Lead Microparticles: Redox Reactions and ROS Formation upon Contact with Water and Air

Lead is an extremely hazardous pollutant that poses a serious threat to the ecosystem. Consequently, gaining new insights into this element enables a better understanding of the associated dangers and risks to public health and the environment. To date, comprehensive studies have been conducted on the properties and environmental distribution of lead in the form of stable compounds—specifically oxides, hydroxides, and salts. However, the role of metallic lead has remained virtually unstudied, even though lead microparticles are released into the atmosphere during industrial metal production and processing. This study helps to bridge this gap to some extent. It continues the authors’ previous work on the investigation of pure lead microparticles (especially the PM2.5 fraction) and their chemical transformations upon contact with water and atmospheric components. New results show that in aerated water and a humid atmosphere, these microparticles trigger complex redox reactions—processes that, in all likelihood, involve reactive oxygen species (ROS). Lead undergoes chemical transformations, yielding products of oxidation, hydrolysis, and interactions with substances present in the water and air. Notably, its interaction with sulfide ions leads to the extensive oxidation of sulfur, resulting in the formation of sulfites and complex lead sulfates. Calculated values of ∆rH0 and ∆rG0 indicate that reactions involving lead microparticles and oxygen in water (or a humid environment) are exothermic and spontaneous. New results expand current knowledge regarding the chemical transformation and transport of various forms of lead in the environment.