Abstract
In order to evaluate the spatio-temporal variation of NO2concentration, a survey was carried out to obtain spatial patterns of daily average concentration during a period of 10days in February 1988, by using diffusion samplers. Sampling sites were located at about 2km intervals in the suburbs of Tokyo and at about 1km inter vals in its subarea. The obtained data were analyzed, along with the data from 4 previous surveys conducted in 1984 to 1986, through the analysis of variance of a two way classification and a median polish fit with main effects for days and sampling sites. Analysis confirmed the previous result that variance between days was larger than variance between sites, variation of these two main effects were related to meteorological condition and/ or to the traffic volume, and that magnitude of variance associated with days, sites and residuals varied with the seasons and areas surveyed. Stability of the spatial distribution was examined in this report, and the following results were obtained:(1) variance due to residual was relatively large for daily average data, that is spatial pattern varied day by day according to meteorological and traffic condition, while spatial pattern of average over 7 or 10 days were comparatively stable, (2) a site near a principal road sometimes showed a large residual, and (3) some parameters indicating spread between tail parts of a distribution should be used to evaluate residuals as well as the standard deviation.
