Characterization of mercury in atmospheric particulate matter in the state of Rio de Janeiro, Brazil

Abstract

Despite its low atmospheric concentration, mercury in particulate matter (PHg) significantly impacts its biogeochemical cycle. This research focused on the airborne Hg concentrations in fine particulate matter (PM_2.5) collected from three distinct sites: an urban area, an urban area affected by sugarcane burning, and protection reserve area within the state of Rio de Janeiro, Brazil, across various seasons during 2022–2023. The findings revealed average concentration of PM_2.5 in Gávea was 19 ± 8 μg m⁻³ (with values ranging from 8 to 37 μg m⁻³), in PARNASO, it was 24 ± 11 μg m⁻³ (with values ranging from 0.2 to 46 μg m⁻³), and in Campos, it was 10 ± 6 μg m⁻³ (with values ranging from 1 to 19 μg m⁻³). Given these values, no day surpassed the threshold outlined by Brazilian regulations. However, 63% of the samples showed daily concentrations exceeding the standards established by the World Health Organization. The average mercury concentrations in PM_2.5 were 81 ± 116 (3–366) pg m⁻³, 169 ± 139 (2–392) pg m⁻³, and 110 ± 71 (8–272) pg m⁻³ for the urban region of the capital, interior with sugarcane burning and forest locations, respectively, throughout the study period. The study also found that PHg concentrations were about twice as high during the dry period compared to the summer season, suggesting contributions from both local sources and transboundary pollution. Furthermore, significant seasonal variation in PHg concentrations was observed, with notably higher levels detected in the interior urban area impacted by burns than in the capital and preserved sites.