Source apportionment of black carbon aerosols from light absorption observation and source-oriented modeling: an implication in a coastal city in China

Abstract

Abstract. Black carbon (BC) is the most important light-absorbing aerosol in the atmosphere. However, sources of atmospheric BC aerosols are largely uncertain, making it difficult to assess its influence on radiative forcing and climate change. In this study, year-round light-absorption observations were conducted during 2014 using an aethalometer in Xiamen, a coastal city in Southeast China. Source apportionment of BC was performed and temporal variations in BC sources were characterized based on both light absorption measurements and a source-oriented air quality model. The annual average concentrations of BC from fossil fuel (BCff) and biomass burning (BCbb) by the aethalometer method were 2932 ± 1444 ng m−3 and 1340 ± 542 ng m−3, contributing 66.7 % and 33.3 % to total BC, respectively. A sensitivity analysis was performed with different absorption Ångström exponent (AAE) values of fossil fuel combustion (αff) and biomass burning (αbb), suggesting that the aethalometer method was more sensitive to changes in αbb than αff. BCbb contribution exhibited a clear diurnal cycle, with the highest level (37.9 %) in the evening rush hour and a seasonal pattern with the maximum (39.9 %) in winter. Conditional probability function (CPF) analysis revealed the large biomass-burning contributions were accompanied by east-northeasterly and northerly winds. Backward trajectory indicated that air masses from North and East–Central China were associated with larger biomass-burning contributions. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) suggested that North and East–Central China and Southeast Asia were potential sources of both BCff and BCbb. The source-oriented modeling results showed that transportation, residential and open biomass burning accounting for 45.3 %, 30.1 % and 17.6 % were the major BC sources. Among the three fuel catalogs, liquid fossil fuel (46.5 %) was the largest source, followed by biomass burning (32.6 %) and coal combustion (20.9 %). Source contributions of fossil fuel combustion and biomass burning identified by the source-oriented model were 67.4 % and 32.6 %, respectively, close to those obtained by the aethalometer method. The findings provide solid support for controlling fossil fuel sources to limit the impacts of BC on climate change and environmental degradation in the relatively clean region in China.

Stable Isotopes Reveal Photoreduction of Particle-Bound Mercury Driven by Water-Soluble Organic Carbon during Severe Haze

“…In fact, WSOC in unban atmosphere is more abundant, 75 compared to remote areas, as a result of anthropogenic sources emission from liquid fossil fuel, biomass burning, and coal combustion. 77 Therefore, during haze episodes with increasing humidity, the photoreduction of Hg(II) on particles could be enhanced due to the increased availability of WSOC. The potential impacts of this process on atmospheric deposition of Hg and its ecological risks should be reappraised in future monitoring programs and in the policy making with respect to environmental Hg toxicity.…”

“…However, our data show large positive odd-MIF for PBM in the urban area as a result of PBM photoreduction driven by WSOC. In fact, WSOC in unban atmosphere is more abundant, compared to remote areas, as a result of anthropogenic sources emission from liquid fossil fuel, biomass burning, and coal combustion . Therefore, during haze episodes with increasing humidity, the photoreduction of Hg­(II) on particles could be enhanced due to the increased availability of WSOC.…”

Atmospheric oxidation capacity and ozone pollution mechanism in a coastal city of southeastern China: analysis of a typical photochemical episode by an observation-based model

“…The maximum hourly temperature was as high as 35 • C, and the average RH was 56.4 ± 12.6 %. Our previous study showed that particulate pollution was slight in Xiamen, which could affect solar radiation by the light-absorbing component, and the concentrations of particulate matter had not exceeded the National Ambient Air Quality Standard (Class II: 75 µg m −3 ) for a whole year (Hu et al, 2021;Deng et al, 2020). Therefore, solar radiation intensity and J (NO 2 ) were strong, compared to those of the Yellow River Delta (Chen et al, 2020), Shanghai (Zhu et al, 2020), and Hong Kong (Xue et al, 2016).…”

Air Quality and Climate Impacts of Biomass Use as an Energy Source: A Review

“…A recent report suggested that increased coverage of aethalometer networks could enhance our ability to track long-term changes in PM from biomass burning, since they can be run in a more automatic way and in general have reasonable correlations with chemical tracer methods . Several examples of long-term trend analysis of atmospheric particulates using aethalometers exist in the literature. − Such studies have facilitated the separation of the effects of localized emissions from wood burning from particulate episodes which occurred due to long-range transport. , They have also provided data on the diurnal and seasonal variability in ratios of BC to OC, which is important for understanding the optical properties of carbonaceous aerosols, thus potentially reducing uncertainties within climate models. , From a policy perspective, availability of long-term trend data is incredibly useful, since the impacts from wood burning on ambient AQ are likely to be less important for breaches of specific concentration targets, but will have greater effects with respect to PM 2.5 exposure reduction targets within for example, EU AQ directives. Long-term aethalometer data can be used to determine the time dependence of source contributions to carbonaceous PM .…”

“…81−83 Such studies have facilitated the separation of the effects of localized emissions from wood burning from particulate episodes which occurred due to long-range transport. 81,83 They have also provided data on the diurnal and seasonal variability in ratios of BC to OC, which is important for understanding the optical properties of carbonaceous aerosols, thus potentially reducing uncertainties within climate models. 84,85 From a policy perspective, availability of long-term trend data is incredibly useful, since the impacts from wood burning on ambient AQ are likely to be less important for breaches of specific concentration targets, but will have greater effects with respect to PM 2.5 exposure reduction targets within for example, EU AQ directives.…”