CHARACTERIZATION AND COMPARISON OF SPECIATED ATMOSPHERIC CARBONACEOUS PARTICULATES AND THEIR POLYCYCLIC AROMATIC HYDROCARBON CONTENTS IN THE CONTEXT OF THE PASO DEL NORTE AIRSHED ALONG THE U.S.-MEXICO BORDER

Abstract

Carbonaceous particulate matter (PM) was collected by both thermal precipitation and glass fiber filters from specific combustion sources and examined by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). PM from various natural gas burner combustion regimes (NGPM), burning tires (TPM), a heavy duty diesel truck (DPM), wood burning (WPM), candle burning (CPM), along with commercial black carbon (BC) powder and multiwall carbon nanotube (MWCNT) aggregates material exhibited similarities in PM microstructure, and average primary spherule diameters. The spherule structures consisted of curved graphene fragments and intercalated polycyclic aromatic hydrocarbons (PAH). PAH concentrations were measured and compared for these PMs, including PAH diagnostic ratios. An analysis of PAH carcinogenicity either as a carcinogenicity index or a potency equivalency factor from literature data indicated that only the TPM PAH content would pose any significant long term, carcinogenicity threat.

Keywords:

• Carbonaceous particulate matter
• electron microscopy
• health effects
• PAHs

This research was supported by grant number 1 S11 ES013339-01A1 from the National Institute of Environmental Health Sciences (NIEHS); NIH. The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official view of the NIEHS-NIH. Scholarship and assistantship support was also received from the Environmental Protection Agency (EPA) Student Support Agency and the Center for Environmental Resource Management (CERM) at the University of Texas at El Paso. We are also grateful to Mike Hernandez, Hitachi — Gaithersburg, MD, for his help with the FESEM work. Dr. W. A. Herndon, UTEP-Chemistry Department critically reviewed the manuscript, and we are grateful for his comments and recommendations.

Notes

∗200 measurements for 3 aggregates on thermal precipitation grids observed by TEM.

^†Includes MWCNT diameters and other fullerenic nanoforms diameters.

^††Manufactured products.

∗MW designates the molecular weight.

^†Natural gas combustion: HFBF-High Flow Blue Flame; LFBF-Low Flow Blue Flame; YELLOW-incomplete combustion (yellow flame).

^††ND denotes “none detected” or below the detection limit.

∗ND denotes “none detected.”

∗Vacuum treated for 1 h.

∗∗Particulates scraped from diesel auto tailpipe.

^†ND denotes “none detected.”

∗Carcinogenicity indices are proportional to the percent of animals developing cancer and inversely proportional to the latent period (measured in days).

^†Potency equivalency factor (PEF) is a scheme developed by Collins et al. (82) where a BaP equivalent concentration (BaP_eq) is calculated by the multiplication of the PAH concentration by its PEF.

^a PEF values from Chen and Liao (79).

^b Carcinogenicity activity indices from Herndon et al. (80).

^c Experimental carcinogenic activity from Herndon (83). (+) indicates small value.

^d Calculated carcinogenic activity from Herndon (83).