Estimation of Metal Emissions From Tropical Peatland Burning in Indonesia by Controlled Laboratory Experiments

Abstract

The tropical peatland burning in Indonesia is one of the most significant types of wildfires on a global scale. Previous studies indicated the importance of metal emissions from Indonesian wildfires. However, metal emission profiles from Indonesian wildfires have not been quantified well yet. To address this issue, we analyzed metals and metalloids emitted from combustion experiments of peat and vegetation growing over peatland in Indonesia. The analyzed elements include Mg, Al, Ca, V, Cr, Fe, Co, Ni, Cu, Zn, Se, Sn, and Pb. The emission ratios of aerosol particles emitted from combustion of the ombrotrophic peat and vegetation agreed within a factor of few, regardless of the variability in the elemental compositions of the original fuel. In both cases, the emission ratios of Ca were the highest, followed by crustal elements Fe and Al. The concentration ratios of crustal and biogenic elements (Fe/Al and Zn/Fe) were found to be a useful metric to infer dominant fuel types. Namely, the concentration ratio of Fe/Al was high (6.2 ± 4.4) for peat combustion particles, while the value was lower (1.9 ± 1.3) when plant burning was conducted. The emission ratios of the metals were combined with an existing emission inventory to estimate the emission rates of the analyzed metals. The emission rates of carcinogenic metals, such as Cr and Ni, were estimated to be 0.02 and 0.013 Gg/year, respectively. The analysis also indicated that the peatland burning could be one of the important sources of atmospheric Fe in the region.

Metal Concentrations and Source Apportionment of PM2.5 in Chiang Rai and Bangkok, Thailand during a Biomass Burning Season

“…In the case of plants, Fe and Zn are micronutrients that are preferentially taken up from soil while Al is considered as a toxin for plants as it inhibits root elongation . Metals emitted from combustion experiments of vegetation from Indonesia have an Fe/Al ratio (0.20–2.73) and a Zn/Al ratio (0.06–1.70), which are higher than the values of haze-related PM 2.5 from Chiang Rai (Figure ). The Fe/Al ratio of PM 2.5 in Chiang Rai ranges from 0.87 to 2.30 and shows a moderately strong negative correlation ( r 2 = −0.72) with PM 2.5 .…”

“…Zn can come from a variety of sources including coal combustion, nonferrous metal production, and industrial emissions . In the case of plants, Fe and Zn are micronutrients that are preferentially taken up from soil while Al is considered as a toxin for plants as it inhibits root elongation . Metals emitted from combustion experiments of vegetation from Indonesia have an Fe/Al ratio (0.20–2.73) and a Zn/Al ratio (0.06–1.70), which are higher than the values of haze-related PM 2.5 from Chiang Rai (Figure ).…”

“…Relationship between Fe/Al and Zn/Al in Chiang Rai and Bangkok aerosols. Average UCC ratio and aerosol generated by biomass burning from Indonesia are plotted for reference.…”

“…There have been several studies on source apportionment of metals in PM generated from biomass burning in Southeast Asia; ,,− however, none of the studies used isotope ratios as a “fingerprinting” tool. Lead (Pb) isotopes are an efficient tool for tracing the sources of Pb pollution , as Pb isotopes do not fractionate during industrial and environmental processes and preserve the source signature even after degradation, processing, and transportation .…”

“…The residence time of Pb aerosols in the atmosphere is around ∼5−10 days. 95 Hence, transboundary pollution remains an important source of atmospheric 66,99 and river sediments in Asia 99 as representative of crust soil in the region and Indonesian plant 18 as representative of biomass burning aerosol from northern Thailand.…”