Rainwater has been sampled weekly from five sites (nos. 1-5) in northeastern Vietnam in the period of May 1997 to Apr. 2000 (except Hoabinh site, from Aug. 1999 to Apr. 2000). Since Aug. 1999, weekly dry deposition samples including acidic gas and aerosol have been additionally collected at Hanoi (no. 4) and Hoabinh (no. 5) using filter pack system. In general, the pH in rainwater was frequently higher than 5.0. However, the trend of lower pH was observed during the winter and the beginning of autumn (from Nov. to Apr.). Interestingly, the highest frequency of the acidifying rainwater (32 %) and the lowest pH value (min. pH = 4.0) were observed in Hoabinh site. Acidic pH of rain water was also observed in Viettri (no. 3) and Hanoi (no. 4), indicating the local effects of human and industrial activities. Ca²⁺ and SO₄^2- were generally found as predominant in both rainwater and aerosol. SO₂ and NH₃ in Hanoi and Hoabinh were monitored out of corresponding environmental features.

Viet P.H., Tuan V.V., Hoai P.M., Anh N.T.K., Yen P.T.

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Từ khóa : Acidity; Aerosols; Composition; Deposition; Monitoring; pH; Rain; Environmental features; Precipitation (chemical); ammonia; calcium ion; rain; sulfate; acidity; chemical composition; precipitation quality; acid rain; acidity; aerosol; article; chemical composition; controlled study; daily life activity; environmental monitoring; filter; gas; industry; pH; precipitation; Viet Nam; water sampling; winter; Viet Nam