Ensemble source apportionment of air pollutants and carbon dioxide based on online measurements

Air pollution and climate change have attracted worldwide attention due to their significant threats to human health and the environment. To maximize the co-benefits of clean air policies on greenhouse gas emissions and vice versa, it is imperative to coordinate emission control measures for air pollutants and carbon dioxide (CO₂). To do this, we first need to better quantify the impacts of different sources to air pollutants and CO₂ at once. Based on a 2-year observation of fine particulate matter (PM_2.5), gaseous pollutants (including sulfur dioxide (SO₂), nitrogen oxides (NO_x), initial volatile organic compounds (In–VOCs)), as well as CO₂, we apportioned the sources of criteria air pollutants and CO₂ simultaneously. We then developed a new source apportionment method to quantitatively determine the relative impacts of different emission sources on (1) gaseous pollutants ensemble (SO₂-NO_x-In-VOCs) and (2) PM_2.5 and CO₂ ensemble (PM_2.5-CO₂). The results demonstrate that vehicle exhaust (35%), industrial emissions (31%), biomass burning (18%), and coal combustion (16%) were the main control targets for the SO₂-NO_x-In-VOCs ensemble, and they were also the dominant contributors to PM_2.5-CO₂ ensemble with similar contribution rates. Not surprisingly, the source impacts are substantially different for the two studied ensembles to those of individual air pollutant alone. This study provides a new source apportionment method to deliver scientific evidence for developing a coordinated strategy to maximize the benefits of clean air and carbon policies to air quality and the climate.