<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:mrow><mml:msup><mml:mi>δ</mml:mi><mml:mn>13</mml:mn></mml:msup></mml:mrow></mml:math>C signatures of organic aerosols: Measurement method evaluation and application in a source study

Zenker, Katrin; Sirignano, Carmina; Riccio, Angelo; Chianese, Elena; Calfapietra, Carlo; Prati, Maria Vittoria; Mašalaitė, Agnė; Remeikis, Vidmantas; Mook, Emily; Meijer, H. A. J.; Dusek, Ulrike

doi:10.1016/j.jaerosci.2020.105534

Cited by 15 publications

(14 citation statements)

References 38 publications

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“…The OC EF was inversely proportional to the MCE (Liu et al, 2014b;Pokhrel et al, 2016;Yokelson et al, 1997), meaning OC is predominantly emitted during RSC. For the prescribed fires, we found less volatile OC to be more depleted than more volatile OC, which is more often the case for BB burning (Yao et al, 2022;Zenker et al, 2020). The conversion EC was relatively stable, though 13 C-depleted with average fractionation of -2.2  2.3‰, which was similar in FC and RSC emissions.…”

Section: Carbon Fractionation In Different Reaction Productssupporting

confidence: 53%

“…OC and EC quantities on the filter samples were determined using a thermal-optical analyser (Sunset Laboratory Inc.), according to the EUSAAR-2 protocol. The measurement setup and measurement protocol for stable carbon isotopes of OC and EC are described in detail by Yao et al (2021) and Zenker et al (2020). To stay within the systems' measurement range of 2-24 g C, small segments of 0.13 to 3.00 cm 2 were punched from the filter samples.…”

Section: Aerosol Sampling and Analysismentioning

confidence: 99%

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Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Vernooij

Dusek

Popa

et al. 2021

Preprint

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Abstract. Landscape fires are a significant contributor to atmospheric burdens of greenhouse gases and aerosols. Although many studies have looked at biomass burning products and their fate in the atmosphere, estimating and tracing atmospheric pollution from landscape fires based on atmospheric measurements is challenging due to the large variability in fuel composition and burning conditions. Stable carbon isotopes in biomass burning (BB) emissions can be used to trace the contribution of C3 plants (e.g., trees or shrubs) and C4 plants (e.g. savanna grasses) to various combustion products. However, there are still many uncertainties regarding changes in isotopic composition (also known as fractionation) of the emitted carbon compared to the burnt fuel during the pyrolysis and combustion processes. To study BB isotope fractionation, we performed a series of laboratory fire experiments in which we burned pure C3 and C4 plants as well as mixtures of the two. Using isotope ratio mass spectrometry (IRMS), we measured stable carbon isotope signatures in the pre-fire fuels and post-fire residual char, as well as in the CO2, CO, CH4, organic carbon (OC), and elemental carbon (EC) emissions, which together constitute over 98 % of the post-fire carbon. Our laboratory tests indicated substantial isotopic fractionation in combustion products compared to the fuel, which varied between the measured fire products. CO2, EC and residual char were the most reliable tracers of the fuel 13C signature. CO in particular showed a distinct dependence on burning conditions; flaming emissions were enriched in 13C compared to smouldering combustion emissions. For CH4 and OC, the fractionation was opposite for C3 emissions (13C-enriched) and C4 emissions (13C-depleted). This indicates that while it is possible to distinguish between fires that were dominated by either C3 or C4 fuels using these tracers, it is more complicated to quantify their relative contribution to a mixed-fuel-fire based on the δ13C signature of emissions. Besides laboratory experiments, we sampled gases and carbonaceous aerosols from prescribed fires in the Niassa special Reserve (NSR) in Mozambique, using an unmanned aerial system (UAS)-mounted sampling set-up. We also provide a range of C3 : C4 contributions to the fuel and measured the fuel isotopic signatures. While both OC and EC were useful tracers of the C3 to C4 fuel ratio in mixed fires in the lab, we found particularly OC to be depleted compared to the calculated fuel signal in the field experiments. This suggests that either our fuel measurements were incomprehensive and underestimated the C3 : C4 ratio in the field, or that other processes caused this depletion. Although additional field measurements are needed, our results indicate that C3 vs C4 source ratio estimation is possible with most BB products, albeit with varying uncertainty ranges.

