Seasonal variation of mercury in settled dust from brick kiln pollution in Sonora, Mexico: Ecological risk and human health implication

Abstract

Seasonal variation in mercury (Hg) spatial distribution in dust was investigated in an arid area with documented resuspension and erosion events. We estimated Hg concentration in settled dust collected at elementary schools associated with dry deposition, and we assessed potential sources and linked health risks. Dust samples (n = 32) were collected from schools close to high traffic roads, industrial corridors, railways, and residential areas during the pre- and post-monsoon period. We determined the total Hg concentration in settled dust by inductively Coupled Plasma Mass Spectrometry (ICP-MS), and used various geochemical indices to analyze the Hg-source apportionment. The average contents of Hg were 0.52 mg kg−1 in the pre-monsoon and 0.28 mg kg−1 in the post-monsoon period. School dust samples showed moderately to extremely contamination of Hg, with the highest content (1.53 mg kg−1) occurring during pre-monsoon. The spatial distribution identified high contamination of Hg in the northern area of the city, which is characterized by brickyard activities. The presence of a bull's eye pattern of Hg during the dry season (pre-monsoon) was evidenced only by the seasonal sampling and related to the emissions from kiln brick production. On the other hand, the HYSPLIT simulation model shows a similar distribution pattern between seasons with particle trajectories going to the north towards the US-Mexico border. Results observed in this study indicate low adverse health effect (HI < 1) but suggest health concerns to children and adults. Finally, this research highlights the potential accumulation of Hgdust during the dry season at an arid climate.