Influence of the meteorological conditions and some pollutants on PM concentrations in Lamphun, Thailand.

Particulate matter (PM) has been occurring regularly during the dry season in the upper north of Thailand including Lamphun Province that might be influenced by various factors including climatologic and other pollutants. This paper aims to investigate the climatologic and gaseous factors influencing the occurrence of PM concentration using Pollution Control Department (PCD) data. The secondary data of 2009 to 2017 obtained from the PCD was used for analysis. We used descriptive statistics, Pearson's correlation coefficient, multiple regression and graphic presentation using R program (R packages of 'open air' and 'ncdf4') and Microsoft Excel Spreadsheet®. In addition, the periodic measurement of PM and PM were investigated to determine the ratio of PM/PM. The results indicated that haze episodes (daily PM concentration always over the PCD standard) normally occur during the dry season from February to April. The maximum concentration was always found in March. The PM concentration was negatively associated with relative humidity and temperature while the PM concentration showed a strongly positive association with CO and NO concentration with correlation values of 0.70 and 0.57, respectively. Furthermore, we found CO and PM concentration was associated with ozone concentration. This finding will benefit local communities and the public health sector to provide a warning system for preparation and response plans to react to PM episodes in their responsible areas.