Mass concentrations and indoor-outdoor relationships of PM in selected educational buildings in Nis, Serbia

Abstract

Mass concentrations of particulate matter (PM) fractions were measured in educational buildings in the city of Nis, Republic of Serbia. Two sampling campaigns were conducted in winter periods. The first campaign was in the period from 21 February to 15 April 2010 at the Faculty of Occupational Safety (FOS) and the second campaign was from 20 March to 4 April 2013 at the primary school Vozd Karadjordje (VK). PM measurements were carried out with low volume samplers Sven/Leckel LVS3. The average daily PM10 concentration inside the FOS (47.0 ?21.8 ?g/m3) was lower than PM10 concentration in outdoor air (50.7 ?28.1 ?g/m3). The average daily PM10 concentration inside the VK (54.6 ? 17.6 ?g/m3) was higher than in outdoor air (47.9 ? 22.8 ?g/m3). The 24 hours average PM10 concentrations at FOS exceeded the EU limit value (50 mg/m3) during 34 % of days outdoors, and 39 % of days indoors. The 24 hours average PM10 concentrations at VK exceeded the limit value during 35 % of days outdoors, and 53 % of days indoors. The 24 hours average PM2.5 concentrations at VK exceeded the WHO daily mean guideline value (25 mg/m3) during 71 % of days outdoors, and 88 % of days indoors. The average PM10 I/O ratio at VK was 1.57 during teaching hours, and 1.00 during no teaching hours. Similarly, average PM2.5 I/O ratio at VK was 1.11 during teaching hours and 0.90 during no teaching hours. Average daily PM2.5/PM10 ratio in the ambient air at VK was 0.87, and 0.82 at FOS. Very strong correlations between the indoor and outdoor PM concentrations were observed at VK during no teaching hours (r>0.8). Moderate to strong negative correlations were found between the wind speed and PM at both schools. High outdoor PM concentrations and resuspension of particles are probably the most possible reasons for the elevated indoor PM concentrations found in the study.