Levels and Composition of Ambient Particulate Matter at a Mountainous Rural Site in Northern Vietnam

Abstract

Samples of 24 h PM 10 and PM 2.5 were collected at a mountainous rural site of Tamdao, Vietnam, using collocated dichotomous and MiniVol samplers. The sampling was done in wet season (20 September-8 October 2005), dry season (17 December 2005-18 January 2006) and transitional season (5 April-26 April 2010). A pair of PM 2.5 and PM 10-2.5 or PM 10 samples was collected on a sampling day using quartz and mixed cellulose filters for each size fraction. The samples were analyzed for mass, BC, water soluble inorganic ions and elemental compositions. Higher PM 2.5 levels were obtained during dry season, at an average of 51 µg/m 3 , followed by the transitional season, 33 µg/m 3 , and the lowest in wet season, 25 µg/m 3 . The ratios between anions and cations, both in equivalence, were all below 1.0, but was higher for PM 2.5 than for PM 10-2.5 . The ammonium balance showed a good agreement between measured and estimated levels for PM 2.5 , suggesting that most of sulfate and nitrate were in their ammonium salts. The reconstructed mass showed high contributions from secondary inorganic particles, OM-biomass (estimated based on K + ), crustal and soot groups, which accordingly helped to reveal major contributing sources. Specifically, the high K-biomass and OM-biomass mass group in the dry season indicated the important contribution from biomass burning. The regional transport from surrounding territories to the site was investigated using 5-day HYSPLIT backward trajectories. The differences in PM mass and compositional species that were statistically significant between the seasons for similar trajectory patterns, or between patterns within a season, suggested the effects of seasons and/or air mass trajectory pathways on PM pollution. The northeast continental type of air masses observed in the dry season, with the longest continental pathway and continental origin, was associated with the highest levels of PM mass and compositional species.

Aerosol Pollutants during Agricultural Biomass Burning: A Case Study in Ba Vi Region in Hanoi, Vietnam

“…24 h PM 10 mass concentrations were on average 79 ± 35 µg m -3 and ranged from 39 to 167 µg m It exceeded the WHO (World Health Organization) 24h standard guideline value of 50 µg m -3 on 11 of total 13 measurement days, indicating that the PM level was highly impacted by pollution. The average PM 10 concentration exceeded that 67 ± 32 µg m -3 reported for a rural site in Vinh Phuc province, northwest of Hanoi city, which was not affected by BB activities (Co et al, 2014).…”

“…Since PM 2.5 mass concentrations are lower than PM 10 with typical ratios of 0.72-0.74 (Co et al, 2014), it can be concluded that PM 10 at the Ba Vi site ranged from low levels of ≤ 54 µg m -3 to high smoke intensity above 109 µg m -3 . The weather during the sampling period was characterized by high temperatures, varying from 27 to 38°C (Table 1).…”

“…The highest concentration was recorded on 4 June, in good agreement with the highest EC level observed on the same day. For comparison, daily BC levels in PM 10 averaged at 4.1 ± 1.4 µg m -3 in Vinh Phuc province, not affected by BB (Co et al, 2014). AAE, obtained from attenuation spectral dependence, was 1.4 ± 0.2 for regional aerosols (Fig.…”

Aerosol Chemical Profile of Near-Source Biomass Burning Smoke in Sonla, Vietnam during 7-SEAS Campaigns in 2012 and 2013

“…(19.6% in PM 2.5 ) in the air mass from China during the dry season (Co et al, 2014). Likewise, Hang and Oanh (2014) have reported 8 ± 4.8 µg m -3 (12.7% in PM 2.5 ) of SO 4 2-in the air mass trajectory originating from the Pacific Ocean, off the coast of South Korea and Japan, and passing over Southern China before arriving at the site in Northeastern Vietnam.…”

“…The average levels of PM 2.5 were comparable with those reported in other studies conducted in Vietnam during the dry season (the season without precipitation or less rainfall during the months of November to April in Indochina). The PM 2.5 average level at the Tamdao, north Hanoi rural site was 51 ± 32 µg m -3 (Co et al, 2014); at the Hanoi urban site, 76 ± 32 µg m -3 (Hai and Oanh, 2013), and at the Mongduong industrial site in the northeast coastline of Vietnam, 60 ± 23 µg m -3 . Other studies reporting on the influence of BB activity in Indochina Peninsula have shown that the PM 2.5 mass concentrations of 24 ± 13 µg m -3 in Phimai, Thailand (Li et al, 2013), 30 ± 24 µg m -3…”