Platinum Group Elements in Airborne Particles in Mexico City

Abstract

Automobile exhaust catalysts using platinum group elements (PGE) have been mandatory on new cars in the Mexico City Metropolitan Area (MCMA) since 1991. Platinum, Pd, Rh, Ir, and Os concentrations and the isotopic composition of Os were determined in PM10 samples from the MCMA. Samples were prepared by isotope dilution NiS fire assay, and analysis was performed by magnetic sector ICP-MS using a single collector instrument for Pt, Pd, Rh, and Ir analysis and a multicollector instrument for Os analysis. Pt, Pd, and Rh concentrations at a downtown location (Merced) increased from < or =1.7 pg of Pt m(-3), 2.7 (4.0) pg of Pd m(-3), and 1.2+/-0.9 pg of Rh m(-3) in 1991 to 9.6 +/- 1.8 pg of Pt m(-3), 10.2+/-1.8 pg of Pd m(-3), and 2.8 +/-0.6 pg of Rh m(-3) in 2003. Concentrations at five sites in MCMA in 2003 averaged 9.3+/-1.9 pg of Pt m(-3), 11+/-4 pg of Pd m(-3), and 3.2+/- 1.0 pg of Rh m(-3). In contrast, Ir and Os concentrations and Os isotopic composition remained relatively constant and were 0.08+/-0.04 pg of Ir m(-3), 0.030 +/-0.007 pg of Os m(-3), and 0.60+/-0.04, respectively, in the MCMA in 2003. Elevated Pt, Pd, and Rh concentrations in the MCMA are attributed to automobile catalysts. A Pt-Pd-Rh concentration peak in 1993 suggests that early catalysts emitted a larger amount of PGE, possibly due to factors inherent in the technology or the use of inappropriate gasoline. Therefore, this study suggests that the current introduction of automobile catalysts in developing countries may result in elevated PGE concentrations if it is not accompanied by infrastructures and policy measures supporting their efficient use.

Increase in platinum group elements in Mexico City as revealed from growth rings of Taxodium mucronatum ten

“…However, the PGE behavior in tree sequences has not been published, in spite that in the last decade, the impact of these elements in urban areas has been demonstrated from different environmental samples (soils, dust, particulate matter, biological tissues). Previously reported data of PGE (Rauch et al 2006;Morton-Bermea et al 2014, 2015. The PGE concentration trends in tree-ring sequences from Chapultepec Park (trees A, B and C) appear to be in accordance with this enrichment, showing a sharp increase after the early 1990s, which is not observed in the tree-ring sequences from tree D (Amealco), growing in a remote area.…”

“…Morton et al (2001) report PGE concentration in urban topsoils. Afterward, Rauch et al 2006 reported data related to de Pt, Pd and Rh concentration in PM 10 collected in representative sites in Mexico City. Morton-Bermea et al 2014 present a spatial and temporal distribution of Pt in PM 2.5 collected in Mexico City.…”

The characteristics of automobile catalyst-derived platinum group elements in road dusts and roadside soils: a case study in the Pearl River Delta region, South China

“…A small anthropogenic input of Os that is originally derived from mantle may reduce the 187 Os/ 188 Os ratios. Elevated Os concentrations have been found in environmental samples and are thought to be the result of emission from automobile catalysts in which Os occurs as an impurity (Fritsche and Meisel 2004;Poirier and Gariepy 2005;Rauch et al 2005Rauch et al , 2006. In this study, almost all samples have higher Os contents and lower 187 Os/ 188 Os ratios than the background values ( Fig.…”

“…Until present, other than Pt, Pd and Rh, only limited studies have been reported for automobile catalyst-related Ru and Ir in environmental samples (Muller and Heumann 2000;Ely et al 2001;Fritsche and Meisel 2004;Rauch et al 2004aRauch et al , b, 2006. Iridium has been used in some new diesel catalysts together with Pt (Palacios et al 2000).…”

A method for determination of PGE–Re concentrations and Os isotopic compositions in environmental materials

“…17 A recent study on sediments from Massachusetts Bay, Cape Cod Bay, and Boston Harbor (all USA) reported background Os concentrations in the range of 22 Os ratios identify an anthropogenic input and thus can be used to trace the PGE source(s). 12,16,[19][20][21][22] The monitoring of Re will be especially important since to date virtually nothing is known about its behavior in the environment and its risk for humans.…”