Particle-bound mercury in Saharan dust-loaded particulate matter in Cabo Verde

Abstract

Particle-bound mercury (PBM) concentrations in particulate matter (PM), PM10 and PM2.5, were investigated during dust and non-dust events at urban and rural sites in Cabo Verde, Africa. During dust events, PBM averaged 35.2 pg m−3 (PM10) and 16.1 pg m−3 (PM2.5) compared to 15.9 pg m−3 (PM10) and 1.21 pg m−3 (PM2.5) during non-dust events representing 2.21- and 13.3-fold increases, respectively. The PM10/PM2.5 PBM ratio was 2.19 during dust and 13.1 in non-dust events, highlighting the role of coarse particles during non-dust periods. Air mass trajectories and elemental markers associate PBM sources to mineral dust, mining, oceanic emissions, and biomass burning. Health risk assessment indicates higher inhalation risk compared to dermal or ingestion pathways. By comparing the PBM concentrations during dust and non-dust events, for PM10, dust and long-range transport contributed about 63 % to the average PBM concentration in urban and 52 % in the rural areas and enriched PBM levels in PM2.5 by about 84 % (urban) and 94 % (rural). This result indicates that fine-mode PM is significantly enriched with PBM during dust events, elevating exposure risks and associated health impacts.