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Section: Carbon Fractionation In Different Reaction Productssupporting

confidence: 53%

Section: Aerosol Sampling and Analysismentioning

confidence: 99%

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Vernooij

Dusek

Popa

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The OC EF was inversely proportional to the MCE (S. Pokhrel et al, 2016;Yokelson et al, 1997), meaning OC is predominantly emitted during RSC. For the prescribed fires, we found less volatile OC to be more depleted than more volatile OC, which is more often the case for BB (Yao et al, 2022;Zenker et al, 2020). The conversion to EC was relatively stable, though 13 C-depleted with average fractionation of −2.2 ± 2.3 ‰, which was similar in FC and RSC emissions.…”

Section: Carbon Fractionation In Different Reaction Productsmentioning

confidence: 57%

“…OC and EC quantities on the filter samples were determined using a thermal-optical analyser (Sunset Laboratory Inc), according to the EUSAAR-2 protocol. The measurement set-up and measurement protocol for stable carbon isotopes of OC and EC are described in detail by Yao et al (2022) and Zenker et al (2020). To stay within the systems' measurement range of 2-24 µg C, small segments of 0.13 to 3.00 cm 2 were punched from the filter samples.…”

Section: Aerosol Sampling and Analysismentioning

confidence: 99%

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C<sub>3</sub> and C<sub>4</sub> plants

et al. 2022

Self Cite

View full text Add to dashboard Cite

Abstract. Landscape fires are a significant contributor to atmospheric burdens of greenhouse gases and aerosols. Although many studies have looked at biomass burning products and their fate in the atmosphere, estimating and tracing atmospheric pollution from landscape fires based on atmospheric measurements are challenging due to the large variability in fuel composition and burning conditions. Stable carbon isotopes in biomass burning (BB) emissions can be used to trace the contribution of C3 plants (e.g. trees or shrubs) and C4 plants (e.g. savanna grasses) to various combustion products. However, there are still many uncertainties regarding changes in isotopic composition (also known as fractionation) of the emitted carbon compared to the burnt fuel during the pyrolysis and combustion processes. To study BB isotope fractionation, we performed a series of laboratory fire experiments in which we burned pure C3 and C4 plants as well as mixtures of the two. Using isotope ratio mass spectrometry (IRMS), we measured stable carbon isotope signatures in the pre-fire fuels and post-fire residual char, as well as in the CO2, CO, CH4, organic carbon (OC), and elemental carbon (EC) emissions, which together constitute over 98 % of the post-fire carbon. Our laboratory tests indicated substantial isotopic fractionation in combustion products compared to the fuel, which varied between the measured fire products. CO2, EC, and residual char were the most reliable tracers of the fuel 13C signature. CO in particular showed a distinct dependence on burning conditions; flaming emissions were enriched in 13C compared to smouldering combustion emissions. For CH4 and OC, the fractionation was the other way round for C3 emissions (13C-enriched) and C4 emissions (13C-depleted). This indicates that while it is possible to distinguish between fires that were dominated by either C3 or C4 fuels using these tracers, it is more complicated to quantify their relative contribution to a mixed-fuel fire based on the δ13C signature of emissions. Besides laboratory experiments, we sampled gases and carbonaceous aerosols from prescribed fires in the Niassa Special Reserve (NSR) in Mozambique, using an unmanned aerial system (UAS)-mounted sampling set-up. We also provided a range of C3:C4 contributions to the fuel and measured the fuel isotopic signatures. While both OC and EC were useful tracers of the C3-to-C4 fuel ratio in mixed fires in the lab, we found particularly OC to be depleted compared to the calculated fuel signal in the field experiments. This suggests that either our fuel measurements were incomprehensive and underestimated the C3:C4 ratio in the field or other processes caused this depletion. Although additional field measurements are needed, our results indicate that C3-vs.-C4 source ratio estimation is possible with most BB products, albeit with varying uncertainty ranges.

