Spatio-Temporal Variations of Daily Average of NO<SUB>2</SUB>Concentration in the Vicinity of a Crossroads

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In order to evaluate the spa tio-temporal variation of NO<SUB>2</SUB>concentration near the principal roads, a survey was carried out in the vicinity of Kamiuma crossroads of Setagaya. Daily average concentration was measured during a period of five days in March 1989, by using passive samplers (filter badges). Sampling sites were located at the grid points distant 0m, 20m, 50m, 100m and 200m from the roadside of two principal roads crossing at a right angle. Analysis of variance of a three way classification with main effects for days and distance from each road showed the following characteristics.(1) Concentrations went down rapidly at the points of 20m from roadside. Attenuation rate varied with wind direction and speeds, height of roadside buildings and so on.(2) At the roadside, concentration did not decline markedly with distance from the crossroads.(3) Spatialpattern varied by meteorological condition of the day. Daily variation of spatial pattern was large at the area including sites at roadside and 20m distant from roads, and error was large when the daily average concentration at the sites within such area was estimated by using an average spatial pattern and daily average concentration.
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