Suspension of Crustal Materials from Wildfire in Indonesia as Revealed by Pb Isotope Analysis

Abstract

Southeast Asia experiences recurring wildfire events. Aerosol particles from these wildfires include metal species, which are suggested to have critical influences on the environment and climate. However, the mechanisms for emission of these elements from the wildfires in the region remains unclear. We analyzed both the elemental composition and the isotope ratios of lead (Pb), which is an environmentally important element. Our samples were collected in Singapore as the total suspended particulate (TSP) matter during 2013, especially focusing on the wildfire haze period in June. The Pb isotope ratios for wildfire fuels as well as crustal materials in the region were also analyzed. The Pb isotopic ratios during the haze period ( 208 Pb/ 207 Pb = 2.448 ± 0.013 and 206 Pb/ 207 Pb = 1.169 ± 0.012) were significantly (p < 0.05) different from those of the non-haze period ( 208 Pb/ 207 Pb = 2.438 ± 0.006, 206 Pb/ 207 Pb = 1.159 ± 0.005). This difference demonstrates that the suspension of the crustal material is the dominant emission source of TSP. Comparison of elemental composition (Al/Pb) with previous studies in the region, which have dominantly been sampled as PM 2.5 , suggests that the emission mechanism of particulate matter from wildfire in the region is likely size-dependent. We suggest that the suspension of crustal soil material needs to be included in future emission inventory for wildfire emission.

Neutralization of Anthropogenic Acidic Particles by NH3 From Wildfire Over Tropical Peatland

“…Detailed characteristics of the observation site are provided in our previous publications (Budisulistiorini et al., 2017, 2018; Chen et al., 2018; Das et al., 2023; Yang et al., 2021). Briefly, Singapore is closely located to the tropical peatland in Indonesia, including the ones in Sumatra and Kalimantan islands (Figure 1).…”

“…In the following, these observation periods will be called as "2015 October," "2018 October," "2019 April," and "2019 September-October," respectively. Detailed characteristics of the observation site are provided in our previous publications (Budisulistiorini et al, 2017(Budisulistiorini et al, , 2018Chen et al, 2018;Das et al, 2023;Yang et al, 2021). Briefly, Singapore is closely located to the tropical peatland in Indonesia, including the ones in Sumatra and Kalimantan islands (Figure 1).…”

The Atmospheric Input of Dissolvable Pb Based on the Radioactive 210Pb Budget in the Equatorial Western Indian Ocean

“…Third, Pb released into the atmosphere from wildfires in southeast Asia and Australia may have been transported by seasonal and easterly winds and deposited into the Indian Ocean. Das et al [41] determined that the ratios of Pb isotopes ( 208 Pb/ 207 Pb and 206 Pb/ 207 Pb) increased during wildfire haze periods in Indonesia, and suggested that the suspension of the crustal material was the dominant emission source of total suspended particulate (TSP) matter. Fourth, it could be the result of the additional dissolution of particulate Pb from the artificial origin (i.e., especially fine particulate forms smaller than 50 µm, which are dissolved very efficiently), which is continuously introduced to the water column on the way to being exported to the deeper layer.…”