292 emission timing, the analysis was limited to quarry operating hours (16:00–20:00 UTC; 10:00– 14:00 local Galápagos time, UTC−6). 2.4 Particle characteristics and atmospheric transport scenario This section describes the input parameters used in the simulations and the methodology for estimating particle transport distances. Particles generated at the Cerro Quemado quarry originate from mechanical processes such as excavation and crushing (Dueñas Tovar et al., 2024). Based on previous studies, PM10 particles, which are considered the dominant component in long-range transport, and 30μm particles as a comparative case were selected for analysis (Sirianni et al., 2008). Particle density was determined by considering the physical properties of porous scoria and basaltic lava, including porosity (Al-Harthi et al., 1999)(Hornby et al., 2020). Previous studies have reported porosities of vesicular basalt ranging from 15% to 29%, with an average of 22% (Nabawy & Wassif, 2017). Accordingly, in this study, the porosity was assumed to be 20%, and the apparent particle density was set to 2,400 kg m⁻³. The air density was set to 1.2 kg m⁻³, and the effective release height was defined as 60 m based on the local topography of the quarry. The gravitational settling velocity, , was calculated assuming spherical particles and laminar flow conditions, using Stokes’ law as follows (Stokes, 1851). vs= g(ρ p - ρf )D2 18μ (1) where “g” is the gravitational acceleration, “ρp” is the particle density, “ρf” is the air density, “D” is the particle diameter, and “μ” is the dynamic viscosity of air. Based on the calculated settling velocity and wind conditions, the theoretical horizontal transport distance of the particles until they reach the sea surface was estimated. 2.5 Marine transport simulation and Lagrangian modeling To evaluate marine transport processes, a two-dimensional horizontal Lagrangian particle tracking simulation driven by ocean current data was conducted. In this model, particle motion was governed solely by horizontal advection, while vertical turbulent mixing and diffusion processes were not explicitly resolved. Instead, the tracking duration was determined based on a prior assessment of particle residence time within the surface mixed layer. The particle settling velocity in seawater, w, was calculated using Stokes’ law following the method described by (Baeye et al., 2021). The kinematic viscosity of seawater was set to 1.1 × 10⁻⁶ m² s⁻¹ based on the reported surface seawater temperature around San Cristóbal Island during the cold season (approximately 20–22 °C (Palacios, 2004)) and the established temperature– viscosity relationship (Sharqawy et al., 2010). The mean residence time of particles within the mixed layer, θ, was estimated using the formulation under well-developed vertical mixing conditions (Deleersnijder et al., 2006).
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