Despite substantial abatement in recent years, PM10 concentrations are still liable to exceed the National
Ambient Air Quality Standard (NAAQS) in Northern Thailand. In order to design effective PM10 control
strategies, it is essential to develop an understanding of the factors influencing its temporal and spatial
variability. The objective of this study is to investigate spatial variation of PM10 concentrations in Northern
Thailand during summer 2009 by analyzing observed dataset of 14 monitoring stations. Moreover, backward
trajectory was applied in order to identify the origin of the polluted air masses. The results show strong spatial
variation of PM10 concentrations in Northern Thailand. Nevertheless, generally main variations of PM10
concentrations of measurement in Northern Thailand vary in the same trend resulting from long-range transport
of particles from open burning emission in Northern Thailand and Myanmar. The major factors affecting to
spatial variation of particulate matter in Northern Thailand are emission characteristic that are distributed
unequally across Northern Thailand and nearby country, especially emission from open burning, and the
variations of meteorological conditions. Data analysis found high meteorological variation in association with
complex terrain in Northern Thailand.