Atmospheric pollutants in Chiang Mai (Thailand) over a five-year period (2005-2009), their possible sources and relation to air mass movement

► 5-year situation of atmospheric pollutants in Chiang Mai, Thailand was analyzed. ► Ammonium from agriculture and sulfate from fuel combustion were the major ions. ► Major air mass approaching Chiang Mai came from southwest direction. ► Long range transport and local emission play important role on air pollution. ► Haze phenomenon in dry season was related with open burning.