Investigation and Optimization of the Analytical Procedure for Total Mercury in Particulate Matter Using Chemical Digestion with BrCl

Abstract

Mercury (Hg) is a highly toxic heavy metal with a complex biogeochemical cycle, especially atmospheric Hg, as it can exist in both particulate and gaseous phases. Although US-EPA Method IO-5 has been widely applied for atmospheric Hg monitoring, it only provides recommendation and lacks details on procedural steps. Therefore, this study aimed to investigate and optimize the PBM analysis protocol using chemical digestion based on the IO-5 guideline, utilizing a WA-5F instrument (NIC, Japan). The results showed that the method detection limit (MDL) reached 0.22 pg/m³, which is sensitive enough for PBM analysis under various environmental conditions. Blank sample analyses indicated low and precise controlled background contamination. The repeatability of the procedure showed a coefficient of variation (CV) mostly below 20%, conforming to the requirements according to reference values from major global Hg monitoring networks. Recovery rates ranged from 84.6-101.6% (average 92.2 ± 6.8%) for spiked samples and 99.8% for certified reference materials, demonstrating the reliability of the procedure. Furthermore, the BrCl oxidizing agent was capable of extracting almost all Hg in a single sample treatment. A comparison with the direct thermal decomposition method using the MA3-Solo instrument showed a high correlation (R² = 0.96), confirming the accuracy and practical applicability of the developed method. The research results contribute to establishing an effective analytical procedure for Hg monitoring in the atmosphere and provide crucial scientific data for assessing health risks from PBM exposure in the context of increasing urban pollution.