Assessment of Air Quality in School Environments in Hanoi, Vietnam: A Focus on Mass-Size Distribution and Elemental Composition of Indoor-Outdoor Ultrafine/Fine/Coarse Particles

Abstract

Indoor and outdoor ultrafine, accumulation mode, and coarse fractions collected at two preschools (S1 and S2) in Hanoi capital, Vietnam were characterized in terms of mass-size distribution and elemental composition to identify major emission sources. The sampling campaigns were performed simultaneously indoors and outdoors over four consecutive weeks at each school. Indoor average concentrations of CO2 and CO at both schools were below the limit values recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (1000 ppm for CO2) and World Health Organization (7 mg/m3 for CO). Indoor concentrations of PM2.5 and PM10 at S1 and S2 were strongly influenced by the presence of children and their activities indoors. The indoor average concentrations of PM2.5 and PM10 were 49.4 µg/m3 and 59.7 µg/m3 at S1, while those values at S2 were 7.9 and 10.8 µg/m3, respectively. Mass-size distribution of indoor and outdoor particles presented similar patterns, in which ultrafine particles accounted for around 15–20% wt/wt while fine particles (PM2.5) made up almost 80% wt/wt of PM10. PM2.5–10 did not display regular shapes while smaller factions tended to aggregate to form clusters with fine structures. Oxygen (O) was the most abundant element in all fractions, followed by carbon (C) for indoor and outdoor particles. O accounted for 36.2% (PM0.5–1) to 42.4% wt/wt (PM0.1) of indoor particles, while those figures for C were in the range of 14.5% (for PM0.1) to 18.1% (for PM1–2.5). Apart from O and C, mass proportion of other major and minor elements (Al, Ca, Cr, Fe , K, Mg, Si, Ti) could make up to 50%, whereas trace elements (As, Bi, Cd, Co, Cr, Cu, La, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, and Zn) accounted for less than 0.5% of indoor and outdoor airborne particles. There were no significant indoor emission sources of trace and minor elements. Traffic significantly contributed to major and trace elements at S1 and S2.

Indoor and outdoor relationships of particle with different sizes in an apartment in Hanoi: mass concentration and respiratory dose estimation

“…The average contributions of fine particles (PM 2.5 ) to coarse particles (PM 10 ) in indoors are about 73.14 % and 74.08 %, those in outdoors are 57.56 % and 61.85 % during winter and summer, respectively. Thus, fine particles (PM 2.5 ) accounts for the major proportions of indoor PM 10 mass concentrations, and higher contributions of indoor fine particles on coarse particles are found in comparison with those of outdoor particles, that are agreed with previous study [11].…”

“…In the summer, proportions of NP contributions on other different sizers are higher than those in winter and proportions of indoor NP increase in comparison with those in outdoor NP. It may be understood that, indoor sources such as cooking, smoking, cleaning activities can release more NP, that were reported in previous studies [8,11,12]. The higher indoor proportions of coarse particles are explained by occupants' activities contributing mainly by the resuspension [11,13].…”

“…It may be understood that, indoor sources such as cooking, smoking, cleaning activities can release more NP, that were reported in previous studies [8,11,12]. The higher indoor proportions of coarse particles are explained by occupants' activities contributing mainly by the resuspension [11,13]. The average contributions of fine particles (PM 2.5 ) to coarse particles (PM 10 ) in indoors are about 73.14 % and 74.08 %, those in outdoors are 57.56 % and 61.85 % during winter and summer, respectively.…”

“…The concentrations of NP and fine particles in indoor are higher than in outdoor, whereas, only concentrations of coarse particles increase in outdoor in summer. The indoor PM concentrations are enriched in both seasons, which is attributable to indoor activities such as cooking, smoking and cleaning activities that can elevate the indoor fine particles [7 -9], whereas resuspensions of coarse particles are contributed by occupant's moving and sweeping [11,13]. It is fact that the investigated apartment often uses gas for cooking and microwave for heating foods daily.…”

“…Recent studies in size resolved airborne particles in atmospheric environment have been conducted in Viet Nam. The number concentrations of NP were measured in indoor and outdoor six householders in Ha Noi [9], whereas, the mass concentration and carbonaceous compositions of PM in urban location were reported [10], the publication documented the elemental composition of indoor-outdoor ultrafine/fine/coarse particles in two preschools in Ha Noi [11]. To the best ofour knowledge, no studies have been found the relationship of indoor and outdoor of particles with different sizes and dose estimation in the residential indoor environment in Ha Noi, Viet Nam.…”