VARIATION IN AIRBORNE PARTICULATE MATTER CONCENTRATION OVER THE FIRST3 METERS FROM GROUND IN A STREET CANYON - IMPLICATIONS FOR HUMAN EXPOSURE

This note presents vertical concentration profiles of various size fra ctions of suspended particulate matter, measured over the first three metres from ground in a street canyon, using a novel sampling system. The daily average percentage difference of airborne particulate matter concentration between receptor heights 0.81 and 2.88 m, with the lowe r height taken as reference, was more than 35% for PM10 and more than 12% for the inhalable fraction, for 5 out of the 7 days of measurement . These preliminary measurements, carried out during June-August 1997, consisting of 37 h of data, corroborate the idea put forward by Cells and Micallef (Atmospheric Environment 31, 4253-4254), that different height groups of the population are exposed to different concentration s. Air-quality standards, based on human exposure estimates, should ta ke this variation into account. These measurements also have implicati ons for the siting of urban air quality monitoring systems. (C) 1998 E lsevier Science Ltd. All rights reserved.