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“…The distinction between OC and EC was based on the EUSAAR_2 protocol (Cavalli and Putaud, 2008) using the transmittance of a laser beam (λ = 630 nm) through the filter to determine the relative contribution of OC and EC of the measured filter (Bauer et al, 2009). The measurement setup and measurement protocol are described in detail by Zenker et al (2020).…”

Section: Ec/oc Analysis Using Sunset Analysermentioning

confidence: 99%

An Unmanned Aerial System (UAS) based methodology for measuring biomass burning emission factors

Vernooij

Winiger

Wooster

et al. 2022

Preprint

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Abstract. Biomass burning (BB) emits large quantities of greenhouse gases (GHG) and aerosols that impact climate and adversely affect human health. Although much research has focused on quantifying BB emissions on regional to global scales, field measurements of BB emission factors (EFs) are sparse, clustered and indicate high spatio-temporal variability. EFs are generally calculated from ground- or aeroplane measurements with respective potential biases towards smouldering or flaming combustion products. Unmanned aerial systems (UAS) have the potential to measure BB EFs in fresh smoke, targeting different parts of the plume at relatively low cost. We propose a light-weight UAS-based method to measure EFs for carbon monoxide (CO), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as PM2.5 (TSI Sidepak AM520) and equivalent black carbon (eBC, microAeth AE51) using a combination of a sampling system with Tedlar bags which can be analysed on the ground and airborne aerosol sensors. In this study, we address the main uncertainties associated with this approach (1) the degree to which taking a limited number of samples is representative for the integral smoke plume and including (2) the reliability of the lightweight aerosol sensors. This was done for prescribed burning experiments in the Kruger national park, South Africa where we compared fire-averaged EF from UAS-sampled bags for savanna fires to integrated EFs from co-located mast measurements. Both measurements matched reasonably well with linear R2 ranging from 0.81 to 0.94. Both aerosol sensors are not factory calibrated for BB particles and therefore require additional calibration. In a series of smoke chamber experiments, we compared the lightweight sensors to high-fidelity equipment to empirically determine specific calibration factors (CF) for measuring BB particles. For the PM mass concentration from a TSI Sidepak AM520, we found an optimal CF of 0.27, using a scanning mobility particle sizer and gravimetric reference methods, albeit that the CF varied for different vegetation fuel types. Measurements of eBC from the Aethlabs AE51 aethalometer agreed well with the multi-wavelength aethalometer (AE33) (linear R2 of 0.95 at λ = 880 nm) and the wavelength corrected Multi-Angle Absorption Photometer (MAAP, R2 0.83 measuring at λ = 637 nm). However, the high variability in observed BB mass absorption cross-section (MAC) values (5.2 ± 5.1 m2 g-1) suggested re-calibration may be required for individual fires. Overall, our results indicate that the proposed UAS setup can obtain representative BB EFs for individual savanna fires if proper correction factors are applied and operating limitations are well understood.

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δ13C signatures of organic aerosols: Measurement method evaluation and application in a source study

Cited by 15 publications

References 38 publications

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C<sub>3</sub> and C<sub>4</sub> plants

An Unmanned Aerial System (UAS) based methodology for measuring biomass burning emission factors

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δ13C signatures of organic aerosols: Measurement method evaluation and application in a source study

Cited by 15 publications

References 38 publications

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C&lt;sub&gt;3&lt;/sub&gt; and C&lt;sub&gt;4&lt;/sub&gt; plants

An Unmanned Aerial System (UAS) based methodology for measuring biomass burning emission factors

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Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C<sub>3</sub> and C<sub>4</sub> plants