Seasonal Variation of Ultrafine Particulate Matter (PM1) and Its Correlation with Meteorological Factors and Planetary Boundary Layer in A Semi-Arid Region

Abstract

The present study critically investigated the effect of meteorological parameters on the mass concentration of Ultrafine Particulate Matter (PM1) between October 2018 and September 2019 (n=102) in a semiarid region of Rajasthan, India. The concentration of PM1 ranged between 72-110.85 μg.m-3 with distinct seasonal variation. Higher PM1 concentrations are closely linked to decreased wind speeds and colder temperatures, according to the findings. The winter season showed the highest concentration followed by post monsoon and pre monsoon season. The cumulative effect of environmental variables such as temperature, relative humidity, and wind speed, as well as the height of the planetary boundary layer, was investigated using multiple regression analysis (HPBL). A significant negative correlation (p < 0.001) with HPBL and wind speed was observed in all three seasons. The temperature was found to have a significant (p<0.001) negative correlation during winters whereas in other seasons there was a positive but no significant (p>0.001) relationship. Relative humidity showed a negative relationship during withers and pre-monsoon season. The multiple regression model indicated a significant negative (p<0.001) relationship with HPBL in winters (R2=0.70) explaining the 70% effect of HPBL on mass concentration of PM1.During the post-monsoon (R2 = 0.69) and pre-monsoon (R2= 0.91) explains 69% and 91% effect of HPBL on mass concentrations of PM1.The results indicate that the concentration of PM1 cannot be explained by a single meteorological parameter but all the parameters show a cumulative effect.