previous reports on the limits of target detection in bees using flat stimuli might
have underestimated the bees’ ability to locate small flowers under natural conditions. Bees use motion parallax, i.e. the
apparent relative motion of a stationary object against a background, for perceiving the third dimension. Our data suggest
that bumblebees can integrate information from at least two types of feature detectors, motion and area, to improve single
target detection. 相似文献
670.
Luke D. Bainard Alexander M. KochAndrew M. Gordon Steven G. NewmasterNaresh V. Thevathasan John N. Klironomos 《Agriculture, ecosystems & environment》2011,144(1):13-20
Tree-based intercropping (TBI) is an ecologically sustainable agricultural practice that may promote a more diverse arbuscular mycorrhizal (AM) fungal community compared to conventional systems, but the influence of the dynamics of these systems on AM fungi has not been established. Soil and root samples were collected in the intercropping alleys along transects perpendicular to tree rows occupied by white ash (Fraxinus americana), poplar (Populus deltoids × nigra), Norway spruce (Picea abies), and rows without trees (control). Molecular analysis of the AM fungal community at the TBI site revealed 17 phylotypes belonging to the Glomeraceae. Overall, the AM fungal community in the TBI site was comparable to other conventional agricultural systems; with the majority of phylotypes belonging to Glomus group A. AM fungal phylotype richness and community composition significantly differed among the treatments in the TBI site. AM fungal communities were more diverse in cropping alleys adjacent to trees that associate with AM fungi than trees that do not associate with AM fungi. Norway spruce had a negative influence on the AM fungal community as tree rows and bordering intercropping alleys had a significantly lower phylotype richness and different community composition. These results suggest that to maintain a diverse AM fungal community throughout TBI systems, it may be best to incorporate tree species that associate with AM fungi. 相似文献