Discipline: Ecology Environmental and Earth Sciences
Subcategory: Pollution/Toxic Substances/Waste
Matthew Fiala - Texas Southern University
Co-Author(s): Hyun-Min Hwang, Texas Southern University, Houston,TX
Operation of motor vehicles is a major source of environmental contaminants, especially in urban areas. Trace metals are released through abrasive wear between brake pads and rotors; tires and pavement surfaces. To investigate the contribution of pavement source materials to contaminants in road dust, road dust and pavement samples were collected on concrete and asphalt sections of Highway 59 in Houston, Texas. Upon arrival at the laboratory, road dusts were sieved to 125-250 µm, 63-125 µm, and <63 µm fractions. Bitumen and aggregates in asphalt pavement were separated using dichloromethane extraction. Cement was separated from sand particles in concrete pavement using dissolution in dilute nitric acid. Total environmental-available trace metals were then quantified using ICP-MS. With decreasing of dust size, trace metal concentrations increased, but trace metal mass decreased. Although <63 µm particles contained highest trace metal concentration, 125-250 µm fraction contributed the greatest overall trace metal mass. Mass weighted average concentrations of <250 µm size fractions for Co, Cd, Ni, Cu, and Zn were 1.8 ppm, 3.1 ppm, 37.3 ppm, 104 ppm, and 185 ppm, respectively, for concrete road dust and 2.7 ppm, 4.2 ppm, 23.2 ppm, 64.4 ppm, and 265 ppm, respectively, for asphalt road dust. The results indicate a significant difference likely exist in Cu and Zn concentrations between asphalt and concrete pavement. Trace metal concentration of pavement source materials will be quantified. Chemical Mass Balance Model will be used to quantify percent contribution of brake pads, tires, and pavement surfaces to trace metals in road dust. The approach used in this study can be a useful tool to determine road construction materials that contribute less contaminants to urban air and streams.
Funder Acknowledgement(s): NSF RISE Grant # HRD-1345173
Faculty Advisor: Hyun-Min Hwang, firstname.lastname@example.org
Role: The entire project.