Biogeochemical Proxy Approaches to Understanding the Atmospheric Dynamics of Microplastics: Perspective and MP-GeoProxy Database

Despite growing evidence for atmospheric transport of microplastics (MPs), there is no established framework for using co-occurring biogeochemical particulate signals to constrain MP source identification and atmospheric processing. We present a decision-gated, multiproxy framework that combines direct MP observations and atmospheric transport modeling with contextual particulate indicators. Geochemical and mineralogical tracers, sea-spray markers, carbonaceous combustion signals, and biological/biogenic indicators are treated as probabilistic constraints, and inference relies on convergence across independent evidence lines rather than any single source tag. The roadmap specifies minimum data requirements (quality assurance/quality control, core MP metrics, and transport-constraint adequacy) and formal gates for proxy availability and transport-proxy consistency; when criteria are unmet, confidence is downgraded, and decoupling is reported rather than forcing attribution. We outline a field-applicable tracer suite and practical sampling and integration steps to support uncertainty-aware inference under realistic analytical budgets. Finally, we introduce the open MP-GeoProxy database linking MP observations, proxy data, and standardized metadata to enable end-member development, cross-study synthesis, and community-driven expansion as the field advances. Used conservatively, the framework can narrow plausible source regimes, identify conditions where proxies and MPs decouple, and prioritize measurements that most effectively reduce the uncertainty in airborne MP dynamics.