Inventory of Pb emissions from one of the largest historic Pb smelter worldwide: 118-year legacy of Pb pollution in northern Mexico.

Abstract

The atmospheric Pb emissions (1901-2019), from one of the world's largest non-ferrous metallurgical complexes (Met-Mex in Torreón, México), were estimated based on historical records of modifications in the design, processes, and production volumes. Eight historical periods, with differing amounts of Pb emissions, were distinguished: (1) Essentially no controls (1901-1960); (2) migration to limited controls (1961-1972) by conversion to a Pb-Zn smelter-refining complex and installation of SO2 collectors in 1961-1963; (3) completion to limited control (1973-1977) by the installation of a third H2SO4 collector and a low-efficiency filtration system; (4) maintenance of limited control with no changes (1978-1987); (5) migration to strict control (1988 to 1998) by updating H2SO4 collectors and installation of fertilizer and SO2 liquid extraction plants; (6) completion to strict control (1999-2000) by the installation of state-art technology filtration systems and roofing working areas; (7) migration to abatement (2001-2003) by implantation of good management practices; and (8) maintenance of abatement following good management practices (2004-2019). Based on differences between those periods, we reconstructed the evolution of the Pb emission reduction efficiency (ER in %) and Pb emission factors (EF in gram/ton) for the Torreón complex. Pb emitted by the complex over the past 118years totaled 23,350-27,580t, with most of it (63-75%) occurring when emission controls were negligible (pre-1960 period). In comparisons with other facilities worldwide (e.g., the USA, Canada, and Europa), the modification in Met-Mex for control the Pb emission occurred several years. Emissions from the primary Pb-Zn smelter-refining are released mostly to the atmosphere from the sintering, smelting, drossing, and refining. While Pb emissions from the facility have declined by over an order of magnitude to contemporary levels (≤ 12.6t/year), the current Pb rates still account for atmospheric Pb levels that are 2-3 times higher the USEPA standard and still constitutes a major health threat in Torreón.