{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T15:31:18Z","timestamp":1789659078193,"version":"4.0.1"},"reference-count":38,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T00:00:00Z","timestamp":1789344000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003443","name":"The Ministry of Education and Science of the Russian Federation","doi-asserted-by":"crossref","award":["075-15-2025-607"],"award-info":[{"award-number":["075-15-2025-607"]}],"id":[{"id":"10.13039\/501100003443","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/00ghqgy32","id-type":"ROR","asserted-by":"crossref"}]},{"award":["075-15-2025-607"],"award-info":[{"award-number":["075-15-2025-607"]}],"id":[{"id":"https:\/\/ror.org\/00ghqgy32","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Molecular transport of low-volatility organic vapors through unsaturated porous media is governed by the coupled effects of diffusion, sorption, and pore structure, yet the relative roles of these processes remain insufficiently quantified. In this work, we develop a physics-based model describing vapor migration from a subsurface source to the soil surface by explicitly accounting for moisture-dependent sorption, air-filled porosity, and pore clogging by fine particles. The model predicts that soil moisture affects vapor transport through two competing mechanisms: thin water films progressively suppress gas\u2013solid sorption, thereby increasing the effective diffusion coefficient, whereas further wetting reduces the connectivity of air-filled pores and ultimately blocks gas-phase transport. As a consequence, vapor migration exhibits a non-monotonic dependence on soil moisture, with a distinct optimum for surface vapor flux. The model further predicts that fine particles substantially decrease vapor transport by reducing pore connectivity, while lower temperatures suppress migration through both reduced molecular diffusivity and enhanced sorption. Laboratory experiments using representative low-volatility energetic compounds through sand with controlled moisture content and particle composition confirmed all major qualitative predictions of the model, including enhanced transport at intermediate moisture, suppression under dry, dusty and highly saturated conditions, and strong temperature dependence. Although energetic compounds were used as representative low-volatility substances, the proposed framework is generally applicable to molecular transport of trace organic vapors in unsaturated porous media and provides a quantitative basis for predicting environmental conditions under which subsurface sources can be detected by surface vapor measurements.<\/jats:p>","DOI":"10.3390\/molecules31183245","type":"journal-article","created":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T09:34:01Z","timestamp":1789378441000},"page":"3245","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Migration of Vapor Molecules in Soils"],"prefix":"10.3390","volume":"31","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0404-8736","authenticated-orcid":false,"given":"Olga","family":"Kudryashova","sequence":"first","affiliation":[{"name":"Faculty of Physics and Engineering, Tomsk State University, 634050 Tomsk, Russia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7903-3096","authenticated-orcid":false,"given":"Vladimir","family":"Gruznov","sequence":"additional","affiliation":[{"name":"Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, 630090 Novosibirsk, Russia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Andrey","family":"Kikhtenko","sequence":"additional","affiliation":[{"name":"Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, 630090 Novosibirsk, Russia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]},{"given":"Alexander","family":"Vorozhtsov","sequence":"additional","affiliation":[{"name":"Faculty of Physics and Engineering, Tomsk State University, 634050 Tomsk, Russia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"150370","DOI":"10.1016\/j.scitotenv.2021.150370","article-title":"Transient migration behavior of VOC vapor in layered unsaturated soils subjected to multiple time-dependent point pollution sources: Analytical study","volume":"806","author":"Ding","year":"2022","journal-title":"Sci. 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