Physical and chemical characterization of Pb-rich particles from a Pb-Zn smelting and refining factory on the environment and health under semiarid conditions

Abstract

Abstract Metal-rich particles originating from non-ferrous metallurgical activities are the primary source of atmospheric metals. These particles vary in size, morphology, and elemental and mineral compositions and become integrated into urban environments alongside aerosols, dust, and soils. Over time, environmental influences cause these particles to weather, leading to alterations in composition, the development of secondary phases, and a significant impact on metal availability and toxicity compared to their initial state. This study focuses on lead (Pb)-rich particles emitted from the Met-Mex Peñoles complex, one of the world's largest Ag-Cd-Pb-Zn smelting and refining facilities, situated in Torreón, North Mexico, operating since 1901. Torreón is characterized by arid conditions, temperature fluctuations, and low humidity. Dry atmospheric particles were collected in 2015 and 2017 from Torreón's urban area within a 3 km radius of the Met-Mex Peñoles complex. Analysis techniques such as scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and X-ray powder diffraction (XRD) were employed to determine the elemental composition and mineralogy of Pb-rich particles. SEM-EDS analysis revealed diverse Pb-rich particle sizes and morphologies with varying Pb and other element contents. XRD analysis confirmed the presence of Pb and Zn sulfides, Pb carbonates, Pb sulfate, and Pb oxides in urban dust, both as individual particles and agglomerates. Primary Pb minerals were linked to fugitive feed concentrates and smelter flue gas at Met-Mex Peñoles, while secondary Pb minerals resulted from direct emissions and weathering processes. Compared to galena, secondary Pb minerals like Pb carbonates, Pb sulfate, and Pb oxides exhibit higher chemical availability in the environment, posing greater risks to both the environment and human health. In summary, physical and chemical transformations in Pb-rich particles contribute to increased lead bioavailability and toxicity in urban dust, with substantial implications for environmental and human health. These findings underscore the potential consequences of lead-rich particle presence in urban areas.