Impact on Visibility and Air Quality from Bushfire Smog in Northern Thailand

摘要

Bushfire events frequently occur during the dry season in northern Thailand. From December to May, this region experiences persistent dry weather and low moisture which create ideal conditions for fire. The sources could be from natural bushfires or burning of agricultural waste materials spreading to the forest. Statistical analysis of daily PM_(10), daily visibility estimates and frequency of bush fire data from 2011 to 2013 were used to establish correlations between pollutant levels in the region and the visibility problems. Based on the monthly averages in 8 provinces, there was a significant correlation between PM_(10) and fire frequency, r = 0.93, 95%CI withp＜ 0.05. The reverse correlation (-r) between PM_(10) data and visibility distance were 0.91, 0.92 and between frequency of fire and visibility distance were 0.86, 0.83 in Chiang Mai and Chiang Rai provinces, respectively. In addition to the daily meteorological visibility data, the local visibilities were determined by photographic analysis, video-camera recordings and global positioning system (GPS). The observed images during periods without bushfires had better visibility than during bushfires. These results indicated the association between visibility and fire events. This work is aimed at creating awareness of the impact on visibility due to bushfires and its pollutants. The results could be applied in fire control planning and bush burning impact studies. Visibility monitoring in the future could involve imaging analysis, meteorological forecasting resources, including real-time satellite imaging and accurate air quality forecasts.