The effects of meteorological conditions and long-range transport on PM2.5 levels in Hanoi revealed from multi-site measurement using compact sensors and machine learning approach

Research Priorities of Applying Low-Cost PM2.5 Sensors in Southeast Asian Countries

“…The average PM 2.5 concentration was 19.1 µg/m 3 in the Petaling Jaya area near Kuala Lumpur using AiRBOXSense, as shown in Table 2 [79]. Compared to those measurements during biomass burning with more than 100 µg/m 3 [32][33][34][35], this demonstrated the significant impacts of the transboundary transport of biomass burning on ambient PM 2.5 levels in Malaysia during burning seasons. Therefore, the multiple deployments of LCPMS in downwind locations can be used to assess the biomass burning impacts due to regional transport in the ambient PM 2.5 levels in areas without EPA stations in SEA.…”

“…In addition, at the household level, a study in Hanoi, Vietnam, showed that incense burning caused a spectacular increase in indoor PM 2.5 concentrations; the indoor PM 2.5 concentrations at homes that used incense sticks increased by 61.6% compared to the homes that did not, which was determined using an AirVisual Pro Monitor (IQ Air, Switzerland) [59]. Additionally, the high concentrations of PM 2.5 due to incense burning were found during the Lunar New Year holidays in another study in Hanoi, Vietnam, using Panasonic PM 2.5 sensors (Panasonic Corporation, Japan) [33]. These studies demonstrated that incense burning caused high personal PM 2.5 exposures and high PM 2.5 levels in households and communities [13,59].…”

“…Particularly during dry seasons, biomass and agricultural burning significantly impact the air quality in SEA, with high PM 2.5 concentrations usually affected by regional wind directions, high temperatures, low rainfall, and phenomena such as the El Niño-Southern Oscillation (ENSO) [30,31]. Field campaigns for biomass and agriculture burning using LCPMS in Asia have been conducted, indicating high PM 2.5 concentrations in Hanoi [32,33], the northern region of Thailand [34], and New Delhi [35] during biomass burning episodes; sometimes the PM 2.5 levels exceeded 100 µg/m 3 . The PM 2.5 concentrations were influenced by the number of hot spots and wind direction toward the sampling stations.…”

“…Consequently, Asian people may be regularly exposed to high levels of PM 2.5 during burning periods [7]. This certainly causes significant health risks for Asian people at any age [33,57].…”

“…In Vietnam, most of the studies using LCPMS have been conducted in the last five years, and mainly in the two largest cities, Hanoi and Ho Chi Minh City. These studies focused on assessing the effectiveness and feasibility of LCPMS [85,93], applying LCPMS in small pilot studies to monitor the ambient PM 2.5 levels [85,93] or to verify an air-quality forecasting system of PM 2.5 [84], in consideration of the impacts of meteorological variables and longrange transports [32,33] (Table 2). These studies all applied calibrated LCPMS but with different reference instruments or calibration approaches.…”