Numerical investigation of the effect of road structures on ambient air quality—for their better design

Tokairin, Takayuki; Kitada, Takahiro

doi:10.1016/j.jweia.2003.10.004

Cited by 10 publications

(6 citation statements)

References 13 publications

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“…7 we conclude that this threshold distance is somewhere between 5h and 35h downwind of our plot fence (the limited data within this fetch range does not allow us to specify a more precise location). A similar result can be seen in the modeling study of Tokairin and Kitada (2004), who considered dispersion downwind of a roadbed with and without a surrounding fence. 4 The addition of the fence increased surface concentration approximately 40% near the fence (2.4h from the fence), but by a distance of 10h the effect of the fence was less than 5%.…”

Section: A Using Ambient Winds For Q Blssupporting

confidence: 80%

Deducing Ground-to-Air Emissions from Observed Trace Gas Concentrations: A Field Trial with Wind Disturbance

Flesch

Wilson

Harper

2005

Journal of Applied Meteorology

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Inverse-dispersion techniques allow inference of a gas emission rate Q from measured air concentration. In "ideal surface layer problems," where Monin-Obukhov similarity theory (MOST) describes the winds transporting the gas, the application of the technique can be straightforward. This study examines the accuracy of an ideal MOST-based inference, but in a nonideal setting. From a 6 m ϫ 6 m synthetic area source surrounded by a 20 m ϫ 20 m square border of a windbreak fence (1.25 m tall), Q is estimated. Open-path lasers gave line-averaged concentration C L at positions downwind of the source, and an idealized backward Lagrangian stochastic (bLS) dispersion model was used to infer Q bLS . Despite the disturbance of the mean wind and turbulence caused by the fence, the Q bLS estimates were accurate when ambient winds (measured upwind of the plot) were assumed in the bLS model. In the worst cases, with C L measured adjacent to a plot fence, Q bLS overestimated Q by an average of 50%. However, if these near-fence locations are eliminated, Q bLS averaged within 2% of the true Q over 61 fifteen-minute observations (with a standard deviation Q/Q ϭ 0.20). Poorer accuracy occurred when in-plot wind measurements were used in the bLS model. The results show that when an inverse-dispersion technique is applied to disturbed flows without accounting for the disturbance, the outcome may still be of acceptable accuracy if judgment is applied in the placement of the concentration detector.

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Section: A Using Ambient Winds For Q Blssupporting

confidence: 80%

Deducing Ground-to-Air Emissions from Observed Trace Gas Concentrations: A Field Trial with Wind Disturbance

Flesch

Wilson

Harper

2005

Journal of Applied Meteorology

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“…The coefficient value of 0.02 in Equation (11) was determined so that the calculated wind agreed well with the observed in the field experiment (Tokairin and Kitada, 2004).…”

Section: Boundary Conditionsmentioning

confidence: 67%

“…These fences are often installed to prevent traffic noise pollution. A previous study (Tokairin and Kitada, 2004) showed that the fences set at the ground level have significant adverse effect to air pollution while those at the upper deck rather enhance vertical dispersion and thus decrease concentration near the ground. Hence we numerically investigated how the porous fences at the ground level influence the pollutant concentration near the road.…”

Section: Effect Of Porous Fences On Pollutant Concentration: Casementioning

confidence: 94%

“…In the concentration calculation, emission source was uniformly distributed over the width of the road. The emission intensity Q of 6.92 × 10 −6 m 3 -N m −1 s −1 was also taken equal to that in a tracer gas experiment performed in Okayama, Japan by Road Environment Division, National Institute for Land and Infrastructure Management, Japan (1998), since another model validation using this emission intensity had been already done in Tokairin and Kitada (2004).…”

Section: Simulation Casesmentioning

confidence: 99%

“…However, since noise barrier does not only reduce traffic noise but also modifies flow pattern near the road, and thus, pollutant concentration distribution, it is desirable to understand how the noise barrier affects ambient air quality. In an investigation to see the effect of road fences on air quality around several types of double-decked roads (Tokairin and Kitada, 2004), it was shown that the fences installed at the ground level can largely increase pollutant concentration near the ground and the "worst" fence-height may exist, which leads to the highest pollutant concentration near the ground.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Study on the effect of porous fence on air quality and traffic noise level around a double-decked road structure

Tokairin

Kitada

2005

Environ Monit Assess

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Fence for traffic noise control sometimes causes adverse effect on air pollution. Thus in this study, performance of porous fence as a tool for control of both air pollution and noise pollution was evaluated. A two-dimensional numerical model for flow and pollutant concentration and an analytical model for traffic noise were utilized in the analysis of a double-decked road structure with fences only at ground (Case 1) and at both ground and upper deck (Case 2). Porous fences were assumed only at the ground level since the solid fences at the upper deck usually leads to desirable result on air pollution. Effects of the variable porosity on air quality and noise level near road were evaluated. Obtained results showed: (1) flow pattern in leeward of fence was drastically changed at 40-50% porosity in Case 1 and 50% in Case 2. The porosity larger than 40% excluded presence of a circulation behind the fence. (2) Effect of porous fence on air pollution was different in Cases 1 and 2. In Case 1, the porous fence generally resulted in the reduction of air pollution at the ground level; on the other hand, in Case 2, it rather led to increase of the concentration. (3) Traffic noise level was also largely changed by the porosity of the fence; an example of simultaneous evaluation of the effects of porous fence on both air and noise pollution in Case 1 showed that the fence of 60% porosity leads to reduction of air pollution by 20% compared with solid fence case, and reduction of noise pollution by 4-6% in dB compared with no fence case, at 1 m high and 10 m from the road.

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Application of a high-temporal resolution method to estimate ammonia emissions from farmland

Yang

Zhu

Zhang

et al. 2013

Nutr Cycl Agroecosyst

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Numerical investigation of the effect of road structures on ambient air quality—for their better design

Cited by 10 publications

References 13 publications

Deducing Ground-to-Air Emissions from Observed Trace Gas Concentrations: A Field Trial with Wind Disturbance

Deducing Ground-to-Air Emissions from Observed Trace Gas Concentrations: A Field Trial with Wind Disturbance

Study on the effect of porous fence on air quality and traffic noise level around a double-decked road structure

Application of a high-temporal resolution method to estimate ammonia emissions from farmland

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