Characterization and sources of elemental carbon and organic carbon in fine particulate matter (PM2.5) in the Southern Key Economic Region of Vietnam

This is the first study to report the characterization and sources of organic carbon (OC) and elemental carbon (EC) in fine particulate matter (PM 2.5 ) at the Southern Key Economic Zone of Vietnam (SKER). A total of 40 PM 2.5 samples were collected in eight provinces and cities in the SKER from January to February 2022. OC and EC in the PM 2.5 samples were analyzed using a model 5L thermal/optical carbon analyzer (Sunset, USA) that followed the NIOSH870 thermal-optical transmittance (TOT) standard method. A wide variation in PM 2.5 mass concentrations was observed, ranging from 9.43 to 98.42 µg/m 3 , with an average value of 43.77 ± 27.58 µg/m 3 . This level of concentration exceeds the World Health Organization (WHO)-recommended 24-hour PM 2.5 limit of 15 µg/m 3 . Approximately 30% of the samples (12 of 40) exceeded the 50 µg/m 3 24-hour PM 2.5 limit defined in Vietnam’s ambient air quality regulation (QCVN 05:2023). The results indicated that the average concentration of OC and EC were 10.82±4.80 µg/m 3 and 2.59±1.84 µg/m 3 , respectively. The total of OC and EC accounted for 23.1% to 53.8% (average 35.1%) of the PM 2.5 mass. The OC and EC concentrations were high in some sites near industry areas. The OC/EC ratios (5.51±2.68) and carbonaceous fractions show that the main sources of carbonaceous aerosols in the SKER during the sampling time were from vehicle exhaust emissions, barbecue cooking, coal combustion and biomass combustion.