Abstract
Carbonaceous particles have been confirmed as major components of ambient aerosols in urban environments and are related to climate impacts and environmental and health effects. In this study, we collected different-size particulate matter (PM) samples (PM1, PM2.5, and PM10) at an urban site in Lanzhou, northwest China, during three discontinuous one-month periods (January, April, and July) of 2019. We measured the concentrations and potential transport pathways of carbonaceous aerosols in PM1, PM2.5, and PM10 size fractions. The average concentrations of OC (organic carbon) and EC (elemental carbon) in PM1, PM2.5, and PM10 were 6.98 ± 3.71 and 2.11 ± 1.34 μg/m3, 8.6 ± 5.09 and 2.55 ± 1.44 μg/m3, and 11.6 ± 5.72 and 4.01 ± 1.72 μg/m3. The OC and EC concentrations in PM1, PM2.5, and PM10 had similar seasonal trends, with higher values in winter due to the favorable meteorology for accumulating pollutants and urban-increased emissions from heating. Precipitation played a key role in scavenge pollutants, resulting in lower OC and EC concentrations in summer. The OC/EC ratios and principal component analysis (PCA) showed that the dominant pollution sources of carbon components in the PMs in Lanzhou were biomass burning, coal combustion, and diesel and gasoline vehicle emissions; and the backward trajectory and concentration weight trajectory (CWT) analysis further suggested that the primary pollution source of EC in Lanzhou was local fossil fuel combustion.
Highlights
Carbonaceous aerosols, including elemental carbon (EC) and organic carbon (OC) [1], have significant effects on human health, the global climate, and visibility reduction [2,3,4]
The uncertainty is due to the arbitrariness when selecting the ratio of primary organic carbon (POC) to EC, because they are affected by various factors, e.g., meteorology, diurnal and seasonal fluctuations in emissions, and local emission sources
Precipitation played a key role in scavenge pollutants, resulting in lower OC
Summary
Carbonaceous aerosols, including elemental carbon (EC) and organic carbon (OC) [1], have significant effects on human health, the global climate, and visibility reduction [2,3,4]. Carbonaceous aerosols deposited on ice and snow surfaces can reduce surface albedo by absorbing more solar radiation, accelerate glacier melting, and result in glaciers changing [9,10,11]. It is of great significance for us to understand the characteristics of carbonaceous aerosols, including their temporal and spatial distribution and their contribution to air pollutants. Some megacities in China, such as Beijing, Tianjin, and some others, have widely carried out investigations on carbonaceous aerosols, insofar as anthropogenic emissions have caused serious air pollution [18,19,20,21,22,23]. The results would help one to understand the characteristics of air pollution in Northwestern China and to propose more effective local air pollution control measures
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