P. D. Hien, V. T. Bac, N. T. H. Thinh Vietnam Atomic Energy Commission

Observations & Approach Observations & Approach Mean PM 10 = 89  gm -3, mean PM 2.2 = 37  gm h PM 10 > 150  gm -3 on days/year, Preliminary source characterization showed mineral dust and long-range transport sulfate are dominant in the coarse and fine fraction, Comparative study on urban and rural pollution would provide significant information on properties and sources of coarse and fine PM 10, For that purpose, coarse and fine PM10 samples were analyzed for elements (Al, Ca, Cl, Fe, K, Mg, Mn, Pb, Si, Ti, V, Zn) by PIXE and water soluble ions (Ca 2+, Mg 2+, K +, Na +, NH 4 +, Cl-, SO 4 2-, NO 3 - ) by IC Dionex 600

Hanoi Lucnam

Hanoi-to-Lucnam concentration ratios

Urban vs. rural PM 10  Coarse mass is 2 times higher in urban  But, fine mass is similar, about 31  gm -3  Fine SO 4, K, K +, BC are similar  Ca 2+ (construction), Pb and Zn (vehicle) are from 3-5 times more abundant in urban,  NH 4 + more abundant in rural,

Similar sources of PM 10 at two sites Coarse: Soil-nitrate, soil-sulphate, distant and local coal fly ash, sea salt, ammonium sulphate, Fine: Long-range transport, soil dust, distant and local coal fly ash, Cl-depleted marine aerosols, biomass burning, But Vehicle derived dust (coarse and fine) found only at the urban site.

Findings (coarse) Soil-derived dust 3 times more abundant at urban site, But coal fly ash is little more abundant at rural site, Common distant coal burning sources affects both sites Mineral dust (MD) provides sites for nitrate and sulfate formation by reactions with nitrogen and sulfur gases. Nitrate bound mainly to Ca-richest soil dust, Sulfate formed on soil dust (with higher Ca/Si ratio) rather than coal fly ash, Coarse ammonium sulfate found on soil organic matter fraction

Findings (fine) The loadings of LRT aerosols are similar (~11  gm -3 ) and largest at both sites – Trans-boundary pollution. LRT aerosols are soot particles (containing EC and K) incorporating SO 4 & NH 4 during atmospheric transport of air masses, Coal fly ash – largest source at rural and second largest source at Hanoi site, Vehicles contribute 3 times less than coal burning at Hanoi and insignificant at rural areas. Biomass burning: 2 times weaker in Hanoi.

Summary

Implications on AQ management  It is a mistake that air quality in rural areas is not “a matter of concern”. In fact, PM 2.5 is not less abundant in rural than urban areas,  Coal fly ash and soil dust are major components of PM 10 in northern Vietnam that should be adequately addressed to improve air quality, Toxic nitrogen and sulfur gases are absorbed on soil and soot particles and transformed into nitrate and sulfate, LRT accounts for ~20% of PM 10 mass in both rural and urban areas indicating the importance of transboundary pollition in the region.