Deposition velocities for full-scale corn and soybean canopies: A wind tunnel simulation

Deposition velocities have been determined for corn and soybeans in the first 4–6 weeks of growth in a full-scale study of canopy flow in a wind tunnel. Particles of 1, 5, 10 and 15 μm aerodynamic diameter made of sodium florescein were injected into the Environmental Wind Tunnel Facility at Colorado State University. Deposition velocities were determined as a function of free stream velocity (183, 305 and 610 cm/s) and approach flow turbulence intensity (～1% and 8%). Plants were arranged in realistic field configurations. Hot-wire anemometer studies confirmed that the fluid velocity profiles developed in the wind tunnel were similar to the flow realized in canopies in natural fields. An increase in velocity and turbulence intensity was found to decrease the deposition velocities. A minimum deposition velocity was observed at a particle diameter of 5 μm.     

A Wind Tunnel Study of Gaseous Pollutants in City Street Canyons

Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Values of concentration measured in the model city were converted to prototype concentrations in ppm and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometries for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions.     

Measuring site-level success in brownfield redevelopments: a focus on sustainability and green building

This research has met the following four objectives within the broader research topic of characterizing and quantifying success in brownfield revitalization: (1) to define 40 total indicators that define and determine the success of brownfield redevelopments in four categories: environment-health, finance, livability, and social-economic; (2) to use these indicators to develop a partially automated tool that stakeholders in brownfield redevelopment may use to more easily assess and communicate success (or failures) in these projects; (3) to integrate "green" building as an important aspect of successful brownfield redevelopments; and (4) to develop this tool within the framework of a specific multi-attribute decision method (MADM), the analytical hierarchical process (AHP). Future research should include the operationalization and application of this tool to specific sites. Currently, no such indicator framework or automated tool is known to exist or be in use. Indicators were chosen because of their ability to reduce data into comprehensible measurements and to systematically measure success in a standardized fashion. Appropriate indicators were selected based on (1) interviews with prominent private developers and national leaders in brownfield redevelopment, (2) a review of the relevant literature, (3) objective hierarchies created in this project, and (4) the ability for each indicator to serve goals in more than one of the four categories described above. These were combined to form the Sustainable Brownfields Redevelopment (SBR) Tool. A survey was conducted to serve as a preliminary assessment and proposed methodology for judging the validity of the SBR Tool. Professionals in the academic, private, and public sector were asked to provide an evaluation of the management tool and a weighting of the relative importance of each indicator and each of the four categories listed previously. Experts rated the tool at 7.68 out of 10 suggesting that this framework will be useful in evaluating these redevelopments upon completion and in formulating initial site plans and building design.     

Emission study of a diesel engine fueled with higher alcohol-biodiesel blended fuels

This work examines the effect of butanol (higher alcohol) on the emission pattern of neat neem oil biodiesel (NBD100) fueled diesel engine. Single-cylinder, 4-stroke, research diesel engine was employed to conduct the trial. Blends comprising the mixture of biodiesel and higher alcohol were prepared by employing an ultrasonic agitator. Four test fuels such as neat neem oil biodiesel, diesel, and two blends of higher alcohol/neem oil biodiesel: 10% and 20% (by volume). Experimental result showed that increasing alcohol content to biodiesel brought down the various emissions such as Smoke, NO_x, HC, and CO by 6.8%, 10.4%, 8.6%, and 5.9%, respectively, at all loads. It was also concluded from the trail that a 20% higher alcohol/neem oil biodiesel blends show the promising signs in reducing all the emissions associated with biodiesel fuelled diesel engine.     

Can constructed wetlands reduce the diffuse phosphorus loads to eutrophic water in cold temperate regions?

