Tight Coupling of Surface and In-Plant Biochemistry and Convection Governs Key Fine Particulate Components over the Amazon Rainforest

Abstract

Combining unique high-altitude aircraft measurements and detailed regional model simulations, we show that inplant biochemistry plays a central but previously unidentified role in fine particulate-forming processes and atmosphere−biosphere− climate interactions over the Amazon rainforest. Isoprene epoxydiol secondary organic aerosols (IEPOX-SOA) are key components of sub-micrometer aerosol particle mass throughout the troposphere over the Amazon rainforest and are traditionally thought to form by multiphase chemical pathways. Here, we show that these pathways are strongly inhibited by the solid thermodynamic phase state of aerosol particles and lack of particle and cloud liquid water in the upper troposphere. Strong diffusion limitations within organic aerosol coatings prevailing at low temperatures and low relative humidity in the upper troposphere strongly inhibit the reactive uptake of IEPOX to inorganic aerosols. We find that direct emissions of 2-methyltetrol gases formed by in-plant biochemical oxidation and/or oxidation of deposited IEPOX gases on the surfaces of soils and leaves and their transport by cloud updrafts followed by their condensation at low temperatures could explain over 90% of the IEPOX-SOA mass concentrations in the upper troposphere. Our simulations indicate that even near the surface, direct emissions of 2-methyltetrol gases represent a ubiquitous, but previously unaccounted for, source of IEPOX-SOA. Our results provide compelling evidence for new pathways related to land surface−aerosol−cloud interactions that have not been considered previously.

Particle phase-state variability in the North Atlantic free troposphere during summertime is determined by atmospheric transport patterns and sources

“…These effects have been previously shown in laboratory studies by measuring the viscosity of organic and inorganic mixtures (Dette and Koop, 2015;Power et al, 2013;Richards et al, 2020;Rovelli et al, 2019;Saukko et al, 2012;Schill and Tolbert, 2014;Song et al, 2021;Wang et al, 2015), and in ambient samples (Liu et al, 2019;Slade et al, 2019). Moreover, the effects of internally mixed inorganics on particle viscosity are not considered in current climate models (Li et al, 2021;Rasool et al, 2021;Schmedding et al, 2020;Shiraiwa et al, 2017;Shrivastava et al, 2022). These liquid particles are expected to be less stable, to have faster heterogeneous reaction rates, to be more reactive, and to be quickly photodegraded in the FT (Berkemeier et al, 2016;Kuwata and Martin, 2012;Lienhard et al, 2015;Liu et al, 2018a;Marshall et al, 2016;Pöschl and Shiraiwa, 2015b;Renbaum-Wolff et al, 2013).…”

Simulating organic aerosol in Delhi with WRF-Chem using the VBS approach: Exploring model uncertainty with a Gaussian Process emulator

“…It is worth mentioning that these structural errors might also be related to representation of other organic aerosol processes not represented by the VBS approach. Recent studies, for example, have examined particle-phase and multiphase chemistry in aqueous aerosols and clouds (Shrivastava et al, 2022), and reactions of SOA precursors with other radicals like chlorine relevant to Indian conditions (Gunthe et al, 2021).…”

“…Statistical analysis to evaluate model performance over parameter uncertainty can be made tractable through the use of a statistical emulator (Carslaw et al, 2018). With a trained emulator, it is possible to study thousands or millions of model variants (parameter combinations) and estimate the sources of uncertainty (Lee et al, 2011;Johnson et al, 2018;Wild et al, 2020) The VBS approach is often tuned to the environment of interest (Bergström et al, 2012;Shrivastava et al, 2013;Tilmes et al, 2019;Shrivastava et al, 2019;Shrivastava et al, 2022) and, as mentioned before, doing this only with WRF-Chem runs is particularly challenging and time consuming. The aim of this study is to determine an effective way of tuning the VBS scheme using observations, and also to learn about the processes controlling OA in Delhi.…”

Emerging investigator series: surfactants, films, and coatings on atmospheric aerosol particles: a review

“…376,377 Atmospheric box models are unable to reproduce concentrations of IEPOX-derived SOA, however, without incorporating particle phase, especially in regions of low RH and cold temperatures. 156,[378][379][380][381] As IEPOX reacts at the surface of acidic sulfate particles, a viscous coating forms that inhibits further uptake. Zhang et al 382 provided experimental evidence for this phenomenon in chamber experiments of IEPOX uptake to acidied ammonium sulfate seeds, and the authors supported their conclusions with thermodynamic modeling.…”