Resolving the SAI Trilemma with a Novel Core–Shell Mineral Aerosol: DoloSil-20, a Silica-Passivated Dolomite Architecture for Simultaneous Optical Efficiency, Thermal Neutrality, and Ozone Safety - Preprint

[Geoengineering News]

https://eartharxiv.org/repository/view/13241/

Authors

ABDUL HASEEB TANOLI, Shams ul Arfeen

29 May 2026

Abstract

Conventional stratospheric aerosol injection (SAI) strategies based on liquid sulfate aerosols (H2SO4.H2O) introduce well-documented risks of catalytic ozone destruction and stratospheric near-infrared heating. From a materials-science perspective, the core challenge is one of multi-objective material selection: identifying a particle composition that simultaneously optimizes optical performance, chemical inertness, and thermal neutrality in the stratospheric environment. We formalize these competing requirements as the SAI Trilemma: (1) radiative efficiency, maximizing shortwave backscattering per unit injected mass; (2) thermal neutrality, suppressing stratospheric heating; and (3) ozone safety, mitigating heterogeneous ozone chemistry. To screen candidates across this Trilemma, we propose and evaluate a novel materials-engineering solution: a novel core-shell mineral aerosol (DoloSil-20)—a dolomite (CaMg(CO3)2) core encapsulated by a 20 nm amorphous silica shell, synthesized via Stober-type wet chemistry and designed as a core-shell heterostructure that combines high refractive index contrast with chemical passivation. This architecture is evaluated against pristine calcite and a liquid sulfate reference using a 1D vertical sectional aerosol model integrated over a 1825-day (~5-year) horizon. At lambda = 550 nm and D = 500 nm outer diameter, the mass-specific backscatter proxy beta_back of the DoloSil-20 reaches 0.3405 m2 g-1—a +45.17% advantage over the sulfate reference (0.2346 m2 g-1)—computed via the Aden-Kerker analytical solution for concentric spheres [Aden & Kerker, 1951; Bohren & Huffman, 1983]. This constitutes a wavelength-specific screening result at lambda = 550 nm; spectrally integrated radiative forcing requires a full broadband radiative transfer calculation not performed here. Both mineral proxies exhibit negligible imaginary refractive indices (k ~ 0 at 1500 nm), yielding temperature-anomaly proxy values at the numerical floating-point noise floor (< 10^-15 K). This result is mechanistically expected from the prescribed optical properties and functions as a model consistency check rather than an independent physical prediction. Using a first-order partial-column (10-40 km) ozone surrogate—not equivalent to three-dimensional photochemical model output, and initialized above typical observed partial columns—the silica-passivated core-shell constrains peak ozone depletion to 10.03% of the model domain column, compared to sulfate's 47.11% and calcite's 14.77%. The principal trade-off is atmospheric persistence: higher particle density yields a day-1825 mass retention of 53.98% versus sulfate's 69.46%, a direct consequence of gravitational sedimentation scaling with particle density. Within the constraints of this reduced-order 1D screening framework, the DoloSil-20 architecture simultaneously addresses all three axes of the SAI Trilemma. These results motivate evaluation in three-dimensional chemistry-climate models, which constitute the necessary next step before deployment-relevant conclusions can be drawn.

Source: Earth ArXiv