Construction of wetlands is a possible supplement to best management practices (BMP) at the field level to mitigate phosphorus (P) pollution from agricultural areas. In this paper, annual results from 17 intensively studied wetlands in the cold temperate or boreal climatic zone are reported and analyzed. Surface areas varied from 0.007 to 8.7% of the catchment area. The average total phosphorus (TP) retention varied from 1 to 88%, and the dissolved reactive phosphorus (DRP) retention from -19 to 89%. Retention varied substantially from site to site, indicating the existence of site-specific factors in the catchment and wetlands that influenced the P removal. Factors important for P retention in wetlands were evaluated through multiple statistical analyses by dividing P into two fractions: particulate phosphorus (PP) and DRP. Both relative (%) PP and DRP retention increased with wetland surface area. However, PP retention was not as sensitive as DRP in terms of wetland size and retention: specific PP retention (gram P retention per m(2) and year) decreased as wetland area (A(w)) increased, suggesting the existence of a site-specific optimal wetland to catchment area (A(c)) ratio. Particulate P retention decreased with increasing DRP to TP ratio, while the opposite was found for DRP. Dissolved reactive P retention was higher in new than in old wetlands, while increasing age did not influence PP retention negatively. Effective BMP in the catchment is important to keep the P loss low, because the outlet concentration of P from wetlands is often positively correlated to the input concentration. However, wetlands act as the last buffer in a catchment, since the retention often increases as the P concentration in streams increases.     

An Automatic Particle Sampler with Beta Gauging

Performance test results and operating characteristics of the Wedding & Associates' (W&A) PM10 Beta Gauge Automated Particle Sampler (Sampler), a U.S. EPA Designated Equivalent Method (Designation No. EQPM-0391-081), are reported. The custom, computer-controlled Sampler utilizes BETASOFT?, a multitasking operating system running the high level language application program. The Sampler employs the Wedding PM10 Inlet (Inlet) and Critical Flow Device (CFD). Analysis, calculations and mechanical control are achieved by use of analog sensing and digital logic. The development and testing program included wind tunnel and field tests to verify experimentally its conformity with theoretical calculations of the relationship of collected mass to 3- particle penetration. Use of a ¹⁴C source and a fast-response detector leads to high sensitivity and precision. The instrument has been tested against the Wedding Reference Method Sampler (Reference Method). The 24-hour means of mass concentration values determined by the Sampler, regressed against 24-hour samples collected with the Reference Method, yielded slopes within 1.2 percent of unity, with intercepts less than 1.5 μg/m³ and coefficients of determination (R²) of 0.99 or higher. Resolution is less than 3 μg/m³.     

Ambient aerosol sampling: Problems,goals and wind tunnel test results of hi-volume samplers

The area of ambient air sampling and its inherent problems and current goals are discussed in general. In particular, recently completed tests of the collection effectiveness of the Rocky Flats Hi-Volume Sampler are compared to previously completed tests of the Standard EPA Hi-Volume Sampler for a variety of field realistic conditions. Collection effectiveness is defined as the ratio of the aerosol collected on the collection substrates of the sampler to that collected by an isokinetic sampling system.The collection effectiveness of the Standard EPA Hi-Volume Sampler was determined as a function of particle size (5–50 μm) and sampler orientation (0° and 45°) at a base condition wind speed of 4.6 m/s and 8% relative turbulence intensity. The results indicated a strong effect of orientation on collection effectiveness at a sampling rate of 1416 l/min. Wind speed over the range of 1.5–4.6 m/s does not greatly influence the collection effectiveness of 15 μm particles. Free stream turbulence levels of 1 and 8% relative intensity has no effect upon collection characteristics.The collection effectiveness of the Rocky Flats Hi-Volume Sampler was determined as a function of particle size (1–34 μm), wind speed (1.52–12.19 m/s) and sampler orientation to the mean flow (0°, 45°, 180°). The results show the sampler, with an inlet flow rate of 880 l/min, has an inlet effectiveness that was a slight function of orientation angle for particles 1–10 μm with a larger effect seen for 20–34 μm; a strong effect of velocity was seen up to 5 m/s where a further increase showed only a slight decrease in effectiveness.The Microsorban-98 filter that is presently used in the Rocky Flats Sampler was tested for efficiency over the size range of particles from 0.01–1 μm and with three different face velocities using the sampler flow rates of 600, 800 and 1 000 l/min corresponding to pressure drops of 20–24 in. of water (3.74–4.49 cm HaG). The filter paper, which was of the fiber type, was found to be 99.9% efficient over the range of particle sizes and pressure drops tested.