Effluent Dilutions Over Mountainous Terrain

Technical Report · Sun Dec 01 04:00:00 EST 1974

DOI:https://doi.org/10.2172/4179019· OSTI ID:4179019

Start, G. E. ^[1]; Ricks, N. R. ^[1]; Dickson, C. R. ^[1]

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1. National Oceanic and Atmospheric Administration (NOAA), Idaho Falls, ID (United States)

The second portion of a two-phase study of atmospheric dilutions of airborne effluents, conducted in the vicinity of mountainous terrain near Garfield, Utah, is described. The first phase of this study was investigated during inversion and neutral cases at another site in a deep, steep-walled canyon and was reported by Start et al. The second phase of the study was designed to quantify atmospheric dilution in rough mountainous terrain, without the strong channeling influences of the deep canyon. Aerial and ground-level sampling of sulfur hexafluoride gaseous tracer were performed. Tracer was released mainly from the 122-m chimney of an operating smelter. Gas analyses were performed using an electron capture gas chromatograph. Meteorological observations included pibals, radio sondes, surface winds from a network of stations, and trajectories of radar-tracked tetroons. Sampled tracer concentrations during lapse conditions are compared with Pasquill's predicted values for flat terrain. Elevated centerline concentrations for a plume having minimal contact with rough topography fit the appropriate Pasquill curve well; plumes crossing the rough terrain averaged two to four times more dilution than predicted for flat terrain. Plume impaction was observed against the elevated terrain. Lateral spreadings of plumes were nearly twice that amount predicted by Pasquill's flat-terrain σ_y-curves. Ground-level concentrations over the elevated terrain may be strongly influenced by an elevated stable layer. In the presence of a low, strongly capping layer, the plume may become trapped in a nearly stagnant elevated layer. With a stable layer somewhat higher, the plume may flow over the ridgetops, contained within a shallow layer. In this case, the plume becomes somewhat uniformly distributed in the vertical direction and, because of ground-reflection effects, ground-level concentrations may be nearly twice as large as aerial concentrations. Without a significant capping stable layer, the plume deflects aloft over the ridges and disproportionately small concentrations are measured at the surface as compared to concentrations aloft. Pibal winds at the plume height were the best indicator of the area of greatest surface-measured tracer concentrations. Winds measured at 3 m above the ground at the inland end of the canyon were nearly as successful as pibal winds for estimating the ground-level plume centerline position. Some aspects of the study are reviewed to aid others involved in similar work, including tracer material used and prediction of plume path using windfield data. A complete data appendix is provided.

• Research Organization: National Oceanic and Atmospheric Administration (NOAA), Idaho Falls, ID (United States)
• Sponsoring Organization: US Department of Commerce; US Energy Research and Development Administration (ERDA)
• NSA Number: NSA-32-027973
• OSTI ID: 4179019
• Report Number(s): NOAA-TM-ERL-ARL--51
• Country of Publication: United States
• Language: English

Related Subjects

*AIR POLLUTION-- MEASURING METHODS
*CHEMICAL EFFLUENTS-- DIFFUSION
500200* --Environmental Sciences
Atmospheric--Chemicals Monitoring & Transport
54 ENVIRONMENTAL SCIENCES
DILUTION
GEOGRAPHY
METEOROLOGY
MOUNTAINS
N44700* --Environmental & Earth Sciences--Chemical Effluents
PLUMES
TRACER TECHNIQUES
VELOCITY
WIND