Air quality assessments for NO2 and SO2 levels in indoor and outdoor environments were conducted in three suburban schools in Imphal. Season-wise, the highest NO2 and SO2 concentrations were observed during winter, while the lowest occurred during the monsoon. The concentration of SO2 in the indoor air was comparatively cleaner than in the outdoor air. Similarly, indoor air was found to be cleaner than outdoor air with respect to NO2. The overall concentration obtained for the entire study period for SO2 was 4.9±1.5 µg m-3, and for NO2, it was 9.2±3.0 µg m-3. The concentrations of the two gases obtained during the study were below the NAAQs and WHO permissible limits. Seasonal variation of SO2 concentrations between the pre-monsoon period and monsoon months and also between the monsoon period and winter months (at p<0.001) was significant. For NO2, seasonal variation in the concentrations between the monsoon and winter (at p<0.001) was found significant. The estimated I/O ratios for the two studied gases, which were below one, plus the positive correlation between the classroom and campus environment concentrations of NO2 (r=0.96), and SO2 (r=0.96), reflected the influence of the indoor air quality by outdoor pollution sources. Data on similar studies for the country’s northeastern region, in particular, is scanty, and that’s why it may provide valuable insights to the scientific world.
Measurements were carried out to determine the PM2.5, PM10 and, CO2 levels in schools located in the urban areas of Imphal, Manipur. The particulate matters (PM2.5 and PM10) were monitored gravimetrically with standardised particulate samplers, while the CO2 in the air was measured by gas chromatography. Average PM2.5 and PM10 concentration in the classrooms was 41.0 ± 9.0 µg/m3 and 79.4 ± 20.2 µg/m3, respectively, and it was comparatively higher than the outdoor concentration of 34.8 ± 8.0 µg/m3 and 64.7 ± 18.9 µg/m3, respectively. The average concentration of CO2 in the indoor and outdoor air was 1250.6 ± 131.3 ∙ 103 µg/m3 and 885.7 ± 94.7 ∙103 µg/m3. The highest levels of PM2.5 (58.3 µg/m3), PM10 (112.5 µg/m3) and CO2 (1457.5 ∙ 103 µg/m3) were recorded indoors, in a school located at the heart of the city, whereas the lowest levels of PM2.5 (25.0 µg/m3), PM10 (45.8 µg/m3) and CO2 (1045.7 ∙ 103 µg/m3) were recorded in a school located away from the city centre. The levels of PM2.5 and PM10 in the air were found to exceed the permissible limits prescribed by the National Ambient Air Quality Standards in more than half of the sampling. There was a strong positive correlation between indoor and outdoor pollutant concentrations.
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