LAUSR

Semi-volatile organic compounds (SVOCs) of polycyclic aromatic hydrocarbons (PAHs) and organo-chlorinated pesticides (OCPs) were sampled (24 h, Hi-Vol XAD-2) in dry and wet season, and separately analyzed for particulate and gaseous phases. To reveal the influence of rice straw open burning (RSOB), SVOC levels and profiles were comparatively analyzed between two areas, rice plantation area (KL) with intensive RSOB activities and remote national park (KY), and with fresh RSOB smoke. PAHs were significantly higher in KL than KY in both seasons. PAHs levels in KL during burning season were ∼10 times above the wet season indicating RSOB influence. In KY, however, PAHs levels in wet season were 2 times above dry season suggesting impacts of local emission transport. OCPs levels were not statistically different between 2 seasons and between 2 sites in each season. RSOB smoke contained 5880 ng/m3 of 14 PAHs and 13.5 ng/m3 of 16 OCPs which were respectively 14 and 7 times above those in KL during burning period. The 4-ring compounds, most remarkably fluoranthene, and 5-ring (BbF and BaP) were dominant PAHs species in RSOB smoke. Similarity in PAH profiles and diagnostic ratios between KL dry season and RSOB smoke suggested its strong influence on the local air quality. Elevated OCPs levels in RSOB smoke may be associated with re-emission of the compounds accumulated in the paddy soil during the burning. RSOB in Southeast Asia has a serious implication on exposure to the toxic air pollutants hence should be eliminated with priority.