A Study of PM2.5 Elemental Composition in Southwest Mexico City and Development of Receptor Models With Positive Matrix Factorization

Abstract

A study of elemental composition of PM2.5 samples collected at the main campus of the Universidad Nacional Autónoma de México, comprising data from 2015, 2016, and 2019, is described. X-ray fluorescence analysis was employed to measure concentrations of up to 19 elements, complemented with ion chromatography for eight ionic species (for samples of 2015 and 2016), and thermo-optical analysis for organic and elemental carbon (for samples of 2015). Positive matrix factorization (PMF) was applied to develop receptor models for each year, to identify polluting sources and their contributions to total mass. Five sources were identified in every case. With the aid of PMF, the influence of biomass burning on a major episode in May, 2019, was recognized. Comparisons with previous studies in this or nearby sites are also presented. It should be noted that only limited compositional data in this site are available since 2005 for the aerosol fine fraction.

Characterization of aerosol particles during a high pollution episode over Mexico City

“…10 reported similar SDA results in MC, demonstrating that ne particles highly contribute to AOD. Similarly, another study of aerosols in the MC during spring 2019 found that ne particles originate mainly from BB and local tra c emissions, while the primary source of coarse particles is dust from re-suspended soil dust 27 .…”

“…The presence of Fe and Si with percentages of 10 % and 7 %, respectively, is the primary evidence of mineral dust particles. That mineral fraction in MC is partially a result of the MC semi-arid areas (e.g., former Texcoco and Chalco lakes), arid hills, and unpaved roads within the MC basin 27,41 . The signi cant Ca contribution could be due to y ash emissions from two sources: construction activities and soil-dust resuspension 27 .…”

“…That mineral fraction in MC is partially a result of the MC semi-arid areas (e.g., former Texcoco and Chalco lakes), arid hills, and unpaved roads within the MC basin 27,41 . The signi cant Ca contribution could be due to y ash emissions from two sources: construction activities and soil-dust resuspension 27 . Furthermore, the trace elements with percentages less than 1% (Ni, Cu, and Zn), have been associated…”

“…with the emissions generated by high tra c in the urban area. For example, most of the Zn detected could originate from the wear of vehicle tires, while Ni and is a typical element in motor fuel additives 27 .…”

“…The XRF spectrometer calibration procedure was achieved using thin-lm standards (MicroMatter Co., Vancouver, Canada), irradiated for 300 s under the same conditions as the sample analysis. Then, accuracy checks were performed using the NIST standard reference material 2783 27,58 .…”