Characterising particulate matter source contributions in the pollution control zone of mining and related industries...

Na Phra Lan Subdistrict is a pollution control zone with the highest PM₁₀ level in Thailand. Major mobile and industrial sources in the area are related to stone crushing, quarrying and mining. This study used statistical techniques to investigate the potential sources influencing high PM₁₀ levels in Na Phra Lan. Hourly PM₁₀ data and related parameters (PM_2.5, PM_coarse and NO_x) from 2014-2017 were analysed using time series, bivariate polar plot and conditional bivariate probability function (CBPF). Results of diurnal variation revealed two peaks of PM₁₀ levels from 06:00-10:00 and 19:00-23:00 every month. For seasonal variation, high PM₁₀ concentrations were found from October to February associated with the cool and dry weather during these months. The bivariate polar plot and CBPF confirmed two potential sources, i.e., resuspended dust from mobile sources close to the air quality monitoring station (receptor) and industrial sources of mining, quarrying and stone crushing far from the station on the northeast side. While the industrial source areas played a role in background PM₁₀ concentrations, the influence of mobile sources increased the concentrations resulting in two PM₁₀ peaks daily. From the study results, we proposed that countermeasure activities should focus on potential source areas, resuspended road dust from vehicles and the industrial sources related to quarrying and mining, rather than distributing equal attention to all sources.