Emissions of isoprenoids from dominant tree species in subtropical China

Abstract

Emission factors (Es) are among the major sources of uncertainty in regional or global emission estimates of biogenic volatile organic compounds (BVOCs). Tropical vegetation contributes approximately 70% of global BVOC emissions, yet in situ measurements of BVOC emissions from tropical tree species, especially naturally grown mature trees, are quite limited. In this study, BVOC emissions from twenty mature trees (15 evergreen broad-leaved and 5 evergreen needle-leaved) were measured using dynamic chambers, and the emitted BVOCs were collected using sorbent tubes and speciated with a thermal desorption-gas chromatography/mass spectrometry system (TD-GC/MS). Twenty BVOC compounds including, isoprene, 14 monoterpene (MT) species and 9 sesquiterpene (SQT) species were quantified to calculate their Es. The results showed that Eucalyptus urophylla had the largest Es of isoprene (26.47 ± 3.70 μg g–1 h–1) among all the measured trees, followed by Ficus hispida (20.74 ± 1.78 μg g–1 h–1), Syzygium hainanense (20.49 ± 1.36 μg g–1 h–1), Casuarina equisetifolia (18.70 ± 2.91 μg g–1 h–1), and Mangifera indica (11.71 ± 7.04 μg g–1 h–1). α-Pinene, β-pinene, and limonene were the most abundant MTs, of which the largest Es were observed for Magnolia denudata (8.33 ± 2.05 μg g–1 h–1), Castanopsis hystrix (5.29 ± 3.24 μg g–1 h–1), and Magnolia denudata (3.11 ± 1.07 μg g–1 h–1), respectively. The Es of SQTs for the measured trees were lower than 0.50 μg g–1 h–1 except for Magnolia denudata (1.10 ± 0.41 μg g–1 h–1). β-Caryophyllene was the most common SQT, with Magnolia denudata having the highest Es of 0.09 ± 0.03 μg g–1h–1. The localized Es for dominant tree species could be used to update BVOC emission factors for typical vegetation types and help improve BVOC emission estimates in typical subtropical regions and narrow their uncertainties.

Updating Biogenic Volatile Organic Compound (BVOC) Emissions With Locally Measured Emission Factors in South China and the Effect on Modeled Ozone and Secondary Organic Aerosol Production

“…Especially in the needleleaf type, the β‐caryophyllene EFs in the NEF case are only 18% (14.6 μg m −2 h −1 ) of the BASE case, and thus leads to a lower EFs in the entire GD (Figure 1). This lower sesquiterpene EF is partially attributed to the underestimation during the field measurements, which was reported in previous studies (Zeng et al., 2022a, 2022b). In addition, the SLA used in Equation can also induce significant differences in all BVOC EFs estimations (Guenther et al., 2020).…”

“…By combining the recently measured BVOC EFs in Zeng et al. (2022a) with measurements from previous studies in this region, a new‐localized BVOC EF database was obtained (Bai et al., 2001; Baker et al., 2005; Huang et al., 2011; Leung et al., 2010; Tsui et al., 2009). This new‐localized EFs database contained three major BVOCs including isoprene, monoterpene, and sesquiterpene.…”

“…for broadleaf trees. The detailed information of the in situ measurements could be found in Zeng et al (2022a).…”

“…Typically, the SLA values are 100, 150, 175 g m −2 , and the LAI values are 5, 5, 2 m 2 m −2 for the broadleaf, needleleaf, and shrubs, respectively (Wang et al, 2011;Zheng et al, 2010). By combining the recently measured BVOC EFs in Zeng et al (2022a) with measurements from previous studies in this region, a new-localized BVOC EF database was obtained (Bai et al, 2001;Baker et al, 2005;Huang et al, 2011;Leung et al, 2010;Tsui et al, 2009). This new-localized EFs database contained three major BVOCs including isoprene, monoterpene, and sesquiterpene.…”

“…In this study, we updated the EFs of major BVOC species, including isoprene, monoterpene, and sesquiterpene in the MEGAN model in south China, which is based on recent in situ measurements in the PRD region (Zeng et al., 2022a). A source‐oriented CMAQ model was applied to quantify their contributions to O 3 and SOA formation.…”