Site Representativeness of Urban Air Monitoring Stations

Abstract

This paper describes a statistic to quantify spatial representativeness for the air measurements of an urban fixed-site ambient air monitoring station. The application of such a statistic of representativeness has also been successfully demonstrated by two data sets collected at the Gu-Ting monitoring station in Taipei. By measuring NO2 at 22 sites simultaneously around the Gu-Ting station, the statistic has characterized different degrees of spatial representativeness for nitrogen dioxide (NO2) at various areas and microenvironments surrounding this fixed-site monitoring station. By measuring ambient air concentrations at six sites sequentially around the Gu-Ting station, the statistic has also characterized different degrees of representativeness for particulates less than 10 urn in size—(PM10), carbon monoxide (CO), sulfur dioxide (SO2), ozone (O3), NO2, nitrogen oxides (NOX), nitrogen monoxide (NO), total hydrocarbons (THC), and nonmethane hydrocarbons (NMHQ—at an open area surrounding this fixed-site monitoring station. This statistical method identifies the Gu-Ting station is well representative of outdoor concentrations of all nine air pollutants for a period of three weeks at the areas within a 700 m radius around this station. The indoor NO2 concentrations, however, are not represented by the measurements at the fixed-site monitoring station.