Temperature response measurements from eucalypts give insight into the impact of Australian isoprene emissions on air quality in 2050

Abstract

Abstract. Predicting future air quality in Australian cities dominated by eucalypt emissions requires an understanding of their emission potentials in a warmer climate. Here we measure the temperature response in isoprene emissions from saplings of four different Eucalyptus species grown under current and future average summertime temperature conditions. The future conditions represent a 2050 climate under Representative Concentration Pathway 8.5, with average daytime temperatures of 294.5 K. Ramping the temperature from 293 to 328 K resulted in these eucalypts emitting isoprene at temperatures 4–9 K higher than the default maximum emission temperature in the Model of Emissions of Gases and Aerosols from Nature (MEGAN). New basal emission rate measurements were obtained at the standard conditions of 303 K leaf temperature and 1000 µmol m−2 s−1 photosynthetically active radiation and converted into landscape emission factors. We applied the eucalypt temperature responses and emission factors to Australian trees within MEGAN and ran the CSIRO Chemical Transport Model for three summertime campaigns in Australia. Compared to the default model, the new temperature responses resulted in less isoprene emission in the morning and more during hot afternoons, improving the statistical fit of modelled to observed ambient isoprene. Compared to current conditions, an additional 2 ppb of isoprene is predicted in 2050, causing hourly increases up to 21 ppb of ozone and 24-hourly increases of 0.4 µg m−3 of aerosol in Sydney. A 550 ppm CO2 atmosphere in 2050 mitigates these peak Sydney ozone mixing ratios by 4 ppb. Nevertheless, these forecasted increases in ozone are up to one-fifth of the hourly Australian air quality limit, suggesting that anthropogenic NOx should be further reduced to maintain healthy air quality in future.

CO2‐responsiveness of leaf isoprene emission: Why do species differ?

“…The [CO 2 ] response of isoprene emission has been included in leaf to large scale models using empirical functions linking isoprene emission to ambient [CO 2 ] (Arneth et al, 2007;Arneth et al, 2011;Guenther et al, 2012;Hantson, Knorr, Schurgers, Pugh, & Arneth, 2017). Incorporation of the [CO 2 ] response is critical as without it, the models would predict a major enhancement of global isoprene emissions in the future due to raising temperature, while with the [CO 2 ]-induced inhibition, the models predict either a constant isoprene emission or a reduced isoprene emission in future climates (Arneth et al, 2007(Arneth et al, , 2011Bauwens et al, 2018;Emmerson et al, 2020;Hantson et al, 2017;Heald et al, 2009). So far, all the models in use incorporate a constant [CO 2 ]responsiveness of isoprene emission for all species, and isoprene emission is considered to be very sensitive to [CO 2 ], much more sensitive than, for example, monoterpene emission to [CO 2 ] (Feng et al, 2019).…”

Seasonal and diurnal variations in biogenic volatile organic compounds in highland and lowland ecosystems in southern Kenya

“…), corresponding to about twice the rainfall received in Voi at 560 m a.s.l. (587 mm; Erdogan et al, 2011).…”

“…This estimate is unfortunately connected with a large degree of uncertainty, since BVOC mea-surements from these ecosystems are rather scarce (e.g., Guenther, 2013). These climate-sensitive ecosystems are widely distributed and cover 55.2 % of tropical Africa (MDAUS BaseVue 2013, 2020, which have high potential on native ecosystem changes (Zabel et al, 2019), e.g., human-modified systems expansion at the expense of grassland and savannas, which can decrease the global BVOC levels (Unger, 2014). However, these aforementioned climatesensitive ecosystems are also estimated to face a higher frequency of heat waves, hot nights, droughts, and flooding in the future climate (Niang et al, 2014;Kharin et al, 2018), which can promote or inhibit the certain BVOC releases and make BVOC emissions more changeable.…”

“…However, these aforementioned climatesensitive ecosystems are also estimated to face a higher frequency of heat waves, hot nights, droughts, and flooding in the future climate (Niang et al, 2014;Kharin et al, 2018), which can promote or inhibit the certain BVOC releases and make BVOC emissions more changeable. Models can simulate certain abiotic effects, for example temperature changes, soil water stress, and CO 2 inhibition, on BVOC emissions from these climate-sensitive ecosystems in current and future climate scenarios through the setting of suitable parameterizations, i.e., emission factors (EFs) and activity factors (Guenther et al, 2012;Emmerson et al, 2020). However, field measurements focusing on volatile organic compounds from African ecosystems are very limited, especially on monoterpenoids (MTs), sesquiterpenes (SQTs), and MBO.…”

The Gas and Aerosol Phase Composition of Smoke Plumes From The 2019-2020 Black Summer Bushfires and Potential Implications For Human Health

“…Significant concentrations of isoprene (up to 6 ppb, mean 1 ppb), isoprene oxidation products and monoterpenes were observed during the campaign. Eucalypt forests of southeast Australia are known to be large sources of these biogenic VOCs (Benjamin et al, 1996;Kesselmeier and Staudt, 1999) and emissions are known to be proportional to local ambient temperature (Emmerson et al, 2020;Ramirez-Gamboa et al, 2021b). Biogenic VOCs such as those observed during COALA can act as precursors to secondary organic aerosols (SOA) (Hu et al, 2013;McFiggans et al, 2019).…”