Source apportionment of carbonaceous aerosols using hourly data and implications for reducing PM2.5 in the Pearl River Delta region of South China

Ambient fine particulate matter (PM2.5) levels in South China have been decreasing in the past decade, but the decreasing rates differed between its major chemical components, e.g., with much small rates for carbonaceous aerosols than for secondary inorganic aerosols. To investigate the sources of carbonaceous aerosols in this region, a comprehensive campaign was carried out in urban Guangzhou in the winter of 2019-2020 using a combination of various instruments. Data generated from this campaign include hourly total carbon (TC), black carbon (BC), criteria air pollutants and meteorological parameters, 4-hourly particle-bound elements, and chemically-resolved daily PM2.5. Similar diurnal patterns were observed for TC, CO and NO2, suggesting TC was very likely related to vehicle exhaust emission. Secondary organic carbon (SOC) estimated using the Minimum R squared (MRS) method accounted for 35 +/- 17% of OC, indicating strong atmospheric oxidation capacity. Four major source factors for carbonaceous aerosols were identified by positive matrix factorization (PMF) model, including coal combustion, traffic emissions, soil dust and ship emissions, which accounted for 37 +/- 23%, 39 +/- 23%, 14 +/- 10% and 10 +/- 13%, respectively, of TC mass concentration, 38 +/- 24%, 38 +/- 23%, 14 +/- 10% and 10 +/- 12%, respectively, of OC mass concentration, and 29 +/- 21%, 43 +/- 22%, 14 +/- 11% and 14 +/- 15%, respectively, of EC mass concentration. Among these sources, traffic emission was the most important one, suggesting the necessity for promoting clean energy vehicles and relieving urban traffic congestion.

Automated summary

Ambient fine particulate matter (PM2.5) levels in South China have been decreasing, with carbonaceous aerosols showing a smaller decrease rate. A comprehensive campaign in urban Guangzhou revealed that traffic emissions were the most important source of carbonaceous aerosols, highlighting the importance of promoting clean energy vehicles and relieving urban traffic congestion.