Water-soluble atmospheric dust as a persistent surface electrolyte: environmental controls and implications for...

Atmospheric dust is widely recognised as an active component of surface-atmosphere systems; however, its chemical influence on carbonate materials is commonly interpreted in terms of bulk deposition, visible crust formation, or episodic pollution events. Such perspectives overlook the water-soluble fraction of deposited dust-a low-mass but chemically reactive component capable of sustaining surface processes under ambient urban conditions. Using a carbonate-based environmental setting exposed to chronic dust deposition as a model context, this study characterises the ionic state, molecular organisation, and surface distribution of the water-soluble dust fraction through an integrated multi-scale approach. Atomic absorption spectroscopy, Fourier transform infrared spectroscopy, optical microscopy, and scanning electron microscopy with EDS were applied to the same material system. Rather than relying solely on absolute ion concentrations, soluble dust chemistry was evaluated using derived ionic-state indicators, revealing seasonally persistent heterogeneity in ionic mobility and surface availability. FTIR spectra suggest the presence of interfacial water and heterogeneous mineral-oxide environments, while microscopic observations show these components occur as sparse, weakly consolidated, and spatially discontinuous particulate assemblages. The findings suggest that carbonate surface-atmosphere interactions may be influenced under dust-dominated, inferred near-neutral environmental conditions, without the need for strong acidity or visible crust formation. The water-soluble dust fraction can be interpreted as a persistent surface electrolyte system in which chemical influence is governed by ionic-state variability, hydration dynamics, and microstructural openness rather than bulk mass loading. These results highlight the importance of soluble particulate chemistry with implications for long-term surface processes in dust-impacted urban environments.