Assessment of particulate matter and particle path trajectory analysis using a HYSPLIT model over Dire Dawa, Ethiopia

Abstract

This work deals with the assessment of particulate matter (PM1, PM2.5, and PM10) over Dire Dawa during the month of May 2021. In the study, purple sensor (PS) and gravimetric methods (GM) were used. The purple sensor was to provide real-time measurements of PM1.0, PM2.5, and PM10 particulates. The GM instruments were constructed using wood with 1 m height (distance to ground), with flat board on top of which filter papers were placed to collect particulate matter. The difference in filter paper weight before and after sampling was used to calculate the particle masses. By dividing the weight gain of the filter by the amount of air measured, the concentrations of suspended particulate matter in the defined size range were estimated. The mean value of PM10 indicated a good status whereas the mean value of PM2.5 revealed a moderate condition as far as pollution is concerned. The purple sensor detected relatively higher values for PM10 measurement as compared to GM method during the study period. According to the calculated results of the ratio of mass concentration of PM1.0 to PM10, coarse particles were dominant whereas in the ratio of PM2.5 to PM10 both coarse and fine mode particles were equally present during the sampling period. The spatial distribution showed variations depending on the locations where the sampling filter papers were placed. The HYSPLIT backward trajectory analysis indicated various air masses and transport channels during different seasons. The predominant pathways were from both urban and desert origins.