STUDY OF AEROSOLS IN INDOOR - OUTDOOR MICROENVIRONMENTS FOR URBAN HOUSEHOLDS OF DELHI

Abstract

Rapid urbanization increases the population density in urban regions, which compromises the standard of living. Indoor air quality in urban regions is a serious concern. To understand the indoor air quality in residential homes of one of the India’s most polluted cities, Delhi. This is a region where detailed studies remain scarce, especially in residential context. This study analyzed the concentration of indoor particulate matter and particle number concentration in urban clusters where significant socioeconomic differences exist within the same geographical domain. To understand the indoor air quality in residential homes of one of the India’s most polluted city, Delhi. This is a region where detailed studies remain scarce, especially in residential context. This study also estimated the seasonal variations of indoor and outdoor particle number concentrations in different socioeconomic household conditions in the urban city Delhi. This study investigated the impact of festival activities on household indoor air quality in megacity Delhi. The study included different phases and activities during the festival and normal conditions and analysed the impact of different emissions. The portable aerosol spectrometer was employed to measure quasi-ultrafine, sub-fine, fine, and coarse particle concentrations in the kitchen, bedroom, and outdoor conditions. Indoor air quality is crucial for the well-being of residents, as people spend 80% of their time indoors. Particulate matters (PM10, PM2.5, and PM1) were measured in two major indoor microenvironments (kitchen and bedroom) along with outdoors of the selected households during winter, summer, and monsoon seasons. Four major income groups were considered for the study. A poorly ventilated kitchen was found to have higher concentrations of PM10 (247 μg/m3), PM2.5 (200 μg/m3), and PM1 (153 μg/m3), respectively. Indoor, PM1 contributed ~40 to 85 % to PM10. During winter, the seasonal mean I/O ratio of PM10, PM2.5, and PM1 ranged between 1.1 and 1.8 in bedroom and between 0.8 and 2.2 in kitchen. The influence of outdoor particulate matter concentration on indoor air was observed to be high during winter, followed by summer and monsoon. The higher concentration in kitchen leads to an exposure of 0.10 μg, and in bedroom, it was 0.11 μg for adults with a higher breathing rate. The exposure depends on the xi concentration and exposure time. The PM2.5 depositions were found more in the lower lung regions. The findings of the study revealed that quasi-ultrafine (250 to 500 nm) particle concentration was high (2.1×106 #cm-3) in urban poor households during the winter season. Indoor quasi-ultrafine particle concentration ranged between ~105–106 #cm-3 in the kitchen and bedroom. In a properly ventilated kitchen, a significant reduction in indoor particle number concentration (1.2×106 #cm-3 to 7.1×105 #cm-3) was observed. The number concentration of coarse particles was found to be the lowest (< 1.1×103 #cm- 3) among other sizes. However, indoor sources resulted in a higher I/O ratio of 40. Lower- income group kitchens exhibited a higher number concentration of different-sized particles, which also influenced bedroom concentration. During the festival period, the indoor ultrafine particle concentration was found to be 6.7 × 104 #cm-3, which was the highest observed indoor concentration throughout the study. The particle number concentration of the nanoparticles in indoor environment ranged from 104 to 105 #cm-3. Ultrafine size range particles contributed up to 85% to the total particle numbers. Fireworks contributed to higher particle numbers in indoors, followed by cooking, dusting, and worshiping. The size distribution pattern of the particles emitted during cooking activities and fireworks were found to be different. Particle size range 10 to 30 nm contributed 31 % to total particle numbers on fireworks day, whereas on a normal day, it contributed only 13 %. During a normal day, 100 to 1000 nm size particles contributed ~50 % to the total particle numbers. The diurnal pattern of the indoor environment was different to the outdoor. The outdoor fireworks activities also influenced indoor pollutants with respect to trace metals, which makes the indoor air quality more toxic and affects the occupants' health. Indoor particle number concentration (PNC) varies significantly in different microenvironments. Cooking, dusting, and incense stick burning are major indoor activities that generate different-sized particle numbers. The number concentration of the quasiultrafine particles (qUFP) was found to be a maximum of (106 #cm-3), followed by subfine (105 #cm-3), fine (104 #cm-3), and coarse (103 #cm-3) particles. The winter season exhibits a higher decay period of particles in indoor. The number concentration of xii particles observed during nighttime was higher than the concentration during daytime. The particles generated during cooking took more time to decay, up to 320 minutes, followed by dusting (120 to 300 minutes) and incense stick usage (< 200 minutes). Roasting, stir frying, and gravy preparation emit a higher concentration of qUFP (4 to 5×106 #cm-3) and sub-fine (6 to 8×105 #cm-3) particles. More fine particles were generated during stir-frying (3×104 #cm-3) and coarse particles (2×103 #cm-3) were emitted at high levels during roasting. The boiling method of cooking generates a very less number of qUFP and subfine particles (< 105 #cm-3). The measured particle number concentration linearly correlated with particulate matter, and the influence of indoor sources was found to be more in the studied microenvironments. Indoor number concentrations were found to be higher than in the outdoor environment. Households with good infrastructure conditions were found to have less influence on one microenvironment than another. Improving indoor air quality relies not only on sources but also on ventilation status, built infrastructure, occupants’ behaviour, and the influence of outdoor air. Since people spend the majority of their time indoors, it will be more vulnerable to residents. Indoor pollution in households needs to be mitigated and regulated for a better standard of living.