Transport Of Carbonaceous Aerosols Research Articles

Causes and Effects of the Long‐Range Dispersion of Carbonaceous Aerosols From the 2019–2020 Australian Wildfires

AbstractAustralia experienced record‐breaking wildfires during 2019–2020, which emitted large amounts of carbonaceous aerosols (CAs) to the atmosphere. In this study, we explored the atmospheric dynamics and thermodynamic mechanism of the long‐range transport of CAs during November 2019–February 2020. The results indicate that the emitted CAs had a ternary advective spreading pattern across the Pacific Ocean in the Southern Hemisphere (SH), influenced mainly by the westerlies and anticyclonic systems. Upward vertical motion over the convergence zone and heat released from smoke pyro‐cumulonimbus clouds and strong light absorption of CAs provided strong vertical lift as the predominant injection pathway of the CAs into the stratosphere in the central Pacific Ocean in the SH. The abundant tropospheric CAs induced atmospheric heating (and potentially surface cooling), with increasing air temperature and decreasing of surface temperature. The anomalous thermal structure led to changes in atmospheric circulation, which weakened the upward vertical motion.

Emission and Transport of Carbonaceous Aerosols in Urbanized Coastal Areas in China

Elemental and organic carbon (EC and OC), the principal short-lived climate forcers, were measured in fine particulate matter (PM2.5) collected at urban and rural sites in continental edge in Southern China. The carbonaceous matter (CM) contributed an average of 28.5 ± 7.2% (1 SD) of the mass of PM2.5 in urban areas and 30.3 ± 8.2% in rural areas. The annual average OC concentrations in PM2.5 in urban and rural areas were 7.6 ± 4.3 and 5.7 ± 3.1 μg/m3, respectively; and the annual average EC concentrations were 2.4 ± 0.8 and 1.3 ± 0.7 μg/m3, respectively. The higher EC concentration in urban area than in rural area showed significant anthropogenic emissions to the urban atmosphere. EC and OC concentrations displayed good correlation in samples collected in urban area during winter monsoon season, suggesting a dominant emission source (mostly traffic-related) in urban area. The carbonaceous aerosol pollution in the rural coastal receptor area can be attributed to the local emission and transport of air pollutants from urbanized areas in the eastern part of China. The surface observation together with backward trajectory analysis, satellite imaging, and meteorological simulation indicate that air pollutants transported from emission hotspots in the urbanized Eastern China area had caused an increase in the concentration of carbonaceous aerosols in the rural continental edge by a factor of 2–3. This significant aerosol forcing of the Chinese outflow plume should be paid attention in the study of air quality and climate changes in Eastern/Southern Asia.

Concentrations, seasonal variations, and transport of carbonaceous aerosols at a remote Mountainous region in western China

Carbonaceous aerosol concentrations were determined for total suspended particle samples collected from Muztagh Ata Mountain in western China from December 2003 to February 2006. Elemental carbon (EC) varied from 0.004 to 0.174 μg m −3 (average = 0.055 μg m −3) while organic carbon (OC) ranged from 0.12 to 2.17 μg m −3 and carbonate carbon (CC) from below detection to 3.57 μg m −3. Overall, EC was the least abundant fraction of carbonaceous species, and the EC concentrations approached those in some remote polar areas, possibly representing a regional background. Low EC and OC concentrations occurred in winter and spring while high CC in spring and summer was presumably due to dust from the Taklimakan desert, China. OC/EC ratios averaged 10.0, and strong correlations between OC and EC in spring–winter suggest their cycles are coupled, but lower correlations in summer–autumn suggest influences from biogenic OC emissions and secondary OC formation. Trajectory analyses indicate that air transported from outside of China brings ∼0.05 μg m −3 EC, ∼0.42 μg m −3 OC, and ∼0.10 μg m −3 CC to the site, with higher levels coming from inside China. The observed EC was within the range of loadings estimated from a glacial ice core, and implications of EC-induced warming for regional climate and glacial ice dynamics are discussed.

Sources, determination, monitoring, and transport of carbonaceous aerosols in Mainz, Germany

Total atmospheric particulate matter, total carbon (TC), and black carbon (BC) were measured over two periods, spring and summer 1994, at a sampling location in Mainz, Germany. An optical (aethalometer) and a thermal method were used to determine BC since previous studies have shown that the optical method is dependent on the source of aerosols. The thermal method chosen for calibration enables the determination of molar hydrogen to carbon ratios for total particulate carbon and BC if quartz fiber filters were pre-treated at 850°C for 4 h. A specific attenuation cross-section of ≈7 m 2 g -1 for BC on the aethalometer filter was calculated which lies between values determined for cities and remote areas. Average concentrations of total particulate matter, TC, and BC were 38±17, 8.0±3.6, and 2.8±1.2 μg m -3, respectively. The paths and thus the source regions of the air masses were obtained by three-day back-trajectories calculated daily using actual meteorological data. Linear relationships were found for BC to TC and to the total aerosol mass indicating a common source, most likely fossil fuel combustion. Despite the linear relationship between BC and TC, a correlation between the variability of the BC/TC ratio and the paths of the air masses was seen. Since organic carbon and BC do influence the solar radiation budget and perhaps atmospheric chemistry, the ratio of BC to TC may serve as a good indicator for the assessment of the impact of carbonaceous aerosols. To better assess the global climatic impact of the carbonaceous component of aerosols, long-term measurements are certainly needed with a sufficient geographical coverage. Measurements of a single component such as BC with an aethalometer, for example, will not represent the whole impact that atmospheric particulate carbon can have on the solar radiation budget and atmospheric chemistry.