Assessment Campaign of the Gravimetric Method (PM10 and PM2.5): Analyzing Environmental Artifacts and Metrological Consistency for the 2030 Regulatory Challenge

Air quality assessment for atmospheric particulate matter (PM) faces significant metrological challenges due to the lack of Certified Reference Materials and sampler design discrepancies. This study evaluates the comparability of the EN 12341 gravimetric reference method using field data from a national interlaboratory comparison organized by the Italian Institute for Environmental Protection and Research (ISPRA) at Castel Romano with 18 Italian regional environmental agencies. The results revealed systematic deviations driven primarily by weather sensitivity—where relative humidity and precipitation compromised PM thermodynamic and mass stability—and, to a lesser extent, a minor filter matrix effect. Because gravimetric measurements provide the sole traceability source for automated measurement systems (AMS), these biases pose potential risks under Directive (EU) 2024/2881. The post-2030 regulatory framework drastically tightens AMS residual uncertainty budgets for daily and annual PM10 and PM2.5 metrics. Near these lower limits, unmitigated humidity effects and declining PM concentrations geometrically amplify residual errors in EN 16450 orthogonal regression calculations, potentially increasing equivalence test failures for certain instruments. To safeguard network data validity and legal defensibility by 2030, agencies should adopt Best Available Techniques (BAT) for sampling and filter conditioning, upgrade QA/QC protocols, and train technical personnel. Minimizing ground-level uncertainty is also crucial for atmospheric modeling and satellite retrieval validation.